Updated efficacy and safety of SHR-1501, an IL-15RαFc superagonist, with or without Bacille Calmette Guerin (BCG) for high-risk non-muscle invasive bladder cancer (NMIBC): A phase 1/2 study.

Abstract

4626 Background: SHR-1501, an IL-15 agonist fusion protein composing of a humanized antibody Fc region fused with IL-15 and IL-15Rα sushi domain, demonstrated promising efficacy, well tolerance, and acceptable safety in alone or in combination with BCG in patients with BCG-naive and BCG-unresponsive high-risk NMIBC ( ASCO 2025 ). Here, we report the updated results of this phase 1/2 study (NCT05410730). Methods: In the dose-escalation phase 1a and 1b parts, SHR-1501 monotherapy (200, 400, and 600 μg) or SHR-1501 (600 μg) in combination with BCG (120 mg) was administered to patients with high-risk NMIBC. In the phase 2 part, patients with BCG-naive NMIBC (cohort A), BCG-unresponsive NMIBC carcinoma in situ (CIS; cohort B), and BCG-unresponsive high-grade Ta/T1 NMIBC without CIS (cohort C) were enrolled to receive SHR-1501 (600 μg) plus BCG (120 mg). During the induction phase, all patients received weekly intravesical study treatment for 6 weeks. In the maintenance phase, instillations were administered weekly for three weeks at months 3, 6, 12, 18, and 24 following the initial induction dose. Primary endpoints were dose-limiting toxicity (DLT), maximum tolerated dose (MTD), and recommended phase 2 dose in phase 1a and 1b parts; and was complete response (CR) rate for cohort B and 12-mo disease-free survival (DFS) rate for cohorts A and C in phase 2 part. Results: As of Oct 31, 2025, 112 patients were enrolled (n=8 in phase 1a; n=6 in phase 1b; n=30, 25, and 43 in cohorts A, B, and C in phase 2). The median follow-up duration was 23.0 months (range 3.5-25.6) in patients with BCG-naive NMIBC, 6.5 months (range 2.6-21.2) in patients with BCG-unresponsive NMIBC CIS, and 13.5 months (range 2.5-23.1) in patients with BCG-unresponsive high-grade Ta/T1 NMIBC without CIS. In cohort B, the overall CR rate was 80.0% (20/25), the median DFS was 12.0 months (95% CI 6.0-NR). The 12-mo DFS rate was 90.3% (95% CI, 72.8-96.8) in patients with BCG-naive NMIBC and 62.7% (95% CI, 44.9-76.1) in patients with BCG-unresponsive high-grade Ta/T1 NMIBC without CIS. The 18-mo DFS rates were 90.3% (95% CI, 72.8-96.8) and 58.2% (95% CI, 39.6-72.9), respectively. Treatment-related adverse events (TRAEs) and grade 3 TRAEs occurred in 90 (86.5%) and 19 (18.3%) of 104 patients with SHR-1501 + BCG. The most common TRAEs were urinary tract infection (62.5%) and pollakiuria (35.6%). No TRAEs led to death. Conclusions: This updated analysis confirms the promising efficacy and manageable safety profile of SHR-1501 monotherapy or in combination with BCG in BCG-naive and BCG-unresponsive high-risk NMIBC patients. Two randomized, controlled phase 3 trials are underway in both BCG-unresponsive and BCG-naïve, high-risk NMIBC populations, with the recommended dose of 600 μg SHR-1501 plus BCG. Clinical trial information: NCT05410730 .