Background A novel approach to differentiate somatic vs. germline BRCA1/2 mutations in cfDNA using a beta binomial model (AACR 2018, abst #4272) may enable identification of pts with advanced GI tumors who are likely to benefit from a PARP inhibitor. The results from the GOZILA study, the Nationwide Cancer Genome Screening Project utilizing Guardant360, are presented here. Methods Pts with advanced GI tumors who were appropriate for any systemic therapy and had progressed following at least one prior treatment were eligible. We investigated the prevalence of somatic vs. germline BRCA1/2 mutations and the association between BRCA1/2 mutations, TMB and MSI. Results From Jan 2018 to Mar 2019, 850 pts were prospectively enrolled among 26 major cancer centers in Japan. Of 40 (4.7%) actionable BRCA1/2 mutations, 14 were germline: esophagus (squamous cell carcinoma only), 2 pts (N = 62, 3.2%); stomach, 2 pts (N = 131, 1.5%); colorectum, 3 pts (N = 377, 0.8%); pancreas, 3 pts (N = 157, 1.9%); biliary tract, 4 pts (N = 77, 5.2%); and others, none (N = 31, 0%). Notably, the majority of BRCA1/2 mutations (75%) in pts with esophageal, pancreas and biliary tract cancers were germline, while 81% of BRCA1/2 mutations in pts with stomach and colorectal cancers were somatic (p = 0.001). Median TMB of pts with germline BRCA1/2 mutations was significantly lower than those with somatic BRCA1/2 mutations (p = 0.042). In addition, all pts with germline BRCA1/2 mutations were microsatellite stable, while 19% of pts with somatic BRCA1/2 mutations were MSI-high. Conclusions Analysis of cfDNA identified a unique subset of pts with germline BRCA1/2 mutations in advanced GI cancers. Given the association of these findings with efficacy of PARP inhibitor and immune-based therapies, these findings suggest that the identification of BRCA1/2 mutations and their germline-somatic origin may have future implications for therapy selection. Clinical trial identification UMI29315. Legal entity responsible for the study SCRUM-Japan GI-SCREEN. Funding Guardant Health, Ono Pharmaceutical. Disclosure Y. Kawamoto: Honoraria (self): Taiho Pharmaceutical Co., Ltd.; Honoraria (self): Daiichi Sankyo Co., Ltd.; Honoraria (self): Takeda Pharmaceutical Co., Ltd.; Honoraria (self): Chugai Pharmaceutical Co., Ltd.; Honoraria (self): Merck Biopharma Co., Ltd.; Honoraria (self): Eli Lilly Japan K.K.. Y. Nakamura: Research grant / Funding (institution): Ono Pharmaceutical; Research grant / Funding (institution): Taiho Pharmaceutical. M. Ikeda: Honoraria (self), Advisory / Consultancy, Research grant / Funding (institution): Novartis Pharma; Honoraria (self), Advisory / Consultancy, Research grant / Funding (institution): Bayer Yakuhin; Research grant / Funding (institution): Bristol-Myers Squibb; Honoraria (self), Advisory / Consultancy, Research grant / Funding (institution): Eisai; Honoraria (self): Taiho Pharmaceutical; Honoraria (self), Advisory / Consultancy, Research grant / Funding (institution): Eli Lilly Japan; Research grant / Funding (institution): Yakult; Advisory / Consultancy: Otsuka Pharmaceutical; Advisory / Consultancy: Daiichi-Sankyo; Honoraria (self): Sumitomo Dainippon Pharma; Honoraria (self), Advisory / Consultancy: Teijin Pharma; Honoraria (self): EA Pharma; Honoraria (self): MSD; Advisory / Consultancy, Research grant / Funding (institution): ASLAN Pharmaceuticals; Advisory / Consultancy, Research grant / Funding (institution): Chugai Pharmaceutical; Research grant / Funding (institution): Ono Pharmaceutical; Research grant / Funding (institution): AstraZeneca; Research grant / Funding (institution): Merck Serono; Research grant / Funding (institution): Nano Carrier; Honoraria (self): Gilead. H. Bando: Honoraria (self): Taiho Pharmaceutical company; Honoraria (self): Eli Lilly; Research grant / Funding (self): Sysmex; Research grant / Funding (self): AstraZeneca. T. Esaki: Honoraria (self), Research grant / Funding (institution): Taiho; Honoraria (self): Chugai; Honoraria (self), Research grant / Funding (institution): Ono; Honoraria (self): Takeda; Honoraria (self): Bayer; Honoraria (self): Eli Lilly; Research grant / Funding (institution): Astellas; Research grant / Funding (institution): MSD; Research grant / Funding (institution): Daiichi-Sankyo; Research grant / Funding (institution): Merck Serono; Research grant / Funding (institution): Dainippon Sumitomo; Research grant / Funding (institution): Novartis. M. Ueno: Honoraria (self), Research grant / Funding (institution): Taiho Pharmaceutical; Honoraria (self), Research grant / Funding (institution): Yakult Honsha; Honoraria (self), Research grant / Funding (institution): AstraZeneca; Honoraria (self): Novartis; Honoraria (self): Lilly; Honoraria (self): Teijin Pharma; Honoraria (self), Advisory / Consultancy, Research grant / Funding (institution): Shire; Honoraria (self), Research grant / Funding (institution): Ono Pharmaceutical; Honoraria (self), Research grant / Funding (institution): Merck Serono; Research grant / Funding (institution): Daiichi Sankyo; Research grant / Funding (institution): Eisai; Research grant / Funding (institution): MSD; Research grant / Funding (institution): NanoCarrier; Research grant / Funding (institution): Dainippon Sumitomo Pharma; Research grant / Funding (institution): Incyte; Research grant / Funding (institution): ASLAN Pharmaceuticals. T. Nishina: Honoraria (self), Research grant / Funding (institution): Taiho pharmaceutinal; Honoraria (self), Research grant / Funding (institution): Chugai Pharma; Honoraria (self), Research grant / Funding (self): Merck Serono; Honoraria (self), Research grant / Funding (institution): Bristol-Myers Suibb; Honoraria (self): Nihonkayaku; Honoraria (self), Research grant / Funding (institution): Lilly Japan; Honoraria (self), Research grant / Funding (institution): Ono Pharmaceutical; Research grant / Funding (institution): Dainippon Sumitomo Pharma; Research grant / Funding (institution): MSD; Research grant / Funding (institution): Diichi Sankyo. E. Oki: Speaker Bureau / Expert testimony: Taiho Pham; Speaker Bureau / Expert testimony: Yakult Honsha; Speaker Bureau / Expert testimony: Merck; Speaker Bureau / Expert testimony: Chugai Pham; Speaker Bureau / Expert testimony: Takeda Pharm; Speaker Bureau / Expert testimony: Eli Lilly; Speaker Bureau / Expert testimony: Bayer. T. Denda: Speaker Bureau / Expert testimony: DAIICHI SANKYO COMPANY, LIMITED. T. Mizukami: Advisory / Consultancy, Speaker Bureau / Expert testimony, Research grant / Funding (institution): Eli Lilly Japan; Advisory / Consultancy: Bristol-Myers Squibb Company; Speaker Bureau / Expert testimony: Takeda Pharmaceutical; Research grant / Funding (institution): TAIHO Pharmaceutical. N. Okano: Honoraria (self): Taiho Pharmaceutical; Honoraria (self): Merck Serono; Honoraria (self): Eisai; Honoraria (self): Ono Pharmaceutical; Honoraria (self): Yakult Honsha; Honoraria (self): Takeda; Honoraria (self): J-Pharma; Honoraria (self): Kyowa Hakko Kirin. M.I. Lefterova: Shareholder / Stockholder / Stock options, Full / Part-time employment: Guardant Health. J.I. Odegaard: Shareholder / Stockholder / Stock options, Full / Part-time employment: Guardant Health. H. Taniguchi: Honoraria (self): Chugai; Honoraria (self), Research grant / Funding (self): Takeda; Honoraria (self): Taiho; Honoraria (self): Eli Lilly; Research grant / Funding (self): Daiichi-Sankyo; Research grant / Funding (self): Sysmex. C. Morizane: Honoraria (self), Research grant / Funding (institution): Pfizer; Honoraria (self), Advisory / Consultancy: Novartis; Honoraria (self), Advisory / Consultancy, Research grant / Funding (institution): Yakult Honsha; Honoraria (self): Lilly; Honoraria (self), Research grant / Funding (institution): Nobelpharma; Honoraria (self): Fujifilm; Honoraria (self): Teijin Pharma; Honoraria (self), Advisory / Consultancy, Research grant / Funding (institution): Taiho Pharmaceutical; Honoraria (self), Research grant / Funding (institution): Eisai; Advisory / Consultancy: Abbvie; Research grant / Funding (institution): ONO PHARMACEUTICAL; Research grant / Funding (institution): J-Pharma. T. Yoshino: Research grant / Funding (self): Novartis Pharma K.K.; Research grant / Funding (self): MSD.K.K.; Research grant / Funding (self): Sumitomo Dainippon Pharma Co., Ltd.; Research grant / Funding (self): CHUGAI PHARMACEUTICAL Co., Ltd.; Research grant / Funding (self): Sanofi K.K.; Research grant / Funding (self): DAIICHI SANKYO Co., Ltd.; Research grant / Funding (self): PAREXEL International Inc.; Research grant / Funding (self): ONO PHARMACEUTICAL Co., Ltd. All other authors have declared no conflicts of interest.

Abstract Background ERBB2 amp occurs in approximately 4% of pts with mCRC. We conducted a phase II trial to evaluate the efficacy and safety of T and P in pts with ERBB2-amplified mCRC identified by tissue and/or ctDNA analysis. Methods We enrolled pts with central tissue and/or ctDNA (Guardant360) confirmed wild-type RAS and ERBB2-amplified mCRC, refractory or intolerant to standard chemotherapy including EGFR blockade. Pts received T and P every 3 weeks. The primary endpoint was confirmed objective response rate (ORR) by investigator assessment, analyzed for two primary populations: tissue-positive and ctDNA-positive. The required sample size for each group was 25 (one-sided α = 2.5%, β = 10%) to test the threshold ORR of 5% against the expected ORR of 30%; 5 confirmed responses were needed to determine statistical significance. Results The first response evaluation was done on Jan 7, 2019. Of 19 pts enrolled at 7 sites, 18 were evaluable for response. ERBB2-amp was confirmed in both tissue and ctDNA for 14 pts, in tissue alone for 3, and in ctDNA alone for 1; therefore, 17 and 15 pts were assigned to the tissue-positive and the ctDNA-positive group, respectively. With median follow-up of 5.4 months, there were 6 confirmed responders in the tissue-positive group (ORR = 35%, 95% confidence interval [CI] 14-62%; 1 CR and 5 PR) and 5 in the ctDNA positive group (ORR = 33%, 95% CI 12-62%; 1 CR and 4 PR). Median progression-free survival for both groups was 4.0 months (95% CI = 1.4-5.6 months and 1.3-5.6 months, respectively). Clonal ctDNA mutations in KRAS, BRAF, PIK3CA, or ERBB2 at baseline were observed only in pts with disease progression as best response. The safety profile of T and P was consistent with prior reports. Severe adverse events were reported in 2 pts: Gr 3 decreased ejection fraction and Gr 3 infusion related reaction. Conclusions The TRIUMPH study met its primary endpoint, demonstrating that combination of T and P has promising activity, with an acceptable toxicity profile, in treatment-refractory mCRC pts with ERBB2 amp in tissue and/or ctDNA. Clonal oncogenic ctDNA driver mutations may predict for primary resistance. Clinical trial identification UMIN000027887. Legal entity responsible for the study SCRUM-Japan GI-SCREEN. Funding Japan Agency for Medical Research and Development. Disclosure Y. Nakamura: Research grant / Funding (institution): Taiho Pharmaceutical; Research grant / Funding (institution): Ono Pharmaceutical. W. Okamoto: Research grant / Funding (self): MSD. T. Kato: Honoraria (self), Research grant / Funding (self): Chugai Pharma; Honoraria (self): Takeda; Honoraria (self): Bayer; Honoraria (self): Lilly; Honoraria (self): Yakult Honsha; Honoraria (self): Sanofi. K. Kato: Advisory / Consultancy, Research grant / Funding (institution): Ono Pharmaceutical; Advisory / Consultancy, Research grant / Funding (institution): BeiGene; Advisory / Consultancy: MSD; Advisory / Consultancy: Oncolys BioPharma; Research grant / Funding (self): Shionogi; Research grant / Funding (self): MSD Oncology. S. Iwasa: Honoraria (self): Taiho Pharmaceutical; Honoraria (self), Research grant / Funding (institution): Lilly Japan; Honoraria (self), Research grant / Funding (institution): Chugai Pharma; Honoraria (self): Ono Pharmaceutical; Research grant / Funding (institution): Daiichi Sankyo; Research grant / Funding (institution): Bristol-Myers Squibb; Research grant / Funding (institution): Eisai; Research grant / Funding (institution): Novartis; Research grant / Funding (institution): Merck Serono; Research grant / Funding (institution): Otsuka; Research grant / Funding (institution): Bayer. T. Esaki: Honoraria (self), Research grant / Funding (institution): Lilly; Honoraria (self): Taiho Pharmaceutical; Honoraria (self), Research grant / Funding (institution): Bristol-Myers Squibb Japan; Honoraria (self): Eisai; Honoraria (self), Research grant / Funding (institution): Daiichi Sankyo; Honoraria (self), Research grant / Funding (institution): Merck Serono; Honoraria (self): Chugai Pharma; Honoraria (self), Research grant / Funding (institution): Ono Pharmaceutical; Honoraria (self): Takeda; Honoraria (self), Research grant / Funding (institution): Bayer; Honoraria (self): Sanofi; Research grant / Funding (institution): MSD; Research grant / Funding (institution): Novartis; Research grant / Funding (institution): Sumitomo Dainippon Pharma; Research grant / Funding (institution): Astellas Pharma; Research grant / Funding (institution): Nihonkayaku; Research grant / Funding (institution): Pfizer. Y. Komatsu: Speaker Bureau / Expert testimony, Research grant / Funding (self): Taiho Pharmaceutical; Speaker Bureau / Expert testimony, Research grant / Funding (self): Lilly; Speaker Bureau / Expert testimony, Research grant / Funding (self): Chugai Pharma; Speaker Bureau / Expert testimony: Merck Serono; Honoraria (self), Speaker Bureau / Expert testimony, Research grant / Funding (self): Novartis; Honoraria (self), Speaker Bureau / Expert testimony: Pfizer; Honoraria (institution), Speaker Bureau / Expert testimony, Research grant / Funding (self): Bayer; Speaker Bureau / Expert testimony, Research grant / Funding (self): Ono Pharmaceutical; Speaker Bureau / Expert testimony: Yakult Honsha; Speaker Bureau / Expert testimony, Research grant / Funding (self): Takeda; Speaker Bureau / Expert testimony, Research grant / Funding (self): Sanofi; Speaker Bureau / Expert testimony: Bristol-Myers Squibb Japan; Speaker Bureau / Expert testimony: Daiichi Sankyo; Speaker Bureau / Expert testimony: TOWA; Speaker Bureau / Expert testimony: Nipro Corporation; Research grant / Funding (self): MSD; Research grant / Funding (self): Yakult Pharmaceutical; Research grant / Funding (self): Sumitomo Dainippon Pharma; Research grant / Funding (self): Boehringer Ingelheim; Research grant / Funding (self): Sysmex. T. Masuishi: Honoraria (self): Taiho Pharmaceutical; Honoraria (self): Merck Serono; Honoraria (self): Chugai Pharma; Honoraria (self), Research grant / Funding (institution): Yakult Honsha; Honoraria (self): Takeda; Honoraria (self): Lilly; Honoraria (self): Bayer Yakuhin; Honoraria (self): Sanofi. T. Nishina: Honoraria (self), Research grant / Funding (institution): Taiho Pharmaceutical; Honoraria (self), Research grant / Funding (institution): Chugai Pharma; Honoraria (self): Lilly; Research grant / Funding (institution): Lilly Japan; Honoraria (self), Research grant / Funding (institution): Merck Serono; Honoraria (self): Takeda; Honoraria (self): Bristol-Myers Squibb; Honoraria (self): Nihonkayaku; Research grant / Funding (institution): Sumitomo Dainippon Pharma; Research grant / Funding (institution): MSD; Research grant / Funding (institution): Daiichi Sankyo; Research grant / Funding (institution): Ono Pharmaceutical. J.I. Odegaard: Shareholder / Stockholder / Stock options, Full / Part-time employment: Guardant Health. S. Olsen: Full / Part-time employment: Guardant Health AMEA; Shareholder / Stockholder / Stock options: Guardant Health; Shareholder / Stockholder / Stock options: AstraZeneca. T. Yoshino: Research grant / Funding (institution): Sumitomo Dainippon Pharma Co., Ltd.; Research grant / Funding (institution): Chugai Pharmaceutical Co., Ltd.; Research grant / Funding (institution): Sanofi. K.K.; Research grant / Funding (institution): Daiichi Sankyo Company, Limited; Research grant / Funding (institution): Parexel International Inc.; Research grant / Funding (institution): Ono Pharmaceutical Co., Ltd.; Research grant / Funding (institution): MSD. K. K. All other authors have declared no conflicts of interest.

Background MET amplification (amp) is rare in untreated metastatic colorectal cancer (mCRC), but cell-free DNA (cfDNA) analysis identifies it in ∼20% with anti-EGFR monoclonal antibody (mAb)-refractory disease. CfDNA analysis reveals both focal gene amp and gene copy number gain due to chromosomal aneuploidy (non-focal MET amp). We analyzed cfDNA from Japanese (JPN) and United States (US) patients (pts) with anti-EGFR mAb-refractory mCRC to investigate the prevalence of focal and non-focal MET amp. Methods We studied MET amp in pts with mCRC in the Nationwide Cancer Genome Screening Project in JPN (GOZILA; UMI29315; JPN cohort) and in a phase I/II trial of cabozantinib (C) +/- panitumumab (P) in pts with RAS wild-type mCRC (NCT02008383; US cohort). MET amp was detected with the Guardant360 assay. Focal MET amp was defined as either the only amp on chromosome (chr) 7q or MET copy number ³4. Non-focal MET amp was defined as co-amp with ³1 other genes (CDK6 or BRAF) located on chr 7q and MET copy number Results 244 JPN cohort pts were analyzed from 2/2018-12/2018, and 81 pts in the US cohort, from 8/2014-2/2018. In pts with prior anti-EGFR mAb (JPN: n = 184; US: n = 70), focal and non-focal MET amp were detected in 8 (4.3%) and 30 (16.3%) pts in the JPN cohort, and in 9 (12.9%) and 4 (5.7%) US pts. Without prior anti-EGFR mAb (JPN: n = 60; US: n = 11), focal and non-focal MET amp were detected in 1 (1.7%) and 4 (6.7%) pts in the JPN cohort, and 0 (0%) and 1 (9.1%) US pts. The focal MET amp rate combined was 6.7% (17/254) with prior anti-EGFR mAb. In the US cohort, 4/6 pts with focal MET amp treated with C or C+P had a reduction in RECIST lesions as best response, with one PR, while 2 pts with non-focal MET amp had tumor growth as best response. Conclusions The prevalence of focal MET amp detected by cfDNA analysis in mCRC pts was similar in the JPN and US cohorts. Given preliminary efficacy results from the US trial, focal MET amp may be a [A1] predictor of benefit from a MET inhibitor. A clinical trial evaluating a MET inhibitor in mCRC pts with focal MET amp is underway. Legal entity responsible for the study The authors. Funding Has not received any funding. Disclosure A. Kawazoe: Honoraria (self), Research grant / Funding (institution): Ono Oharmaceutical; Honoraria (self), Research grant / Funding (institution): Taiho Pharmaceutical; Research grant / Funding (institution): Dainippon Sumitomo Pharma; Research grant / Funding (institution): Takeda Pharmaceutical; Research grant / Funding (institution): Astellas Pharmaceutical; Research grant / Funding (institution): MSD. Y. Nakamura: Research grant / Funding (institution): Ono Pharmaceutical; Research grant / Funding (institution): Taiho Pharmaceutical. J.I. Odegaard: Full / Part-time employment: Guardant Health. M.I. Lefterova: Full / Part-time employment: Guardant Health. R. Lanman: Full / Part-time employment: Guardant Health. T. Yoshino: Research grant / Funding (institution): Novartis Pharma K.K.; Research grant / Funding (institution): MSD.K.K.; Research grant / Funding (institution): Sumitomo Dainippon Pharma Co., Ltd.; Research grant / Funding (institution): CHUGAI PHARMACEUTICAL CO., LTD.; Research grant / Funding (institution): Sanofi K.K.; Research grant / Funding (institution): DAIICHI SANKYO COMPANY, LIMITED; Research grant / Funding (institution): PAREXEL International Inc.; Research grant / Funding (institution): ONO PHARMACEUTICAL CO., LTD.. J.H. Strickler: Honoraria (self), Advisory / Consultancy, Research grant / Funding (institution): Amgen; Honoraria (self), Advisory / Consultancy: Bayer; Honoraria (self): Chugai; Honoraria (institution), Advisory / Consultancy, Research grant / Funding (institution): Seattle Genetics; Advisory / Consultancy, Research grant / Funding (institution): Genentech/Roche; Advisory / Consultancy: AstraZeneca; Advisory / Consultancy, Leadership role, Research grant / Funding (institution): OncoMed; Advisory / Consultancy: Celgene; Advisory / Consultancy: Proteus Digital Health; Advisory / Consultancy: Chengdu Kanghong Biotechnology Co., Ltd; Research grant / Funding (institution): Exelixis; Research grant / Funding (institution): Sanofi; Research grant / Funding (institution): Nektar; Research grant / Funding (institution): Abbvie; Research grant / Funding (institution): Gilead Sciences; Research grant / Funding (institution): Macrogenics; Research grant / Funding (institution): Leap Therapeutics; Research grant / Funding (institution): MedImmune. All other authors have declared no conflicts of interest.