Enfortumab vedotin (EV) alone or in combination with pembrolizumab (P) in previously untreated cisplatin-ineligible patients with locally advanced or metastatic urothelial cancer (la/mUC): Subgroup analyses of confirmed objective response rate (cORR) from EV-103 cohort K.

Abstract

499 Background: In EV-103 Cohort K (NCT03288545), EV and P in combination (EV+P) showed encouraging antitumor activity and a manageable safety profile when used as 1L therapy in patients (pts) w/ la/mUC who are ineligible for cisplatin, a population w/ high unmet need. Here we report results of an analysis of prespecified Cohort K subgroups known to be associated w/ poor outcomes. Methods: Pts who are cisplatin-ineligible w/ previously untreated la/mUC were randomized 1:1 to EV (1.25 mg/kg) as monotherapy on Days 1 and 8 or in combination w/ P (200 mg) on Day 1 of 3-week cycles. Primary endpoint is cORR per RECIST v1.1 by blinded independent central review w/ no formal statistical comparison between arms. Secondary endpoints included duration of response and safety (e.g. treatment-related adverse events, TRAEs). The cORR analysis was performed in prespecified subgroups including age, ECOG PS, liver metastasis, PD-L1 expression status, metastatic disease site at baseline, and primary disease site of origin. Results: 149 pts were treated: EV+P n=76; EV n=73; cORRs across key subgroups for both EV+P and EV monotherapy are shown in the table. For EV+P overall cohort, cORR (95%CI): 64.5% (52.7, 75.1); median DOR was not reached. cORRs were consistent across subgroups for EV+P including those w/ ECOG PS score of 1-2: 62.8% (46.7, 77.0) and presence of liver metastasis: 53.8% (25.1, 80.8). Among TRAEs of special interest in the EV+P arm, skin reactions occurred in n=51 (67.1%); peripheral neuropathy occurred in n=46 (60.5%). For EV+P, 68.4% of pts had TRAEs leading to interruption of either EV or P; 48.7% of pts had TRAEs leading to EV dose reduction. Median duration of EV+P treatment was 11 cycles. Conclusions: EV+P showed promising cORR in 1L cisplatin-ineligible pts w/ la/mUC; activity was consistently observed across a range of pre-specified subgroups including those with poor prognosis. EV+P TRAEs were manageable w/ close monitoring and appropriate dose modifications w/ a meaningful duration of treatment. EV+P has the potential to address high unmet needs in 1L la/mUC and MIBC and is being further evaluated in 3 Phase 3 trials (NCT04223856, NCT04700124, NCT03924895). Clinical trial information: NCT03288545 . [Table: see text]