Background Novel second-line treatments are needed for patients with advanced urothelial cancer (UC). Interim analysis of the phase III KEYNOTE-045 study showed a superior overall survival (OS) benefit of pembrolizumab, a programmed death 1 inhibitor, versus chemotherapy in patients with advanced UC that progressed on platinum-based chemotherapy. Here we report the long-term safety and efficacy outcomes of KEYNOTE-045. Patients and methods Adult patients with histologically/cytologically confirmed UC whose disease progressed after first-line, platinum-containing chemotherapy were enrolled. Patients were randomly assigned 1 : 1 to receive pembrolizumab [200 mg every 3 weeks (Q3W)] or investigator’s choice of paclitaxel (175 mg/m 2 Q3W), docetaxel (75 mg/m 2 Q3W), or vinflunine (320 mg/m 2 Q3W). Primary end points were OS and progression-free survival (PFS) per Response Evaluation Criteria in Solid Tumors, version 1.1 (RECIST v1.1) by blinded independent central radiology review (BICR). A key secondary end point was objective response rate per RECIST v1.1 by BICR. Results A total of 542 patients were enrolled (pembrolizumab, n = 270; chemotherapy, n = 272). Median follow-up as of 26 October 2017 was 27.7 months. Median 1- and 2-year OS rates were higher with pembrolizumab (44.2% and 26.9%, respectively) than chemotherapy (29.8% and 14.3%, respectively). PFS rates did not differ between treatment arms; however, 1- and 2-year PFS rates were higher with pembrolizumab. The objective response rate was also higher with pembrolizumab (21.1% versus 11.0%). Median duration of response to pembrolizumab was not reached (range 1.6+ to 30.0+ months) versus chemotherapy (4.4 months; range 1.4+ to 29.9+ months). Pembrolizumab had lower rates of any grade (62.0% versus 90.6%) and grade ≥3 (16.5% versus 50.2%) treatment-related adverse events than chemotherapy. Conclusions Long-term results (>2 years’ follow-up) were consistent with those of previously reported analyses, demonstrating continued clinical benefit of pembrolizumab over chemotherapy for efficacy and safety for treatment of locally advanced/metastatic, platinum-refractory UC. Trial registration ClinicalTrials.gov: NCT02256436.

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PURPOSE The phase II single-arm KEYNOTE-052 study evaluated the efficacy and safety of first-line pembrolizumab for patients with locally advanced or metastatic cisplatin-ineligible urothelial carcinoma (UC). PATIENTS AND METHODS Three hundred seventy patients received pembrolizumab 200 mg intravenously every 3 weeks for up to 24 months. Positive tumor programmed death ligand 1 (PD-L1) expression was defined as combined positive score (CPS) ≥ 10. Response was assessed by independent central review every 9 weeks per RECIST v1.1. The primary end point was objective response rate (ORR). RESULTS At data cutoff (September 26, 2018), the minimum follow-up was 2 years since the last patient enrolled. ORR was 28.6% (95% CI, 24.1% to 33.5%); 33 patients (8.9%) and 73 patients (19.7%) achieved complete and partial response, respectively. The median duration of response was 30.1 months (95% CI, 18.1 months to not reached [NR]); responses lasted ≥ 12 and ≥ 24 months in 67% and 52% of patients, respectively. Forty patients with complete or partial response completed 2 years of study treatment, and 32 had ongoing response at completion. Median overall survival (OS) was 11.3 months (95% CI, 9.7 to 13.1 months), and 12- and 24-month OS rates were 46.9% and 31.2%, respectively. In patients with CPS ≥ 10, ORR was 47.3% (95% CI, 37.7% to 57.0%) and median OS was 18.5 months (95% CI, 12.2 to 28.5 months). In patients with lymph node–only disease, ORR was 49.0% (95% CI, 34.8% to 63.4%), and median OS was 27.0 months (12.4 months to NR). There were no new safety signals. CONCLUSION First-line pembrolizumab confers meaningful and durable clinical response in cisplatin-ineligible patients with advanced UC and is associated with prolonged OS, particularly with PD-L1 CPS ≥ 10 and lymph node–only disease.

The discovery of vibegron, a potent and selective human β3-AR agonist for the treatment of overactive bladder (OAB), is described. An early-generation clinical β3-AR agonist MK-0634 (3) exhibited efficacy in humans for the treatment of OAB, but development was discontinued due to unacceptable structure-based toxicity in preclinical species. Optimization of a series of second-generation pyrrolidine-derived β3-AR agonists included reducing the risk for phospholipidosis, the risk of formation of disproportionate human metabolites, and the risk of formation of high levels of circulating metabolites in preclinical species. These efforts resulted in the discovery of vibegron, which possesses improved druglike properties and an overall superior preclinical profile compared to MK-0634. Structure-activity relationships leading to the discovery of vibegron and a summary of its preclinical profile are described.

350 Background: The PD-1 inhibitor pembro has durable antitumor activity in pts with metastatic urothelial carcinoma. Upregulation of the PD-1 pathway has been observed in BCG-resistant NMIBC, suggesting pembro may benefit. Efficacy and safety of pembro in pts with HR, BCG-unresponsive NMIBC was evaluated in the single-arm phase 2 KEYNOTE-057 study; updated results for pts with carcinoma in situ (CIS) with or without papillary tumor (cohort A) are reported. Methods: Pts with histologically confirmed HR, BCG-unresponsive CIS with or without papillary disease, who received adequate BCG therapy and were unable/unwilling to undergo radical cystectomy received pembro 200 mg Q3W for 24 mo or until recurrence, progression, or unacceptable toxicity. Pts with HR NMIBC or progressive disease during treatment were required to discontinue. Primary end point: complete response rate (CRR); key secondary end points: duration of response and safety. Results: 103 pts (median age 73 years; CIS alone 71.8%; median number of prior BCG instillations 12) have enrolled in cohort A. 3-mo CRR rate was 38.8% (95% CI 29.4%-48.9%) by central assessment. Among 40 pts who achieved CR at 3 mo, 72.5% maintained CR at last follow-up (median 14.0 mo; range 4.0-26.3) and median CR duration has not been reached (range 0+ to 14.1+ mo). 80.2% of pts had a CR duration of ≥6 mo (Kaplan-Meier method). 10 (25.0%) experienced recurrent NMIBC after CR; at the time of analysis, none progressed to muscle invasive or metastatic disease. Treatment-related adverse events (AEs) occurred in 65 (63.1%) pts; most frequent were pruritus (10.7%), fatigue (9.7%), diarrhea (8.7%), hypothyroidism (5.8%), and maculopapular rash (5.8%). Grade 3/4 treatment-related AEs occurred in 13 (12.6%) pts; 1 death was considered treatment-related (colitis in patient inadequately treated with steroids). Immune-mediated AEs occurred in 19 (18.4%) pts. Conclusions: Pembro had encouraging activity in pts with HR, BCG-unresponsive CIS with or without papillary tumors and a safety profile consistent with that of previous experience. Updated data using additional follow-up will be presented. Clinical trial. Clinical trial information: NCT02625961.