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Background Many patients do not respond or eventually relapse on treatment with programmed cell death protein-1 (PD-1)/programmed death-ligand 1 (PD-L1) checkpoint inhibitors due to secondary or acquired resistance; therefore, there is a need to investigate novel PD-1/PD-L1 inhibitors. Methods This open-label, non-randomised study investigated the safety and anti-tumour activity of BGB-A333, a PD-L1 inhibitor, alone and in combination with tislelizumab in patients with advanced solid tumours with progression during/after standard therapy. The primary objectives were to determine the recommended Phase 2 dose (RP2D), safety and tolerability for BGB-A333 alone and in combination with tislelizumab (Phase 1a/1b) and to determine the overall response rate (ORR) with BGB-A333 plus tislelizumab (Phase 2). Results Overall, 39 patients across Phase 1a (N = 15), 1b (N = 12) and 2 (N = 12) were enroled. In Phase 1a, an RP2D of 1350 mg was determined. In Phase 1a and 1b/2, serious treatment-emergent adverse events (TEAEs) were reported in five and eight patients, respectively. Two patients experienced TEAEs that led to death. In Phase 2, the ORR was 41.7% (n = 5/12; 95% confidence interval: 15.17%, 72.33%). Conclusions TEAEs reported with BGB-A333 were consistent with other PD-L1 inhibitors. Encouraging preliminary anti-tumour activity was observed with BGB-A333 in combination with tislelizumab. Clinical trial registration NCT03379259.

Purpose:BRAF V600E mutant metastatic colorectal cancer represents a significant clinical problem, with combination approaches being developed clinically with oral BRAF inhibitors combined with EGFR-targeting antibodies. While compelling preclinical data have highlighted the effectiveness of combination therapy with vemurafenib and small-molecule EGFR inhibitors, gefitinib or erlotinib, in colorectal cancer, this therapeutic strategy has not been investigated in clinical studies.Patients and Methods:We conducted a phase Ib/II dose-escalation/expansion trial investigating the safety/efficacy of the BRAF inhibitor vemurafenib and EGFR inhibitor erlotinib.Results:Thirty-two patients with BRAF V600E positive metastatic colorectal cancer (mCRC) and 7 patients with other cancers were enrolled. No dose-limiting toxicities were observed in escalation, with vemurafenib 960 mg twice daily with erlotinib 150 mg daily selected as the recommended phase II dose. Among 31 evaluable patients with mCRC and 7 with other cancers, overall response rates were 32% [10/31, 16% (5/31) confirmed] and 43% (3/7), respectively, with clinical benefit rates of 65% and 100%. Early ctDNA dynamics were predictive of treatment efficacy, and serial ctDNA monitoring revealed distinct patterns of convergent genomic evolution associated with acquired treatment resistance, with frequent emergence of MAPK pathway alterations, including polyclonal KRAS, NRAS, and MAP2K1 mutations, and MET amplification.Conclusions:The Erlotinib and Vemurafenib In Combination Trial study demonstrated a safe and novel combination of two oral inhibitors targeting BRAF and EGFR. The dynamic assessment of serial ctDNA was a useful measure of underlying genomic changes in response to this combination and in understanding potential mechanisms of resistance.

Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned co-primary or secondary analyses are not yet available. Clinical Trial Updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported.In the longest follow-up, to our knowledge, for a KRASG12C inhibitor, we assessed the long-term efficacy, safety, and biomarkers of sotorasib in patients with KRAS G12C-mutated advanced non-small-cell lung cancer (NSCLC) from the CodeBreaK 100 clinical trial (ClinicalTrials.gov identifier: NCT03600883). This multicenter, single-group, open-label phase I/phase II trial enrolled 174 patients with KRAS G12C-mutated, locally advanced or metastatic NSCLC after progression on prior therapies. Patients (N = 174) received sotorasib 960 mg once daily with the primary end points for phase I of safety and tolerability and for phase II of objective response rate (ORR). Sotorasib produced an ORR of 41%, median duration of response of 12.3 months, progression-free survival (PFS) of 6.3 months, overall survival (OS) of 12.5 months, and 2-year OS rate of 33%. Long-term clinical benefit (PFS ≥ 12 months) was observed in 40 (23%) patients across PD-L1 expression levels, in a proportion of patients with somatic STK11 and/or KEAP1 alterations, and was associated with lower baseline circulating tumor DNA levels. Sotorasib was well tolerated, with few late-onset treatment-related toxicities, none of which led to treatment discontinuation. These results demonstrate the long-term benefit of sotorasib, including in subgroups with poor prognosis. ispartof: J Clin Oncol vol:41 issue:18 pages:3311-3317 ispartof: location:United States status: published

Gastrointestinal stromal tumours (GISTs) are the most common gastrointestinal tract mesenchymal tumours. Tyrosine kinase inhibitors (TKIs) have transformed the management of advanced GIST. Imatinib was the first TKI to gain approval as management for patients with advanced GIST, establishing a new standard of care. Since then, as a result of several trials including the GRID and INVICTUS studies, we now have five lines of approved targeted therapy, including imatinib, sunitinib, regorafenib, ripretinib and avapritinib for the treatment of unresectable, advanced GISTs. In this review, the Australasian Gastrointestinal Trials Group (AGITG) provide an overview of the key trials that have changed clinical practice, discuss the molecular drivers of GISTs, the importance of molecular testing and directing therapy according to molecular targets, as well as future strategies in the management of advanced GISTs.

Background CD73 upregulation in tumors leads to local immunosuppression. This phase I, first-in-human study evaluated oleclumab (MEDI9447), an anti-CD73 human IgG1λ monoclonal antibody, alone or with durvalumab in patients with advanced colorectal cancer (CRC), pancreatic ductal adenocarcinoma (PDAC), or epidermal growth factor receptor-mutant non-small-cell lung cancer (NSCLC). Methods Patients received oleclumab 5–40 mg/kg (dose-escalation) or 40 mg/kg (dose-expansion) intravenously every 2 weeks (Q2W), alone (escalation only) or with durvalumab 10 mg/kg intravenously Q2W. Results 192 patients were enrolled, 66 during escalation and 126 (42 CRC, 42 PDAC, 42 NSCLC) during expansion. No dose-limiting toxicities occurred during escalation. In the monotherapy and combination therapy escalation cohorts, treatment-related adverse events (TRAEs) occurred in 55 and 54%, respectively, the most common being fatigue (17 and 25%). In the CRC, PDAC, and NSCLC expansion cohorts, 60, 57, and 45% of patients had TRAEs, respectively; the most common were fatigue (15%), diarrhea (9%), and rash (7%). Free soluble CD73 and CD73 expression on peripheral T cells and tumor cells showed sustained decreases, accompanied by reduced CD73 enzymatic activity in tumor cells. Objective response rate during escalation was 0%. Response rates in the CRC, PDAC, and NSCLC expansion cohorts were 2.4% (1 complete response [CR]), 4.8% (1 CR, 1 partial response [PR]), and 9.5% (4 PRs), respectively; 6-month progression-free survival rates were 5.4, 13.2, and 16.0%. Conclusions Oleclumab ± durvalumab had a manageable safety profile, with pharmacodynamic activity reflecting oleclumab’s mechanism of action. Evidence of antitumor activity was observed in tumor types that are generally immunotherapy resistant. Clinical trial registration Clinicaltrials.gov, NCT02503774; date of registration, July 17, 2015.

The EGFR/RAS/MEK/ERK signaling pathway (ERK/MAPK) is hyperactivated in most colorectal cancers. A current limitation of inhibitors of this pathway is that they primarily induce cytostatic effects in colorectal cancer cells. Nevertheless, these drugs do induce expression of proapoptotic factors, suggesting they may prime colorectal cancer cells to undergo apoptosis. As histone deacetylase inhibitors (HDACis) induce expression of multiple proapoptotic proteins, we examined whether they could synergize with ERK/MAPK inhibitors to trigger colorectal cancer cell apoptosis. Combined MEK/ERK and HDAC inhibition synergistically induced apoptosis in colorectal cancer cell lines and patient-derived tumor organoids in vitro, and attenuated Apc-initiated adenoma formation in vivo. Mechanistically, combined MAPK/HDAC inhibition enhanced expression of the BH3-only proapoptotic proteins BIM and BMF, and their knockdown significantly attenuated MAPK/HDAC inhibitor–induced apoptosis. Importantly, we demonstrate that the paradigm of combined MAPK/HDAC inhibitor treatment to induce apoptosis can be tailored to specific MAPK genotypes in colorectal cancers, by combining an HDAC inhibitor with either an EGFR, KRASG12C or BRAFV600 inhibitor in KRAS/BRAFWT; KRASG12C, BRAFV600E colorectal cancer cell lines, respectively. These findings identify a series of ERK/MAPK genotype-tailored treatment strategies that can readily undergo clinical testing for the treatment of colorectal cancer.

Desmoid tumors (aggressive fibromatosis) are soft tissue mesenchymal tumors that can be locally invasive and life-threatening. Depending on the location, these tumors are often unresectable or tend to recur after surgery. To date, there are no approved systemic therapies for desmoid tumors. These tumors typically harbor mutations in the β-catenin oncogene CTNNB1 or the tumor suppressor gene adenomatous polyposis coli, resulting in constitutive activation of the WNT pathway. The Notch pathway is part of the underlying cause for desmoid tumor development, possibly due to crosstalk with the WNT pathway, providing a rationale for Notch inhibition as a therapeutic strategy. The gamma secretase activation of the Notch receptor can be targeted with investigational gamma secretase inhibitors. In this case report, we follow the course of 2 patients with desmoid tumors treated with the highly potent, parenterally administered investigational gamma secretase inhibitor AL101, resulting in long-lasting responses. Case 1 reports on a patient with a mesenteric desmoid tumor who participated in a phase 1 trial and then transitioned into a compassionate use program; Case 2 reports on a patient with recurrent pelvic tumors receiving AL101 through a compassionate use program. After tumor progression on other systemic therapies, Cases 1 and 2 had confirmed partial responses (41% and 60% maximal tumor size decrease from baseline) recorded after 1.0 and 1.6 years of treatment with AL101, with a duration of response of 8.6+ and 2.6+ years, respectively. Also, in a phase 1 study of AL102, a potent orally administered gamma secretase inhibitor that shares structural features with AL101, a patient with a desmoid tumor was noted to have tumor shrinkage. Formal clinical testing of AL102 for the treatment of patients with desmoid tumors that are not amenable to surgery or are refractory to/recurrent from other prior therapies is currently underway.

Complex genomic profiling (CGP) has transformed cancer treatment decision making, yet there is a lack of robust and quantifiable evidence for how utilisation of CGP improves patient outcomes.This study evaluated cohort level clinical effectiveness of CGP to improve overall survival (OS) in real-world advanced cancer patients using a registry-based matched control population.Two cohorts of advanced and refractory cancer patients were seen in consecutive series for early phase trial enrolment consideration. The first cohort (CGP group) accessed tumour profiling via a research study; while the second cohort that followed was not profiled. Overall survival between cohorts was compared using Kaplan-Meier curves and Cox proportional hazard models. Potential confounding was analysed and adjusted for using stabilised weights based on propensity scores.Within the CGP group, 25 (17.6%) patients received treatment informed by CGP results and this subgroup had significantly improved survival compared with CGP patients in whom results did not impact their treatment (unadjusted HR = 0.44, (0.22-0.88), p = 0.02). However, when comparing the entire CGP cohort with the No CGP cohort, no significant survival benefit was evident with adjusted median OS for CGP of 13.5 months (9.2-17.0) compared with 11.0 (9.2-17.4) for No CGP (adjusted HR = 0.92, (0.65-1.30), p = 0.63).This study utilised real-world data to simulate a control arm and quantify the clinical effectiveness of genomic testing. The magnitude of survival benefit for patients who had CGP result-led treatments was insufficient to drive an overall survival gain for the entire tested population. Translation of CGP into clinics requires strategies to ensure higher rates of tested patients obtain clinical benefit to deliver on the value proposition of CGP in an advanced cancer population.

While several resources exist that interpret therapeutic significance of genomic alterations in cancer, many regional real-world issues limit access to drugs. There is a need for a pragmatic, evidence-based, context-adapted tool to guide clinical management based on molecular biomarkers. To this end, we have structured a compendium of approved and experimental therapies with associated biomarkers following a survey of drug regulatory databases, existing knowledge bases, and published literature. Each biomarker-disease-therapy triplet was categorised using a tiering system reflective of key therapeutic considerations: approved and reimbursed therapies with respect to a jurisdiction (Tier 1), evidence of efficacy or approval in another jurisdiction (Tier 2), evidence of antitumour activity (Tier 3), and plausible biological rationale (Tier 4). Two resistance categories were defined: lack of efficacy (Tier R1) or antitumor activity (Tier R2). Based on this framework, we curated a digital resource focused on drugs relevant in the Australian healthcare system (TOPOGRAPH: Therapy Oriented Precision Oncology Guidelines for Recommending Anticancer Pharmaceuticals). As of November 2020, TOPOGRAPH comprised 2810 biomarker-disease-therapy triplets in 989 expert-appraised entries, including 373 therapies, 199 biomarkers, and 106 cancer types. In the 345 therapies catalogued, 84 (24%) and 65 (19%) were designated Tiers 1 and 2, respectively, while 271 (79%) therapies were supported by preclinical studies, early clinical trials, retrospective studies, or case series (Tiers 3 and 4). A companion algorithm was also developed to support rational, context-appropriate treatment selection informed by molecular biomarkers. This framework can be readily adapted to build similar resources in other jurisdictions to support therapeutic decision-making.

B-Raf proto-oncogene (BRAF)-V600E mutations (BRAFmt) in colorectal cancer (CRC) predominantly occur in right-side (RS) primaries. In metastatic CRC (mCRC), there is substantial overlap between the reported features of BRAFmt and of an RS primary. To explore the significance of BRAFmt in a left-side (LS) primary, we analysed data from a multi-site mCRC registry. Tumours distal to the splenic flexure were considered LS. Of 3380 patients enrolled from June 2009 to June 2020, 214 (13%) of 1657 with known status were BRAFmt: 127 (24%) of 524 RS and 87 (8%) of 1133 LS. LS versus RS BRAFmt were younger (mean 59.5 vs. 65.1 years; p = 0.01), whereas sex (48 vs. 59% female; p = 0.13), mismatch repair-deficiency (dMMR) (16 vs. 21%; p = 0.47), and overall survival (OS) (median 15.1 vs. 17.7 months; p = 0.98) were similar. LS BRAFmt versus LS BRAF wildtype (wt) were of similar age (59.5 vs. 61.3 years; p = 0.28) with more females (48 vs. 37%; p = 0.04), more dMMR (16 vs. 1%; p < 0.0001), and inferior OS (median 15.1 vs. 36.6 months; p < 0.0001). Initial treatment with chemotherapy plus an epidermal growth factor receptor inhibitor produced median progression-free survival (PFS) of 4.3 versus 12.3 months (p = 0.20) for LS BRAFmt (n = 9) versus LS BRAFwt (n = 104). Initial chemotherapy and bevacizumab produced a median PFS of 7.6 versus 11.6 months (p = 0.02) for LS BRAFmt (n = 36) versus LS BRAFwt (n = 438), respectively. LS BRAFmt cancers share many features with RS BRAFmt cancers, including poor survival outcomes. Mature data on the activity of BRAF-targeted therapies in the first-line setting are eagerly awaited.

This phase I study was conducted to evaluate the safety and Maximum Tolerated Dose of PENAO (4-(N-(S-penicillaminylacetyl)amino)-phenylarsonous acid), a second-generation organic arsenical with anti-mitochondrial activity, when given as a continuous intravenous infusion (CIVI), in patients with advanced solid tumours. Eligibility criteria for this trial included age ≥ 18 years, advanced solid tumour, ECOG Performance Status ≤ 1 and adequate organ function. PENAO was administered by CIVI, with dose levels initially increased by infusion duration in a 21-day cycle at a fixed daily dose and then increased daily dose. Standard dose-limiting toxicity (DLT) definitions were used in a “3 + 3” design. Patients had regular monitoring of toxicity and efficacy. Pharmacokinetic assays of serum and urine As were performed. Twenty-six patients were treated across 8 dose levels. The only dose-limiting toxicity (DLT) observed was fatigue, that occurred in one patient treated at the highest dose level of 9 mg/m2/day. No significant organ toxicity or objective responses were observed, although there were two patients with stable disease lasting up to 7 months. Pharmacokinetic analysis unexpectedly indicated a half-life of 9–19 days, invalidating the CIVI dosing resulting in discontinuation of the study before the RP2D was defined. PENAO was administered by CIVI at dose levels up to 9 mg/m2/day with only one DLT noted. Pharmacokinetic studies invalidated the rationale for continuous dosing and led to discontinuation of the trial without defining a RP2D. Future clinical development of PENAO will use intermittent dosing schedule, alone and in combination with rapamycin.

Mesenchymal chondrosarcoma (MCS) is an ultra-rare sarcoma that follows a more aggressive course than conventional chondrosarcoma. This study evaluates prognostic factors, treatments (surgery, chemotherapy, and radiation), and outcomes in an Australian setting.We collected demographics, clinicopathological variables, treatment characteristics, and survival status from patients with MCS registered on the national ACCORD sarcoma database. Outcomes include overall survival (OS) and progression-free survival (PFS).We identified 22 patients with MCS between 2001-2022. Median age was 28 (range 10-59) years, 19 (86%) had localised disease at diagnosis of whom 16 had surgery (84%), 11 received radiation (58%), and 10 chemotherapy (53%). Ten (52%) developed recurrence and/or metastases on follow-up and three patients with initial metastatic disease received surgery, radiation, and chemotherapy. At a median follow-up of 50.9 (range 0.4-210) months nine patients had died. The median OS was 104.1 months (95% CI 25.8-182.3). There was improved OS for patients with localised disease who had surgical resection of the primary (p = 0.003) and those with ECOG 0-1 compared to 2-3 (p = 0.023) on univariate analysis.This study demonstrates contemporary Australian treatment patterns of MCS. The role of chemotherapy for localised disease remains uncertain. Understanding treatment patterns and outcomes help support treatment decisions and design of trials for novel therapeutic strategies.

Purpose The presence of tumor-infiltrating lymphocytes (TILs) in tumors is superior to conventional pathologic staging in predicting patient outcome. However, their presence does not define TIL functionality. Here we developed an assay that tests TIL cytotoxicity in patients with locally advanced rectal cancer before definitive treatment, identifying those who will obtain a pathologic complete response (pCR). We also used the assay to demonstrate the rescue of TIL function after checkpoint inhibition blockade (CIB). Patients and Methods Thirty-four consecutive patients were identified initially, with successful completion of the assay before surgery in those 17 patients who underwent full treatment. An in vitro cytotoxic assay of rectal cancer tumoroids cocultured with patient-matched TILs was established and validated. Newly diagnosed patients were recruited with pretreatment biopsy specimens processed within 1 month. Evaluation of TIL-mediated tumoroid lysis was performed by measuring the mean fluorescence intensity of cell death marker, propidium iodide. CIB (anti–programmed cell death protein 1 [anti–PD-1] antibody) response was also assessed in a subset of patient specimens. Results Six of the 17 patients achieved an objective pCR on final evaluation of the resected specimen after neoadjuvant chemoradiotherapy. Cytotoxic killing identified the pCR group with a higher mean fluorescence intensity (27,982 [95% CI, 25,340 to 30,625]) compared with the non-pCR cohort (12,428 [95% CI, 9,434 to 15,423]; p < .001). Assessment of the effectiveness of CIB revealed partial restoration of cytotoxicity in TILs with increased PD-1 expression with anti–PD-1 antibody exposure. Conclusion Evaluating TIL function can be undertaken within weeks of the diagnostic biopsy, affording the potential to alter patient management decisions and refine selection for a watch-and-wait protocol. This cytotoxic assay also has the potential to serve as a platform to assist in the additional development of CIB.

Background: GDC-6036 is an oral, highly potent and selective KRAS G12C inhibitor that demonstrated anti-tumor activity in patients with KRAS G12C-positive advanced solid tumors, including CRC. In a previously reported single-agent cohort, GDC-6036 achieved a best response of partial response or complete response in 35% (19/55) of patients, with a confirmed overall response rate (ORR) of 24% (13/55 patients) in KRAS G12C-positive CRC patients (Desai et. al., ESMO 2022). EGFR blockade may sensitize tumors to KRAS G12C inhibition and the combination of an anti-EGFR antibody (cetuximab) with a KRAS G12C inhibitor showed greater anti-tumor activity than single-agent KRAS G12C inhibition in preclinical models (Amodio et. al., 2020). Methods: In an ongoing Phase I study (NCT04449874), patients with advanced or metastatic KRAS G12C-positive CRC were administered GDC-6036 (200-400 mg orally once a day) with cetuximab (400 mg/m2 intravenously initially, then 250 mg/m2 weekly) until intolerable toxicity or disease progression. Endpoints included safety (NCI-CTCAE v5), pharmacokinetics (PK), and preliminary anti-tumor activity (RECIST v1.1). Results: As of the clinical data cut-off date of 21 Nov 2022, 29 patients (enrolled by 07 Oct 2022) had received GDC-6036 and cetuximab. The median lines of prior metastatic therapy was 2 (range 1-8) and the median time on study treatment was 5.2 (range 1.4-11.2) months. All patients experienced at least one treatment-related adverse event (TRAE); the most common TRAEs (≥15%) were rash (grouped terms), diarrhea, nausea, vomiting, dry skin, and paronychia. Grade 3-4 TRAEs occurred in 11 patients (38%). Five patients (17%) experienced at least one serious AE, none of which were treatment-related (including 2 patients who died of CRC progression during the safety follow-up). AEs led to GDC-6036 modifications (interruptions and/or reductions) in 13 (45%) patients, dose reduction in 3 (10%) patients, and no patients discontinued due to AEs. Eleven patients discontinued from study treatment (10 due to disease progression and 1 due to physician’s discretion). The PK profile of GDC-6036 (400 mg once a day) was similar in combination with cetuximab when compared with single-agent. A partial response was achieved in 66% (19/29) of patients, with a confirmed ORR of 62% (18/29 patients). Conclusions: GDC-6036 in combination with cetuximab demonstrated a manageable safety profile and promising clinical activity. These data support that the addition of anti-EGFR therapy to GDC-6036 may lead to robust clinical benefit in patients with KRAS G12C-positive CRC. Citation Format: Jayesh Desai, Sae-Won Han, Jong-Seok Lee, Einat Shacham-Shmueli, Erminia Massarelli, Andrés Cervantes, Elena Garralda, Alejandro Falcon, Wilson H. Miller, Eelke Gort, Thomas Karasic, Salvatore Siena, Rafal Stec, Laura Medina, Luis Paz-Arez, Angelo Delmonte, Adrian Sacher, Hans Prenen, Martin Forster, Tae Won Kim, Matthew G. Krebs, Rasha Cosman, Yoonha Choi, Sandhya Mandlekar, Mark T. Lin, Kenneth K. Yau, Julie Chang, Stephanie Royer-Joo, Neekesh V. Dharia, Jennifer L. Schutzman, Manish Patel. Phase Ib study of GDC-6036 in combination with cetuximab in patients with colorectal cancer (CRC) with KRAS G12C mutation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT029.

Background: BGB-3245 is a RAF dimer inhibitor with preclinical activity in MAPK-altered tumor models harboring BRAF V600 mutations, atypical BRAF mutations/fusions, and RAS mutations. This study is investigating the safety, pharmacokinetics, and preliminary antitumor activity of BGB-3245 in patients (pts) with advanced or refractory MAPK-altered solid tumors. Methods: Eligible pts were ≥18 yrs old with ECOG 0-1 and had solid tumors harboring MAPK pathway alterations. Dose-escalation and cohort-size decisions were made using the Modified Toxicity Probability Interval Design. The starting dose was 5 mg QD. Treatment emergent adverse events (TEAEs) were graded per NCI CTCAE v5.0. Tumor responses were assessed by investigators using RECIST v1.1. Results: As of 1 Sep 2022, 42 pts were treated across 6 cohorts (5-60 mg QD). The median age was 60 yrs; pts had received a median of 3 prior lines of treatment. All pts had TEAEs; 79% had treatment-related (TR) AEs. The most common TRAEs (≥ 10%) were rash acneiform (33%), rash maculopapular (24%), fever (17%), ALT elevations and nausea (both 12%). Gr ≥3 TRAEs were reported in 29% of pts, events in ≥ 2 pts included decreased platelet count and rash maculopapular (3 each), ALT and AST elevations, and fever (2 each). Dose reductions occurred in 5 pts: rhabdomyolysis (1), LVEF decreased (1), hand-foot syndrome (1), rash maculopapular (1), and liver function abnormalities (1). Dose interruptions due to AEs occurred in 60% of pts. Dose discontinuations occurred in 79% of pts, 57% due to disease progression or death, 21% due to AE. Dose limiting toxicities were observed at 10 mg, 40 mg, and 60 mg. 40 mg QD was determined as the MTD. PK results showed generally dose-proportional increases in exposure. Tmax was at ~2 h; BGB-3245 had a long terminal half-life and 7.4-fold average accumulation in exposure at steady-state. 79% of pts were efficacy evaluable. The disease control rate was 48% with 1 CR, 5 cPR, 2 uPR and 8 SD≥24 wks. Objective responders included BRAF V600E melanoma pts post-BRAF/MEK and checkpoint inhibitors (2; 1 CR, 1 cPR), 1 NRAS G12S melanoma and 1 NRAS Q61K melanoma (post checkpoint inhibitors), 1 BRAF V600E LGSOC (progressed on BRAF inhibitor), 1 BRAF V600E cholangiocarcinoma (progressed on BRAF/MEK inhibitors), 1 BRAF K601E/PIK3CA endometrial cancer, and 1 KRAS G12D appendiceal cancer. Preliminary analysis of circulating tumor DNA showed correspondence to clinical response. Conclusions: BGB-3245 has a manageable safety profile and a generally dose-proportional PK. Antitumor activity was observed in pts with no approved targeted therapy options. The safety and early efficacy profile of BGB-3245 supports further investigation in selected MAPK-altered tumors. Citation Format: Alison M. Schram, Vivek Subbiah, Ryan Sullivan, Rasha Cosman, Jia Liu, Eric I. Sbar, Thuy Hoang, Jiarong Chen, Mark Johnson, Vincent Amoruccio, Todd Shearer, Adeela Kamal, Jocelyn Lewis, Wenlin Shao, Badreddin Edris, Lusong Luo, Jayesh Desai. A first-in-human, phase 1a/1b, open-label, dose-escalation and expansion study to investigate the safety, pharmacokinetics, and antitumor activity of the RAF dimer inhibitor BGB-3245 in patients with advanced or refractory tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT031.

Background: Inactivation of the Hippo pathway is a common finding in MM and other cancers, leading to constitutive YAP activation, but has thus far been undruggable. NF2 encodes Merlin that activates Hippo kinase resulting in inactivation of YAP, which is the major effector of Hippo signaling. NF2-deficient tumors, often due to inactivating NF2 mutations (NF2m), are dependent on YAP for growth. VT3989 is an oral, highly potent and selective inhibitor of TEAD palmitoylation, which blocks YAP function and has shown promising preclinical activity. Materials and Methods: This FIH trial used a 3 + 3 dose escalation design and evaluated VT3989 from 25 to 200 mg QD continuously and 50 to 200 mg intermittently. Pts with refractory solid tumors, ECOG PS 0-1, serum albumin > 2.5, urinary protein creatinine ratio ≤ 0.5 mg/mg and albumin creatinine ratio ≤ 100 mg/g were enrolled. Objectives were to determine the safety, tolerability and recommended Phase 2 dose (RP2D) of VT3989; to evaluate antitumor activity, pharmacokinetics (PK) and correlate NF2m and other alterations in tumor and ctDNA with response. Results: 67 pts have been enrolled. Median age 63.5y (21-83y), ECOG PS 0:1 13:54 pts. Median prior therapies 3 (range 0-8). Tumor types: 42 MM (29 pleural and 13 non-pleural) and 25 solid tumors including 9 meningioma and 4 sarcoma pts. 34 pts had NF2m (29 somatic and 5 germline). All MM pts had progressed on prior platinum/pemetrexed; all but 2 had prior immune checkpoint inhibitors. VT3989 is safe and well tolerated with no dose limiting toxicities. No MTD was defined up to 200 mg QD. The most common AEs are proteinuria, albuminuria and peripheral edema, mainly observed with the continuous schedule. There were 7 possibly related G3 AEs (fatigue, ALT, AST, dehydration, dyspnea, hypotension and peripheral edema) and 1 G4 cardiomyopathy. No pt developed decreased renal function or nephrotic syndrome. VT3989 has a 12-15 day half-life, dose proportional PK and reaches steady state within 2 weeks. Seven pts (6 refractory MM and 1 NF2m sarcoma) achieved RECIST v1.1 partial responses (PRs) with 4 confirmed, 3 unconfirmed (1 pending). 3 PRs in MM pts are ongoing up to 18+ months. The clinical benefit response rate (PR + SD > 8 weeks, per protocol) in MM pts is 57%. Of the 6 MM pts (1 pericardial, 1 pleural/peritoneal and 4 peritoneal) with PR, 2 have NF2m, 3 are wildtype, and 1 is unknown. Conclusions: VT3989 is safe and well tolerated with durable RECIST v1.1 antitumor responses in pts with advanced MM and NF2m cancers, providing the first early clinical proof-of-concept for effectively drugging the Hippo-YAP-TEAD pathway. RP2D optimization including further schedule evaluation and expansion are ongoing in pts with MM and NF2m tumors. Citation Format: Timothy A. Yap, David J. Kwiatkowski, Jayesh Desai, Ibiayi Dagogo-Jack, Michael Millward, Hedy L. Kindler, Anthony W. Tolcher, Sophia Frentzas, Archie W. Thurston, Len Post, F Andrew Dorr. First-in-class, first-in-human phase 1 trial of VT3989, an inhibitor of yes-associated protein (YAP)/transcriptional enhancer activator domain (TEAD), in patients (pts) with advanced solid tumors enriched for malignant mesothelioma and other tumors with neurofibromatosis 2 (NF2) mutations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT006.

Background: RAF dimer inhibition can suppress RAF-dependent MEK reactivation leading to sustained MAPK pathway inhibition. RAF dimer inhibitor lifirafenib (L) synergized with MEK inhibitor mirdametinib (M) in RAS-mutated cancer models. In this ongoing Phase 1b study of L+M in patients (pts) with advanced/refractory solid tumors harboring MAPK pathway aberrations, we investigate preliminary safety, PK, and efficacy. Methods: Pts were enrolled by a 3+3 design and treated with L (15-20 mg QD) + M (2-4 mg QD or BID) across 9 dose levels (DLs). Primary objectives were to evaluate safety/tolerability, estimate MTD, and identify recommended Phase 2 dose (RP2D). Tumor responses were investigator assessed using RECIST v1.1. AEs were graded per NCI CTCAE v5.0. Results: Table 1 presents demographic, efficacy, and safety results as of 01 Sep 2022. Objective responses (1 CR, 14 PRs) were achieved in 15/54 (27.8%) efficacy-evaluable pts, including 10/17 low-grade serous ovarian cancer (LGSOC) (58.8%; median exposure ~23 mo), 2 NSCLC (1 NRAS Q61K, 1 BRAF-V600E), 2 endometrial cancer (1 BRAF ZC3HAv1 fusion, 1 KRAS G12A), and 1 LG serous adenocarcinoma of Mullerian origin (KRAS G12V). For L and M, plasma maximum drug concentration (Cmax) and exposure (AUC) were comparable to that of each compound at same DL in monotherapy studies, suggesting low likelihood of drug-drug interaction. L+M was generally well tolerated, with limited DLTs and discontinuations. There were 2 deaths due to TEAEs considered unrelated to L+M. The MTD/RP2D were not yet determined. Conclusions: L+M demonstrated a favorable safety profile and showed antitumor activity in pts with various KRAS, NRAS, and BRAF mutations across several solid tumor types, including LGSOC, NSCLC, and endometrial cancer. The combination warrants further clinical investigation. (Acknowledgements: We thank patients/their families, investigators, and site staff for participating in this study, which is sponsored by BeiGene. Support for abstract preparation was funded by BeiGene and provided by Traci Ginnona, inSeption Group, Lansdale, PA, USA) Table 1. Demographics (N=56) Age (y), median (range) 59.5 (29-78) ECOG PS 0/1, n (%) 56 (100.0) Prior lines of therapy, median (range) 1 (1-6) Efficacy Set (N=54), n (%) LGSOC (n=17) Other than LGSOC (n=37) All malignancies (n=54) ORR (CR+PR) 10 (58.8) 5 (13.5) 15 (27.8) CR 1 (5.9) 0 1 (1.9) PR 9 (52.9) 5 (13.5) 14 (25.9) SD 6 (35.3) 18 (48.6) 24 (44.4) DCR (CR+PR+SD) 16 (94.1) 23 (62.2) 39 (72.2) Safety Set (N=56), n (%) TEAEa 55 (98.2) SAE 23 (41.1) Grade 3 TEAE 24 (42.9) TEAE leading to treatment discontinuation 3 (5.4) DLT 6 (10.7) CR, complete response; DCR, disease control rate; DLT, dose-limiting toxicity; ECOG PS, Eastern Cooperative Oncology Group performance status; LGSOC, low-grade serous ovarian cancer; ORR, objective response rate; PR, partial response; SAE, serious adverse event; SD, stable disease; TEAE, treatment-emergent adverse event. a Commonly reported (>40%): fatigue (55.4%), dermatitis acneiform (46.4%), and diarrhea (44.6%). Citation Format: Benjamin Solomon, Bo Gao, Vivek Subbiah, Michael Millward, Lee Rosen, Jayesh Desai, Eric I. Sbar, Neal Collins, Thuy Hoang, Xi Song, Wenlin Shao, Jaspreet Jaggi, Badreddin Edris, Paraneedharan Ramachandran, Lusong Luo, Michael Friedlander. Safety, pharmacokinetics, and antitumor activity findings from a phase 1b, open-label, dose-escalation and expansion study investigating RAF dimer inhibitor lifirafenib in combination with MEK inhibitor mirdametinib in patients with advanced or refractory solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT033.

Background: NRG1 fusions represent a rare and potentially actionable oncogenic alteration found in ~0.2% of solid tumors. Seribantumab is a fully human anti-HER3 IgG2 monoclonal antibody that blocks aberrant NRG1 fusion protein binding to HER3 thereby preventing ligand-dependent activation and dimerization resulting in complete inhibition of the PI3K/AKT and MAPK downstream signaling pathways. Seribantumab has shown significant anti-tumor activity in PDX models and in patients (pts) with solid tumors harboring NRG1 fusions. Methods: CRESTONE (NCT04383210) is a phase 2 study of seribantumab in adult pts with solid tumors harboring NRG1 fusions who received at least one prior therapy and were naïve to ERBB-targeted therapy (Cohort 1); pts previously treated with ERBB-targeted therapies (exploratory Cohort 2) and pts with tumors harboring additional molecular alterations (exploratory Cohort 3). Here, we present updated efficacy results for pts in Cohort 1 dosed at 3 g IV QW. Safety data are evaluated for pts enrolled in Cohort 1 and exploratory Cohorts 2 and 3. Results: As of Dec 2, 2022, 51 pts were enrolled across all cohorts with 30 pts in Cohort 1 dosed at 3 g IV QW. Median age was 62 years (range 19-84); median prior lines of therapy was 2 (range 1-7); tumor types included non-small cell lung cancer (NSCLC, n=30), pancreatic adenocarcinoma (PDAC, n=6), biliary tract/cholangiocarcinoma (CCA, n=6), breast (n=4), and others (n=5); 15 different NRG1 fusion partners were identified with CD74 (22%) and SLC3A2 (16%) as the most frequently reported. In the overall safety population, 41 pts (80%) reported at least one treatment-related adverse event (TRAE). The most common TRAEs (occurring in ≥20% of pts) were diarrhea (41%), fatigue (29%), rash (24%), and nausea (22%). Four pts (8%) experienced Gr 3/4 TRAEs; no Gr 5 TRAEs. The safety profile for Cohort 1 was similar to the overall safety population. Among the 30 pts in Cohort 1, 22 were evaluable for investigator assessed (INV) response per RECIST v1.1; 2 pts (9%) had confirmed complete response (CR), 6 pts (27%) had confirmed partial response (PR), and 13 pts (59%) had stable disease (SD) as their best overall response (BOR). The INV objective response rate (ORR, confirmed PR + CR) was 36% and disease control rate (DCR, confirmed PR+CR+SD) was 95%. The overall duration of response ranged from 1.4 to 17.2 months. In pts with NSCLC, the INV-ORR was 39% and DCR was 94%. Conclusions: Seribantumab has an acceptable safety and tolerability profile as a single agent in pts with solid tumors harboring NRG1 fusions. Updated efficacy data indicate seribantumab has robust and durable clinical activity, including CRs, across different tumor types harboring an NRG1 fusion and is a promising treatment option. Citation Format: Tejas Patil, Daniel R. Carrizosa, Mark E. Burkard, Karen L. Reckamp, Jayesh Desai, Young Kwang Chae, Stephen V. Liu, Kartik Konduri, Shirish M. Gadgeel, Jessica J. Lin, Parneet K. Cheema, David R. Spigel, Alison M. Schram, Valerie M. Jansen, Yasir Y. Elamin. CRESTONE: A Phase 2 study of seribantumab in adult patients with neuregulin-1 (NRG1) fusion positive locally advanced or metastatic solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT229.

119 Background: Based on the phase 3 BEACON study (NCT02928224), BRAF inhibitor (i) encorafenib (E) + EGFRi cetuximab (C) was approved for the treatment (tx) of previously treated patients (pts) with BRAFV600E mCRC, with mPFS of 4.3 months (mo) and ORR of 19.5%. In the phase 2 ANCHOR study (NCT03693170), mPFS was 5.8 mo and ORR was 48% for 1L EC + binimetinib in BRAFV600E mCRC. To further assess 1L approaches, the ongoing phase 3 BREAKWATER study (NCT04607421) is evaluating EC ± chemotherapy vs standard-of-care chemotherapy in BRAFV600E mCRC. Here, we present updated safety and antitumor activity data as well as biomarker data from the BREAKWATER SLI. Methods: Inclusion criteria for the SLI were BRAFV600E mCRC (blood or tumor tissue), ≤1 prior systemic tx for mCRC, and ECOG PS 0/1. Pts previously treated with BRAFi/EGFRi or both oxaliplatin and irinotecan were excluded. Pts received E 300 mg daily + C 500 mg/m2 every 2 weeks (Q2W) + either mFOLFOX6 Q2W (n=27) or FOLFIRI Q2W (n=30) in 28-day cycles until disease progression or unacceptable toxicity. The primary endpoint was frequency of dose-limiting toxicities. Secondary endpoints included safety, pharmacokinetics, and antitumor activity. Exploratory endpoints included evaluation of plasma (circulating tumor DNA [ctDNA] genomic profiling) and tumor tissue (molecular profiling) biomarkers. Updated results from the BREAKWATER SLI will be presented, including overall safety and tolerability and antitumor activity. Biomarker data, including changes from baseline in BRAFV600E ctDNA following treatment (Cycle 1 Day 15, Cycle 2 Day 15 and Cycle 7 Day 1) and MSI status of pts, will also be presented. Expected conclusions will be included in the final abstract. Clinical trial information: NCT04607421 .

The EGFR/RAS/MEK/ERK signaling pathway (ERK/MAPK) is hyper-activated in most colorectal cancers (CRCs). A current limitation of inhibitors of this pathway is that they primarily induce cytostatic effects in CRC cells. Nevertheless, these drugs do induce expression of pro-apoptotic factors, suggesting they may prime CRC cells to undergo apoptosis. As histone deacetylase inhibitors (HDACi) induce expression of multiple pro-apoptotic proteins, we examined whether they could synergize with ERK/MAPK inhibitors to trigger CRC cell apoptosis. Combined MEK/ERK and HDAC inhibition synergistically induced apoptosis in CRC cell lines and patient-derived tumor organoids in vitro,and attenuated Apc-initiated adenoma formation in vivo. Mechanistically, combined MAPK/HDAC inhibition enhanced expression of the BH3-only pro-apoptotic proteins BIM and BMF, and their knockdown significantly attenuated MAPK/HDAC inhibitor-induced apoptosis. Importantly, we demonstrate that the paradigm of combined MAPK/HDAC inhibitor treatment to induce apoptosis can be tailored to specific MAPK genotypes in CRCs, by combining a HDAC inhibitor with either an EGFR, KRASG12C or BRAFV600 inhibitor in KRAS/BRAFWT ; KRASG12C , BRAFV600E CRC cell lines respectively. These findings identify a series of ERK/MAPK genotype tailored treatment strategies that can readily undergo clinical testing for the treatment of colorectal cancer. Citation Format: Laura J. Jenkins, Ian Y. Luk, Walter D. Fairlie, Erinna F. Lee, Michelle Palmieri, Kael L. Schoffer, Tao Tan, Irvin Ng, Natalia Vukelic, Sharon Tran, Janson Tse, Rebecca Nightingale, Zakia Alam, Fiona Chionh, George Iatropoulos, Matthias Ernst, Shoukat Afshar-Sterle, Jayesh Desai, Peter Gibbs, Oliver M. Sieber, Amardeep S. Dhillon, Niall C. Tebbutt, John M. Mariadason. Genotype-tailored ERK/MAPK pathway and HDAC inhibition rewires the apoptotic rheostat to trigger colorectal cancer cell death [abstract]. In: Proceedings of the AACR Special Conference on Colorectal Cancer; 2022 Oct 1-4; Portland, OR. Philadelphia (PA): AACR; Cancer Res 2022;82(23 Suppl_1):Abstract nr B014.

BACKGROUND: Panobinostat treatment has been shown to terminally differentiate malignant rhabdoid tumours (MRT) and atypical teratoid rhabdoid tumours (ATRT) in pre-clinical models. We report results of the open label, phase II study of oral panobinostat in patients with newly diagnosed or relapsed MRT/ATRT. AIMS: To assess the anti-tumour activity of low dose, continuous oral panobinostat as well as its associated toxicities. To assess the biological activity of low dose panobinostat by measuring histone H4 acetylation status in peripheral mononuclear cells (PMNC), and differentiation markers. METHODS: Following primary institutional standard of care induction and consolidation chemotherapy and/or radiation treatment, patients were enrolled and commenced on panobinostat as a continuous daily oral dose starting at 10mg/m2/day, with a three-week wash out period between therapies. Real-time acetylation status, measuring acetylated H4 on PMNC, was performed to determine the pharmacodynamics of panobinostat at different dosing levels. Patients were monitored for toxicity; dose reductions were in decrements of 2mg/m2/day. RESULTS: A total of 13 patients with newly diagnosed ATRT/MRT and one patient with relapsed MRT have been enrolled. The average age at enrollment was 3.6 years (range 0.8-6.8 years). The mean treatment duration was 206 days (13-344 days). Currently, six patients (42.9%) remain on study with a mean study duration of 531 days (range 13-895 days). 6/14 patients (42.9%) were removed due to disease progression at a mean study duration of 245 days (44-560 days). 2/14 patients (14.3%) withdrew due to toxicity. 12/14 patients (85.7%) required dose reductions. The main toxicities were thrombocytopaenia and leukopaenia (Grade III-IV). Real-time pharmacodynamic assessment of panobinostat, at a dose as low as 6mg/m2/day resulted in significant acetylation of histone H4 in PMNC. CONCLUSIONS: Treatment with low dose panobinostat is well tolerated in infants and children with MRT/ATRT, with significant acetylation of histone H4 in PMNC.

KRAS is the most frequently mutated oncogene in cancer and encodes a key signalling protein in tumours1,2. The KRAS(G12C) mutant has a cysteine residue that has been exploited to design covalent inhibitors that have promising preclinical activity3–5. Here we optimized a series of inhibitors, using novel binding interactions to markedly enhance their potency and selectivity. Our efforts have led to the discovery of AMG 510, which is, to our knowledge, the first KRAS(G12C) inhibitor in clinical development. In preclinical analyses, treatment with AMG 510 led to the regression of KRASG12C tumours and improved the anti-tumour efficacy of chemotherapy and targeted agents. In immune-competent mice, treatment with AMG 510 resulted in a pro-inflammatory tumour microenvironment and produced durable cures alone as well as in combination with immune-checkpoint inhibitors. Cured mice rejected the growth of isogenic KRASG12D tumours, which suggests adaptive immunity against shared antigens. Furthermore, in clinical trials, AMG 510 demonstrated anti-tumour activity in the first dosing cohorts and represents a potentially transformative therapy for patients for whom effective treatments are lacking. Treatment of KRASG12C-mutant cancer cells with the KRAS(G12C) inhibitor AMG 510 leads to durable response in mice, and anti-tumour activity in patients suggests that AMG 510 could be effective in patients for whom treatments are currently lacking.

Background: Venetoclax, a potent and selective inhibitor of the survival protein BCL-2 (recently approved in CLL and in development in other hematopoietic malignancies), has yet to be evaluated in pts with solid tumors. BCL-2 is overexpressed in ˜85% of ER+ breast cancer. Pre-clinical findings using patient-derived xenograft breast tumor models suggest that venetoclax synergizes with endocrine therapy by increasing apoptosis. Here we report mBEP, an investigator-initiated phase 1b study of venetoclax with tamoxifen in 33 pts with ER+ (>1%), BCL-2+ (>10%, 2-3+ intensity) and HER2– MBC. Methods: We conducted a 3+3 dose escalation study comprising cohorts receiving venetoclax 200, 400, 600 or 800 mg/d with tamoxifen 20 mg/d (continued until progression). The primary endpoint was to determine the maximum tolerated dose (MTD), define dose-limiting toxicities (DLTs) and identify the recommended phase 2 dose (RP2D). In a dose expansion phase (at the RP2D), secondary endpoints including safety and tolerability, response at 24 wks (RECIST v1.1), clinical benefit rate (CBR) and progression-free survival (PFS) were studied. Results: In the escalation phase (n=15 pts), treatment was well tolerated with no DLTs or high-grade (Gd 3/4) adverse events observed, apart from asymptomatic on-target lymphopenia (Gd 3, 2/15 pts). MTD was not reached. The 800 mg/d dose was selected as the RP2D and the cohort expanded to include 24 pts with ≥24 wks follow up (range 24-105 wks). Fifteen pts had received prior regimens for MBC (median 3, range 1-9) that included tamoxifen in 5/15. For the RP2D cohort (n=24), overall responses (OR) included 1 CR (4%) and 12 PR (50%), with 5 SD (21%), corresponding to a CBR of 75%. The 9 pts treated in the first line setting experienced a 78% OR (7/9 pts) and 11% SD (1/9 pts), equating to an 89% CBR. The data are immature for determining median PFS for the RP2D cohort (currently 40+ wks). Treatment responses were pre-empted by metabolic responses (FDG-PET) at 4 wks (seen in 13/16 (81%) pts studied), and correlated with serial changes in circulating tumor DNA (ctDNA). Intriguingly, responses and clinical benefit were observed in pts with plasma-detected ESR1 mutations (4/10 and 7/10, respectively). The most common treatment-related AEs (CTCAE v4.0) for all pts were lymphopenia in 29/33 (88%; 57% Gd 1-2, 30% Gd 3-4), neutropenia in 24/33 (73%; 67% Gd 1-2, 6% Gd 3), nausea in 22/33 (67%; all ≤Gd 2), anemia in 13/33 (39%; 33% Gd 1-2, 6% G3), thrombocytopenia in 11/33 (33%; all ≤Gd 2), vomiting in 11/33 (33%, all ≤Gd 2), diarrhea in 10/33 (30%; 24% Gd 1-2, 6% Gd 3), infection in 9/33 (27%; 18% Gd 2, 9% Gd 3) and fatigue in 7/33 (21%; all ≤Gd 2). There was one possible treatment-related SAE (infection). Conclusions: In the first clinical study to evaluate venetoclax in a solid tumor, we demonstrate that combining venetoclax with endocrine therapy has a tolerable safety profile and elicits remarkable activity in ER+ and BCL-2+ MBC. These findings support further investigation of combination therapy for patients with BCL-2-positive breast cancer. Sponsor: The Royal Melbourne Hospital (ACTRN12615000702516) Citation Format: Lindeman GJ, Lok SW, Whittle JR, Siow ZR, Bergin AR, Dawson S-J, Desai J, Gray DH, Liew D, Mann GB, Murugasu A, Roberts AW, Rosenthal MA, Shackleton K, Sherman P, Silva MJ, Teh C, Travers A, Vaillant F, Visvader JE. A phase 1b dose-escalation and expansion study of the BCL-2 inhibitor venetoclax combined with tamoxifen in ER and BCL-2–positive metastatic breast cancer (MBC) [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD1-06.

Background Among sarcomas, which are rare cancers, many types are exceedingly rare; however, a definition of ultra-rare cancers has not been established. The problem of ultra-rare sarcomas is particularly relevant because they represent unique diseases, and their rarity poses major challenges for diagnosis, understanding disease biology, generating clinical evidence to support new drug development, and achieving formal authorization for novel therapies. Methods The Connective Tissue Oncology Society promoted a consensus effort in November 2019 to establish how to define ultra-rare sarcomas through expert consensus and epidemiologic data and to work out a comprehensive list of these diseases. The list of ultra-rare sarcomas was based on the 2020 World Health Organization classification, The incidence rates were estimated using the Information Network on Rare Cancers (RARECARENet) database and NETSARC (the French Sarcoma Network's clinical-pathologic registry). Incidence rates were further validated in collaboration with the Asian cancer registries of Japan, Korea, and Taiwan. Results It was agreed that the best criterion for a definition of ultra-rare sarcomas would be incidence. Ultra-rare sarcomas were defined as those with an incidence of approximately ≤1 per 1,000,000, to include those entities whose rarity renders them extremely difficult to conduct well powered, prospective clinical studies. On the basis of this threshold, a list of ultra-rare sarcomas was defined, which comprised 56 soft tissue sarcoma types and 21 bone sarcoma types. Conclusions Altogether, the incidence of ultra-rare sarcomas accounts for roughly 20% of all soft tissue and bone sarcomas. This confirms that the challenges inherent in ultra-rare sarcomas affect large numbers of patients.

The EGFR/RAS/MEK/ERK signalling pathway (ERK/MAPK) is hyper-activated in most colorectal cancers (CRCs). A current limitation of inhibitors of this pathway is that they primarily induce cytostatic effects in CRC cells. Nevertheless, these drugs do induce expression of pro-apoptotic factors, suggesting they may prime CRC cells to undergo apoptosis. As histone deacetylase inhibitors (HDACi) induce expression of multiple pro-apoptotic proteins, we examined whether they could synergize with ERK/MAPK inhibitors to trigger CRC cell apoptosis. Combined MEK/ERK and HDAC inhibition synergistically induced apoptosis in CRC cell lines and patient-derived tumour organoids in vitro, and attenuated Apc-initiated adenoma formation in vivo. Mechanistically this effect was mediated through induction of the BH3-only pro-apoptotic proteins BIM and BMF. Importantly, we demonstrate that this treatment paradigm can be tailored to specific MAPK genotypes in CRCs, by combining HDACi with EGFR, KRASG12C or BRAFV600 inhibitors in KRAS/BRAFWT; KRASG12C, BRAFV600E CRC cell lines respectively. These findings identify a novel ERK/MAPK genotype-targeted treatment paradigm for colorectal cancer.

PURPOSE BEACON CRC evaluated encorafenib plus cetuximab with or without binimetinib versus investigators' choice of irinotecan or FOLFIRI plus cetuximab in patients with BRAFV600E–mutant metastatic colorectal cancer (mCRC), after progression on 1-2 prior regimens. In the previously reported primary analysis, encorafenib, binimetinib plus cetuximab (ENCO/BINI/CETUX; triplet) and encorafenib plus cetuximab (ENCO/CETUX; doublet) regimens improved overall survival (OS) and objective response rate (ORR; by blinded central review) versus standard of care. The purpose of this analysis was to report updated efficacy and safety data. METHODS In this open-label, phase III trial, 665 patients with BRAF V600E–mutant mCRC were randomly assigned 1:1:1 to receive triplet, doublet, or control. Primary end points were OS and independently reviewed ORR comparing triplet to control. OS for doublet versus control was a key secondary end point. Updated analyses include 6 months of additional follow-up and ORR for all randomized patients. RESULTS Patients received triplet (n = 224), doublet (n = 220), or control (n = 221). Median OS was 9.3 months (95% CI, 8.2 to 10.8) for triplet and 5.9 months (95% CI, 5.1 to 7.1) for control (hazard ratio [HR], 0.60 [95% CI, 0.47 to 0.75]). Median OS for doublet was 9.3 months (95% CI, 8.0 to 11.3) (HR v control, 0.61 [95% CI, 0.48 to 0.77]). Confirmed ORR was 26.8% (95% CI, 21.1% to 33.1%) for triplet, 19.5% (95% CI, 14.5% to 25.4%) for doublet, and 1.8% (95% CI, 0.5% to 4.6%) for control. Adverse events were consistent with the prior primary analysis, with grade ≥ 3 adverse events in 65.8%, 57.4%, and 64.2% for triplet, doublet, and control, respectively. CONCLUSION In the BEACON CRC study, encorafenib plus cetuximab improved OS, ORR, and progression-free survival in previously treated patients in the metastatic setting compared with standard chemotherapy. Based on the primary and updated analyses, encorafenib plus cetuximab is a new standard care regimen for previously treated patients with BRAF V600E mCRC.

Background: High tumor mutational burden (TMB-H) is associated with elevated neoantigen expression across tumors, linked with an improved response to PD-(L)1 inhibitors. Here we report data from the final analysis of a Phase 1 trial that enrolled patients (pts) with various solid tumors treated with tislelizumab (NCT02407990). We evaluated the association of TMB with clinical outcomes, integrative biomarker analysis of genomic alterations and gene expression profiling by TMB status. Methods:451 pts were enrolled and treated with different doses of tislelizumab. Baseline tumor tissue was evaluated for gene expression (HTG EdgeSeq Precision Immuno-Oncology Panel) and genomic profiling (FoundationOne CDx). TMB-H and gene hyperamplification (HA) were defined as ≥ 10 mutations/Mb and a minimum of copy number gain > 5, respectively. Associations with progression-free survival (PFS) and overall survival (OS) were examined using Cox proportional hazards models. Results: The overall objective response rate was 13.3% (95% CI: 10.3, 16.8), median (m) PFS 2.1 months (95% CI: 2.1, 2.7), and mOS 10.3 months (95% CI: 8.5, 11.6). Improved clinical outcomes were observed in pts with TMB-H tumors (n=43, 16.2% of TMB evaluable pts), and response was further enriched in pts without gene HA (TMB-H/HA-) (Table). This population showed elevated cytotoxic T-cell activity and interferon signaling in the TME, along with fewer hyper-amplified genes in RTK-RAS-PI3K pathway. This was validated in an independent PD-(L)1 inhibitor treated pan-cancer cohort (n=837): TMB-H/HA-(n=139) had longer OS than TMB-H/HA+ (n=89) (mOS: 34 vs 15 months, P=0.07). Conclusions: The combination of TMB and HA was found to be predictive of clinical benefit across various solid tumor types, treated with tislelizumab. This joint algorithm, as reported by one clinically approved assay, may provide new insights to the identification of pts who are most likely to gain benefit from PD-(L)1 blockade. Clinical outcomes in pts subgroups by TMB and HA status TMB-H TMB-L Overall HA- HA+ Overall HA- HA+ n (% in TMB BEP [N=266]) 43 (16.2) 20 (7.5) 23 (8.6) 223 (83.8) 103 (38.7) 120 (45.1) ORR, % (95% CI) 32.6 (19.1, 48.5) 50.0 (27.2, 72.8) 17.4 (5.0, 38.8) 10.3 (6.7, 15.1) 11.7 (6.2, 19.5) 9.2 (4.7, 15.8) mPFS, months (95% CI) 8.3 (2.0,11.5) 15.1 (8.1, NR) (2.0, 1.2, 8.3) 2.1 (2.0, 2.1) 2.1 (2.1, 4.0) 2.0 (2.0, 2.1) mOS, months (95% CI) 20.1 (10.3, 37.4) 30.9 (11.1, NR) 9.7 (2.8, 23.8) 11.1 (7.7, 11.9) 13.9 (11.1, 18.2) 6.7 (5.6, 8.1) BEP, biomarker evaluable population; CI, confidence interval; HA, hyperamplification; NR, not reached; ORR, objective response rate; mOS, median overall survival; mPFS, median progression-free survival; TMB-H, high tumor mutational burden; TMB-L, low tumor mutational burden Citation Format: Sanjeev Deva, Michael Millward, Michael Friedlander, Hui K. Gan, Lisa G. Hovarth, Jong-Seok Lee, Andrew Hill, Shahneen Sandhu, Liang Liang, Jingwen Shi, Yun Zhang, Yang Shi, Xiaopeng Ma, Xikun Wu, Zhirong Shen, Jayesh Desai. The combination of hyper-amplification and tumor mutational burden as a pan-cancer biomarker in patients treated with tislelizumab [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr LB511.

Background: The over-expression of CD73 has been linked to many cancers. NZV930, an investigational, CD73-targeting monoclonal antibody (mAb), forms bidentate structures with the CD73 dimer, shutting down the catalytic activity of cell surface and soluble CD73. Taminadenant is an investigational A2AR antagonist and spartalizumab is an anti-PD-1 mAb. Preclinical studies provide compelling antitumor activity when combining CD73, A2AR, and PD-1 blockade. Methods: This first-in-human study (NCT03549000) comprised dose-escalation and dose-expansion parts. Here, we present the dose-escalation results of the four treatment (tx) arms: NZV930 single agent (SA; 60-1000 mg Q2W), NZV930 (200-600 mg Q2W) + spartalizumab (400 mg Q4W) or taminadenant (80-240 mg Q2W), or in combination with spartalizumab (400 mg Q4W) + taminadenant (80-240 mg BID). Eligible pts had selected malignancies, and disease progression following standard therapy. Primary objectives included assessing safety and tolerability and determining the recommended dose for expansion (RDE) of NZV930 SA and its combinations. Secondary objectives were to determine efficacy, characterize the pharmacokinetics (PKs) of NZV930 SA and its combinations, and assess the immunogenicity of spartalizumab and NZV930. Biomarker tumor samples were obtained at screening, C2D1, and C4D1. Results: As of June 10, 2021, 105 pts were enrolled for dose escalation, including pts with CRC (n=63), ovarian cancer (n=15), pancreatic cancer (n=11), NSCLC (n=8), TNBC (n=5), RCC (n=2), and prostate cancer (n=1). Most pts (81%) had been treated with ≥3 lines of prior therapy. In total, 98 pts discontinued, mainly due to disease progression (72%); six were ongoing. At least one tx-related adverse event (TRAE) was reported by 89 pts (85%); these were mostly grade 1-2. A triad of headache, fever, and nausea/emesis was observed after the first infusion of NZV930. Most common TRAEs (≥30%) were headache (67%), nausea and vomiting (32% each), and pyrexia (30%). At least one grade ≥3 TRAE was reported in 15 pts (14%); headache (4%) was most common, accounting for 4/7 DLTs (all grade ≥3). There were no tx-related deaths. Overall, no responses were reported; 12 pts (11%) had stable disease and 69 pts (66%) had progressive disease. NZV930 has good PK properties, with target-mediated drug disposition at lower doses, which normalize to typical IgG-like PKs at higher doses. Biomarker data confirm CD73 target engagement in plasma. Adenosine pathway modulation in tumors and plasma was seen post-NZV930 tx. Conclusions: NZV930 reduced adenosine levels in plasma and tumors. The RDE of NZV930 SA or in combination with spartalizumab and/or taminadenant is 600 mg Q2W with a step-up dosing regimen. NZV930 SA and its combinations exhibited a tolerable safety profile in multiple advanced solid tumors and showed good PK properties. Citation Format: Siqing Fu, Udai Banerji, Philippe L. Bedard, Aitana Calvo Ferrándiz, Alberto Chiappori, Jayesh Desai, Rahima Jamal, Desamparados Roda Perez, Noboru Yamamoto, Erica Vieira, Gabrielle Wong, Kulandayan K. Subramanian, Shunguang Wang, Britta Mueller, Javier A. Otero, Si-Lin Koo. A phase I/Ib study of the safety and preliminary efficacy of NZV930 alone and in combination with spartalizumab and/or taminadenant in patients (pts) with advanced malignancies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT503.

Introduction: Sotorasib, a first-in-class KRASG12C inhibitor, has been FDA-approved for adults with KRAS p.G12C-mutated locally advanced or metastatic NSCLC who received prior systemic therapies based on the Phase 1/2 global, single-arm CodeBreaK100 trial. We will report the longest follow-up for a KRASG12C inhibitor, including 2-year survival, safety, and genomic profiles associated with durable clinical benefit. Methods: Sotorasib was administered orally at 960 mg once daily to patients who progressed on prior therapies and had KRAS p.G12C-mutated locally advanced, metastatic NSCLC. Primary endpoint was objective response rate (ORR) assessed by central review. Key secondary endpoints included duration of response (DOR), progression-free survival (PFS), overall survival (OS), and safety. In an exploratory analysis, baseline tumor tissue and/or plasma samples were collected and analyzed for genomic alterations. Tumor samples were analyzed for PD-L1 levels to evaluate correlates with prolonged tumor response, defined as patients with PFS ≥ 12 months, in comparison with those with PFS ≤ 3 months. Results: In the first analysis of the combined Phase 1 and Phase 2 study (N=174), the median number of prior lines of therapy was 2.0 (range 1-4+). 90.2% received prior anti-PD1 or anti PD-L1 treatment; 82.8% received both prior platinum-based chemotherapy and anti-PD1/PD-L1. Updated ORR by central review was 40.7% (95% CI: 33.2, 48.4) and median DOR was 12.3 months (7.1, 14.6). Median PFS and OS was 6.3 months (95% CI: 5.3, 8.2) and 12.5 months (10.0, 17.8). One and two-year OS was 50.8% and 30.3%. Sotorasib was well-tolerated in the long-term with mild and manageable toxicities, and no new safety signals emerged. Prolonged tumor response was observed across PD-L1 expression, including in tumors with low PDL-1 expression and STK11 co-mutation that may derive less benefit from immunotherapy. Conclusions: In the longest follow-up of any KRASG12C inhibitor, sotorasib continued to demonstrate a favorable safety profile and durable efficacy, including a 2-year OS observed in 30% of patients. Current analyses continue to support long-term clinical benefit across subgroups in patients with KRAS p.G12C-mutated NSCLC, and additional biomarker data will be presented. Citation Format: Grace K. Dy, Ramaswamy Govindan, Vamsidhar Velcheti, Gerald S. Falchook, Antoine Italiano, Juergen Wolf, Adrian G. Sacher, Toshiaki Takahashi, Suresh S. Ramalingam, Christophe Dooms, Dong-Wan Kim, Alfredo Addeo, Jayesh Desai, Martin Schuler, Pascale Tomasini, Qui Tran, Simon Jones, Agnes Ang, Abraham Anderson, Antreas A. Hindoyan, David S. Hong, Bob T. Li. Long-term outcomes with sotorasib in pretreated KRASp.G12C-mutated NSCLC: 2-year analysis of CodeBreaK100 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT008.

9537 Background: Programmed death receptor-1 (PD-1)–blocking antibodies are approved as monotherapy treatment for patients (pts) with metastatic or locally advanced cutaneous squamous cell carcinoma (CSCC) who are not candidates for curative surgery or radiation. Cosibelimab is a high-affinity, fully human programmed death ligand-1 (PD-L1)–blocking antibody with a functional Fc domain capable of inducing antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) against tumor cells. Study CK-301-101 (NCT03212404) is a global, multicenter, multicohort, pivotal trial that enrolled pts with select advanced cancers for treatment with cosibelimab. Here we present the primary analysis of the registration-enabling expansion cohort in pts with metastatic CSCC. Methods: Adult pts with Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 who had metastatic (nodal and/or distant) CSCC not amenable to local therapy were eligible to participate. Cosibelimab was administered as a fixed dose of 800 mg every 2 weeks (Q2W) intravenously. The primary endpoint was confirmed objective response rate (ORR; complete response [CR] + partial response [PR]) assessed by independent central review according to Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 and the key secondary endpoint was duration of response. Results: Seventy-eight pts with metastatic CSCC were treated with cosibelimab and comprise the efficacy and safety populations (59M/19F; median age: 71 years). The confirmed ORR was 47.4% (95% CI: 36.0, 59.1; 6 CRs and 31 PRs) and the median duration of response was not reached at the time of data cutoff (median duration of follow-up: 15.2 months), with 76% of responses ongoing (range: 1.4-31.8+ months). The Kaplan–Meier estimated probability of maintaining a response at 6 and 24 months was 88.1% and 72.5%, respectively. Treatment-related adverse events (TRAEs) were reported in 54 pts (69.2%); 7 pts (9.0%) experienced at least 1 grade 3 TRAE (no grade 4 or grade 5 TRAEs were reported) with the most common being increased serum lipase in 2 pts. Conclusions: Treatment with cosibelimab monotherapy resulted in a robust ORR with durable responses and demonstrated a predictable and manageable safety profile in pts with metastatic CSCC, supporting its use in the treatment of this cancer. Clinical trial information: NCT03212404.

3006 Background: NRG1 fusions are rare oncogenic drivers found in ̃0.2% of all solid tumors. These fusions elicit ERBB3/HER3 overactivation to drive tumor growth and cancer cell survival. Currently there are no approved targeted therapies for NRG1 fusion-positive tumors. Furthermore, patients (pts) with tumors harboring NRG1 fusions have poor outcomes with standard therapies. Seribantumab is a fully human anti-HER3 IgG2 monoclonal antibody that suppressed tumor growth in NRG1 fusion-driven preclinical models. Here, we present initial clinical data from the CRESTONE study (NCT04383210). Methods: CRESTONE is a Phase 2, global, multicenter, open-label study of seribantumab in adult pts with locally advanced or metastatic solid tumors harboring NRG1 fusions. A dose ranging phase established the RP2D as a 3g once weekly (QW) intravenous dose administered until treatment discontinuation criteria are met. In the expansion phase, cohort 1 will enroll at least 55 pts who had received at least one prior therapy and are naïve to ERBB-targeted therapy. Exploratory cohorts 2 or 3 will enroll pts previously treated with ERBB-targeted therapies and/or tumors harboring additional molecular alterations. The primary endpoint is objective response rate (ORR) by independent central review per RECIST v1.1. Initial data from cohort 1 pts who received seribantumab 3g QW with investigator (INV)-assessed response per RECIST v1.1 are reported. Results: By JAN-13-2022, 12 pts have received seribantumab 3g QW in cohort 1. Median age was 65 years (range 44–76), 67% were female, and median number of prior therapies was 1 (range 1–5). 92% (11/12) of pts had non-small cell lung cancer (NSCLC); 5 different NRG1 fusion partners ( ATP1B1, CD74, ITG B1, SDC4, SLC3 A2) were reported by local next-generation sequencing tests. Among 10 pts evaluable for INV-assessed response, the confirmed ORR was 30%, and the disease control rate was 90% (1 complete response, 2 partial responses, 6 stable disease, 1 progressive disease). 58% (7/12) of pts remain on study treatment, including 2 pts with NSCLC who achieved objective responses with an ongoing duration of response of 6 and 8.5 months. Seribantumab 3g QW was well tolerated with no drug discontinuations or dose reductions. Across all cohorts (n = 29), the most frequently (≥20%) reported treatment-related adverse events (TRAEs) were diarrhea (38%), fatigue (34%), and rash (24%), all were grade 1 or 2. One grade 3 TRAE of vomiting occurred; there were no Grade 4 or 5 TRAEs. Efficacy analysis is ongoing and updated efficacy data from evaluable pts in cohort 1 will be presented. Conclusions: Initial data indicate seribantumab induced durable responses in advanced solid tumors harboring NRG1 fusions and has a favorable safety profile. These data support the continued evaluation of seribantumab in NRG1 fusion-positive solid tumors in the ongoing CRESTONE study. Clinical trial information: NCT04383210.

Author(s): Gelderblom, Hans; Wagner, Andrew J; Tap, William D; Palmerini, Emanuela; Wainberg, Zev A; Desai, Jayesh; Healey, John H; van de Sande, Michiel AJ; Bernthal, Nicholas M; Staals, Eric L; Peterfy, Charles G; Frezza, Anna Maria; Hsu, Henry H; Wang, Qiang; Shuster, Dale E; Stacchiotti, Silvia | Abstract: BackgroundThe objective of this study was to report on the long-term effects of pexidartinib on tenosynovial giant cell tumor (TGCT).MethodsThis was a pooled analysis encompassing 3 pexidartinib-treated TGCT cohorts: 1) a phase 1 extension study (NCT01004861; 1000 mg/d; n = 39), 2) ENLIVEN patients randomized to pexidartinib (1000 mg/d for 2 weeks and then 800 mg/d; n = 61), and 3) ENLIVEN crossover patients (NCT02371369; 800 mg/d; n = 30). Eligible patients were 18 years old or older and had a histologically confirmed TGCT that was unresectable and symptomatic. Efficacy endpoints included the best overall response (complete or partial response) and the duration of response (DOR) by the Response Evaluation Criteria in Solid Tumors (RECIST) and the tumor volume score (TVS). The safety assessment included the frequency of treatment-emergent adverse events (TEAEs) and hepatic laboratory abnormalities (aminotransferase elevations and mixed/cholestatic hepatotoxicity). The data cutoff was May 31, 2019.ResultsOne hundred thirty patients with TGCT received pexidartinib (median treatment duration, 19 months; range, 1 to 76+ months); 54 (42%) remained on treatment at the end of the analysis (26 months after initial data cut of March 2017). The RECIST overall response rate (ORR) was 60%; the TVS ORR was 65%. The median times to response were 3.4 (RECIST) and 2.8 months (TVS), with 48 of the responding patients (62%) achieving a RECIST partial response by 6 months and with 72 (92%) doing so by 18 months. The median DOR was reached for TVS (46.8 months). Reported TEAEs were mostly low-grade, with hair color changes being most frequent (75%). Most liver abnormalities (92%) were aminotransferase elevations; 4 patients (3%) experienced mixed/cholestatic hepatotoxicity (all within the first 2 months of treatment), which was reversible in all cases (recovery spanned 1-7 months).ConclusionsThis study demonstrates the prolonged efficacy and tolerability of long-term pexidartinib treatment for TGCT.

© 2020 The Author(s)., Sarcomas are a heterogeneous group of malignancies with mesenchymal lineage differentiation. The discovery of neurotrophic tyrosine receptor kinase (NTRK) gene fusions as tissue-agnostic oncogenic drivers has led to new personalized therapies for a subset of patients with sarcoma in the form of tropomyosin receptor kinase (TRK) inhibitors. NTRK gene rearrangements and fusion transcripts can be detected with different molecular pathology techniques, while TRK protein expression can be demonstrated with immunohistochemistry. The rarity and diagnostic complexity of NTRK gene fusions raise a number of questions and challenges for clinicians. To address these challenges, the World Sarcoma Network convened two meetings of expert adult oncologists and pathologists and subsequently developed this article to provide practical guidance on the management of patients with sarcoma harboring NTRK gene fusions. We propose a diagnostic strategy that considers disease stage and histologic and molecular subtypes to facilitate routine testing for TRK expression and subsequent testing for NTRK gene fusions., GDD was supported in part by the Ludwig Center at Harvard; the Dr Miriam and Sheldon G. Adelson Medical Research Foundation; and the Pan Mass Challenge (no grant numbers). IMS is supported by the National Institutes of Health/National Cancer Institute (grant number K08 CA241085). JYB was supported by NetSARC (INCA & DGOS) and RREPS (INCA & DGOS), RESOS (INCA & DGOS), EURACAN (EC 739521), LYRICAN (INCA-DGOS-INSERM 12563), LabEx DEvweCAN (ANR-10-LABX-0061), Institut Convergence PLASCAN (17-CONV-0002), RHU4 DEPGYN (ANR-18-RHUS-0009).

BACKGROUND: No therapies for targeting KRAS mutations in cancer have been approved. The KRAS p.G12C mutation occurs in 13% of non–small-cell lung cancers (NSCLCs) and in 1 to 3% of colorectal cancers and other cancers. Sotorasib is a small molecule that selectively and irreversibly targets KRAS(G12C). METHODS: We conducted a phase 1 trial of sotorasib in patients with advanced solid tumors harboring the KRAS p.G12C mutation. Patients received sotorasib orally once daily. The primary end point was safety. Key secondary end points were pharmacokinetics and objective response, as assessed according to Response Evaluation Criteria in Solid Tumors (RECIST), version 1.1. RESULTS: A total of 129 patients (59 with NSCLC, 42 with colorectal cancer, and 28 with other tumors) were included in dose escalation and expansion cohorts. Patients had received a median of 3 (range, 0 to 11) previous lines of anticancer therapies for metastatic disease. No dose-limiting toxic effects or treatment-related deaths were observed. A total of 73 patients (56.6%) had treatment-related adverse events; 15 patients (11.6%) had grade 3 or 4 events. In the subgroup with NSCLC, 32.2% (19 patients) had a confirmed objective response (complete or partial response) and 88.1% (52 patients) had disease control (objective response or stable disease); the median progression-free survival was 6.3 months (range, 0.0+ to 14.9 [with + indicating that the value includes patient data that were censored at data cutoff]). In the subgroup with colorectal cancer, 7.1% (3 patients) had a confirmed response, and 73.8% (31 patients) had disease control; the median progression-free survival was 4.0 months (range, 0.0+ to 11.1+). Responses were also observed in patients with pancreatic, endometrial, and appendiceal cancers and melanoma. CONCLUSIONS: Sotorasib showed encouraging anticancer activity in patients with heavily pretreated advanced solid tumors harboring the KRAS p.G12C mutation. Grade 3 or 4 treatment-related toxic effects occurred in 11.6% of the patients. (Funded by Amgen and others; CodeBreaK100 ClinicalTrials.gov number, NCT03600883.)

Objectives Tumor‐infiltrating lymphocytes (TIL), particularly CD8+ TILs in patients with colorectal cancer (CRC), are highly prognostic in the early‐disease stages (I‐II). In metastatic disease (stage IV; mCRC), their influence is less well defined. It has presumably failed to contain tumor cells to the primary site; however, is this evident? We explored the prognostic impact of TILs at the primary site in patients who presented de novo with mCRC. Methods Treatment‐naïve patients (109) with mCRC were assessed for CD8+ TILs and PD‐L1 expression. Microsatellite instability (MSI) was evaluated by IHC for PMS2 and MSH6 proteins and/or by PCR using the Bethesda panel. Results Microsatellite instability‐high tumors had significantly more CD8+ TILs, with no significant survival advantage observed between MSI‐H and microsatellite stable (MSS) tumors (12 vs 19 months, P = 0.304). TIL density for all cases had no impact on OS (low: 20 vs high: 13 months, P = 0.426), while PD‐L1 of 1% or higher was associated with reduced mean survival (9.6 vs 18.9 months; P = 0.038). MSI‐H tumors and associated immune cells had higher PD‐L1 expression than in MSS cases. A positive correlation between PD‐L1 on immune cells and CD8+ve TILs was found. A subset of MSS tumors had relatively high TILs approximating that of MSI‐H tumors. Conclusion In contrast to early‐stage CRC, the immune response in primary tumors of patients with de novo mCRC does not appear to influence survival. A subgroup of MSS tumors was identified with increased TILs/PD‐L1 comparable to MSI‐H tumors, traditionally not be considered for immune checkpoint blockade and perhaps should be., Unlike early‐stage colorectal cancer (CRC), the immune response in primary tumors of patients with de novo mCRC does not appear to influence survival despite MSI‐H tumors having higher tumor infiltrating lymphocytes (TILs). This unique cohort of patients with synchronous mCRC by definition represents the breakdown of immune containment of the primary tumor. Despite this, we also identified a subgroup of MSS tumors with a high TILs comparable to MSI‐H tumors and this group traditionally would not be considered for immune checkpoint blockade, and perhaps should be.

Background: KRAS mutations are found in 20–30 % of non-small cell lung cancers (NSCLC) and were traditionally considered undruggable. KRASG12C mutation confers sensitivity to KRASG12C covalent inhibitors, however its prognostic impact remains unclear. This study assesses the frequency, clinical features, prevalence of brain metastases and outcomes in KRASG12C NSCLC in a real-world setting. Methods: Patients enrolled in the prospective Thoracic Malignancies Cohort (TMC) between July 2012 to October 2019 with recurrent/metastatic non-squamous NSCLC, available KRAS results, and without EGFR/ALK/ROS1 gene aberrations, were selected. Data was extracted from TMC and patient records. Clinicopathologic features, treatment and overall survival (OS) was compared for KRAS wildtype (KRASWT) and KRAS mutated (KRASmut); and KRASG12C and other (KRASother) mutations. Results: Of 1386 NSCLC patients, 1040 were excluded: non-metastatic/recurrent (526); unknown KRAS status (356); ALK/EGFR/ROS1 positive (154); duplicate (4). Of 346 patients analysed, 144 (42 %) were KRASmut, of whom 65 (45 %) were KRASG12C. All patients with KRASG12C were active or ex-smokers, compared to 92 % of KRASother and 83 % of KRASWT. The prevalence of brain metastases during follow-up was similar between KRASmut and KRASWT (33 % vs 40 %, p = 0.17), and KRASG12C and KRASother (40 % vs 41 %, p = 0.74). The proportion of patients receiving one or multiple lines of systemic therapy was comparable. OS was similar between KRASmut and KRASWT (p = 0.54), and KRASG12C and KRASother (p = 0.39). Conclusion: Patients with KRASmut and KRASWT, and KRASG12C and KRASother NSCLC have comparable clinical features, treatment and survival. While not prognostic, KRASG12C may be an important predictive biomarker as promising KRASG12C covalent inhibitors continue to be developed.

Colorectal cancer (CRC) is the second leading cause of cancer-related mortality in the USA. Over 80% of CRC develop from adenomatous polyps. Hence, early treatment and prevention of adenomas would lead to a significant decrease of disease burden for CRC. MYB is a transcription factor that is overexpressed in both precancerous adenomatous polyps and colorectal cancer, and hence an ideal immunotherapeutic target. We have developed a cancer vaccine, TetMYB, that targets MYB and aim to evaluate its efficacy in the prophylactic and therapeutic management of adenomatous polyps. Six- to eight-week-old Apcmin/+ (Familial Adenomatous Polyposis model) and Apc580S (sporadic model) C57BL/6 mice were used. The Apcmin/+ mice are carried a germline mutation of one Apc allele whereas the Apc580S model has an inducible silencing of one Apc allele, when exposed to tamoxifen, via the Cre-Lox recombination enzyme system. In the prophylactic treatment group, Apcmin/+ and Apc580S C57BL/6 mice were vaccinated and surveyed for clinical signs of distress. Number of adenoma and survival were measured. In the therapeutic cohort, Apc580S C57BL/6 mice were given tamoxifen-laced food to activate Cre-Lox recombinase mediated silencing of one Apc allele and thus inducing adenoma development. Following adenoma detection, mice were vaccinated with TetMYB and treated with anti-PD-1 antibody and were analyzed for overall survival. In both the prophylactic and therapeutic setting, mice vaccinated with TetMYB had a significantly improved outcome, with the vaccinated Apcmin/+ mice having a median survival benefit of 70 days (p = 0.008) and the vaccinated Apc580S mice having a mean survival benefit of 134 days (p = 0.01) over the unvaccinated mice. In the prophylactic cohort, immunofluorescence confirmed a stronger cytotoxic CD8+ T cell infiltrate in the vaccinated group, implying an anti-tumor immune response. In the therapeutic cohort, vaccinated Apc580S mice showed significantly reduced adenoma progression rate compared to the unvaccinated mice (p = 0.0005). TetMYB vaccine has shown benefit in a prophylactic and therapeutic setting in the management of colonic adenoma in a murine model. This will form the basis for a future clinical trial to prevent and treat colonic adenomatous polyps.

BackgroundThe programmed cell death-1/programmed cell death ligand-1 (PD-1/PD-L1) axis plays a central role in suppressing antitumor immunity; axis dysregulation can be used by cancer cells to evade the immune system. Tislelizumab, an investigational monoclonal antibody with high affinity and binding specificity for PD-1, was engineered to minimize binding to FcγR on macrophages to limit antibody-dependent phagocytosis, a potential mechanism of resistance to anti-PD-1 therapy. The aim of this phase IA/IB study was to investigate the safety/tolerability, antitumor effects and optimal dose and schedule of tislelizumab in patients with advanced solid tumors.MethodsPatients (aged ≥18 years) enrolled in phase IA received intravenous tislelizumab 0.5, 2, 5 or 10 mg/kg every 2 weeks; 2 or 5 mg/kg administered every 2 weeks or every 3 weeks; or 200 mg every 3 weeks; patients in phase IB received 5 mg/kg every 3 weeks. Primary objectives were to assess tislelizumab’s safety/tolerability profile by adverse event (AE) monitoring and antitumor activity using RECIST V.1.1. PD-L1 expression was assessed retrospectively with the VENTANA PD-L1 (SP263) Assay.ResultsBetween May 2015 and October 2017, 451 patients (n=116, IA; n=335, IB) were enrolled. Fatigue (28%), nausea (25%) and decreased appetite (20%) were the most commonly reported AEs. Most AEs were grade 1–2 severity; anemia (4.9%) was the most common grade 3–4 AE. Treatment-related AEs led to discontinuation in 5.3% of patients. Grade 5 AEs were reported in 14 patients; 2 were considered related to tislelizumab. Pneumonitis (2%) and colitis (1%) were the most common serious tislelizumab-related AEs. As of May 2019, 18% of patients achieved a confirmed objective response in phase IA and 12% in phase IB; median follow-up duration was 13.6 and 7.6 months, respectively. Pharmacokinetics, safety and antitumor activity obtained from both phase IA and IB determined the tislelizumab recommended dose; ultimately, tislelizumab 200 mg intravenous every 3 weeks was the dose and schedule recommended to be taken into subsequent clinical trials.ConclusionsTislelizumab monotherapy demonstrated an acceptable safety/tolerability profile. Durable responses were observed in heavily pretreated patients with advanced solid tumors, supporting the evaluation of tislelizumab 200 mg every 3 weeks, as monotherapy and in combination therapy, for the treatment of solid tumors and hematological malignancies.Trial registration numberNCT02407990.

PURPOSE Lifirafenib is an investigational, reversible inhibitor of B-RAFV600E, wild-type A-RAF, B-RAF, C-RAF, and EGFR. This first-in-human, phase I, dose-escalation/dose-expansion study evaluated the safety, tolerability, and efficacy of lifirafenib in patients with B-RAF– or K-RAS/N-RAS–mutated solid tumors. METHODS During dose escalation, adult patients with histologically/cytologically confirmed advanced solid tumors received escalating doses of lifirafenib. Primary end points were safety/tolerability during dose escalation and objective response rate in preselected patients with B-RAF and K-RAS/N-RAS mutations during dose expansion. RESULTS The maximum tolerated dose was established as 40 mg/d; dose-limiting toxicities included reversible thrombocytopenia and nonhematologic toxicity. Across the entire study, the most common grade ≥ 3 treatment-emergent adverse events were hypertension (n = 23; 17.6%) and fatigue (n = 13; 9.9%). One patient with B-RAF–mutated melanoma achieved complete response, and 8 patients with B-RAF mutations had confirmed objective responses: B-RAFV600E/K melanoma (n = 5, including 1 patient treated with prior B-RAF/MEK inhibitor therapy), B-RAFV600E thyroid cancer/papillary thyroid cancer (PTC; n = 2), and B-RAFV600E low-grade serous ovarian cancer (LGSOC; n = 1). One patient with B-RAF–mutated non–small-cell lung cancer (NSCLC) had unconfirmed partial response (PR). Patients with K-RAS–mutated endometrial cancer and K-RAS codon 12–mutated NSCLC had confirmed PR (n = 1 each). No responses were seen in patients with K-RAS/N-RAS–mutated colorectal cancer (n = 20). CONCLUSION Lifirafenib is a novel inhibitor of key RAF family kinases and EGFR, with an acceptable risk-benefit profile and antitumor activity in patients with B-RAFV600–mutated solid tumors, including melanoma, PTC, and LGSOC, as well as K-RAS–mutated NSCLC and endometrial carcinoma. Future comparisons with first-generation B-RAF inhibitors and exploration of lifirafenib alone or as combination therapy in patients with selected RAS mutations who are resistant/refractory to first-generation B-RAF inhibitors are warranted.

TPS211 Background: Approximately 10% of patients (pts) with mCRC have BRAF mutations (mostly V600E). First-line tx options for BRAFV600E mCRC are limited to cytotoxic chemotherapy ± anti-VEGF or anti-EGFR; or immune checkpoint inhibitors in pts with MSI-H tumors. In Europe, Japan, and USA, the combination of BRAF inhibitor enco + EGFR inhibitor cet is approved for tx of BRAFV600E mCRC after prior therapy. In BEACON CRC, enco + cet resulted in a median overall survival (OS) of 9.3 months (95% confidence interval [CI]: 8.0–11.3) and an objective response rate (ORR) of 19.5% (95% CI: 14.5%–25.4%) in previously treated pts with BRAFV600E mCRC (median follow-up: 12.8 months); 57.4% of pts had grade 3/4 adverse events (AEs), and 9% discontinued due to AEs. Given the poor prognosis of pts with BRAFV600E mCRC and based on the efficacy and tolerability of enco + cet from BEACON CRC, the BREAKWATER study will evaluate the efficacy and safety of enco + cet ± chemotherapy in tx-naive pts with BRAFV600E mCRC. Methods: BREAKWATER is an open-label, global, multicenter, randomized, phase 3 study with a safety lead-in (SLI). Approximately 60 and 870 pts will be enrolled in the SLI and phase 3 parts of the study, respectively. Pts must have mCRC with BRAF V600E-mutation (determined using tumor tissue or blood); ECOG performance status 0/1; and adequate bone marrow, hepatic, and renal function. Pts in the SLI must have evaluable disease (RECIST v1.1) and have received ≤ 1 prior tx regimen; those previously treated with a BRAF or EGFR inhibitor, or both oxaliplatin and irinotecan, will be excluded. Pts in the phase 3 study must have measurable disease and be tx naive for metastatic disease. Study tx and endpoints are shown in the table. Enrollment began on 06-Jan-2021. Clinical trial information: NCT04607421. [Table: see text]

162 Background: In the randomized phase 3 BEACON study, encorafenib + binimetinib + cetuximab (triplet) and encorafenib + cetuximab (doublet) regimens improved overall survival (OS) and objective response rate (ORR) versus standard of care (control) in patients (pts) with previously treated BRAF V600E-mutant metastatic colorectal cancer. To identify whether detection of a BRAF V600E mutation in baseline circulating tumor DNA (ctDNA) correlated with response, we evaluated the status and allele frequency of BRAF V600E compared with clinical outcomes. Methods: Plasma samples were collected at Cycle 1 Day 1 and end of treatment for ctDNA analysis and analyzed using GuardantOMNI. Variant allele frequency (VAF) of BRAF V600E was grouped into high (> median) and low (≤median) categories. Low VAF samples included those where BRAF V600E mutation was not detected or no ctDNA was detected. ORR, based on blinded independent central review, and OS were compared between treatment arms according to VAF levels. ORR comparisons used Chi-square test and logistic regression. OS was summarized using the Kaplan-Meier method. HRs and 95% CIs were estimated using a Cox model. Additional correlation analyses between BRAF V600E status in baseline tumor tissue, as well as clonality, will be presented. Results: Baseline plasma samples were analyzed from 544 of 631 pts in the ctDNA analysis: 88.3% (196/222) in the triplet arm, 86.6% (187/216) in the doublet arm, and 83.4% (161/193) in the control arm. BRAF V600E mutations were detected in 90.4% (492/544) of pts (90.3% [177/196] triplet, 90.4% [169/187] doublet, and 90.7% [146/161] control). Pts with BRAF V600E mutations with high VAF had significantly ( P≤0.0001) increased ORR (95% CI) in the triplet and doublet arms (27.3% [19.5–36.8] and 15.9% [9.7–25.0], respectively) compared with control (0% [0.0–4.3]). Similar response trends were observed in pts with BRAF V600E mutations with low VAF (triplet: 28.9% [20.8–38.9]; doublet: 25.3% [17.7–34.6]; control: 5.3% [2.1–12.8]). OS decreased in BRAF V600E pts with high VAF (median OS [95% CI]: triplet 7.2 [6.0–8.0] months, n = 99; doublet 5.4 [4.4–6.1] months, n = 88; control 4.2 [3.4–4.8] months, n = 85) compared with pts with low VAF (triplet 14.8 [10.2–19.8] months, n = 97; doublet 14.8 [11.7–23.0] months, n = 99; control 9.3 [7.5–11.3] months, n = 76). Conclusions: ctDNA analyses showed the majority of pts in BEACON analyzed at baseline had a detectable BRAF V600E mutation. Increased response rates were observed in pts treated with triplet or doublet therapy compared with control, independent of VAF. Pts with a higher VAF for BRAF V600E may have a worse prognosis. Clinical trial information: NCT04607421.

134 Background: Currently, there are no 1L tx options indicated specifically for patients (pts) with BRAFV600E mCRC. Based on results of BEACON CRC (NCT02928224), BRAF inhibitor encorafenib + EGFR inhibitor cetuximab was approved for tx of previously treated pts with BRAFV600E mCRC. BREAKWATER (NCT04607421), an ongoing, open-label, global, multicenter, randomized phase 3 study, evaluates 1L EC ± chemotherapy for tx of pts with BRAFV600E mCRC. Here we present preliminary data on safety and pharmacokinetics (PK) from the BREAKWATER SLI, which aimed to identify the chemotherapy backbone for EC for the phase 3 portion of BREAKWATER. Methods: SLI inclusion criteria were BRAFV600E mCRC (determined using tumor tissue or blood); evaluable disease (RECIST v1.1); ≤1 prior systemic tx for mCRC; European Cooperative Oncology Group performance status (ECOG PS) 0/1; and adequate bone marrow, hepatic, and renal function. Pts previously treated with BRAF/EGFR inhibitors or both oxaliplatin and irinotecan were excluded. Pts received encorafenib 300 mg daily + cetuximab 500 mg/m2 every 2 weeks (Q2W) + either FOLFIRI Q2W or mFOLFOX6 Q2W in 28-day cycles. The primary endpoint was frequency of dose-limiting toxicities (DLTs). PK were a secondary endpoint. Data cutoff date: Sep 13, 2021. Results: 57 pts were enrolled (EC + FOLFIRI, n = 30; EC + mFOLFOX6, n = 27). Median (range) age was 57 (28–78) years; 25% were Asian; 65% had ECOG PS 0; 37% had ≥3 organs involved; 58% were treatment naive. At cutoff date, tx was ongoing in 45 (79%) pts. Median (range) duration of tx for encorafenib in EC + FOLFIRI and EC + mFOLFOX6 was 15 (0–31) and 14 (0–27) weeks, respectively. One DLT was observed: grade 4 neutropenia in 1 pt in EC + FOLFIRI. Tx-emergent all-cause serious adverse events (AEs) occurred in 20% and 19% and grade ≥3 AEs in 33% and 56% of pts in EC + FOLFIRI and EC + mFOLFOX6, respectively. The table shows frequent (all grade in ≥30% pts or grade ≥3 in ≥10% with either tx) tx-emergent all-cause AEs. One pt died due to disease progression. In EC + FOLFIRI, in the presence of steady-state encorafenib, AUCinf of irinotecan and its active metabolite, SN-38, significantly decreased ̃25% and ̃40%, respectively, compared with values in the absence of encorafenib. In EC + mFOLFOX6, oxaliplatin PK was not significantly altered by steady-state encorafenib. Conclusions: Based on these data, BREAKWATER phase 3 will compare EC ± mFOLFOX6 with mFOLFOX6/FOLFOXIRI/CAPOX ± bevacizumab. Clinical trial information: NCT04607421. [Table: see text]

For many cancers, adolescents and young adults (AYA) have worse outcomes than for children and adults. Many factors may contribute to the AYA survival gap, including differences in biology, therapeutic intent, and adherence to therapy. It has been observed that male AYAs have poorer outcomes than females. The purpose of this work was to test the proposition that gender-related pharmacologic factors may account for a component of the AYA survival gap. A prospective, multi-institutional pharmacologic study of 79 patients in total with chemosensitive cancers (Ewing sarcoma, osteosarcoma and Hodgkin lymphoma) was conducted, with conventional doxorubicin treatment. Pharmacokinetic data of 13 children, 40 AYAs and 13 adults were valid for analysis. Population pharmacokinetics models were developed for doxorubicin and its metabolite doxorubicinol based on the data created in this study. Consequently, model-based analysis was conducted to investigate the relevant topics. The clearance of doxorubicinol (normalized to body surface area), the main active metabolite of doxorubicin, appears faster in male AYAs than female (p = 0.04, 95% CI 0.1–3.9 L/h). The exposure of doxorubicinol (normalized to dose) is lower in male AYA than female (p = 0.03, 95% CI − 0.005 to − 0.0002 h/L). These might be correlated to the observed difference on nadir neutrophil count between male AYA and female (p = 0.027, 95% CI 0.09–1.4). Gender-related differences in doxorubicin pharmacology may account for worse outcomes for male AYAs with chemosensitive cancers compared to females. These findings may reduce the AYA survival gap compared to other age groups.

ADP-ribosylation is an important posttranslational protein modification that regulates diverse biological processes, controlled by dedicated transferases and hydrolases. Here, we show that frequent deletions (∼30%) of the MACROD2 mono-ADP-ribosylhydrolase locus in human colorectal cancer cause impaired PARP1 transferase activity in a gene dosage–dependent manner. MACROD2 haploinsufficiency alters DNA repair and sensitivity to DNA damage and results in chromosome instability. Heterozygous and homozygous depletion of Macrod2 enhances intestinal tumorigenesis in ApcMin/+ mice and the growth of human colorectal cancer xenografts. MACROD2 deletion in sporadic colorectal cancer is associated with the extent of chromosome instability, independent of clinical parameters and other known genetic drivers. We conclude that MACROD2 acts as a haploinsufficient tumor suppressor, with loss of function promoting chromosome instability, thereby driving cancer evolution. Significance: Chromosome instability (CIN) is a hallmark of cancer. We identify MACROD2 deletion as a cause of CIN in human colorectal cancer. MACROD2 loss causes repression of PARP1 activity, impairing DNA repair. MACROD2 haploinsufficiency promotes CIN and intestinal tumor growth. Our results reveal MACROD2 as a major caretaker tumor suppressor gene. Cancer Discov; 8(8); 988–1005. ©2018 AACR. See related commentary by Jin and Burkard, p. 921. This article is highlighted in the In This Issue feature, p. 899

Background Immuno-oncology (IO) is rapidly evolving in early drug development. We aimed to develop and prospectively validate a prognostic index for patients treated in IO phase I trials to assist with patient selection. Methods The development cohort included 192 advanced solid tumor patients treated in 13 IO phase I trials, targeting immune checkpoint and/or co-stimulatory molecules. A prognostic scoring system was developed from multivariate survival analysis of 10 clinical factors, and subsequently validated in two independent validation cohorts (n = 152 and n = 80). Results In the development cohort, median age was 57.5 years (range = 20.4–84.8 years). Median progression-free survival and overall survival (OS) were 13.4 and 73.6 weeks, respectively, 90-day mortality was 16%, and overall response rate was 20%. In multivariate analysis, Eastern Cooperative Oncology Group performance status greater than or equal to 1 (hazard ratio [HR] = 3.2, 95% confidence interval [CI] = 1.8 to 5.7; P Conclusions The PM-IPI is a validated prognostic score for patients treated in phase I IO trials and may aid in improving patient selection.

Immune checkpoint inhibitor blockade has vastly changed treatment paradigms and improved outcomes of many solid organ malignancies. The achievements of the last decade have transformed the outcomes of several tumour types, most notably metastatic melanoma. There are, however, still large numbers of patients who receive checkpoint inhibitor therapy and do not respond. In addition to potential lack of efficacy, checkpoint inhibitors also come with a unique and sometimes devastating side-effect profile. There exists a strong need for biomarkers to accurately predict response, improve treatment selection and avoid exposing patients to toxicity where there is minimal likelihood of response. There is a wide range of methodologies investigating predictive biomarkers in this space; in this review, we address the major putative biomarkers of interest. These include conventional serum tests such as lymphocyte indices and lactate dehydrogenase, and more novel research markers such as interleukin-6 and T receptor clonality. We discuss tumorous factors that may be of interest in certain tumour types, and finally gene expression profiling. Significant research continues into many of these potential predictive biomarkers in response to the emergent need to better select patients who will benefit from treatment.