3081 Background: E is an investigational, novel, chimeric monoclonal IgG1 antibody derived from an immunogenic neoantigen with sequence homology to MUC5AC that is preferentially expressed with exquisite specificity to pancreatic cancer and CRC. Its mechanism of action is via antibody-dependent cellular cytotoxicity (ADCC). The efficacy and safety of E was evaluated in a single-arm, open-label, phase 1/2 clinical trial of adult pts with refractory mCRC. Methods: Pts were selected based on > 20% expression of tumor antigen, as measured by immunohistochemistry. Based on phase 1 results, E was administered 3 mg/kg IV every 2 weeks until unacceptable toxicity or disease progression. Primary endpoint was overall survival (OS). Serum cytokine levels were analyzed at baseline, day 4, and day 15. E-mediated ADCC of CD16 genotype V/V, V/F, and F/F pt PBMCs was measured with an IN-111 release assay using the E target-expressing ASPC-1 pancreatic cancer cell line. Results: Fifty-seven and 63 pts were evaluable for OS and safety, respectively. Median OS was significantly longer than historical control: 6.8 vs 5.0 months (mo); p = 0.007; 95% CI: 5.39,8.02. Three pts were alive at end of study (21, 21, and 24 mo); 21 pts survived ≥ 12 mo. Pts had a median of 4 prior therapies (range 2-9); 25% had received regorafenib. Forty-seven pts were evaluable by RECIST, and 20 (43%) had stable disease of target lesions at end of first course (day 57). E was well tolerated, with < 2% grade 3 and no grade 4 toxicities. There were no trends in serum cytokine and chemokine levels. Analysis of 56 samples (8 V/V, 26 V/F, 17 F/F, and 5 undetermined) showed that V/V PBMCs had significantly higher E-mediated ADCC than PBMCs harboring other genotypes. No correlation between CD16 polymorphism and pt outcome was observed. Conclusions: E demonstrated excellent tolerability and encouraging OS in this heavily pretreated population. Correlative in vitro data suggest that E can mediate higher levels of ADCC activity in individuals with a V/V versus other genotypes. The lack of correlation between CD16 polymorphism and pt outcomes in this study suggests that other immune-related factors (under investigation) may impact the efficacy of E in vivo. Clinical trial information: NCT01040000.
Read full abstract