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725 Background: Immune checkpoint blockade (ICB) has a modest signal in the treatment of patients with genomically unselected pancreatic cancer (PDAC). Synergistic effects of combined radiotherapy and ICB are postulated. Preliminary results of a phase 1/2 trial of anti-PD-L1 antibody durvalumab (D) and SABR in locally advanced (LA) and borderline resectable PDAC (Tuli, AACR; 2019; Abstr B58), noted SABR and D to be safe and tolerable following induction chemotherapy. We sought to further evaluate the tolerability and efficacy of D and SABR, in LA PDAC. Methods: A single-arm, open-label phase 2 trial was conducted at Memorial Sloan Kettering (MSK). Key eligibility: histologically confirmed LA unresectable PDAC, with stable or responding disease following 4-6 months (m) of FOLFIRINOX (FFX), ECOG 0-2. Therapy: D and SABR; D dosed on day 1 750mg x 4 doses Q14 days, and subsequently 1500mg Q 28 days x 11 doses (1 year total), or until progression of disease (POD), or limiting toxicity. All patients received MRI adaptive ablative radiation, 50Gy in 5 fractions between doses 1 and 2 of D. Primary endpoint: 6-m progression free survival (6 m PFS) by RECIST v1.1. Secondary endpoints were Duration of Response, Overall Response Rate (ORR), CA 19-9 response, rates of downstaging/resection, and survival outcomes (overall survival (OS) and progression-free survival (PFS)) calculated from date of enrolment. OS and PFS were estimated using Kaplan-Meier method. Pre- and on-treatment tissue, blood and microbiome samples were collected to evaluate tumor-intrinsic and peripheral immunogenomic correlates of response. Results: Between 09/2020 and 05/2022, N = 18 enrolled. Median age 67.5 years (IQR; 62.5, 71.5), 28% (5/18) female. Baseline Performance Status: N = 8 (44%) ECOG 0; N = 10 (56%) ECOG 1. Tumor location: Head/uncinate N = 9 (50%), body N = 7 (39%), neck N = 2 (11%). Median # doses FFX prior to enrolment: 8.5 (IQR; 8.0- 11.0). At median follow-up of 13.8 m, 6-m PFS: 62% (95% CI 43%, 91%). Median PFS: 10.2 m (95% CI; 5.03, NA) and median OS 17.2 m (95% CI; 12.98, NA). Disease progression (any time) N = 12, of which local POD in N = 7 (58%). N = 3 completed maintenance D; N = 5 on active treatment. ORR: N = 17 (94.4%) stable disease (95% CI; 64.6%, 99.4%). Toxicity endpoints of special interest: Grade 3 ICB-related: in N = 4 patients; diarrhea N = 2; elevated AST/ALT N = 2; G3 lipase elevation N = 1; attribution uncertain. Conclusions: D and SABR following FFX in LA PDAC had an encouraging 6-m PFS of 62% (43-91%) and a tolerable safety profile. Immuno-genomic analyses of correlative biospecimens is underway. Funding support AstraZeneca. Clinical trial information: NCT03245541 .

Background A phase 1 trial was used to evaluate a combination of cisplatin, gemcitabine, and escalating doses of veliparib in patients with untreated advanced pancreatic ductal adenocarcinoma (PDAC) in 2 cohorts: a germline BRCA1/2-mutated (BRCA+) cohort and a wild-type BRCA (BRCA-) cohort. The aims were to determine the safety, dose-limiting toxicities (DLTs), maximum tolerated dose, and recommended phase 2 dose (RP2D) of veliparib combined with cisplatin and gemcitabine and to assess the antitumor efficacy (Response Evaluation Criteria in Solid Tumors, version 1.1) and overall survival. Methods Gemcitabine and cisplatin were dosed at 600 and 25 mg/m2 , respectively, over 30 minutes on days 3 and 10 of a 21-day cycle. Four dose levels of veliparib were evaluated: 20 (dose level 0), 40 (dose level 1), and 80 mg (dose level 2) given orally twice daily on days 1 to 12 and 80 mg given twice daily on days 1 to 21 (dose level 2A [DL2A]). Results Seventeen patients were enrolled: 9 BRCA+ patients, 7 BRCA- patients, and 1 patient with an unknown status. DLTs were reached at DL2A (80 mg twice daily on days 1 to 21). Two of the 5 patients in this cohort (40%) experienced grade 4 neutropenia and thrombocytopenia. Two grade 5 events occurred on protocol. The objective response rate in the BRCA+ cohort was 7 of 9 (77.8%). The median overall survival for BRCA+ patients was 23.3 months (95% confidence interval [CI], 3.8-30.2 months). The median overall survival for BRCA- patients was 11 months (95% CI, 1.5-12.1 months). Conclusions The RP2D of veliparib was 80 mg by mouth twice daily on days 1 to 12 in combination with cisplatin and gemcitabine; the DLT was myelosuppression. Substantial antitumor activity was seen in BRCA+ PDAC. A randomized phase 2 trial is currently evaluating cisplatin and gemcitabine with and without veliparib for BRCA+ PDAC (NCT01585805). Cancer 2018;124:1374-82. © 2018 American Cancer Society.

BACKGROUND ADI-PEG 20 is a pegylated form of the arginine-depleting enzyme arginine deiminase. Normal cells synthesize arginine with the enzyme argininosuccinate synthetase (ASS1); ADI-PEG 20 selectively targets malignant cells, which lack ASS1. METHODS A single-arm, nonrandomized, open-label, phase 1/1B, standard 3 + 3 dose escalation with an expansion cohort of 9 patients at the recommended phase 2 dose (RP2D) was conducted. Patients who had metastatic pancreatic cancer, up to 1 line of prior treatment (the dose-escalation cohort) or no prior treatment (the expansion cohort), and an Eastern Cooperative Oncology Group performance status of 0 to 1 were included. Patients received both gemcitabine (1000 mg/m2) and nab-paclitaxel (125 mg/m2) for 3 of 4 weeks and intramuscular ADI-PEG 20 at 18 mg/m2 weekly (cohort 1) or at 36 mg/m2 weekly (cohort 2 and the expansion cohort).The primary endpoint was to determine the maximum tolerated dose and RP2D of ADI-PEG 20 in combination with nab-paclitaxel and gemcitabine. RESULTS Eighteen patients were enrolled. No dose-limiting toxicities (DLTs) were observed in cohort 1; cohort 2 was expanded to 6 patients because of 1 DLT occurrence (a grade 3 elevation in bilirubin, aspartate aminotransferase, and alanine aminotransferase). The most frequent adverse events (AEs) of any grade were neutropenia, thrombocytopenia, leukopenia, anemia, peripheral neuropathy, and fatigue; all 18 patients experienced grade 3/4 AEs. The most frequent grade 3/4 toxicities, regardless of the relation with any drugs, included neutropenia (12 patients or 67%), leukopenia (10 patients or 56%), anemia (8 patients or 44%), and lymphopenia (6 patients or 33%). The RP2D for ADI-PEG 20 was 36 mg/m2 weekly in combination with standard-dose gemcitabine and nab-paclitaxel. The overall response rate among patients treated at the RP2D in the first-line setting was 45.5% (5 of 11).The median progression-free survival time for these patients treated at the RP2D was 6.1 months (95% confidence interval, 5.3-11.2 months), and the median overall survival time was 11.3 months (95% confidence interval, 6.7 months to not reached). CONCLUSIONS ADI-PEG 20 was well tolerated in combination with gemcitabine and nab-paclitaxel. Activity was observed in previously treated and untreated patients with advanced pancreatic cancer and in patients with ASS1-deficient and -proficient tumors. Cancer 2017. © 2017 American Cancer Society.

639 Background: gBRCA 1,2 mutations occur in 5-8% PDAC. Platinum and poly-ADP ribose polymerase inhibitors (PARPi) effective in BRCA-mut cancers. Phase I GC + V high RR 78%; combination may delay resistance in PDAC (O’Reilly, Cancer, 2018). Herein, we evaluate GC +/- V in a multi-national, randomized phase II trial. Methods: Eligibility: Untreated germline (g)BRCA, PALB2 mut PDAC; measurable stage III/IV; ECOG 0-1. Randomized 1:1 Arm A or B. Treatment: Arm A: G 600 mg/m2 IV, C 25 mg/m2 IV, d3 and 10, V 80 mg PO BID day 1-12, all q 3 weeks or Arm B: GC only. Primary endpoint: RECIST 1.1 response rate (RR). Simon 2-stage per arm: null hypothesis 10% vs promising 28%; type I, II error 10%. Secondary endpoints: progression-free survival (PFS), OS (m), disease control rate (CR+PR+SD), safety and correlative analyses. PFS, OS compared between arms using log-rank test and RR, DCR using Fisher’s exact test between arms. Results: N = 52 enrolled 01/14- 11/18. N = 2 withdrew Arm B. N = 50 for ITT. Male = 22 (44%), Female = 28. Median age = 64 years (range 37-82). BRCA1 N = 12, BRCA2 N = 35, PALB2 N = 3. Stage III N = 8; Stage IV N = 42. Hematologic Toxicity: Arm A vs Arm B: Gd 3-4 neutropenia 13 (48%) vs 7 (30%); Gd 3-4 platelets 15 (55%) vs 2 (9%); Gd 3-4 anemia 14 (52%) vs 8 (35%). Non-hematologic toxicity similar Arm A vs B. Exploratory analyses (combined Arms): Med OS if > 4 m platinum → PARPi: 23 m (95%CI 6.5- 53.9). Med OS by BRCA: BRCA1: 14 m (8.1- 18.5); BRCA2: 20.2 m (12.3- 24.4). Med OS by ECOG: ECOG 0: 23 m (13.8- 24.5); ECOG 1: 14.3 (8.1 vs 16.4). Two-year OS rate for entire cohort: 30.6% and 3-year OS: 17.8%. Conclusions: GC +/- V very active in gBRCA/PALB2 mut PDAC with high RR, PFS, OS with both A, B significantly exceeding threshold RR. Improved DCR arm A vs B, but with greater heme toxicity A vs B. Study confirms GC as reference treatment in gBRCA/PALB2 with durable survival in subset. Funding: National Cancer Institute, CTEP, Lustgarten Foundation, AbbVie. Clinical trial information: NCT01585805 . [Table: see text]

BACKGROUND: Identification of pathogenic germline alterations (PGAs) has important clinical and therapeutic implications in pancreas cancer. We performed comprehensive germline testing (GT) in an unselected prospective cohort of patients with exocrine pancreatic neoplasms with genotype and phenotype association to facilitate identification of prognostic and/or predictive biomarkers and examine potential therapeutic implications. METHODS: Six hundred fifteen unselected patients with exocrine pancreatic neoplasms were prospectively consented for somatic tumor and matched sample profiling for 410–468 genes. GT for PGAs in 76 genes associated with cancer susceptibility was performed in an “identified” manner in 356 (57.9%) patients and in an “anonymized” manner in 259 (42.1%) patients, using an institutional review board–approved protocol. Detailed clinical and pathological features, response to platinum, and overall survival (OS) were collected for the identified cohort. OS was analyzed with Kaplan-Meier curves. RESULTS: PGAs were present in 122 (19.8%) of 615 patients involving 24 different genes, including BRCA1/2, ATM, PALB2, and multiple additional genes associated with the DNA damage response pathway. Of 122 patients with germline alterations, 41.8% did not meet current guidelines for GT. The difference in median OS was not statistically significant between patients with and without PGA (50.8 months, 95% confidence interval = 34.5 to not reached, two-sided P = .94). Loss of heterozygosity was found in 60.0% of BRCA1/2. CONCLUSIONS: PGAs frequently occur in pancreas exocrine neoplasms and involve multiple genes beyond those previously associated with hereditary pancreatic cancer. These PGAs are therapeutically actionable in about 5% to 10% of patients. These data support routinely offering GT in all pancreatic ductal adenocarcimona patients with a broad panel of known hereditary cancer predisposition genes.

A phase 1 trial was used to evaluate a combination of cisplatin, gemcitabine, and escalating doses of veliparib in patients with untreated advanced pancreatic ductal adenocarcinoma (PDAC) in 2 cohorts: a germline BRCA1/2-mutated (BRCA+) cohort and a wild-type BRCA (BRCA-) cohort. The aims were to determine the safety, dose-limiting toxicities (DLTs), maximum tolerated dose, and recommended phase 2 dose (RP2D) of veliparib combined with cisplatin and gemcitabine and to assess the antitumor efficacy (Response Evaluation Criteria in Solid Tumors, version 1.1) and overall survival.Gemcitabine and cisplatin were dosed at 600 and 25 mg/mSeventeen patients were enrolled: 9 BRCA+ patients, 7 BRCA- patients, and 1 patient with an unknown status. DLTs were reached at DL2A (80 mg twice daily on days 1 to 21). Two of the 5 patients in this cohort (40%) experienced grade 4 neutropenia and thrombocytopenia. Two grade 5 events occurred on protocol. The objective response rate in the BRCA+ cohort was 7 of 9 (77.8%). The median overall survival for BRCA+ patients was 23.3 months (95% confidence interval [CI], 3.8-30.2 months). The median overall survival for BRCA- patients was 11 months (95% CI, 1.5-12.1 months).The RP2D of veliparib was 80 mg by mouth twice daily on days 1 to 12 in combination with cisplatin and gemcitabine; the DLT was myelosuppression. Substantial antitumor activity was seen in BRCA+ PDAC. A randomized phase 2 trial is currently evaluating cisplatin and gemcitabine with and without veliparib for BRCA+ PDAC (NCT01585805). Cancer 2018;124:1374-82. © 2018 American Cancer Society.

ADI-PEG 20 is a pegylated form of the arginine-depleting enzyme arginine deiminase. Normal cells synthesize arginine with the enzyme argininosuccinate synthetase (ASS1); ADI-PEG 20 selectively targets malignant cells, which lack ASS1.A single-arm, nonrandomized, open-label, phase 1/1B, standard 3 + 3 dose escalation with an expansion cohort of 9 patients at the recommended phase 2 dose (RP2D) was conducted. Patients who had metastatic pancreatic cancer, up to 1 line of prior treatment (the dose-escalation cohort) or no prior treatment (the expansion cohort), and an Eastern Cooperative Oncology Group performance status of 0 to 1 were included. Patients received both gemcitabine (1000 mg/mEighteen patients were enrolled. No dose-limiting toxicities (DLTs) were observed in cohort 1; cohort 2 was expanded to 6 patients because of 1 DLT occurrence (a grade 3 elevation in bilirubin, aspartate aminotransferase, and alanine aminotransferase). The most frequent adverse events (AEs) of any grade were neutropenia, thrombocytopenia, leukopenia, anemia, peripheral neuropathy, and fatigue; all 18 patients experienced grade 3/4 AEs. The most frequent grade 3/4 toxicities, regardless of the relation with any drugs, included neutropenia (12 patients or 67%), leukopenia (10 patients or 56%), anemia (8 patients or 44%), and lymphopenia (6 patients or 33%). The RP2D for ADI-PEG 20 was 36 mg/mADI-PEG 20 was well tolerated in combination with gemcitabine and nab-paclitaxel. Activity was observed in previously treated and untreated patients with advanced pancreatic cancer and in patients with ASS1-deficient and -proficient tumors. Cancer 2017;123:4556-4565. © 2017 American Cancer Society.

405 Background: PEGPH20 (P) degrades hyaluronan (HA), a key component of pancreatic adenocarcinoma (PDAC) tumor microenvironment, leading to reduction of tumor interstitial pressure, decompression of tumor blood vessels and improvement in delivery of chemotherapeutics. A prior study of P with chemotherapy in PDAC (HALO-202) found an increased risk of thromboembolic (TE) events, 43%, effectively reduced with subcutaneous enoxaparin treatment. Rivaroxaban (R) is a safe and effective oral anticoagulant for treating cancer-related TE. Methods: 28 patients with advanced PDAC, KPS ≥ 70 and without prior TE were enrolled from January to June 2017. Patients received treatment with PAG (P; 3 µg/kg IV 2x/wk x 3 wks in C1, then 1x/wk x 3 wks in C2+, plus AG) every 28 days, with R (15 mg twice daily for 21 days, followed by 20 mg once daily). Primary endpoint is symptomatic TE event rate; secondary endpoints include PFS, OS, major bleeding rate and RR. Results: All 28 patients are evaluable for efficacy and safety. Key patient characteristics: age = 62 (range 45-76), M/F = 15/13, stage III/IV = 4/24, KPS 70/80/90 = 1/13/14. Median follow-up is 5.4 mo. No symptomatic and one grade 2, asymptomatic TE event (DVT) occurred (1/28 = 3.6%). Two grade 3 GI hemorrhages occurred. Best responses: partial response 11 (39%), stable disease 13 (46%), progressive disease 4 (14%), and overall disease control rate of 86%. Median PFS and OS have not been reached. Conclusions: Interim analysis shows R is safe and effectively prevents TE events in patients receiving PAG. Responses and disease control rate are encouraging in this tumor HA-level unselected patient population. Updated safety and efficacy data will be reported. Clinical trial information: NCT02921022.

295 Background: ADI-PEG 20 (A) is a pegylated form of arginine depleting enzyme, arginine deaminase. Normal cells synthesise arginine using the enzyme argininosuccinate synthetase (ASS). A selectively targets malignant cells which lack ASS. A has shown encouraging pre clinical activity as monotherapy in PC, and synergistic activity with gem and taxanes. Methods: Eligibility: Metastatic PC, up to one line of prior treatment (dose escalation cohort:ct) no prior treatment (expansion ct), ECOG 0-1.Treatment: gem 1,000 mg/m2, nab-P 125mg/m2 3 out of 4 weeks, A 18 mg IM weekly (ct 1), A 36mg weekly (ct 2 and expansion ct). Primary endpoint: determine MTD of A in combination with nab-P and gem. Statistical plan: Single arm, non-randomized, open-label, phase IB, standard 3 + 3 dose escalation with expansion ct of 9 patients at MTD. Secondary endpoints: progression-free survival (PFS), response rate, overall survival (OS), safety, tolerability, blood and archival tumor analyses for ASS expression and immunogenicity. Pts treated at MTD and on expansion cohort were eligible for primary and secondary endpoints. Results: Between 11/14 and 09/15, 18 pts enrolled. 4 pts (22%) had 1 prior line of therapy. Toxicity attributable to A was limited to grade 1 rash/erythema at injection site (n = 3). Cohort 2 was expanded to 6 pts due to DLT of elevated LFTs, no further DLTs observed. ≥ grade 3 toxicity attributable to gem and/or nab-P included elevation in AST/ALT, hematologic toxicity, fatigue, diarrhea, neutropenic fever, alopecia as expected. No A related grade 3-5 toxicities were observed. Response: 6 pts (40%) PR, including one previously treated pt, 8 pts (53%) stable disease (SD), 1 pt inevaluable. Two pts continue on study, median PFS 6.5 months (95% CI 5.3 – 15.2), median OS 11.3 months (95% CI 4.9- . ). Eight of 15 pts treated at MTD received 2nd-line chemotherapy at progression. Five of 11 archival tumors samples tested for ASS1 expression by IHC were deficient. Conclusions: A was well tolerated in combination with gem and nab-P. Activity was observed in treated and untreated pts, and in pts with ASS deficient and proficient tumors; synergy of A with cytotoxics may be independent of ASS status and future investigation in an unselected population is warranted. Clinical trial information: NCT02101580.