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e21581 Background: ICI with/without chemotherapy has become the standard of care for the treatment of advanced NSCLC. Little is known about the clinical and molecular predictors of DoR to these agents. We previously reported clinical predictors of DoR to ICI in NSCLC patients (pts). Here we report the correlation of molecular alterations with DoR and clinical/molecular characteristics of super responders (DoR ≥ 2yr) to ICI. Methods: A retrospective chart review of pts with advanced NSCLC treated with ICI based therapy between 2015-2018 at Karmanos Cancer Institute was conducted. Clinical, tumor, and molecular characteristics data were collected. DoR was grouped into: < / = 6 weeks, > 6weeks-6months, > 6mo-1yr, > 1yr, and super responders. Results: Of 147 pts, 68% had adenocarcinoma, 61% received prior radiation, 21% had brain metastasis (mets), 26% developed irAEs, 33% were on statin, 27% were on aspirin, 83% were current or former smokers, 55% had right sided primary tumor, ICI was 1st line treatment (tx) in 20% and 2nd line tx in 52%. Overall median DoR was 168 days (95% CI, 132-231 days). Pts with right sided primary tumors and those who received ICI as 1st line tx had longer DoR (p = 0.012 and p = 0.017; respectively). Other aforementioned covariates, including brain mets, had no significant relationship with DoR. Molecular profile (MP) of 592 genes was available for 57 (38.8%) pts. PD-L1 ≥50%, CDKN2A and NOTCH1 mutations were associated with statistically significant longer DoR. Mutations/alterations in EGFR, ALK, ROS1, MET, RET, HER2, KRAS, STK11 and TP53 did not appears to have an impact on the DoR, although some of the analysis was limited because of very small number of pts. Of the 10 super responders, majority had adenocarcinoma, received prior radiation and were current/former smokers. Two had brain mets. Most did not have concurrent use of anti-inflammatory agents (statin or ASA). Only 2 of the super responders had MP available with negative NOTCH1 and CDKN2A mutations. Conclusions: Receiving ICI as 1st line of therapy and having right sided primary tumors predicted longer DoR. Presence of brain mets did not adversely affect the DoR. Super responders were more likely to have adenocarcinoma, prior radiation therapy, and current/former smoking history. PD-L1 expression ≥ 50%, CDKN2A, and NOTCH1 were associated with longer DoR. Presence of actionable genomic alterations, STK11, KRAS and TP53 did not appear to impact DoR to ICI.

11516 Background: Malignant PEComa is a rare, aggressive sarcoma, with no approved medical treatment. Cytotoxic chemotherapies have limited benefit for patients with advanced disease. The AMPECT trial measured the effects of nab-sirolimus (ABI-009) and is the first prospective study in advanced malignant PEComa. nab-Sirolimus is a nanoparticle albumin-bound mTOR inhibitor with significantly higher intratumoral drug levels, mTOR target suppression, and anti-tumor activity in animal models versus other mTOR inhibitors. This report presents long-term follow-up of DoR after the primary analysis. Methods: Patients (N=34) received nab-sirolimus (100mg/m2 IV, weekly, 2/3 weeks) until progression or unacceptable toxicity. Primary endpoint: ORR by IRR. Key secondary endpoints included DoR, PFS6, OS, and safety. Exploratory endpoints included correlation of tumor genotype and outcome. The sample size of 30 efficacy-evaluable patients was based on an estimated ORR of 30% and the lower bound of the 95%CI of ORR to exclude values less than 14.7%. The primary analysis was conducted when all patients were treated ≥6 months (May 22, 2019). This report updates the primary response analysis and DoR with an additional 8.5-month of follow-up. Results: As of Feb 06, 2020, of the 31 efficacy-evaluable patients, the confirmed ORR by IRR was 39% (12/31, 95%CI: 21.8, 57.8), with 1 complete response (CR) and 11 partial responses (PR), 52% stable disease (SD, 16/31, with 10/16 SD ≥12 weeks), and 10% progressive disease (3/31); the disease control rate (CR+PR+SD ≥12 weeks) was 71%. PFS6 was 71% (95%CI: 47.7, 85.1). The majority of responses (67%) were reached at the first post-baseline scan at week 6, with a median time to response of 1.4 months (95%CI: 1.3 to 2.8). The median DoR by IRR was not yet reached (range 5.6-38.7+ months; calculated median 22.2+ months) with 8/12 (67%) responders still on treatment for >1 year and 5/12 (42%) >2 years. Mutational analysis available for 25 patients identified that TSC2 loss-of-function mutations significantly correlated with response; 8/9 (89%) patients with TSC2 had a confirmed response. Conclusions: Responses of advanced malignant PEComa to nab-sirolimus were highly durable and occurred in 39% of patients based on independent review. The high disease control rate with manageable toxicities suggest that nab-sirolimus is effective and represents an important new treatment option for these patients. NCT02494570. Clinical trial information: NCT02494570 .

e15777 Background: FOLFIRINOX is a reasonable option in LAPC. GONO FOLFOXIRI has been shown to provide similar efficacy in advanced disease. ETS and DoR, emerging as relevant endpoints in colorectal cancer, have been rarely investigated in LAPC. Methods: Unresectable LAPC pts treated with FOLFOXIRI were identified. Computed tomography (CT) scan was performed every 8 weeks; after that, multidisciplinary team assessed resectability. ETS was defined as the reduction of ≥20% of target lesions’ diameters at first evaluation. DoR was the % of maximal tumor shrinkage at the nadir compared to baseline. Primary endpoint was the correlation of ETS and DoR with radical (R0) resection. Secondary endpoints were correlation of ETS and DoR with overall survival (OS) and progression-free survival (PFS). Radiologist was blinded to survival data. Survival curves were estimated using the Kaplan-Meier method. Log-rank and chi-square tests were applied. Results: Sixty pts were included. Median age was 62 years (range: 34-74), tumor location was head in 68% and body-tail in 32%. At a median follow-up of 26.9 months, response rate was 37%, median OS and PFS were 15.7 and 10.3 months, respectively. Thirty patients (50%) underwent R0 surgery after chemotherapy. Two pts died due to early surgical complication and were censored at the date of surgery for survival analyses. Among 55 evaluable pts, ETS was reached in 19 pts and median DoR was -17% (range: -65 to +100). A strong association between ETS (p = 0.0002) and DoR (p < 0.0001) with R0 resection was observed. In the overall population, ETS was significantly associated with better PFS (14.5 vs 9.4 months, p = 0.037), while no difference in OS was shown (p = 0.63). DoR was significantly associated both with PFS (13.6 vs 7.8 months, p = 0.014) and OS (19.8 vs 14.5 months, p = 0.047). Conclusions: FOLFOXIRI may allow achieving resectability in selected pts. ETS and DoR are significantly associated with R0 resection. Maximizing response with active regimens could be an effective strategy in LAPC. Further validation of ETS and DoR as surrogate endpoints in larger prospective series is required.

521 Background: The TRIBE trial demonstrated that first-line FOLFOXIRI plus bevacizumab (bev) improves PFS, response rate (RECIST), and OS in comparison to FOLFIRI plus bev (ASCO Annual Meeting 2013). Recent experiences evidenced that both ETS and DoR may implement the assessment of response and correlate with survival in metastatic colorectal cancer (mCRC). Methods: ETS was defined as the relative change in the sum of longest diameters of RECIST target lesions at week 8 compared to baseline. A 20% decrease was adopted as cut-off value to discriminate early responders and non-responders. DoR was defined as the relative change in the sum of longest diameters of RECIST target lesions at the nadir in the absence of new lesions or progression of non-target lesions compared to baseline. The median value was used as cut-off. Results: Out of 508 randomized patients, 443 and 484 patients were evaluable for ETS and DoR, respectively. Early responders achieved longer PFS (median PFS: 12.7 vs 10.0 mos, HR: 0.66 [0.52-0.79], p

464 Background: Hepatocellular carcinoma (HCC) is a highly malignant liver cancer and a leading cause of cancer related mortality. Sorafenib was the first approved systemic treatment for HCC, and remains one of few front-line treatments for this malignancy. Tumor treating fields (TTFields) are low intensity (1-3 V/cm), intermediate frequency (100-500 kHz), alternating electric fields that exert antimitotic effects on cancerous cells. Results of the phase 2 HEPANOVA study of TTFields (150 kHz) plus sorafenib for advanced HCC support investigation of TTFields in a randomized controlled phase 3 study. The current research aimed to describe the in vitro and in vivo efficacy of this combination and to elucidate details regarding the underlying mechanism of action. Methods: In vitro examinations were performed in HepG2 and Huh-7D12 human HCC cell lines, to which TTFields at a frequency of 150 kHz were applied using the inovitro system. Autophagy was examined by western blot and fluorescence detection of microtubule-associated protein light chain 3 (LC3) levels, an accepted autophagy marker. The effect of TTFields in combination with sorafenib was evaluated using cytotoxic, clonogenic, and apoptotic assays. In vivo, SD rats were inoculated orthotopically into the left hepatic lobe with N1S1 HCC cells. 7 days later, TTFields or sham (heat) were applied to the abdominal region of the rats, continuously for 6 days. Daily intraperitoneal injections of sorafenib (10 mg/kg/day) or vehicle were performed during this time. To determine tumor volume growth, MRI images were acquired before and after treatment. Levels of autophagy and apoptosis were examined in tumor sections by immunohistochemistry for LC3 and cleaved PARP, respectively. Results: Application of TTFields induced autophagy in HCC cells. TTFields delivery was cytotoxic to the cells, reduced their colony forming ability, and induced apoptosis while combination with sorafenib elevated these effects. In vivo, tumor volume increased 6-fold in control animals vs 1.6-fold in animals treated with TTFields plus sorafenib. This effect was accompanied by significantly elevated levels of cleaved PARP and LC3 within the tumors of treated relative to control rats. Conclusions: The results demonstrate induction of autophagy and apoptosis in HCC following treatment with TTFields. Concomitant application of TTFields with sorafenib enhanced efficacy via a mechanism that may involve overwhelming autophagy, in vitro and in vivo.

1086 Background: The impact of the interval of radiological assessment on the magnitude of benefit observed in randomized trials (RCTs) in metastatic breast cancer is undefined. Methods: All RCTs investigating anti-neoplastic drugs for metastatic breast cancer published between 2006 and 2019 were identified. Intervals for restaging were categorized as short ( < 9 weeks) or long (≥9 weeks). Hazard ratios (HRs) and 95% confidence intervals for progression-free survival (PFS) and overall-survival (OS) were pooled in a meta-analysis and compared between trials employing short and long restaging intervals assessed as subgroup analyses. Analyses were repeated for pre-specified subgroups according to disease subtype, drug type, whether experimental therapy was added to or replaced standard treatment and whether HR for PFS was < 1 or ≥1. Results: Eighty-nine studies comprising 95 comparisons and 44,901 patients were included. The magnitude of PFS benefit was non-significantly larger in trials which employed short compared to long restaging intervals (HR 0.79 vs. 0.86, p = 0.15). Short restaging interval was associated with significantly higher magnitude of effect on PFS in pre-specified subgroups including non-first line studies (HR 0.78 vs. 0.92, p = 0.04), studies with drugs replacing standard treatment (HR 0.86 vs. 1.04, p = 0.02) and studies performed exclusively in human epidermal growth factor receptor 2 (HER2) positive disease (HR 0.72 vs. 0.90, p = 0.02). Restaging interval was not associated with OS for all included studies (HR 0.92 vs. 0.93, p = 0.66) or for any of the pre-specified subgroups. Conclusions: Shorter restaging intervals are associated with a higher magnitude of effect of PFS, but not OS. Awareness of the impact of the restaging interval on quantification of intermediate endpoints such as PFS is important for the design and interpretation of RCTs.

PURPOSE Pirtobrutinib is a highly selective, non-covalent (reversible) Bruton tyrosine kinase inhibitor (BTKi). We report the safety and efficacy of pirtobrutinib in patients with covalent (c) BTKi pre-treated mantle cell lymphoma (MCL), a population with poor prognosis. PATIENTS AND METHODS Patients with cBTKi pre-treated relapsed/refractory MCL received pirtobrutinib monotherapy in a multicenter phase 1/2 trial (BRUIN, NCT03740529). Efficacy was assessed in the first 90 consecutively enrolled patients who met criteria for inclusion in the primary efficacy cohort. The primary endpoint was overall response rate (ORR). Secondary endpoints included duration of response (DOR) and safety. RESULTS Median patient age was 70 years (range, 46-87), median prior lines of therapy 3 (range, 1-8), 82.2% had discontinued a prior cBTKi due to disease progression, and 77.8% had intermediate or high risk sMIPI score. The ORR was 57.8% (95% CI, 46.9-68.1), including 20.0% complete responses (n=18). At a median follow-up of 12 months, the median DOR was 21.6 months (95% CI, 7.5-not reached). The 6- and 12-month estimated DOR rates were 73.6% and 57.1%, respectively. In the MCL safety cohort (n=164), the most common treatment-emergent adverse events (TEAE) were fatigue (29.9%), diarrhea (21.3%), and dyspnea (16.5%). Grade ≥3 TEAE of hemorrhage (3.7%) and atrial fibrillation/flutter (1.2%) were less common. Only 3% of patients discontinued pirtobrutinib due to a treatment-related AE. CONCLUSION Pirtobrutinib is a first-in-class novel non-covalent (reversible) BTKi, and the first BTKi of any kind to demonstrate durable efficacy following prior cBTKi therapy in heavily pre-treated relapsed/refractory MCL. Pirtobrutinib was well tolerated with low rates of treatment discontinuation due to toxicity.

PURPOSE There is limited evidence on the clinical utility of monitoring measurable residual disease (MRD) in patients with acute myeloid leukemia treated with lower-intensity therapy. Herein, we explored the outcomes of patients treated with venetoclax and azacitidine who achieved composite complete remission (CRc; complete remission + complete remission with incomplete hematologic recovery) and MRD < 10–3 in the VIALE-A trial. METHODS The patients included in this report were treated with venetoclax and azacitidine. Bone marrow aspirate samples for multiparametric flow cytometry assessments were collected for central analysis at baseline, end of cycle 1, and every three cycles thereafter. MRD-negative response was defined as < 1 residual blast per 1,000 leukocytes (< 10–3 or 0.1%) with an estimated analytic sensitivity of 0.0037%-0.0027%. CRc, duration of remission (DoR), event-free survival (EFS), and overall survival (OS) were assessed. A multivariate Cox regression analysis identified prognostic factors associated with OS. RESULTS One hundred sixty-four of one hundred ninety (86%) patients with CRc were evaluable for MRD. MRD < 10–3 was achieved by 67 of 164 (41%), and 97 of 164 (59%) had MRD ≥ 10–3. The median DoR, EFS, and OS were not reached in patients with CRc and MRD < 10–3, and the 12-month estimates for DoR, EFS, and OS in this group were 81.2%, 83.2%, and 94.0%. Among patients with CRc and MRD ≥ 10–3, the median DoR, EFS, and OS were 9.7, 10.6, and 18.7 months. Multivariate analysis showed that CRc with MRD < 10–3 was a strong predictor of OS (adjusted hazard ratio = 0.285; 95% CI, 0.159 to 0.510; P < .001). CONCLUSION Patients who achieved CRc and MRD < 10–3 with venetoclax and azacitidine had longer DoR, EFS, and OS, than responding patients with MRD ≥ 10–3.

PURPOSEAs yet, no checkpoint inhibitor has been approved to treat nasopharyngeal carcinoma (NPC). This study was aimed to evaluate the antitumor activity, safety, and biomarkers of toripalimab, a new programmed death-1 (PD-1) inhibitor for recurrent or metastatic NPC (RM-NPC) refractory to standard chemotherapy.PATIENTS AND METHODSIn this single-arm, multicenter phase II study, patients with RM-NPC received 3 mg/kg toripalimab once every 2 weeks via intravenous infusion until confirmed disease progression or unacceptable toxicity. The primary end point was objective response rate (ORR). The secondary end points included safety, duration of response (DOR), progression-free survival (PFS), and overall survival (OS).RESULTSAmong all 190 patients, the ORR was 20.5% with median DOR 12.8 months, median PFS 1.9 months, and median OS 17.4 months. Among 92 patients who failed at least two lines of systemic chemotherapy, the ORR was 23.9%. The ORRs were 27.1% and 19.4% in PD-L1+ and PD-L1− patients, respectively ( P = .31). Patients with ≥ 50% decrease of plasma Epstein-Barr virus (EBV) DNA copy number on day 28 had significantly better ORR than those with < 50% decrease, 48.3% versus 5.7% ( P = .0001). Tumor mutational burden had a median value of 0.95 muts/mega-base in the cohort and had no predictive value for response. Whole-exome sequencing results from 174 patients revealed that the patients with genomic amplification in 11q13 region or ETV6 genomic alterations had poor responses to toripalimab.CONCLUSIONThe POLARIS-02 study demonstrated a manageable safety profile and durable clinical response of toripalimab in patients with chemorefractory metastatic NPC. An early decrease in plasma EBV DNA copy number correlated with favorable response.

425082 Background: KRAS, a mediator of signalling pathways essential for cellular growth, proliferation, and survival, is the most frequently mutated oncogene in cancer. Notably, KRAS mutations occur in ~90% of pancreatic cancers, of which ~2% are KRASG12C mutations. Other gastrointestinal (GI) tumors also harbor KRASG12C mutations, such as biliary tract cancer (BTC; 1%) and appendiceal cancer (3–4%), and they are also seen in non-GI tumors, such as endometrial and ovarian cancer (1–2%). Adagrasib, a covalent KRASG12C inhibitor that irreversibly and selectively binds KRASG12C in its inactive state, was selected for favorable properties, including long half-life (23 h), dose-dependent pharmacokinetics, and central nervous system penetration. Methods: KRYSTAL-1 is a multicohort phase 1/2 study (NCT03785249) evaluating adagrasib in patients (pts) with advanced solid tumors harboring a KRASG12C mutation. Here we report data from a phase 2 cohort evaluating adagrasib monotherapy administered orally at 600 mg BID in pts with unresectable or metastatic KRASG12C-mutated solid tumors (excluding non-small cell lung cancer and colorectal cancer), including pancreatic ductal adenocarcinoma (PDAC), BTC, other GI, and non-GI tumors. Study objectives include evaluation of clinical activity (ORR, DCR, DOR, PFS, OS) and safety. Results: As of October 1, 2022, 64 pts with KRASG12C-mutated solid tumors were enrolled and 63 were treated with adagrasib (median follow-up, 16.8 months); of these, 21 pts had PDAC, 12 BTC, 16 other GI tumors (9 appendiceal, 4 gastro-esophageal junction/esophageal, 3 small bowel), and 14 non-GI tumors (5 ovarian, 4 unknown primary, 3 endometrial, 1 breast, 1 glioblastoma). Overall, median age was 65 years, 61% had ECOG PS 1, and median prior lines of systemic therapy was 2. Among 57 pts with measurable disease (blinded independent central review), ORR was 35.1% (20/57; all partial responses); DCR was 86.0% (49/57); median DOR was 5.3 months (n=20; 95% CI 2.8–7.3); median PFS was 7.4 months (95% CI 5.3–8.6); and median OS was 14.0 months (n=64; 95% CI 8.5–18.6). Among 21 pts with PDAC, ORR was 33.3% (7/21); DCR was 81.0% (17/21); median PFS was 5.4 months (95% CI 3.9–8.2); and median OS was 8.0 months (95% CI 5.2–11.8). Among 12 pts with BTC, ORR was 41.7% (5/12); DCR was 91.7% (11/12); median PFS was 8.6 months (95% CI 2.7–11.3); and median OS was 15.1 months (95% CI 8.6–not estimable). Overall (n=63), treatment-related adverse events (TRAEs) of any grade were observed in 96.8% of pts (most commonly [≥20%] nausea [49.2%], diarrhea [47.6%], fatigue [41.3%], vomiting [39.7%]), grade 3 TRAEs in 25.4%, and grade 4 TRAEs in 1.6%. No grade 5 TRAE occurred. Conclusions: Adagrasib is well tolerated and demonstrates promising clinical activity in pretreated pts with PDAC, BTC, and other solid tumors harboring a KRASG12C mutation. Clinical trial information: NCT03785249 .

LBA441 Background: Two interim OS analyses from IMvigor130 demonstrated non-statistically significant OS benefit with atezo monotherapy (Arm B) vs placebo + platinum (investigator [INV] choice of carboplatin or cisplatin [carbo or cis])/gemcitabine (plt/gem; Arm C) in patients (pts) with PD-L1–high (IC2/3) mUC, as well as a favorable safety profile vs chemo (Galsky Lancet 2020, Davis AACR 2021). Exploratory data showed clinical benefit with atezo monotherapy in cis-ineligible pts with IC2/3 tumors. Here, we report the final OS analysis from IMvigor130 Arms B and C. Methods: Pts were randomly assigned 1:1:1 to Arm A (atezo + plt/gem; not reported here), B or C. Due to the statistical testing hierarchy, no formal comparison of OS (co-primary endpoint) in Arm B vs C was performed in ITT and IC2/3 pts. ORR and DOR, both per INV-assessed RECIST 1.1 (secondary endpoints), and safety were assessed. Subgroup analyses of OS in cis-ineligible pts and disease control rate (DCR, confirmed CR, PR or [SD ≥6 mo]) were exploratory. Results: As of data cutoff Aug 31, 2022, time since last pt randomly assigned was 49 mo. OS data (Table) did not show benefit for ITT pts, while an HR of 0.56 (0.34, 0.91) was seen in the cis-ineligible IC2/3 subgroup. In the ITT population, the 24-mo OS rates were 34% in Arm B and 32% in Arm C. ORR was 24% (87/359; 38% DCR) in Arm B and 44% (158/356; 59% DCR) in Arm C; median DOR was 29.6 and 8.1 mo, respectively. In cis-ineligible IC2/3 pts, ORR was 40% (20/50) in Arm B and 33% (14/43) in Arm C. Median DOR was not evaluable in Arm B and 6.2 mo in Arm C. Of safety-evaluable pts, 57 of 354 in Arm B (16%) and 312 of 389 in Arm C (80%) had a Gr 3/4 treatment-related AE (TRAE); 3 (1%) and 4 (1%), respectively, had a Gr 5 TRAE. Gr 3/4 AEs of special interest occurred in 36 pts (10%) in Arm B and 17 (4%) in Arm C. Conclusions: The final OS analysis was consistent with previous data. Atezo monotherapy continued to show better tolerability vs chemo with no new safety concerns. These exploratory data support the benefit-risk ratio of atezo monotherapy vs chemo for first-line cis-ineligible IC2/3 mUC. Clinical trial information: NCT02807636 . [Table: see text]

521 Background: Sacituzumab govitecan (SG) demonstrated an objective response rate (ORR) of 27% and median overall survival (OS) of 10.5 months (Mo) in metastatic urothelial carcinoma (mUC) patients (pts) progressing after platinum-based chemotherapy and PD1/L1 inhibitor, which led to accelerated US FDA approval in this setting. The combination of SG and pembrolizumab is safe and active following platinum-based chemotherapy. Nivolumab (NIVO) 1mg/kg plus Ipilimumab (IPI) 3mg/kg has shown promising activity in post-platinum mUC pts. Given the potential synergism between immunogenic cell death induced by SG and IPI-NIVO, we hypothesized that the combination of SG and IPI-NIVO would be safe and active as a frontline treatment for cisplatin ineligible mUC. Methods: 3+ 3 design was used for the phase I dose escalation of SG at 8 mg/kg and 10 mg/kg dose levels. IPI and NIVO were given at 3mg/kg and1mg/kg (I3+N1) intravenously (IV) every 3 weeks x 4 cycles followed by NIVO 360 mg IV day 1 every 3 weeks. SG was given IV at days 1,8 every 3 weeks The primary endpoint was safety and recommended phase 2 dose (RP2D) based on dose limiting toxicity (DLTs) observed in cycle 1; key secondary endpoints include ORR, DOR, PFS and OS. Key inclusion criteria were ECOG-PS 0-1, cisplatin-ineligibility, treatment naïve, no prior PD1/L1 inhibitor except >3 months earlier for non-metastatic disease. Results: The study has completed the phase I dose escalation after enrolling a total of 9 patients (8 men, 1-woman, median age: 74 years). 6 patients were enrolled at SG 8 mg/kg with 1 DLT, and 3 patients at 10 mg/kg with 2 DLTs. DLTs included grade 3 skin rash (n=2) and grade 3 pneumonitis (n=1). The RP2D of SG was determined to be 8 mg/kg with I3+N1. The most common treatment related adverse events (TRAE) included anemia (66.6%) neutropenia (66.6%), pruritus (66.6%), fatigue (66.6%), diarrhea (66.6%) and lymphopenia (55.5%). 2 patients developed grade 2 infusion reactions to SG. Other grade ≥ 3 TRAE included neutropenia (55.5%), anemia (33.3%), arthralgia (11.1%), and elevated amylase/lipase (11.1%). Both grade 2 pneumonitis and myositis were seen in 1 patient. Of the 9 pts, 6 pts (4 pts at SG dose of 8mg/kg and 2 pts at 10 mg/kg) were considered evaluable for response of whom 4 responded (ORR 66.6%) with 1 complete response and 3 partial responses. Median DOR was 9.2 Mo (range 4.6-12.0); mPFS was 8.8 Mo (95% CI 3.8-NR) and mOS was not reached. Conclusions: The RP2D of SG was identified as 8mg/kg in combination with Ipilimumab 3 mg/kg+ Nivolumab 1 mg/kg as first-line therapy for cisplatin-ineligible mUC. Early signals of promising activity were observed in a small cohort of evaluable pts. The Phase 2 trial is ongoing coupled with exploratory biomarker analyses. Clinical trial information: NCT04863885 .

TPS591 Background: The PD-1 inhibitor pembro showed antitumor activity in cohort A of the phase 2 KEYNOTE-057 study (NCT02625961), with 41% of pts with HR BCG-unresponsive carcinoma in situ (CIS) of the bladder ± papillary tumors achieving a CR at 3 months with a median DOR of 16.2 months. Based on these results, pembro was approved in the United States for treatment of pts with BCG-unresponsive HR NMIBC with CIS ± papillary tumors who are ineligible for or have elected not to undergo radical cystectomy (RC). However, novel combinations that improve the efficacy of pembro are needed. Immune checkpoints TIGIT and LAG-3 have been shown to contribute to treatment resistance in many cancers, and their inhibition may enhance the activity of pembro. Cohort C of KEYNOTE-057 will evaluate the efficacy and safety of coformulations of pembro and TIGIT inhibitor vibostolimab or LAG-3 inhibitor favezelimab in pts with HR BCG-unresponsive NMIBC with CIS ± papillary tumors. Methods: Key eligibility criteria include adults with histologically confirmed HR NMIBC that is unresponsive to BCG (defined as persistent or recurrent CIS alone or with Ta/T1 ≤12 months of completion of adequate BCG therapy) who are ineligible for or elect not to undergo RC, have CIS ± papillary tumors at baseline (CIS alone, Ta + CIS or T1 + CIS), and have an ECOG score of 0-2. Approximately 60 pts will be randomly assigned 1:1 to Arm 1 (coformulation of pembro 200 mg and vibostolimab 200 mg) or Arm 2 (coformulation of pembro 200 mg and favezelimab 800 mg) IV Q3W (≤35 administrations) until central pathology-confirmed ≥T1 at any time point or persistent or recurrent CIS or high-grade ≥Ta at the 24-week efficacy review or thereafter. Pts with central pathology–confirmed low-grade pTa at any time point may continue treatment following resection of visible tumors. In the absence of disease persistence/recurrence or progression, treatment will continue until unacceptable toxicity, decision to withdraw, or administrative reasons. Tumor evaluations will be performed Q12W until year 2, then Q24W thereafter for up to 5 years. The primary efficacy end point is 12-month CR rate of HR NMIBC as determined by cystoscopy, cytology, biopsy, and radiologic imaging by central pathology and radiology review. Secondary efficacy end points include DOR of HR NMIBC in responders; overall CR rate and CR rate at 3 and 6 months; PFS to worsening of grade, stage, or death; PFS to muscle-invasive or metastatic disease or death; and OS. The safety objective will characterize the safety and tolerability in all pts who received ≥1 dose of study treatment. Efficacy will be evaluated in all pts who received ≥1 dose of study treatment and have a baseline evaluation consisting of pre-enrollment cystoscopy, TURBT/biopsy, urine cytology, and baseline CT urography imaging. Clinical trial information: NCT02625961 .

481 Background: In this study, we evaluated RECIST criteria-based objective response rate (ORR) as potential surrogate endpoints for overall survival (OS) in patients who were treated with immune checkpoint inhibitors therapy (ICT) and with long-term follow-up in metastatic urothelial carcinoma. Methods: The primary endpoint was overall ORR and OS, duration of treatment (DOR) with ICT. ORR was analyzed using Fisher’s exact test. Median follow-up and OS were estimated by using the Kaplan-Meier method. Results: The median follow-up time was 58 (1.15–71) months (mo). Progression developed in 94 (47%) patients during the first three months of treatment with ICT. The rate of complete response (CR) to ICT, partial response (PR) rate, and stable disease were 10% (n=20), 23% (n=46), and 20% (n=41), respectively. There was an imbalance in baseline characteristics between patients who had ORR and non-responder groups (Table). The 5–year OS rates for CR and PR were 73% and 23%, respectively. The median DOR for CR, PR, and SD were 51.8 mo% (44.5–59.1), 20.7mo (16.7–24.6), and 8.8 mo (5.5–12.1), respectively. Of the sixteen (80%) patients who had CR and 14 (30%) patients who had PR had an ongoing response at the time of the analysis. In univariate analysis, neutrophil-to-lymphocyte ratio (NLR) >3, liver metastases, ECOG PS ≥1, and hemoglobin levels below 10 mg/dl, PR, and CR were all significantly associated with OS. In multivariate analysis, liver metastases [HR=2.3; 95% CI 1.3-4.2; p < (0.004)] were independent related variable with short OS. Other hand, PR [HR=0.3; 95% CI 0.15-0.5; p < (0.001)] and CR [HR=0.06; 95% CI 0.014-0.27; p < (0.001)] were associated with improved OS. Conclusions: This five-year analysis of real-world data indicated a significant correlation between ORR, especially CR and OS in patients who received immune checkpoint inhibitors in metastatic urothelial cancer. Therefore, the identification of a potential surrogate marker for survival in patients treated with ICT would represent an important advance in the early identification of patients’ response or resistance to ICT.

526 Background: SG is an antibody-drug conjugate composed of an anti-Trop-2 antibody coupled to SN-38, a topoisomerase-I inhibitor, via a proprietary hydrolyzable linker. SG received accelerated FDA approval in April 2021 in pts with mUC who previously received PT-based therapy and a CPI based on the primary analysis of the pivotal TROPHY-U-01 Cohort 1 study. With 9.1 mo median (med) follow-up, SG monotherapy demonstrated a 27% objective response rate (ORR) and med overall survival (OS) of 10.9 mo in 113 pts with locally advanced or mUC progressing after receiving at least a PT-based therapy and a CPI (Tagawa, et al. J Clin Oncol. 2021). Here we report updated Cohort 1 outcomes. Methods: TROPHY-U-01 (NCT03547973) is a multicohort, open-label, phase 2 study. Cohort 1 pts (≥18 y) had progression of mUC following PT (as first-line metastatic therapy or as (neo)adjuvant therapy with recurrence/progression ≤12 mo) and CPI, had ECOG PS 0-1, and creatinine clearance ≥30 mL/min. Pts received 10 mg/kg of SG intravenously on D1 and D8 of 21-D cycles. The primary endpoint was ORR per central review by RECIST 1.1. Key secondary endpoints included duration of response (DOR), progression-free survival (PFS), clinical benefit rate (CBR), OS, and safety. Results: As of July 26, 2022, med follow-up was 10.5 mo (range, 0.3-40.9) for treated pts (N=113). As previously reported, pts (78% men; med age, 66 y; 66% with visceral metastases, 34% liver), were heavily pretreated with a med of 3 prior therapies (range, 1-8). Med time since last prior therapy was 1.5 mo (range, 0-60.0). At data cutoff, per central review, ORR was 28% (95% CI, 20.2-37.6); CBR was 38% (95% CI, 29.1-47.7), med DOR was 6.1 mo (95% CI, 4.7-9.7, n=32) and med PFS was 5.4 mo (95% CI, 3.5-6.9). Med time to response was 1.6 mo (range, 1.2-5.6) and med OS was 10.9 mo (95% CI, 8.9-13.8). DOR, PFS, and OS rates (95% CI) at 12 mo were 30% (13.6-48.8), 14% (7.2-23.3), and 45% (35.4-53.8), respectively, with 7 (6%) pts still receiving SG at 12 mo. In pts who received prior enfortumab vedotin (n=10) and prior PT in the (neo)adjuvant setting (n=39), results were consistent with the overall population. Grade ≥3 treatment-related adverse events (TRAEs) occurred in 65% of pts and were similar to prior reports; the most common Grade ≥3 TRAEs were neutropenia (35%), leukopenia (18%), anemia (14%), diarrhea (10%), and febrile neutropenia (10%). One treatment-related death occurred due to febrile neutropenia-related sepsis. Conclusions: At 10.5-mo med follow-up, the response rate remains high in pts with heavily pretreated mUC, including pts with visceral metastases, prior EV therapy and prior (neo)adjuvant PT therapy. No new safety signals were observed. These data support the use of SG in pts with mUC who received PT and a CPI and further evaluation of SG in earlier lines of therapy. Clinical trial information: NCT03547973 .

518 Background: Pembro is standard of care for pts with mUC who progress after 1L PT therapy but only ~21% of pts respond, highlighting an unmet need (Bellmunt, et al. NEJM. 2017). SG is an antibody-drug conjugate composed of an anti-Trop-2 antibody coupled to SN-38 via a hydrolyzable linker. In Cohort 1 of the TROPHY-U-01 study, SG demonstrated a 27% objective response rate (ORR) with manageable safety in 113 pts with locally advanced or mUC who previously received PT and a checkpoint inhibitor (CPI; Tagawa, et al. J Clin Oncol. 2021), leading to accelerated FDA approval in this pt population. Preliminary results of the phase 2 TROPHY-U-01 Cohort 3 study showed that SG plus Pembro demonstrated a high ORR (34%) as a 2L therapy in 41 CPI-naive pts with mUC who progressed after PT (Grivas et al. J Clin Oncol. 2021). Here we present the primary analysis of Cohort 3. Methods: Cohort 3 pts (≥18 y) had progression of mUC following PT in the metastatic setting or following ≤12 mo of PT in the (neo)adjuvant setting and ECOG PS 0-1. Pts received 10 mg/kg of SG on D1 and D8 and 200 mg of Pembro on D1 of a 21-D cycle for ≤2 y. The primary endpoint was ORR [complete response (CR) + partial response (PR)] per central review by RECIST 1.1. Secondary endpoints include clinical benefit rate [CBR; CR + PR + stable disease for at least 6 mo], duration of response (DOR) and progression-free survival (PFS) per central review; and safety. Target enrollment was approximately 41 pts based on a Simon two-stage design for 90% power at one-sided α of 0.05 to demonstrate 21% improvement in ORR, with a null hypothesis of historical ORR ≤20% and an alternate hypothesis of ORR ≥41%. Results: As of July 26, 2022, median follow-up was 12.5 mo (range, 0.9-24.6) for treated pts (N=41); median age, 67 y (range, 46-86), 83% male, 61% ECOG PS 1, 76% ≥1 Bellmunt risk factors, and 78% visceral metastases (29% liver). Median duration of last prior anti-cancer therapy was 2.7 mo (range, 0-13). Per central review, ORR was 41% (95% CI, 26.3-57.9; 20% CR); CBR was 46% (95% CI, 30.7-62.6); median DOR was 11.1 mo (95% CI, 4.8-NE [not estimable]; n=17); and median PFS was 5.3 mo (95% CI, 3.4-10.2). Median time to response was 1.4 mo (95% CI, 1.3-2.7) and median OS was 12.7 mo (95% CI, 10.7-NE). Grade ≥3 treatment-related adverse events (TRAEs) occurred in 61% of pts; most common Grade ≥3 TRAEs were neutropenia (37%; 10% febrile neutropenia), leukopenia (20%), and diarrhea (20%). TRAEs led to a 15% discontinuation rate. Systemic steroid and G-CSF use were both 34%. No treatment-related death occurred. Conclusions: SG plus Pembro demonstrated a high ORR and CBR with a manageable safety profile in 2L mUC in CPI-naive pts who progressed after PT-based therapy. No new safety signals were observed with the combination. These data support further evaluation of SG plus CPI in mUC. Clinical trial information: NCT03547973 .

520 Background: Pts with PT-ineligible mUC have limited treatment options following CPI therapies; thus, new treatment options are needed. SG is an antibody-drug conjugate composed of an anti-Trop-2 antibody coupled to SN-38, a topoisomerase-I inhibitor, via a proprietary hydrolyzable linker. SG received accelerated FDA approval in April 2021 for pts with mUC who progressed after PT and CPI therapies based on the positive results of the pivotal TROPHY-U-01 Cohort 1 study. In Cohort 1, SG demonstrated an objective response rate (ORR) of 27%, a median overall survival (OS) of 10.9 mo, and a manageable safety profile in 113 pts with locally advanced or mUC (Tagawa, et al. J Clin Oncol. 2021). SG demonstrated an ORR of 28% in PT-ineligible pts with mUC who progressed after CPI therapy in preliminary results of the phase 2 TROPHY-U-01 Cohort 2 study (Petrylak et al. J Clin Oncol. 2020). Here, we report the primary analysis of TROPHY-U-01 Cohort 2. Methods: Cohort 2 pts (≥18 y) were PT-ineligible at screening, had ECOG PS 0-1, and creatinine clearance ≥30 mL/min. Pts received 10 mg/kg of SG on D1 and D8 of 21-day continuous cycles. The primary endpoint was ORR per central review by RECIST 1.1. Secondary endpoints included duration of response (DOR) and progression-free survival (PFS), per central review, and OS. Target enrollment was approximately 40 pts. Assuming the second-line ORR of 40%, 40 pts would give a 95% CI with a lower limit of 25% (CI is 0.25 to 0.57) for ORR. Results: As of July 26, 2022, the median follow-up was 9.3 mo (range, 0.5-30.6) for treated pts (N=38); median age, 72.5 y (range, 41-87), 61% male, 50% ECOG PS 1, and 66% visceral metastases (29% liver). Median number of prior therapies was 2 (range, 1-5); 50% received prior (neo)adjuvant PT, 18% received prior enfortumab vedotin, and 3% received prior erdafitinib. Median time since last prior anticancer therapy was 1.6 mo (range, 1-8) and median duration of last prior anticancer therapy was 4.2 mo (range, 1-12). Per central review, ORR was 32% (95% CI, 17.5-48.7; 32% partial response); median DOR was 5.6 mo (95% CI, 2.8-13.3; n=12); and median PFS was 5.6 mo (95% CI, 4.1-8.3). Median time to response was 1.4 mo (range, 1.3-1.5) and median OS was 13.5 mo (95% CI, 7.6-15.6). Grade ≥3 treatment-related adverse events (TRAEs) occurred in 68% of pts; the most common Grade ≥3 TRAEs were neutropenia (34%), anemia (21%), leukopenia (18%), fatigue (18%), and diarrhea (16%). TRAEs resulted in an 18% discontinuation rate. No treatment-related deaths were reported. Conclusions: SG monotherapy demonstrated a high response rate with an overall manageable safety profile in PT-ineligible pts with mUC who progressed after CPI therapy. No new safety signals were observed. These data support further evaluation of SG in pts with mUC post CPI therapy. Clinical trial information: NCT03547973 .

630 Background: The introduction of immunotherapies has changed the first-line treatment landscape for advanced/metastatic renal cell carcinoma (aRCC). This study examines patient preferences in this rapidly changing environment to better understand the tradeoffs patients with aRCC are willing to make when choosing treatment. Methods: Patients with self-reported aRCC in the United States completed an online, cross-sectional survey. A discrete choice experiment was used to assess preferences for attributes of aRCC treatments. Patients completed a series of choice tasks showing 2 treatment profiles that varied in 7 important attributes identified through literature and qualitative research: overall survival, progression-free survival (PFS), objective response rate (ORR), duration of response (DOR), risk of adverse events, quality of life (QOL) changes, and treatment administration. Descriptive statistics were reported, and a hierarchical Bayesian logistic model was used to calculate preference weights. Relative importance estimates (mean ± standard error) were computed for each attribute; these represent the mean percentage of the variation in preferences explained by the attribute. Results: Survey results from a total of 299 patients were analyzed (male, 50%; mean age, 56 years). All 7 attributes were statistically significant for influencing the choice of treatment. Key attributes included treatment regimen convenience and QOL improvement, which ranked similarly to increasing survival time. Among the efficacy attributes, increasing survival time was most important, followed by ORR, PFS, and DOR. Reducing the risk of serious adverse events from 82% to 65% was prioritized after the efficacy parameters. Conclusions: Patients with aRCC highly value less burdensome treatment regimens and improved QoL in addition to improvement in survival. This highlights the need for a broader context beyond efficacy and safety when discussing treatment options with patients. Funding: This study was supported by Bristol Myers Squibb.

684 Background: In the COSMIC-021 phase 1b study (NCT03170960) evaluating cabozantinib plus atezolizumab in advanced solid tumors, this combination therapy demonstrated encouraging clinical activity in patients with advanced non-clear cell renal cell carcinoma (nccRCC) with a median follow-up of 13 mo (Pal. JCO 2021). Results after extended follow-up in nccRCC are presented. Methods: Patients with advanced nccRCC and ECOG PS 0/1 who had ≤1 prior VEGFR-targeting tyrosine kinase inhibitor (TKI) were eligible. Prior treatment with TKIs targeting MET or immune checkpoint inhibitors was not allowed. Patients received cabozantinib 40 mg PO QD plus atezolizumab 1200 mg IV Q3W until unacceptable toxicity or progression; dose reductions of cabozantinib (40 mg QD to 20 mg QD, then to 20 mg QOD) were permitted to manage adverse events. The primary endpoint was objective response rate (ORR) per RECIST v1.1 by the investigator; other endpoints included safety, duration of response (DOR), PFS, and OS. Results: The study enrolled 32 patients with nccRCC (2 from dose escalation phase, and 30 from expansion phase of the study): median age, 62 y; male, 81%; ECOG PS 0/1, 75%/25%; histology, papillary/chromophobe/clear cell/other, 47%/28%/3%/22%; sarcomatoid feature, 13%; IMDC risk favorable/intermediate/poor, 50%/41%/9%; ≥3 tumor sites, 56%; tumor sites, lung/kidney/bone/liver, 50%/25%/16%/16%; prior nephrectomy, 63%; prior VEGFR TKI, 22%; 0/1 lines of prior therapy (locally advanced/metastatic setting), 81%/19%. As of July 21, 2022, median follow-up was 37.2 mo (range 32.1–58.5) with 5 (16%) patients remaining on study treatment. ORR by investigator was 31% (all PRs) and disease control rate was 94% (Table); median DOR was 8.1 mo. Median PFS was 9.3 mo (95% CI 5.5–12.3), and median OS was not reached (95% CI 23.0–NE). PFS and OS estimates at 12 mo were 34% and 84%, respectively; 24-mo estimates were 6% and 70%. Treatment-related AEs occurred in 97% (grade 3/4, 53%); the most common AEs included diarrhea (69%), palmar-plantar erythrodysesthesia (50%), fatigue (44%), dysgeusia (41%), hypertension (31%) and nausea (31%). One grade 5 treatment-related AE of pulmonary hemorrhage occurred. Treatment-related AEs leading to discontinuation of both study treatments occurred in 13% of patients. Conclusions: Extended 3-year follow-up reinforces the encouraging clinical activity of cabozantinib plus atezolizumab in advanced nccRCC with a manageable safety profile. Clinical trial information: NCT03170960 . [Table: see text]

156 Background: The low efficacy of single-agent BRAF inhibitor in metastatic colorectal cancer (mCRC) is usually due to EGFR feedback upregulation caused by BRAF blockade. Therefore, multi-drug combination therapy with BRAF inhibitor has been tried. Here, we reported the preliminary results of quadruple therapy with dabrafenib, a selective BRAF inhibitor, trametinib, a selective MEK inhibitor, irinotecan and cetuximab in patients with BRAF V600E-mutated mCRC. Methods: This was an ongoing phase Ib study, patients with mCRC who relapse or refractory to standard treatments were enrolled. Patients were treated with dabrafenib (150mg/150mg doses orally twice daily), trametinib (2mg orally once daily), irinotecan (80mg/m2 weekly) and cetuximab (400mg/m2 in first dose and 250mg/m2 weekly). Treatment was continued until disease progression, development of unacceptable toxicity, or drawal of consent. The primary end-point was disease control rate (DCR), and the secondary end-points included progression-free survival (PFS) and duration of disease remission (DOR). This trial is registered with Chinese ClinicalTrials.gov, number ChiCTR2200063316. Results: From July 2018 to January 2021, 10 patients were enrolled. The median age was 53.5 (age 25-65), nine with colon cancer and one with rectal cancer. The most common adverse events (AEs) (50% or more) were fatigue, fever, rash, vomit, leukopenia, anemia, ALT elevation, and AST elevation. Four patients suffered rash which was the most common severe AE (SAE). Two patients presented with grade 3/4 anemia. Only one patient suffered grade 3/4 AEs with nausea and vomit. The DCR was 90% (9/10). After a median follow-up of 19.7 months, the median PFS was 7.5 months (range 1.8-32.4 months). The median DOR was 5.2 months (range 0-27.7 months). Conclusions: Dabrafenib, trametinib, irinotecan and cetuximab has tolerable toxicity and promising antitumor activity in BRAF V600E-mutated mCRC. This regimen warrants a further phase II clinical trial. Clinical trial information: ChiCTR2200063316 . [Table: see text]

491 Background: VEGF blockade coupled with cytotoxic chemotherapy can promote an immune-permissive tumor microenvironment that can augment response to PD-L1 inhibition. IMbrave151 (NCT04677504) is a randomized, double-blind, global Phase II study evaluating the efficacy of atezolizumab (atezo), bevacizumab (bev) and cisplatin and gemcitabine (CisGem) as first-line treatment for patients with advanced biliary tract cancer (aBTC). Methods: Patients with previously untreated aBTC were randomized 1:1 to receive atezo (1200 mg every 3 weeks [q3w]) + bev (15 mg/kg q3w) or placebo + CisGem (cisplatin 25 mg/m2 and gemcitabine 1000 mg/m2 on Days 1 and 8 q3w) for up to 8 cycles, followed by atezo (1200 mg q3w) + bev (15 mg/kg q3w) or placebo until disease progression or unacceptable toxicity. Patients were stratified by disease status, geographic region and primary tumor location. The primary endpoint was progression-free survival (PFS). Secondary endpoints included overall survival (OS), objective response rate (ORR), duration of response (DOR), disease control rate and safety. No formal hypothesis testing was performed. Results: In total, 162 patients were randomized to receive either atezo + bev + CisGem (n=79) or atezo + placebo + CisGem (n=83). Median age 63 years, Asia/Rest of World (43/57%), ECOG PS 0/1 (53/48%), intrahepatic/extrahepatic cholangiocarcinoma and gallbladder (54/19/27%), and metastatic/locally advanced stage (82/18%). The HR for PFS was 0.76 (95% CI: 0.51, 1.14). Median PFS was 8.4 months for atezo + bev + CisGem and 7.9 months for atezo + placebo + CisGem; the 6-month PFS rates were 78% and 63%, respectively. The confirmed ORR was 24% for atezo + bev + CisGem and 25% for atezo + placebo + CisGem. DOR ≥6 months was 89% for atezo + bev + CisGem vs 47% for atezo + placebo + CisGem. The incidence of Grade 3 or 4 adverse events was 73% and 74% with atezo + bev + CisGem and atezo + placebo + CisGem, respectively. Median OS is not reached. Conclusions: Both combinations of IMbrave151 showed a manageable safety profile. The aggregate of data suggests that combining atezo with bev and chemotherapy may provide clinical benefit in a subset of patients with aBTC. Follow-up is ongoing for OS. Clinical trial information: NCT04677504 .

340 Background: TIS, an anti-programmed cell death protein 1 (PD-1) antibody, + chemo as 1L therapy demonstrated statistically significant and clinically meaningful improvement in overall survival (OS) vs PBO + chemo in patients with advanced or metastatic ESCC (hazard ratio [HR] 0.66 [95% confidence interval (CI) 0.54, 0.80]; P< 0.0001), with a manageable safety profile, at interim analysis of the phase 3, double-blind RATIONALE-306 study (NCT03783442). Here, we report data from the non-Asia subgroup (Europe, Northern America, and Oceania). Methods: Adults with advanced or metastatic ESCC, with no prior systemic treatment for advanced disease were randomized 1:1, (stratified by region, prior definitive therapy, and investigator [INV]-chosen chemo) to receive TIS 200 mg intravenously (IV) once every 3 weeks (Q3W) (Arm A) or PBO IV Q3W (Arm B), with platinum + fluoropyrimidine, or platinum + paclitaxel until disease progression by INV per RECIST v1.1, intolerable toxicity, or withdrawal. The primary endpoint was OS in the intent-to-treat population. Secondary endpoints included: progression-free survival (PFS), objective response rate (ORR), and duration of response (DoR) by INV per RECIST v1.1; OS in the programmed death-ligand 1 score ≥10%; and safety. Results: Of 649 randomized patients, 163 (25.1%) were from the non-Asia subgroup (Arm A, n = 83; Arm B, n = 80). At data cutoff (Feb 28, 2022), the median study follow-up time in the non-Asia subgroup was 16.0 months (mo) in Arm A vs 8.4 mo in Arm B. OS (median 16.3 vs 9.0 mo; unstratified HR 0.66 [95% CI 0.45, 0.96]) and PFS (median 7.7 vs 5.5 mo; unstratified HR 0.59 [95% CI 0.41, 0.83]) were improved in Arm A vs Arm B, respectively. Arm A had higher ORR (61.4% vs 41.3%, odds ratio 2.27 [95% CI 1.21, 4.25]) and longer median DoR (7.1 mo [95% CI 5.6, 9.6] vs 5.7 mo [95% CI 3.8, 8.3]) than Arm B. More patients in Arm A vs Arm B experienced ≥1 treatment-related adverse event (TRAE; 94.0% vs 88.5%), serious TRAEs (25.3% vs 17.9%), and discontinuation due to treatment-emergent AEs (42.2% vs 35.9%, respectively). Similar proportions of patients in Arm A vs Arm B had ≥grade 3 TRAEs (56.6% vs 52.6%), and TRAEs leading to death (1.2% vs 1.3%), respectively. Conclusions: In the non-Asia subgroup, 1L TIS + chemo showed a clinically meaningful improvement in OS vs PBO + chemo in patients with advanced or metastatic ESCC, with a manageable safety profile, consistent with published results in the overall population. Clinical trial information: NCT03783442 .

138 Background: Anlotinib is an oral multi-target tyrosine kinase inhibitor, mainly targeting VEGFR1-3, FGFR 1-4, PDGFR a/b and c-kit. Previous trial had demonstrated that anlotinib monotherapy was effective and safe in advanced colorectal cancer. ALTER-C002 trial is an open-label, single-arm, phase II study, aimed to evaluate the efficacy and safety of anlotinib plus CAPEOX as first-line therapy in patients with RAS/ BRAF wild-type unresectable metastatic colorectal cancer (mCRC). Preliminary results demonstrated significant antitumor activity and manageable toxicity. Here we reported the updated results at the data cutoff of August 19, 2022. Methods: RAS/BRAF wild-type unresectable mCRC patients with no prior systemic treatment received anlotinib (12 mg p.o. qd, d1-d14, q3w), capecitabine (850 mg/m2 p.o., bid, d1-d14, q3w) and oxaliplatin (130 mg/m2 i.v., d1, q3w) for 6 cycles followed by anlotinib and capecitabine as maintenance therapy until disease progression. Tumor response was assessed every 6 weeks according to RECIST v1.1 by investigator. The primary endpoint was ORR, and secondary endpoints included safety, DCR, DOR and PFS. Results: From Nov 2019 to February 2021, 30 eligible patients were enrolled, of whom, median age was 60y (range, 32-72y), 26 (86.7%) had left colon or rectal cancer, and 25 (83.3%) had liver metastases. The ORR was 76.7% (95% CI, 57.7-90.1%) with 2 patient achieved a complete response (CR); DCR was 93.3% (95% CI, 77.9-99.2%). At the data cutoff date, the median DOR was 7.9 months (95% CI, 4.3–11.4) and the median DOT was 8.38 months (95%CI, 5.9-10.9). The median OS has not reached yet, the 24-month OS rate was 72.8% (95%CI, 50.7-86.3%) and the 30-month OS rate was 58.3% (95%CI:25.5-80.8%). Grade 3-4 treatment-emergent adverse events (TEAEs) occurred in 25 (83.3%) patients; the most common grade 3 or 4 TEAEs ( > 10%) were hypertension (50%, 15/30 pts), neutropenia (26.7%, 8/30 pts) and diarrhea (13.3%, 4/30 pts). No grade 5 treatment-related events occurred. Conclusions: Anlotinib combined with CAPEOX exhibited promising ORR in the first-line treatment of mCRC compared to those of previous treatment. A longer follow-up is needed for a more complete assessment, and we launched a phase III, multicenter, open-label trial to assess the efficacy of this regimen comprehensively. Clinical trial information: NCT04080843 .

347 Background: Zanidatamab (zani) is an anti-HER2 bispecific antibody against ECD4 and ECD2 with demonstrated activity and tolerability in a range of HER2-expressing cancers. This Phase (Ph) 2 study (NCT03929666) evaluates zani in combination with chemotherapy (chemo) as first-line treatment for patients (pts) with advanced HER2-expressing mGEA. Methods: Eligible pts for this ongoing, open-label study had not received any prior systemic therapy for mGEA. Pts received zani + physician’s choice of multi-agent chemo (mFOLFOX6, CAPOX, or FP). Antidiarrheal prophylaxis for cycle 1 was added after the first 25 pts were treated. Following demonstration of tolerability of the regimens in an initial safety cohort, the primary study objective was to evaluate antitumor activity. Results: Pts were enrolled between Aug 29, 2019 and Feb 18, 2022 with a data cutoff of July 28, 2022 (N=46 pts; zani + mFOLFOX6 [24], zani + CAPOX [20], or zani + FP [2]). Median age was 58 yrs; 85% male; 42 pts (91%) had HER2+ tumors (IHC 3+ or 2+ with ISH-positivity) based on central testing. Median duration of follow-up among all 46 pts was 21.5 months (mo) and 20 pts (43%) remain on treatment. In 38 response-evaluable pts with HER2+ tumors, confirmed objective response rate (cORR) was 79% (95% CI: 63-90%) and disease control rate was 92% (95% CI: 79-98%); 3 pts achieved complete response. Median duration of response (DOR) was 20.4 mo (95% CI: 6.8-not estimable [NE]), with 57% (17/30) pts having an ongoing response at data cut-off (1 pt has ongoing response >29 months). In all 42 pts with HER2+ tumors, median progression-free survival (PFS) was 12.5 mo (95% CI: 7.1-NE) and median overall survival (OS) was not yet reached. Survival rate at 18 mo was estimated to be 87.3%. The most common (≥25% pts) treatment-related (zani and/or chemo) adverse events (TRAE) in all pts were diarrhea, nausea, peripheral sensory neuropathy, decreased appetite, fatigue, vomiting, and hypokalemia. Diarrhea was the most common Gr3+ TRAE, lasting a median (interquartile range) of 3 (2-5) days, with the majority of events occurring in cycle 1; incidence of all Gr3+ events was 56% in 25 pts who did not receive prophylaxis and 14% in 21 pts who did. There were no treatment-related deaths. Conclusions: In pts with HER2+ mGEA, zani + chemo is a highly active treatment regimen with a manageable safety profile. This maturing data set demonstrates durable disease control with encouraging cORR, DOR, PFS and OS results. A global Ph 3 study (HERIZON-GEA-01; NCT05152147) evaluating zani in combination with physician’s choice of standard chemo with or without the PD-1 inhibitor, tislelizumab, for first-line treatment of advanced HER2+ mGEA is currently enrolling. Clinical trial information: NCT03929666 .

570 Background: ORIENT-32 trial (NCT03794440) assessed sintilimab (anti-PD-1 antibody) plus a bevacizumab biosimilar (anti-VEGF antibody) versus sorafenib (Sor) as first-line treatment for unresectable HCC and demonstrated a significant improvement in both overall survival and progression-free survival. Here we report the updated results of objective response rate (ORR), time to response (TTR), duration of response (DoR) and depth of response (DpR). Methods: 571 eligible patients (pts) with unresectable HCC were enrolled and randomized (2:1) to receive sintilimab (200 mg IV Q3W) plus IBI305 (15 mg/kg IV Q3W) or Sor (400 mg orally, BID) until disease progression or unacceptable toxicity. Tumors were evaluated using Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST 1.1)and HCC-modified RECIST (mRECIST). ORR, TTR, DoR, and DpR were analyzed. The DpR was defined as the minimum percentage of (1) sum of longest diameter (SLD) change and (2) longest diameter (LD) change described as mean (standard deviation, SD). Results: At the data cutoff on Dec 30th, 2021, the median follow-up time was 26.7 months. The ORR in sintilimab plus IBI305 and Sor group was 21.0% (77/367) vs 4.7 (8/169) per RECIST 1.1 and 25.1% (92/367) vs 7.7% (13/169) per mRECIST. The median TTR in sintilimab plus IBI305 group was 2.8 (2.4–3.3) months per RECIST 1.1 and 2.6 (1.6–2.9) months per mRECIST. The median DoR in sintilimab plus IBI305gourp was 20.3 (12.3-NE) months per RECIST 1.1. The minimum percentage of SLD change was larger in the sintilimab plus IBI305 arm than in the Sor arm: (−13.4% (35.8) vs 3.2%(26.5) per RECIST 1.1). Similarly, the LD change in the largest liver lesion also favored sintilimab plus IBI305 arm (−27.6% (31.6) vs −11.5% (20.9)), including larger tumors (≥7 cm; −21.2% (30.4) vs −9.9% (23.7)) all per RECIST 1.1. Conclusions: Sintilimab plus IBI305 showed a significant improvement in ORR, TTR, DOR and DpR vs Sor in unresectable HCC. Clinical trial information: NCT03794440 .

122 Background: TAPUR is a phase II basket study evaluating antitumor activity of commercially available targeted agents in pts with advanced cancers with genomic alterations. Results in a cohort of pts with CRC with ATM mut treated with O are reported. Methods: Eligible pts had advanced CRC with ATM mut, no standard treatment (tx) options, measurable disease, ECOG Performance Status (PS) 0-2, and adequate organ function. Genomic testing was done in CLIA-certified, CAP-accredited labs. Recommended dosing for O was 300 mg twice daily (tablets) or 400 mg twice daily (capsules) until disease progression. Primary end point was disease control (DC), defined as complete or partial (PR) response per RECIST v. 1.1, or stable disease (SD) at 16+ weeks (wks) (SD16+). Simon 2-stage design tested the null DC rate of 15% vs. 35% (power = 0.85; α = 0.10). If ≥2 of 10 pts in stage 1 has DC, 18 more pts are enrolled; otherwise, cohort is closed for futility. If ≥7 of 28 pts has DC, the null DC rate is rejected. Secondary end points were progression-free survival (PFS), overall survival (OS), duration of response (DOR), duration of SD, and safety. DOR is defined as time from the pt’s first documented objective response (OR) until progressive disease (PD). Duration of SD is defined as time from start of tx to PD. Results: 30 pts with CRC and ATM mut were enrolled from Sept 2016 to Aug 2019. 3 pts were not included in efficacy outcomes: 2 pts had no post-baseline tumor evaluation; 1 pt was found to be ineligible after receiving 1 dose. 1 PR ( ATM P938fs*11 and RAD50 variant of unknown significance (VUS); DOR was 18.6 wks) and 3 SD16+ ( ATM R1875*, splice site 4237-11_4241del16, E522*; duration of SD was 19.7, 25.3 and 27.0 wks, respectively) were observed for DC rate of 23% (95% CI, 6% to 39%) and OR rate of 4% (95% CI, 0.1% to 19%). The null DC rate was not rejected (p=0.38). 6/30 pts had a BRCA2 co-alteration, but none of these pts achieved OR or SD16+; no pts had a BRCA1 co-alteration; aside from the pt with PR and RAD50 VUS, only 1 other pt who achieved OR or SD16+ had a co-alteration among the other homologous recombination-related genes examined ( ATR VUS). 7 pts had ≥1 Grade 3 adverse or serious adverse event (SAE) at least possibly related to O, including urinary tract infection, white blood cell decreased, febrile neutropenia (SAE), anemia (1 SAE), lung infection (SAE), fatigue (SAE), and nausea (SAE). Conclusions: Monotherapy O does not show sufficient antitumor activity in pts with advanced CRC with ATM mut to warrant further study. Clinical trial information: NCT02693535 . [Table: see text]

404 Background: DNA damage response (DDR) gene alterations are observed in 27% of gastric cancer (GC), therefore, targeting DDR might be an interesting strategy in GC. Olaparib plus paclitaxel showed numerically improved overall survival (OS) compared to paclitaxel in 2L GC patients (pts), even though it did not meet the endpoint. (Lancet Oncol 2017). Besides DNA damage repair, olaparib induces immune modulation. The role of immune checkpoint inhibitor (ICI) is established in 1L and 3L+ GC. The combination of cytotoxic chemotherapy, DDR acting agent and ICI might have synergistic effects in GC, which has not been tested in clinical studies. Here, we report biomarker-oriented phase II study of paclitaxel/olaparib/durvalumab combination in 2L GC. (NCT03579784). Methods: Advanced GC pts who have failed to 1L chemotherapy were enrolled. During 1st cycle, paclitaxel (80 mg/m2, D1, 8, 15 Q 4wk) and olaparib (150mg bid, D1-28) was administered. From 2nd cycle, durvalumab (1500 mg, D1 Q 4wk) was added on them. Tumor biopsy (pretreatment, after 1st cycle, at disease progression) and blood collection (every cycle) was mandatory. Primary endpoint was the disease control rate (DCR). Secondary endpoints included ORR, DoR, PFS, OS and safety. For biomarker study, multiplex IHC, NGS, ctDNA, and cytokines and angiogenic factors analysis were performed. Efficacy analysis set (ES) and safety analysis set (SS) were defined as pts who underwent at least one tumor assessment and all pts who received cycle1 day1 or more, respectively. Results: Fifty pts were enrolled (6 screening fail or withdrawal of consent, 44 in SS, 38 in ES) HER2+ GC were 13.2%. Among 38 in ES, DCR and ORR were 84.1% (95% CI, 72.5-95.7) and 39.5% (95% CI, 24.0-55.0) (1 CR, 14 PR and 17 SD). PFS, DoR and OS were 6.7 (95% CI, 4.5-10.3), 6.5 (95% CI, 5.1-10.7) and 11.4 (95% CI, 9.2-13.2) months. Homologous recombination repair (HRR) genetic alterations (9.6 vs. 5.9 in PFS, p=0.037), high CD8/CD3 ratio (8.8 vs. 3.7 in PFS, p=0.008), high PD-L1 (CPS≥10) (9.6 vs 5.1 in PFS, p=0.031), low ATM IHC (13.3 vs. 9.8 in OS, p=0.066), and low serum IL-6 (12.9 vs. 8.3 in OS, p=0.001) were associated with prolonged PFS or OS. In SS, most adverse events (AEs) were mild, and Gr 3/4 leukopenia and anemia were observed in 52.2% and 31.8%. There were no treatment related AEs resulted in study discontinuation. Conclusions: Paclitaxel/olaparib/durvalumab is a promising combination in 2L GC, and is worth to be further explored, especially in biomarker-enriched patients with HRR, specific T-cells subsets, high PD-L1, low ATM and IL-6. Clinical trial information: NCT03579784 .

746 Background: Depth of response (DpR; max% reduction from baseline in sum of target lesion diameters), has been reported to be associated with improved prognosis in several malignancies. However, there have been few reports regarding DpR in patients with locally advanced pancreatic cancer (LAPC). Thus, we investigated the association between DpR and overall survival (OS), and whether there were any differences in treatment efficacy on DpR between modified FOLFIRINOX (mFFX) versus gemcitabine plus nab-paclitaxel (GnP) as 1st-line chemotherapy for LAPC, using the results from JCOG1407 which was a randomized phase II trial comparing these regimens. Methods: Of the 126 patients enrolled in JCOG1407, patients were eligible except for the followings; patients who never had an imaging study or had only non-target lesions. The association between DpR and OS was investigated by dividing DpR into 3 groups at the tertile point (T1, T2 and T3 from largest to smallest), and whether DpR contributes to OS was examined by multivariable analysis. The differences in treatment efficacy between both regimens were investigated byevaluating DpR, time to DpR, and duration of response (DoR). Results: A total of 109 patients were eligible for this study (n = 53/56 in mFFX/GnP). The number of patients in T1, T2, and T3 were 37, 36, and 36, respectively. The median OS of T1, T2, and T3 were 29.3 (95% CI, 21.0-NE), 20.6 (95% CI, 15.8-24.5), and 19.0 months (95% CI, 12.7-22.4), respectively ( P= 0.0237). Multivariable analysis identified DpR as an independent prognostic factor for OS (HR 1.883, 95% CI 1.030-3.442, P= 0.040 for T2 vs. T1, and HR 2.523, 95% CI 1.342-4.744, P= 0.004 for T3 vs. T1). The median DpR in GnP was better than that in mFFX (28.9 vs. 22.7%; P= 0.041). The median DoR in mFFX tended to be longer compared to that in GnP (8.2 vs. 5.3 months; P= 0.132). No differences in mean time to DpR were observed between the two regimens. Conclusions: In LAPC patients receiving 1st-line chemotherapy, larger DpR contributed to OS. Although OS and PFS between mFFX and GnP were similar, the treatment efficacy on DpR and DoR might be different between the two regimens. Clinical trial information: UMIN000023143 .

610 Background: Erdafitinib (erda) is an oral selective pan-FGFR tyrosine kinase inhibitor approved to treat locally advanced or metastatic urothelial carcinoma in adults with susceptible FGFR3/2alt who have progressed during or after ≥1 line of platinum-containing chemotherapy . Interim results from the ongoing phase 2 RAGNAR study (NCT04083976) demonstrated tumor agnostic efficacy and safety of erda in adults with advanced solid tumors harboring prespecified FGFRalt after failure of standard therapies (Loriot Y, et al. J Clin Oncol 2022;40(suppl 16):3007). Here we report results from an expansion cohort of the RAGNAR study that enrolled only patients (pts) with CCA. Methods: Adults (aged ≥18 y) with advanced or metastatic CCA with predefined FGFR1-4alt (mutations/fusions [excluding amplifications] based on local/central test) and documented disease progression on ≥1 prior line of systemic therapy received oral erda until disease progression or intolerable toxicity. The primary end point is objective response rate (ORR) by independent review committee (IRC). Secondary end points include duration of response (DOR), disease control rate (DCR), clinical benefit rate (CBR), progression-free survival (PFS), overall survival (OS), investigator-assessed efficacy end points, and safety. Results: At data cutoff (median follow-up 20.4 mo), 35 pts with CCA received erda (median age 57 y [range 40-74], median 2 prior systemic therapy [range 1-6]); 90.9% had visceral metastasis, and 17.1% responded to last line of therapy. ORR by IRC was 60.0% (95% CI 42.1-76.1). Median time to onset of response was 1.5 mo (range 1.1-8.2). Responses were observed in pts harboring FGFR mutations and fusions and in pts with co-occurring genomic alterations. Median DCR and CBR were 100.0% (95% CI 90.0-100.0) and 71.4% (95% CI 53.7-85.4), respectively. Median DOR, PFS, and OS were 5.6 mo (95% CI 2.8-8.3), 8.4 mo (95% CI 5.5-9.7), and 18.7 mo (95% CI 8.9-not evaluable), respectively. Investigator-assessed efficacy end points were aligned with IRC results. The most common treatment-emergent adverse events (TEAEs) were hyperphosphatemia (82.9%), diarrhea (80.0%), and stomatitis (74.3%). The majority of pts (80.0%) had grade ≥3 TEAEs, the most common being anemia (22.9%), stomatitis (20.0%), and acute kidney injury (11.4%); 42.9% had serious TEAEs; 11.4% discontinued treatment due to TEAEs. No treatment-related deaths were observed. Conclusions: Data from the CCA expansion cohort of the phase 2 RAGNAR study demonstrate robust efficacy of erda in heavily pretreated adults with CCA harboring prespecified FGFR fusions or mutations, irrespective of co-occurring genomic alterations. Safety data were consistent with the known safety profile of erda. Clinical trial information: NCT04083976 .

546 Background: TAPUR is a phase II basket study evaluating antitumor activity of commercially available targeted agents in pts with advanced cancers with genomic alterations. Results in a cohort of pts with BTC with ERBB2/3 amp, oe, or mut treated with P+T are reported. Methods: Eligible pts had advanced BTC, no standard treatment (tx) options, measurable disease, ECOG Performance Status (PS) 0-2, and adequate organ function. Genomic testing was done in CLIA-certified, CAP-accredited labs. Dosing of P was 840 mg IV over 60 minutes (m), then 420 mg IV over 30-60 m Q3 weeks (wks); T was 8 mg/kg IV over 90 m, then 6 mg/kg IV over 30-60 m Q3 wks until disease progression. Primary end point was disease control (DC), defined as complete (CR) or partial (PR) response per RECIST v. 1.1, or stable disease (SD) at 16+ wks (SD16+). Simon 2-stage design tested the null DC rate of 15% vs. 35% (power = 0.85; α = 0.10). If ≥2 of 10 pts in stage 1 has DC, 18 more pts are enrolled; otherwise, cohort is closed for futility. If ≥7 of 28 pts has DC, the null DC rate is rejected. Secondary end points were progression-free survival (PFS), overall survival (OS), duration of response (DOR), duration of SD and safety. DOR is defined as time from pt’s first documented objective response (OR) to progressive disease (PD). Duration of SD is defined as time from start of tx to PD. Results: 29 pts with BTC (15 gallbladder (GB), 11 biliary duct (BD), 3 ampulla of Vater) and ERBB2/3 amp, oe, or mut were enrolled from Feb 2017 to Jan 2022. Median (med) age was 66 years (yrs) (range, 34-83 yrs). 66% of pts were female; 52% were White, 21% were Black/African American, 10% were Asian/Asian American; 83% were not Hispanic or Latino. 83% of pts had ECOG PS 0-1 and 48% had ≥3 prior systemic regimens. 1 pt was not evaluable and excluded from efficacy analysis. The table shows efficacy outcomes. 1 pt had CR (GB; ERBB2 amp; DOR: 71.1 wks), 8 pts had PR (6 GB/2 BD; 5 ERBB2 amp; 2 ERBB2 mut; 1 ERBB3 mut/ ERBB2 amp; med DOR: 30.4 wks (4.4 to 68.9 wks)) and 2 pts had SD16+. 4 pts with a KRAS mut did not achieve OR or SD16+. 4 pts had a Grade 3 drug-related adverse or serious adverse event (SAE): anemia, diarrhea, infusion related reaction (SAE), and fatigue. Conclusions: P+T demonstrated antitumor activity in pts with advanced BTC with ERBB2/3 alterations. These data, along with results previously reported by other studies, support continued study of P+T in pts with ERBB2 amplified BTC tumors. Clinical trial information: NCT02693535 . [Table: see text]

PURPOSE Anti-CD19 chimeric antigen receptors (CARs) are artificial fusion proteins that cause CD19-specific T-cell activation. Durability of remissions and incidence of long-term adverse events are critical factors determining the utility of anti-CD19 CAR T-cell therapy, but long-term follow-up of patients treated with anti-CD19 CAR T cells is limited. This work provides the longest follow-up of patients in remission after anti-CD19 CAR T-cell therapy. METHODS Between 2009 and 2015, we administered 46 CAR T-cell treatments to 43 patients (ClinicalTrials.gov identifier: NCT00924326 ). Patients had relapsed B-cell malignancies of the following types: diffuse large B-cell lymphoma or primary mediastinal B-cell lymphoma (DLBCL/PMBCL; n = 28), low-grade B-cell lymphoma (n = 8), or chronic lymphocytic leukemia (CLL; n = 7). This report focuses on long-term outcomes of these patients. The CAR used was FMC63-28Z; axicabtagene ciloleucel uses the same CAR. Cyclophosphamide plus fludarabine conditioning chemotherapy was administered before CAR T cells. RESULTS The percentages of CAR T-cell treatments resulting in a > 3-year duration of response (DOR) were 51% (95% CI, 35% to 67%) for all evaluable treatments, 48% (95% CI, 28% to 69%) for DLBCL/PMBCL, 63% (95% CI, 25% to 92%) for low-grade lymphoma, and 50% (95% CI, 16% to 84%) for CLL. The median event-free survival of all 45 evaluable treatments was 55 months. Long-term adverse effects were rare, except for B-cell depletion and hypogammaglobulinemia. Median peak blood CAR-positive cell levels were higher among patients with a DOR of > 3 years (98/µL; range, 9-1,217/µL) than among patients with a DOR of < 3 years (18/µL; range, 0-308/μL, P = .0051). CONCLUSION Complete remissions of a variety of B-cell malignancies lasting ≥ 3 years occurred after 51% of evaluable anti-CD19 CAR T-cell treatments. Remissions of up to 9 years are ongoing. Late adverse events were rare.

PURPOSE We assessed the safety and efficacy of cabozantinib and nivolumab (CaboNivo) and CaboNivo plus ipilimumab (CaboNivoIpi) in patients with metastatic urothelial carcinoma (mUC) and other genitourinary (GU) malignances. PATIENTS AND METHODS Patients received escalating doses of CaboNivo or CaboNivoIpi. The primary objective was to establish a recommended phase II dose (RP2D). Secondary objectives included objective response rate (ORR), progression-free survival (PFS), duration of response (DoR), and overall survival (OS). RESULTS Fifty-four patients were enrolled at eight dose levels with a median follow-up time of 44.6 months; data cutoff was January 20, 2020. Grade 3 or 4 treatment-related adverse events (AEs) occurred in 75% and 87% of patients treated with CaboNivo and CaboNivoIpi, respectively, and included fatigue (17% and 10%, respectively), diarrhea (4% and 7%, respectively), and hypertension (21% and 10%, respectively); grade 3 or 4 immune-related AEs included hepatitis (0% and 13%, respectively) and colitis (0% and 7%, respectively). The RP2D was cabozantinib 40 mg/d plus nivolumab 3 mg/kg for CaboNivo and cabozantinib 40 mg/d, nivolumab 3 mg/kg, and ipilimumab 1 mg/kg for CaboNivoIpi. ORR was 30.6% (95% CI, 20.0% to 47.5%) for all patients and 38.5% (95% CI, 13.9% to 68.4%) for patients with mUC. Median DoR was 21.0 months (95% CI, 5.4 to 24.1 months) for all patients and not reached for patients with mUC. Median PFS was 5.1 months (95% CI, 3.5 to 6.9 months) for all patients and 12.8 months (95% CI, 1.8 to 24.1 months) for patients with mUC. Median OS was 12.6 months (95% CI, 6.9 to 18.8 months) for all patients and 25.4 months (95% CI, 5.7 to 41.6 months) for patients with mUC. CONCLUSION CaboNivo and CaboNivoIpi demonstrated manageable toxicities with durable responses and encouraging survival in patients with mUC and other GU tumors. Multiple phase II and III trials are ongoing for these combinations.

PURPOSE Axicabtagene ciloleucel (axi-cel) was approved by the Food and Drug Administration for relapsed aggressive B-cell non-Hodgkin lymphoma in part on the basis of durable remission rates of approximately 40% in a clinical trial population. Whether this efficacy, and the rates of toxicity, would be consistent in a postcommercial setting, with relaxed eligibility criteria and bridging therapy, is unknown. This study describes the efficacy and safety correlates and outcomes in this setting. PATIENTS AND METHODS One hundred twenty-two patients from 7 medical centers in the United States were treated with axi-cel and were included in a modified intent-to-treat (mITT) analysis. Seventy-six patients (62%) were ineligible for the ZUMA-1 trial. Response and toxicity rates, duration of response (DOR), survival, and covariates are described on the basis of the mITT population. Correlative studies on blood and tumor samples were performed to investigate potential biomarkers of response and resistance. RESULTS Median follow-up was 10.4 months. In the mITT population, the best overall and complete response (CR) rates were 70% and 50%, respectively. Median DOR and progression-free survival (PFS) were 11.0 and 4.5 months in all patients and were not reached (NR) in CR patients. Median overall survival (OS) was NR; 1-year OS was 67% (95% CI, 59% to 77%). Although response rates were similar in the ZUMA-1–eligible and ZUMA-1–ineligible groups (70% v 68%), there was a statistically significant improvement in CR rate (63% v 42%, P = .016), DOR (median, NR v 5.0 months; P = .014), PFS (median, NR v 3.3 months; P = .020), and OS (1-year OS, 89% v 54%; P < .001) in patients who were ZUMA-1 eligible. Rates of grade ≥ 3 cytokine release syndrome and neurotoxicty were 16% and 35%, respectively. CONCLUSION Axi-cel yields similar rates of overall response and toxicity in commercial and trial settings, although CR rates and DOR were more favorable in patients eligible for ZUMA-1.

LBA9023 Background: Tissue-based biomarker testing remains challenging as tumor biopsies are often inadequate for comprehensive biomarker testing and repeat biopsies can be risky in pts with advanced/metastatic NSCLC. These challenges could be overcome by using blood-based testing to identify the most appropriate targeted therapy. BFAST (NCT03178552) is a global open-label, multicohort trial evaluating the efficacy and safety of selected therapies in pts with advanced/metastatic NSCLC harboring actionable genetic alterations, as identified by next-generation sequencing (NGS) in cell-free DNA (liquid biopsies). We present data from the ROS1+ cohort: this is the first evaluation of entrectinib efficacy in pts identified by prospective blood-based NGS. Methods: In this single-arm analysis, adults (≥18 years) with treatment-naïve measurable stage IIIB/IV NSCLC, identified as ROS1+ by the FoundationOne®Liquid CDx CTA blood-based NGS test, received oral entrectinib 600 mg/day until disease progression (PD), unacceptable toxicity, consent withdrawal or death. Pts with asymptomatic brain metastases at screening were eligible. Tumor scans were performed at baseline and every 8 weeks thereafter for all disease involvement areas (brain imaging not mandated in pts without baseline CNS disease). Primary endpoint: investigator (INV)-assessed objective response rate (ORR; RECIST 1.1). Secondary endpoints: INV-assessed duration of response (DoR) and progression-free survival (PFS); independent review facility (IRF)-assessed ORR, DoR, PFS; overall survival (OS); time to CNS PD; safety. Results: 55 pts with ROS1+ NSCLC identified by blood-based NGS were enrolled and treated with entrectinib. Median age was 56 yrs; 58% of pts were female and 75% had no history of tobacco use. Non-squamous adenocarcinoma was the most common histology (n = 48/55; 87%); 4 pts (7.3%) had baseline CNS disease. Median follow-up: 18.3 months. At data cut-off (26 Nov 2021, n = 54 pts with measurable disease), confirmed ORR was 81.5% (n = 44/54; 95% CI 68.6–90.8) by INV (2 complete responses [CR], 42 partial responses [PR]) and IRF (3 CR, 41 PR). Median DoR was 13.0 months (95% CI 6.3–18.4) by INV and 16.7 months (95% CI 5.6–24.0) by IRF. Median PFS was 12.9 months (95% CI 8.7–18.5) by INV, and 14.8 months (95% CI 7.2–24.0) by IRF. OS data were immature with 20 events (36.4%) recorded. Median time to CNS PD was not reached (INV: 9 events; IRF: 6 events). Most treatment-related adverse events were non-serious with no treatment-related deaths. Conclusion: These data support the clinical value of blood-based NGS as another method to inform clinical decision-making in ROS1+ NSCLC. Pts with ROS1+ NSCLC (by blood-based NGS) treated with entrectinib showed deep and durable responses, consistent with results from entrectinib trials that used tissue-based testing. No new safety signals were observed. Clinical trial information: NCT03178552.

LBA9009 Background: CNS metastases (mets) occur in 27–42% of NSCLC harboring KRASG12C mutations and are associated with poor prognosis. Adagrasib (ada), an investigational agent, is a KRASG12C inhibitor that irreversibly and selectively binds KRASG12C, locking it in its inactive state, and is optimized for favorable PK properties, including a long half-life (̃24 h) and dose-dependent PK. Ada has demonstrated dose-dependent CNS penetration and intracranial (IC) tumor regression in preclinical models of CNS mets. Methods: KRYSTAL-1 (NCT03785249) is a multicohort Phase 1/2 study evaluating ada as monotherapy or in combination with selected agents in patients (pts) with advanced solid tumors harboring a KRASG12C mutation. In a Phase 1b cohort, pts with KRASG12C-mutant NSCLC and active, untreated CNS mets were treated with ada 600 mg BID. The objectives for this Phase 1b cohort were to evaluate safety and clinical activity, including systemic and IC objective response rate (ORR) by blinded independent central review (BICR), duration of response (DOR), progression-free survival (PFS), and overall survival (OS). Systemic responses were assessed by RECIST 1.1; IC responses were assessed by modified RANO criteria and IC RECIST. Cerebrospinal fluid (CSF) was collected when feasible and was used to measure ada concentrations for optional evaluation. Results: As of 31 December 2021, 25 pts with NSCLC were enrolled and treated. Median follow-up was 6.6 months at the cutoff date. Median age was 66 years, 52% were female, 28%/72% had ECOG PS 0/1, and median lines of prior systemic therapy was one (range 0–4+). IC ORR per modified RANO criteria by BICR was 31.6% (6/19; 3 CRs, 2 PRs, 1 unconfirmed PR); IC disease control rate (DCR) was 84.2% (16/19, including 10 SDs). Median IC DOR was not reached (95% CI 4.1–NE); median IC PFS was 4.2 months (95% CI 3.8–NE). CSF samples were obtained for two pts for whom regression of CNS mets was observed and ada CSF concentrations exceeded the CNS penetrance partition coefficients observed for other therapies with demonstrated CNS penetration and CNS antitumor activity (Kp,uu 0.47). Systemic ORR by BICR was 35.0% (7/20), DCR was 80.0% (16/20) and median DOR was 9.6 months (95% CI 2.7–9.6); median PFS was 5.6 months (95% CI 3.8–11.0). For all pts enrolled, OS was immature, and the median had not been reached at the time of analysis. Safety was consistent with that previously reported with ada; any grade TRAEs occurred in 96% of pts, grade 3 TRAEs in 36%, and there were no grade 4/5 TRAEs. Further data describing IC activity assessed by IC RECIST will be presented. Conclusions: Ada was well tolerated, and these preliminary data demonstrate CNS penetration and encouraging IC activity in pretreated pts with NSCLC harboring a KRASG12C mutation and active, untreated CNS mets. These are the first clinical data demonstrating CNS-specific activity of a KRASG12C inhibitor in this population. Clinical trial information: NCT03785249.

LBA9025 Background: In CheckMate 227 part 1 (NCT02477826), 1L NIVO + IPI demonstrated long-term, durable survival benefit vs platinum-doublet chemo in patients (pts) with metastatic NSCLC regardless of tumor programmed death ligand 1 (PD-L1) expression level. Here we present the longest reported follow-up (5 y) of a phase 3 trial of 1L combination immunotherapy in metastatic NSCLC. Methods: Adults with previously untreated stage IV or recurrent NSCLC, no known EGFR/ ALK alterations , and an ECOG performance status ≤ 1 were enrolled and stratified by histology. Pts with tumor PD-L1 ≥ 1% were randomized 1:1:1 to NIVO (3 mg/kg Q2W) + IPI (1 mg/kg Q6W), NIVO (240 mg Q2W), or chemo. Pts with tumor PD-L1 < 1% were randomized 1:1:1 to NIVO + IPI, NIVO (360 mg Q3W) + chemo, or chemo. Pts were treated until progression, toxicity, or ≤ 2 y for immunotherapy. Assessments included overall survival (OS), progression-free survival (PFS), objective response rate (ORR), duration of response (DOR), and a novel efficacy endpoint, treatment-free interval. Treatment-free interval was measured in pts who discontinued study therapy (for any reason including treatment completion) and was defined as the time from last study dose to start of subsequent systemic therapy or death, whichever occurred first. Results: Minimum follow-up was 61.3 mo (database lock, Feb 15, 2022). In pts with tumor PD-L1 ≥ 1% (N = 1189), continued long-term OS benefit was seen with NIVO + IPI vs chemo (HR, 0.77 [95% CI, 0.66–0.91]); 5-y OS rates were 24% (NIVO + IPI), 17% (NIVO), and 14% (chemo). OS benefit also continued in pts with tumor PD-L1 < 1% (N = 550) for NIVO + IPI vs chemo (HR, 0.65 [95% CI, 0.52–0.81]); 5-y OS rates were 19% (NIVO + IPI), 10% (NIVO + chemo), and 7% (chemo). Clinical benefit with NIVO + IPI vs chemo was observed across additional efficacy endpoints in the overall population and in pts alive at 5 y (table). PFS, ORR, and DOR with NIVO and NIVO + chemo will be presented. Among pts alive at 5 y in the NIVO + IPI group, 66% (PD-L1 ≥ 1%) and 64% (PD-L1 < 1%) remained treatment-free ≥ 3 y after discontinuing study therapy; median (range) duration of NIVO ± IPI therapy was 17.7 (0-25.5) mo (PD-L1 ≥ 1%) and 9.5 (0-25.1) mo (PD-L1 < 1%). No new safety signals were observed. Conclusions: With a 5-y minimum follow-up, NIVO + IPI continues to provide long-term, durable clinical benefit vs chemo in previously untreated pts with metastatic NSCLC, regardless of PD-L1 expression. NIVO + IPI led to increased 5-y survivorship; the majority of these pts were treatment-free for ≥ 3 y post-treatment discontinuation. Clinical trial information: NCT02477826. [Table: see text]

e15539 Background: High microsatellite instability (MSI-H) tumors have been associated with good responses to check-point inhibitors (CPI). With overall response rates (ORR) ranging between 36-46% among colorectal cancer (CRC) and other solid malignancies. Data regarding predictors of response and responses in non-CRC malignancies remains limited. We sought to evaluate the response to PD-1/PDL-1 CPI in patients with MSI-H and/or high TMB solid malignancies. Methods: Retrospective analysis of 16 patients (pts) who received 18 CPI-based therapies between October 2017 and February 2022. MSI-H and TMB status was assessed by CARIS, Guardant360 or INVITAE genetic testing. Primary objective was to determine objective response rate (ORR), defined as complete response (CR) or partial response (PR) by RECIST1.1. Secondary outcomes included progression-free survival(PFS); overall survival (OS), and duration of overall response (DOR). Results: A total of 16 pts were included. The median age of 72 years (range 53-83), 44% were male and 75% Hispanic. 44% of pts had RCR and 50% were previously treated, and 50% were stage IV at diagnosis. The most common mutations were BRCA2 31%, PIK3cA 31%, KRAS 25%, and GNAS 25%. The majority of pts received single-agent CPI therapy (72%). After a median follow-up of 52 months, 11 pts continued to receive therapy, 2 pts completed treatment. 3 pts died from progression of the disease. 1 pts switched from single-agent pembrolizumab to nivolumab-ipilimumab combination followed by nivolumab maintenance due to disease progression. 15 pts were evaluable for response with an ORR of 33%, including 33% among pts with CRC and 27% for non-CRC malignancies. (Table - Response rates) The OS was not reached (NR), with a PFS of 53 months (PFS of 64% at 1 year and 56% at 4 years). The median DOR was not reached (NR). The treatment was well tolerated and pts received a median of cycles was 19 (range 3-51) with no discontinuations due to toxicities. The molecular mutations, clinical characteristics, type of malignancy, MSI-H, or H-TMB status were not significantly associated with response to CPI after logistical regression analysis. Conclusions: CPIs are an effective treatment option for patients with MSI-H and/or High TMB, with an ORR of 33%. However, pts achieved durable responses, with a median DOR not reached. We identify a higher incidence of SD rates among CRC pts (67% vs. 18% non-CRC). We did not identify any predictors associated with response to CPI, likely due to the small number of pts. However, there was a tendency to highest response rates among pts with MSI-H and high TMB.[Table: see text]

7549 Background: MZL is a rare indolent B-cell malignancy considered incurable at recurrent stage. Bruton tyrosine kinase (BTK) inhibitors have produced durable responses in patients (pts) with R/R MZL. Acalabrutinib (acala) is a potent next-generation BTK inhibitor with high selectivity for BTK. We report data for acala monotherapy from the R/R MZL cohort (phase 2) of a phase 1b/2 clinical trial (NCT02180711). Methods: Pts with histologically confirmed MZL, ECOG performance status ≤2, and ≥1 prior therapy (including ≥1 CD20-directed regimen) received oral acala 100 mg twice daily until disease progression or unacceptable toxicity ± R. The primary objective was overall response rate (ORR; Lugano criteria as assessed by the investigator). Secondary objectives were duration of response (DOR), progression-free survival (PFS), overall survival (OS), and safety. Data were analyzed descriptively (no formal hypothesis testing). Results: Forty-two pts received acala (median age 69 y [range 42–84]; median 2 prior systemic regimens [range 1–4]). MZL subtypes were extranodal (43%), nodal (31%), and splenic (26%). At data cutoff (Oct 15, 2021), median follow-up duration was 10.7 mo (range 0.4–42.8). Sixteen (38%) pts discontinued acala, most commonly due to disease progression (26%). Among pts evaluable for response (n = 37; 3 pts had not reached the first assessment timepoint and 2 pts exited the study without response assessment), ORR was 54% (95% CI 37%–71%) with 6 complete (16%) and 14 partial (38%) responses; 17 (46%) pts had stable disease. ORRs in extranodal, nodal, and splenic subtypes were 65%, 44%, and 45%, respectively. Median time to initial response was 3.0 mo; median DOR was 19.3 mo (95% CI 8.4–not estimable). Median PFS was 27.4 mo with a 12-mo PFS rate of 66%. Four pts died (disease progression, n = 2; transformation to diffuse large B-cell lymphoma after stopping treatment, n = 1; adverse event [AE], n = 1 [septic shock unrelated to treatment]); median OS was not reached. Treatment was well tolerated with most AEs being grade 1 or 2. Sixteen pts (38%) had grade ≥3 AEs, most commonly (in ≥2 pts) anemia, dyspnea, neutrophil count decrease (n = 3 each), fatigue, thrombocytopenia, and neutropenia (n = 2 each). AEs led to treatment discontinuation in 2 pts (grade 3 hypotension and grade 1 myalgia). Among AEs of clinical interest, hypertension was reported in 2 pts (both grade 2); no cases of atrial fibrillation/flutter or major hemorrhage were reported. Conclusions: These early results indicate that acala is efficacious and well tolerated in pts with R/R MZL. The AE profile is consistent with the known safety profile of acala. Clinical trial information: NCT02180711.

9116 Background: Investigational agent pelcitoclax is a dual BCL-2/BCL-xL inhibitor, which enhanced antitumor effects of osimertinib in preclinical models. A report presented at International Association for the Study of Lung Cancer 2021 World Conference on Lung Cancer demonstrated that the combination of pelcitoclax and osimertinib at the recommended phase 2 dose (RP2D) was safe, and preliminary efficacy was observed in some patients whose disease failed prior osimertinib or other third-generation EGFR-TKI treatments. Here, we further provide safety and efficacy results of this combination therapy. Methods: After RP2D was determined to be pelcitoclax 160 mg per week plus osimertinib 80 mg QD, pts were enrolled into 3 expansion cohorts of 20 pts each: Cohort 1 (EC-1) included those with disease resistant to third-generation EGFR-TKIs; Cohort 2 (EC-2) included those with osimertinib-naïve, EGFR-sensitive or T790M-positive mutations; and Cohort 3 (EC-3) included those with the EGFR exon 20 insertion mutation. Results: At the data cutoff date of January 6, 2022, 61 pts (median age, 56 years [69% female]) had been treated with pelcitoclax plus osimertinib. Among them, 13 were in dose escalation cohorts, 20 in EC-1, 20 in EC-2, and 8 in EC-3. Sixteen pts in EC-2 were EGFR-TKI naïve, and 4 were T790M positive with prior TKI treatment. All pts in EC-2 experienced treatment-related adverse events (TRAEs) but only 4 (20%) had grade ≥ 3. Common TRAEs included increased aspartate aminotransferase (90%) and alanine aminotransferase (85%) levels, reduced platelets (40%), diarrhea (40%), and increased lipase (35%). Among 20 evaluable pts, 17 PRs (85%) were observed and 16 (80%) confirmed. The median (range) time to response was 1.4 (1.2-7.0) months, and the median duration of response (DOR) was not reached. The DOR rate at 9 months after first response was 71.4% (95% CI 25.8-92.0). Seven pts had brain metastases at baseline in EC-2; 2 CRs and 3 PRs were observed intracranially. Conclusions: Osimertinib in combination with targeted therapies has been of clinical interest to improve the outcomes of patients with EGFR-mutant NSCLC. Pelcitoclax plus osimertinib was well tolerated and showed comparable efficacy in TKI-naïve pts. Further randomized control trials are warranted to elucidate the role of pelcitoclax when combined with osimertinib. Clinical trial information: NCT04001777.

TPS3172 Background: Ulixertinib (BVD-523) is a small molecule inhibitor of extracellular signal-regulated kinases 1/2 (ERK1/2) in development as a novel anti-cancer drug. Early clinical data demonstrated anti-tumor activity, especially for patients with tumors harboring atypical BRAF or MEK1/2 alterations (Sullivan et al., Cancer Discov. 2018;8(2):184-195). Atypical BRAF (non-V600) alterations can be categorized according to characteristics of molecular signaling (Class II or III), are seen in approximately 3% of all human cancers, and there are currently no approved therapies for this indication. Similar to atypical BRAF alterations, the incidence of MEK1/2 alterations are rare in human tumors (< 1 %). Preclinical data have demonstrated activity of ulixertinib in MEK mutant models. Ulixertinib has FDA fast-track designation for patients with solid tumors, other than CRC, with specific BRAF mutations (G469A, L485W, or L597Q). Designed with intent to register, the BVD-523-ABC clinical trial will continue evaluation of ulixertinib in patients with tumors harboring any atypical BRAF or MEK1/2 alteration (NCT04488003). Methods: This multi-center, phase II study, will be conducted in two parts and assess the clinical benefit, safety, pharmacokinetics, and pharmacodynamics of ulixertinib in patients with advanced malignancies. Ulixertinib will be administered at the RP2D of 600 mg BID for 28-day treatment cycles. Eligible patients will have locally advanced or metastatic cancer which progressed following standard systemic therapies, or for which the patient is not a candidate or refused systemic therapy. Planned correlative analyses include reverse phase protein array and transcriptomics of tumor tissue. Part A is open-label and tumor agnostic, except for group 4 and 6 (CRC patients only). Patients will enroll into one of six groups based on BRAF (groups 1-4) or MEK1/2 (groups 5-6) tumor alteration (38 patients per group). Overall response rate (ORR) is the primary endpoint for Part A, with secondary endpoints including duration of response (DOR), progression-free survival (PFS), and overall survival (OS). Part B is tumor histology specific. Patients will be randomized to receive either ulixertinib or physician's choice of treatment in a 2:1 ratio. Up to three specified tumor histologies will be defined, guided by available Part A data (n = 80-100 per histology). The primary endpoint of Part B is PFS, and secondary endpoints include OS, ORR, and DOR. This study has enrolled 43 patients of the planned 228 in Part A at the time of abstract submission. Clinical trial information: NCT04488003.

9002 Background: KRAS is a key mediator of the RAS/MAPK signaling cascade that promotes cellular growth and proliferation. KRASG12C mutation occurs in ̃14% of NSCLC. Adagrasib, an investigational agent, is a KRASG12C inhibitor that irreversibly and selectively binds KRASG12C, locking it in its inactive state. Adagrasib is optimized for favorable pharmacokinetic (PK) properties, including long half-life (̃24 h), dose-dependent PK, and central nervous system penetration; it has demonstrated objective response and favorable tolerability in the Phase 1/1b setting. Methods: KRYSTAL-1 (NCT03785249) is a multicohort Phase 1/2 study evaluating adagrasib as monotherapy or in combination regimens in patients with advanced solid tumors harboring a KRASG12C mutation. Here we report the first disclosure from all patients enrolled in Cohort A, a Phase 2 cohort with registrational intent, evaluating adagrasib given 600 mg orally BID in patients with NSCLC previously treated with platinum-based chemotherapy and anti-PD-1/L1 therapy. Study objectives include evaluating efficacy (objective response rate [ORR], duration of response [DOR], progression-free survival [PFS], overall survival [OS]), safety, PK, and exploratory correlative analyses. Objective tumor response was assessed per RECIST v1.1 by blinded independent central review (BICR). Results: As of the 15 October 2021 data cutoff, 116 patients with NSCLC harboring a KRASG12C mutation were enrolled and treated, with a median follow-up of 12.5 months. Baseline characteristics include median age 64 years, 65% female, and 15.5%/83.6% with ECOG PS 0/1; 98.3% of patients received adagrasib following prior treatment with immunotherapy and chemotherapy, with a median of 2 prior systemic therapies. The ORR (by BICR) was 42.9% (48/112) and the disease control rate was 79.5% (89/112); 31 patients remain on treatment. Median DOR was 8.5 months (95% CI 6.2–13.8), median PFS was 6.5 months (95% CI 4.7–8.4), median OS was 12.6 months (95% CI 9.2–NE). Treatment-related AEs (TRAEs) of any grade occurred in 97.4% of patients, grade ≥3 TRAEs in 45.7%, 2 grade 5 TRAEs, and 8 (6.9%) TRAEs led to discontinuation. The most commonly reported (≥25%) TRAEs (any grade) were diarrhea (62.9%), nausea (62.1%), vomiting (47.4%), fatigue (40.5%), ALT/AST increased (27.6%/25%), blood creatinine increased (25.9%); the most commonly reported (≥5%) TRAEs (grade 3/4) were lipase increased (6%) and anemia (5.2%). Additional subgroup analyses will be presented, including selected demographics, molecular markers and sites of metastases. Conclusions: Adagrasib is well tolerated and demonstrates promising efficacy in pretreated patients with NSCLC harboring a KRASG12C mutation. A Phase 3 trial evaluating adagrasib monotherapy versus docetaxel in previously treated patients with KRASG12C-mutant NSCLC is ongoing (NCT04685135). Clinical trial information: NCT03785249.

9033 Background: In advanced NSCLC (aNSCLC) with PD-L1 < 50% chemo-immunotherapy is the standard of care. Although the activity of single agent pembrolizumab was reported, no biomarkers have been identified able to select patients who mostly benefit. The trial aimed to identify immune biomarkers associated with PFS in aNSCLC patients with PD-L1 levels < 50% treated with first-line pembrolizumab. Here we reported for the first time the clinical outcomes of the trial and circulating immune profiling (CIP) biomarkers correlated to PFS. Methods: This phase II trial was conducted at Fondazione IRCCS Istituto Nazionale dei Tumori of Milan. Eligible patients were previously untreated stage IIIB-IV NSCLC, EGFR and ALK wild type with PD-L1 < 50%, PS 0-2. PD-L1 was assessed with 22-C3 antibody (Dako). Patients received pembrolizumab 200 mg every 3 weeks until 35 cycles, disease progression or unacceptable toxicity. The primary endpoint was the association of immune biomarkers with PFS. OS, ORR, DCR, DoR and safety were secondary endpoints. CIP was performed by determination of absolute cell counts for 36 innate and adaptive immunity subsets through multiparametric flow cytometry on freshly isolated whole blood samples at baseline. An orthoblique principal components-based clustering approach and multivariable Cox regression model adjusted for clinical variables were used to analyse CIP variables and their correlation with clinical endpoints. Results: From May 2018 to October 2020, of 87 screened, 65 patients were enrolled. The median age was 70.9 years, most patients were male (67.7%), smoker (87.7%), non-squamous (83.1%), PDL1 + (70.8%). 12 patients (18.5%) had PS 2. During a median follow-up of 26.4 months (mo), 51 radiological progressions, 46 deaths and 60 PFS events were observed. The median PFS was 2.9 mo (95%CI 1.8 - 5.6) and the median OS was 12.1 mo (95%CI 8.7 - 17.1). The ORR was 24.1% (2 complete and 12 partial responses), DCR was 53.4% and median DoR was 14.5 mo (95%CI 6.4 - 24.9). Drug related G3-G4 adverse events were: 2 hyponatremia, 2 lipase increased, 1 pneumonitis. Out of 7 CIP clusters identified, 2 were statistically significant at multivariable analysis on 57 patients. Higher baseline counts of 8 subsets within these two clusters were associated with better PFS (HR values range: 0.88-0.98; p values range: 0.001- 0.016). The significant subsets included lymphocytes (cells expressing CD3, or CD19 or CD56, but lacking granulocyte and monocyte markers) and main NK subsets (including CD56dim CD16+, CD56dim CD16- and HLA-DR+ NK cells). Conclusions: This trial confirmed that pembrolizumab as first-line single agent is safe and active also in a subgroup of aNSCLC patients with PD-L1 < 50%. CIP biomarkers can be useful to identify patients with a favourable outcome, thus avoiding the adding toxicity of chemotherapy. Clinical trial information: NTC03447678.

4035 Background: NIVO + chemo and NIVO + IPI demonstrated significant overall survival (OS) benefit vs chemo in previously untreated patients (pts) with advanced ESCC in the phase 3 CheckMate 648 study. We report expanded results from the primary analysis with 13-month (mo) minimum follow-up. Methods: Pts with previously untreated, unresectable advanced, recurrent, or metastatic ESCC were randomized to NIVO (240 mg Q2W) + chemo (fluorouracil + cisplatin Q4W), NIVO (3 mg/kg Q2W) + IPI (1 mg/kg Q6W), or chemo. Primary endpoints were OS and progression-free survival (PFS) per blinded independent central review (BICR) in pts with tumor cell programmed death ligand 1 (PD-L1) ≥ 1%. Secondary endpoints planned for hierarchical testing included OS, PFS, and objective response rate (ORR) per BICR in all randomized pts. Duration of response (DOR) per BICR and PFS2 per investigator (time from randomization to progression after subsequent systemic therapy, initiation of second subsequent systemic therapy, or death) were exploratory endpoints. Results: Among all pts randomized to NIVO + chemo (n = 321), NIVO + IPI (n = 325), or chemo (n = 324), PFS2 favored NIVO + chemo (HR 0.64, 95% CI 0.54–0.77) and NIVO + IPI (HR 0.74, 95% CI 0.62–0.88) vs chemo. ORR (95% CI) was 47% (42–53), 28% (23–33), and 27% (22–32), respectively. More responders with NIVO + chemo or NIVO + IPI vs chemo had prolonged DOR (≥12 mo; 39%, 48%, and 23%, respectively). Efficacy data by tumor cell PD-L1 and PD-L1 combined positive score will be presented. Grade 3/4 treatment-related adverse events with potential immunologic etiology (select TRAEs) occurred in ≤ 6% of pts with NIVO + chemo and NIVO + IPI, and non-endocrine select TRAEs resolved in 57%–95% of pts across organ categories (Table). Conclusions: NIVO + chemo and NIVO + IPI demonstrated favorable PFS2 and a higher proportion of pts with prolonged DOR vs chemo, as well as acceptable safety profiles. These results provide further support for each regimen as a new potential 1L standard of care in advanced ESCC. Clinical trial information: NCT03143153. [Table: see text]

4109 Background: Pembrolizumab monotherapy showed durable antitumor activity and a manageable safety profile in patients with sorafenib-treated (cohort 1) and treatment-naive (cohort 2) aHCC in the open-label, phase 2 KEYNOTE-224 (NCT02702414) study. Longer term data from KEYNOTE-224 after ̃3 years of follow-up for patients with treatment-naive aHCC are reported. Methods: Eligible patients in cohort 2 had histologically, cytologically, or radiologically confirmed aHCC, Barcelona Clinic Liver Cancer stage C or B not amenable or refractory to locoregional therapy and not amenable to curative treatment, Child-Pugh A liver function, measurable disease per RECIST v1.1 by blinded independent central review (BICR), and ECOG PS 0 or 1. Patients received pembrolizumab 200 mg intravenously every 3 weeks for ≤35 cycles (̃2 years). Primary end point was ORR assessed per RECIST v1.1 by BICR. Secondary end points included DOR, DCR, TTP, and PFS, all assessed per RECIST v1.1 by BICR, OS, and safety/tolerability. Results: All 51 patients enrolled in cohort 2 received ≥1 dose of pembrolizumab. Median follow-up, defined as the time from first dose to the data cutoff (October 1, 2021), was 35 months (range, 31-37). ORR was 16% (95% CI, 7-29). Median DOR was not reached (NR; range, 3 to 24+ months); 58% of responders were estimated to have a response duration ≥18 months. Best overall response was 8 (16%) PRs, 21 (41%) SDs, and 17 (33%) PDs; no CRs were observed and response was not evaluable for 2 patients (4%) and not assessed for 3 patients (6%). DCR was 57% (95% CI, 42-71). ORR was generally consistent among patients with a viral and nonviral etiology for HCC, although sample sizes were small. The median TTP was 4 months (95% CI, 3-9). Median PFS was 4 months (95% CI, 2-8). Estimated PFS rate at 24 months was 15%. Median OS was 17 months (95% CI, 8-23). Estimated OS rate at 24 months was 34%. No new or unexpected adverse events (AEs) occurred. Treatment-related AEs were reported in 28 patients (55%; grade 3-5, 8 [16%]). Conclusions: Updated results from cohort 2 of the KEYNOTE-224 study continued to demonstrate durable antitumor activity, promising OS, and manageable safety for pembrolizumab monotherapy in patients with aHCC and no prior systemic therapy. These data, together with recent positive results from KEYNOTE-394, underscore the broad applicability of pembrolizumab in patients with aHCC both as monotherapy and in combination with other therapies. Clinical trial information: NCT02702414.

7512 Background: In low–tumor burden follicular lymphoma (FL), maintenance rituximab (MR) has been shown to improve progression-free survival (PFS) when compared with observation. RESORT study (Kahl et al. 2014) clearly showed that Rituximab (R) retreatment strategy provided similar time to treatment failure that maintenance strategy with less rituximab use. It is not known whether short MR using sub-cutaneous (sc) route could improve PFS while reducing R infusions. Methods: Patients with the diagnosis of low-tumor burden FL (GELF criteria) within the last 4 months before signing informed consent were randomly assigned to either Iv-Arm : 4-weekly iv infusions of R 375 mg/m2 or Sc-Arm: one iv infusion of R (D1, 375 mg/m2) followed by 3 sc infusions of R (1400 mg, on days 8, 15 and 22) followed by Rsc maintenance on months (M) 3, 5, 7 and 9. The primary endpoint was PFS and secondary endpoints included safety, response rates (M3, M12), duration of response (DOR), time to next anti-lymphoma treatment (TTNTL) and overall survival (OS). Results: A total of 202 patients were included, 102 in Iv-Arm and 100 in Sc-Arm and constitute the intent to treat population. The median uses of R were 4 infusions (range: 1-4, Iv-Arm) and 8 infusions (range: 2-8, Sc-Arm). With a median follow-up of 50.2 months (95% CI: 48.3-54.5), 4‐year PFS was 41.2% (95% CI: 30.6%; 51.6%) in Iv-Arm and 58.1% (95% CI: 47.5%; 67.4%) in Sc-Arm. Median PFS was then 36.1 months (95% IC: 23.9-52.6) in Iv-Arm and 73.8 months (95% CI: 39.4-NA) in Sc-Arm (Fig 1.) (HR: 0.58; 95% CI: 0.39-0.87; P = 0.0076). Patients with at least one AE grade ≥ 3 were 8 (7.8%) and 12 (12.4%) in Iv-Arm and Sc-Arm, respectively. According to Cheson criteria, ORR at M3 were: 83% and 80% including 38% and 29% of CR/CRu, in Iv-Arm and Sc-Arm, respectively. According to Lugano criteria, 36.3% (Iv-Arm; 95% CI: 27.0%. 46.4%) and 59.0% (Sc-Arm; 95% CI: 48.7%; 68.7%) were in CMR at M12. The median DOR was 32.7 months (95% IC: 20.6-49.7) and 70.8 months (36.4-NR) (HR: 0.56; 95% IC: 0.37-0.84) in Iv-Arm and Sc-Arm, respectively. 4-year TTNLT was 54% (95% CI: 42.9%; 63.8%) in Iv-Arm and 61.8% (95% CI: 50.8.6%; 71.0%) in Sc-Arm (HR: 0.81, 95% IC: 0.53-1.24). 4-year TTNLT chemotherapy was 60.8 % (95% CI: 49.6%; 70.3%) in Iv-Arm and 71.4% (95% CI: 60.7%; 79.8%) in Sc-arm (HR: 0.69, 95% IC: 0.42-1.12) (Fig 2.). OS was not different according to treatment arm, 4-year OS was 95.0% (95% CI: 88.5%; 97.9%) in Iv-Arm and 96.7% (95% CI: 89.9%; 98.9%) in Sc-Arm. Conclusions: This phase III study met its primary endpoint and demonstrated that Rsc induction followed by a short MRsc improves PFS of patients with low-tumor burden. MRsc did not however improved TTNLT. R in low-tumor burden FL allowed to avoid cytotoxic use in most patients 6 years after treatment initiation. Clinical trial information: NCT02303119.

7501 Background: R/R ENKTL is a rare and aggressive type of non-Hodgkin’s lymphoma. Responses to chemotherapy after failure of prior asparaginase-based regimen were not durable with a median OS of < 7 months (mos) and 1-year OS rate of < 20% (Lim et al, Ann Oncol 2017; Bellei et al, Haematologica 2018). The only targeted therapy approved in China for R/R peripheral T cell lymphoma (ENKTL included) showed an ORR of 18.8% and a CR rate of 6.3% (Shi et al, Ann Oncol 2015). Here, we present the primary analysis from GEMSTONE-201, the largest registrational study reported to date to evaluate an anti-PD-L1 mAb in R/R ENKTL. Suge received breakthrough therapy designation from US FDA in 2021 for adult R/R ENKTL pts based on preliminary data of this study. Methods: Pts with ECOG PS of 0/1 and histologically confirmed ENKTL who failed prior asparaginase-based regimen were enrolled. Pts accepted suge at 1200 mg Q3W, iv, for up to 24 mos, until progression, death, or withdrawal from study. The primary endpoint was ORR (CR+PR) assessed by independent radiological review committee (IRRC) per Lugano 2014 criteria. Key secondary endpoints included investigator-assessed ORR, CR and PR rate, DoR assessed by IRRC and investigators, and safety. Results: As of the data cutoff date, Nov 10, 2021, 80 pts were enrolled and treated (median follow-up of 13.4 mos). Median age was 48 years (range 29-74); 64% were males; 74% had ECOG PS of 1 at baseline; 68% had stage IV disease; about half (49%) received ≥ 2 lines of prior systemic therapy. The median duration of treatment was 5.2 mos (range 0.7-37.4); 23 pts remained on treatment. Among the 78 evaluable pts as per IRRC, ORR was 46.2% (95% CI: 34.8%, 57.8%); 29 (37.2%) pts achieved CR; median DoR was not reached (NR); 12-mo DoR rate was 86%. Investigator’s assessments in 79 evaluable pts were consistent with IRRC results, i.e. ORR of 45.6% (95% CI: 34.3%, 57.2%), 24 (30.4%) pts with CR, and median DoR of NR. The 1- and 2-year OS rates were 68.6% and 54.6%, respectively; median OS was NR (range 0.9-37.2+ mos). Of all pts, 96% (n = 77) had at least one AE. The most common AEs were pyrexia and WBC decreased (n = 24 each, 30%). Grade ≥ 3 AEs occurred in 31 (39%) pts. Suge-related AEs occurred in 61 (76%) pts and were mostly (60%) Grade 1/2. The most common irAE assessed by sponsor was hypothyroidism (n = 13, 16%). SAEs occurred in 18 (23%) pts; 5 (6%) pts had suge-related SAEs which had all been resolved (1 with sequelae). Fatal AEs occurred in 5 (6%) pts and none were suge-related as assessed by investigators. Conclusions: Suge has demonstrated deep and durable anti-tumor activity in R/R ENKTL pts, with a high CR rate and a promising OS benefit trend comparing to historical data. Suge had a well-tolerated safety profile and no new safety signals were detected. Primary analysis indicates that suge could provide a new treatment option to R/R ENKTL pts. Clinical trial information: NCT03595657.

3100 Background: Neurotrophic tyrosine receptor kinase ( NTRK) gene fusions are oncogenic drivers in multiple tumors. Larotrectinib is a highly selective, central nervous system (CNS)-active tropomyosin receptor kinase (TRK) inhibitor, approved to treat adult and pediatric patients (pts) with TRK fusion cancer. In an integrated analysis of 206 pts with non-primary CNS TRK fusion cancer, larotrectinib demonstrated an investigator-assessed objective response rate (ORR) of 75%; median progression-free survival (PFS) was 35.4 months (mo; Hong et al, ASCO 2021). We report updated efficacy and safety data based on central review assessments in an expanded dataset. Methods: Data were pooled from three clinical trials (NCT02576431, NCT02122913, and NCT02637687) of pts with non-primary CNS TRK fusion cancer treated with larotrectinib. Larotrectinib was administered until disease progression, withdrawal, or unacceptable toxicity. ORR was assessed by independent review committee (IRC) per RECIST v1.1. Data cut-off was July 20, 2021. Results: As of data cut-off, 244 of 269 larotrectinib-treated pts were evaluable for efficacy by IRC. There were 25 different tumor types. The most common were soft tissue sarcoma (STS [43%], including infantile fibrosarcoma [18%] and other STS [25%]), thyroid (11%), lung (10%), salivary gland (9%), and colorectal (7% [colon, n = 18; rectal, n = 1]). Ninety-four (35%) pts were aged < 18 years; 175 (65%) were ≥18 years. Pts had gene fusions involving NTRK1 (46%), NTRK2 (3%), or NTRK3 (51%). A total of 27%, 28%, and 45% of pts had 0, 1, and ≥2 prior lines of systemic therapy, respectively. The ORR was 69% (95% confidence interval [CI] 63–75): 64 (26%) complete response (CR), including 13 (5%) pathological CR, 104 (43%) partial response,41 (17%) stable disease, 20 (8%) progressive disease, and 15 (6%) not determined. Median time to response was 1.8 mo (range 0.9–16.2). Median duration of response (DoR) was 32.9 mo (95% CI 27.3–41.7); median follow-up was 28.3 mo. Median PFS was 29.4 mo (95% CI 19.3–34.3); median follow-up was 29.3 mo. At a median follow-up of 32.2 mo, median overall survival (OS) was not reached; the 48-mo OS rate was 64% (95% CI 55–73). Treatment duration ranged from 0.1 to 67.9 months. Treatment-related adverse events (TRAEs) were mainly Grade 1–2; 50 (20%) pts had Grade 3–4 TRAEs. Five (2%) pts discontinued treatment due to TRAEs. To exclude the possible confounding effect of ongoing enrollment on median DoR, we conducted an exploratory analysis in the subset of 164 pts who were analyzed as of July 2019. The ORR was 74% (95% CI 67–81) and median DoR was 34.5 mo (95% CI 27.6–43.3); median follow-up was 34.1 mo. Conclusions: With longer follow-up, larotrectinib continued to demonstrate rapid and durable responses, extended survival benefit, and a favorable safety profile. These results highlight the importance of testing for NTRK gene fusions in cancer pts. Clinical trial information: NCT02576431, NCT02122913, NCT02637687.

2514 Background: Checkpoint inhibitors (CPIs) are usually ineffective in patients (pts) with immune-cold microsatellite stable colorectal cancer (MSS-CRC) or pancreatic cancer (PDAC) and in those who progressed on previously treated with antibodies against PD1 or PD-L1. Here, we report the combination of NT-I7 plus pembrolizumab (pembro) on CPI-naïve MSS-CRC and PDAC cohorts, and patients (pts) with CPI-treated triple-negative breast cancer (TNBC), non-small cell lung cancer (NSCLC), and small cell lung cancer (SCLC) cohorts of this ongoing phase 2a trial. Methods: Pts with CPI-naïve relapsed/refractory (R/R) MSS-CRC and PDAC, and CPI-treated R/R TNBC, NSCLC, and SCLC, were enrolled. NT-I7 (efineptakin alfa) 1200 µg/kg intramuscularly every 6 weeks and 200 mg pembro intravenously every 3 weeks were administered until disease progression/unacceptable toxicity. The primary endpoint of the Phase 2a is the objective response rate (ORR), assessed by RECIST v1.1 and iRECIST. The secondary endpoints are duration of response (DoR), disease control rate, progression-free survival, and overall survival. Results: As of 14 Jan 2022, 92 pts with metastatic or locally advanced cancer who had received a median of 3 prior treatments were enrolled in the study; 32 in PDAC, 28 in MSS-CRC, 22 in NSCLC, 6 in TNBC, and 4 in SCLC. The median age was 62 years [29-81], ECOG PS 0 in 23 (25%), 1 in 68 (74%) and 2 in 1 (1%). Among 71 evaluable pts, the median follow up (months) was 7.7, 5.3, 5.0, 3.7, and 2.4 in TNBC, MSS-CRC, NSCLC, PDAC and SCLC, respectively. The ORR was 50% (1/2) in SCLC, 12% (3/25) in MSS CRC, 8% (2/26) in PDAC 6% (1/16) in NSCLC and 0% (0/2) in TNBC per iRECIST; and 50% (1/2) in SCLC, 4% (1/25) in MSS CRC, and 4% (1/26) in PDAC per RECIST 1.1. All 7 responders are ongoing. The two PDAC pts had DoR over 1.35 months (mos) and 6.64 mos with the best tumor reduction 100% and 72% respectively. The one SCLC pt had DoR over 1.5 mos with the tumor reduction 67%. The one NSCLC pt had DoR over 2.73 mos with the tumor reduction 60%, and the three MSS-CRC pts had DoR 6.34, 2.96, and 0.03 mos with the tumor reduction 60%, 56%, and 43% respectively. A sustained and significant (approximate 3X from baseline) increase of peripheral lymphocytes in all arms was observed as shown in our previous report. Among 92 treated pts, NT-I7-related adverse events (AEs) occurred in 67 (72.8%) pts, including 52 (56.5%) Grade (G)1-2, 13 (14.1%) G3, and 2 (2.2%) G4. There were no NT-I7 related G5 AEs. Additional updated efficacy, safety and biomarker data will be presented. Conclusions: The combination of NT-I7 and pembro demonstrated antitumor activity and manageable toxicity profile in heavily pretreated pts with CPI-naïve MSS-CRC and PDAC and CPI-treated TNBC, NSCLC, and SCLC, suggesting that the addition of NT-I7 to CPI can overcome the primary resistance to CPI in the former group and acquired resistance in the latter. Clinical trial information: NCT04332653.

4040 Background: Outcomes of second or later-line treatment for pts with advanced GC/GEJC remain inferior. KN026 is a novel HER2-targeted bispecific antibody composed of VH regions of trastuzumab and pertuzumab, targeting the HER2 juxtamembrane domain (IV) and the dimerization domain (II) simultaneously. KN026 has shown promising antitumor efficacy in preclinical and phase I studies. Here we present the results of KN026 monotherapy in previously treated, advanced HER2-expressing GC/GEJC. Methods: In this multi-center, single-arm, open-label, 2-cohort phase II study, adult pts with previously treated, advanced GC/GEJC were assigned into a HER2 high-level cohort (Cohort 1: IHC3+ or IHC 2+ ISH+) or a HER2 low-level cohort (Cohort 2: IHC 1+/2+ ISH- or IHC 0/1+ISH+). KN026 was given intravenously in 10 mg/kg QW, 20 mg/kg Q2W, or 30 mg/kg Q3W. Primary endpoints were objective response rate (ORR) and duration of response (DoR) assessed by investigators per RECIST 1.1. Secondary endpoints included progression-free survival (PFS), overall survival (OS), and safety outcomes. This trial is registered at ClinicalTrials.gov (NCT03925974). Results: At data cut-off (Oct. 29, 2021), 45 pts were enrolled and treated with KN026; 39 were eligible for response evaluation (25 pts in Cohort 1 and 14 pts in Cohort 2). In Cohort 1, ORR was 56% (95%CI 35%-76%) with 14 PR; the median DoR was 9.7 months (mo) (95%CI 4.2-not evaluable (NE)). At a median follow-up of 14.7 mo (95%CI 9.4-16.5), the median PFS was 8.3 mo (95%CI 4.2-11.4), and median OS was 16.3 mo (95% CI 11.0- NE). In Cohort 2, ORR was 14% (95%CI 2%-43%), with median DoR being 6.2 mo (95%CI 3.2-NE). At a median follow-up of 27.5 mo (95%CI 4.1-NE), the median PFS was 1.4 mo (95%CI 1.4-4.1), and median OS was 9.6 mo (95% CI 3.5-14.9). The table shows efficacy in Cohort 1 pts who have progressed on the prior trastuzumab treatment. KN026-related adverse events (TRAEs) were observed in 37 (82%) pts; the most common TRAEs (any grade) were increased aspartate aminotransferase (12, 27%), increased alanine aminotransferase (9, 20%), rash (7,16%), anemia (7,16%), and infusion-related reaction (7,16%). Four pts reported 5 grade 3 TRAEs, including infusion-related reaction, renal hydrocele, ureteral stenosis, increased blood pressure, and abnormal hepatic function (1 each). No grade 4 or 5 TRAEs occurred. Conclusions: KN026 monotherapy yielded promising efficacy with mild to moderate toxicities in pts with previously treated, advanced GC/GEJC. Further investigation is warranted. Clinical trial information: NCT03925974. [Table: see text]

105 Background: NRG1 fusions are rare oncogenic drivers that have been identified in a variety of solid tumors. These proteins bind HER3, leading to HER2/HER3 heterodimerization and oncogenic transformation. Zenocutuzumab (MCLA-128; Zeno) is a Biclonics antibody that overcomes HER3 mediated NRG1 (or NRG1 fusion) signaling in tumor cells. Zeno docks on HER2, then binds to and blocks the NRG1 fusion-HER3 interaction and HER3 heterodimerization with HER2. Zeno is being evaluated in patients (pts) with NRG1+ cancer in the ongoing pivotal phase 2 part of the eNRGy study and early access program (EAP). Methods: Pts with NRG1 + solid tumors previously treated with or not candidates for standard therapy, aged ≥ 18 years, with ECOG PS ≤ 2, and measurable (RECIST 1.1) or evaluable disease, were enrolled. NRG1 fusions were determined by next generation sequencing (NGS) before enrollment. Zeno (750 mg IV Q2W) was administered until disease progression or unacceptable toxicity. Tumor imaging was conducted every 8 weeks. The primary endpoint is investigator (INV)-assessed objective response rate (ORR) and secondary endpoints include duration of response (DOR) and safety. Results: As of 12 Jan 2022, 99 pts with NRG1 + cancer (85 eNRGy, 14 EAP) were enrolled. Efficacy was assessed in 73 pts who received ≥ 1 dose of Zeno and who were enrolled as of 12 Jul 2021 to allow for the opportunity to have ≥ 6 months (mo) follow-up and met the criteria for the primary efficacy population. Median age was 59 y (range 22–84), 58% were female, 47%/53% pts had ECOG PS 0/1. Tumor types were non-small cell lung cancer (NSCLC; 41 pts), pancreas cancer (18 pts), breast cancer (5 pts), cholangiocarcinoma (3 pts), colorectal cancer (2 pts), and 4 other tumor types (1 pt each), with a median 2 prior systemic therapies (range 0-9). The most frequent fusion partners were CD74 (27%), SLC3A2 (18%), and ATP1B1 (15%). Among the 71 pts with measurable disease, the INV-assessed confirmed ORR was 34% (90% CI, 25;44), including responses in NSCLC (35%; 14/40 pts), pancreas cancer (39%; 7/18 pts), breast cancer (2/4 pts), and cholangiocarcinoma (1/3 pts). Responses occurred at the first tumor assessment in 20/24 responders, and are ongoing in 13 pts. Treatment is ongoing in 22 pts (13 NSCLC, 6 pancreas, 3 other solid tumors). Median DOR was 9.1 mo (95% CI, 5.2-12.0). Kaplan-Meier estimate of DOR rate at 6 mo was 70%. Among the 208 pts treated with Zeno monotherapy across all dosing schedules in the phase 2 setting, for individual adverse events irrespective of causality, grade ≥ 3 events were reported in