533PDBACCI: A phase II randomized, double-blind, multicenter, placebo-controlled study of capecitabine (C) bevacizumab (B) plus atezolizumab (A) or placebo (P) in refractory metastatic colorectal cancer (mCRC): An ACCRU network study

Abstract Background The benefit of immune checkpoint blockade in mCRC is currently limited to mismatch repair (MMR) deficient tumours. Increasing evidence suggests that the vascular endothelial growth factor (VEGF) pathway plays a role in cancer immune evasion. Co-targeting the PD-1/PD-L1 and VEGF axes may result in clinical activity in mCRC. Methods 133 patients (pts) were randomized 2:1 to receive C/B/P (Arm A) or C/B/A (Arm B), stratifying by ECOG and RAS. Pts had progressed on 5-FU, oxaliplatin, irinotecan, bevacizumab, and anti-EGFR therapy (if RAS wt). Prior anti-PD-1/PD-L1 therapy was not permitted. Doses were C 850 or 1000 mg/m² d1-14, B 7.5 mg/kg d1, and A 1200 mg d1 in 21 day cycles. Primary endpoint was progression free survival (PFS). 110 events were required to detect PFS hazard ratio (HR) of 0.65 at 1-sided α = 0.1 with 80% power. Secondary endpoints were objective response rate (ORR), overall survival (OS), and safety/tolerability. Primary and secondary efficacy analyses were performed using modified intent to treat analysis (mITT). Results Analysis includes 46 pts (Arm A) and 82 pts (Arm B) with median age 58 yo, 40% female, 47% ECOG 0. As of 4/12/19, median follow-up was 12.35 months (mo). Proficient MMR or microsatellite stable (MSS) is present in 86.7% vs 85.7%. In mITT analysis, median PFS is 3.3 mo (2.1-6.2) vs 4.4 mo (4.1-6.4) with a HR of 0.725 (0.491-1.07), 1-sided log-rank p-value 0.051. In MSS only pts, HR for PFS is 0.67 (0.44-1.03). ORR is 4.35% (0.5-14.8) vs 8.54% (3.5-16.8), p = 0.5. The 12 mo OS is 43% (29-63) vs 52% (42-65), HR 0.94 (0.56-1.56), p = 0.4. Most common grade > = 3 related adverse events are hypertension (7% vs 9%), hand-foot syndrome (4% vs 6%), and diarrhea (2% vs 7%). Conclusions The study reached its prespecified primary endpoint and the addition of A to CB results in a significantly longer PFS. No new or increased safety signals are identified. Further investigation in a larger phase III study may be warranted. This is the first positive study co-targeting PD-1/PD-L1 and VEGF axes in mCRC and correlative analyses may help identify predictors of benefit. Clinical trial identification NCT0287319. Legal entity responsible for the study ACCRU. Funding Genentech Roche. Disclosure H.J. Lenz: Advisory / Consultancy, Speaker Bureau / Expert testimony, Research grant / Funding (institution): Genentech Roche; Advisory / Consultancy, Speaker Bureau / Expert testimony, Research grant / Funding (institution): Bayer; Advisory / Consultancy, Research grant / Funding (institution): Bristol-Myers Squibb. P.M. Boland: Research grant / Funding (institution): Merck; Research grant / Funding (institution): Genentech; Research grant / Funding (institution): Boehringer Ingelheim; Research grant / Funding (institution): Hemispherx; Research grant / Funding (institution): Boston Biomedical; Research grant / Funding (institution): Isofol Medical; Research grant / Funding (institution), Travel / Accommodation / Expenses: Ipsen; Research grant / Funding (institution): Athenex; Research grant / Funding (institution): Bayer; Research grant / Funding (institution): Clinical Genomics. A.B. Nixon: Research grant / Funding (self): Seattle Genetics; Research grant / Funding (self): MedPacto; Research grant / Funding (self): Genentech Roche; Advisory / Consultancy, Research grant / Funding (self): Tracon Pharma; Research grant / Funding (self): Acceleron Pharma; Research grant / Funding (self): Leadiant Biosciences; Research grant / Funding (self): Sanofi-Aventis; Advisory / Consultancy: Eli Lilly. H. Hurwitz: Shareholder / Stockholder / Stock options, Full / Part-time employment: Genentech Roche. M.G. Fakih: Honoraria (self), Advisory / Consultancy, Speaker Bureau / Expert testimony, Research grant / Funding (self): Amgen; Advisory / Consultancy: Array; Advisory / Consultancy: Bayer; Research grant / Funding (self): AstraZeneca; Research grant / Funding (self): Novartis. All other authors have declared no conflicts of interest.