Phase II/III clinical results of IL-15RαFc superagonist N-803 with BCG in BCG-unresponsive non-muscle invasive bladder cancer (NMIBC) carcinoma in situ (CIS) patients.
Karim Chamie, Sam S. Chang, Mark L. Gonzalgo, Eugene V. Kramolowsky, Wade J. Sexton, Sandeep K. Reddy, Paul Bhar, Chad Garner, Patrick Soon‐Shiong
Abstract
510 Background: Patients with NMIBC CIS unresponsive to BCG have limited treatment options. N-803 (Anktiva) is a mutant IL-15-based immunostimulatory fusion protein complex (IL-15RαFc) that promotes proliferation and activation of natural killer (NK) cells and CD8+ T cells, but not regulatory T cells. Phase Ib data in BCG-naive patients with NMIBC demonstrate that intravesical administration of N-803 with BCG induced complete response in all patients, without recurrences for the study duration of 24 months. An open-label, 3 cohort multicenter phase II/III study (QUILT 3.032) of intravesical BCG plus N-803 in patients with BCG-unresponsive high-grade NMIBC (NCT03022825) was opened. We report here the interim analysis of Cohort A, BCG-unresponsive (CIS) [with or without Ta or T1 disease], as of December 2020 data cutoff. Methods: All treated patients received intravesical N-803 plus BCG, consistent with the standard induction/maintenance treatment schedule. The primary endpoint for Cohort A of this phase II/III study is incidence of complete response (CR) of CIS at any time. Results: To date, 80 patients have enrolled in cohort A of this phase II/III trial. Evaluable analysis at this time shows CR rate at any time of 72% (N=51/71); for patients achieving CR, the probability of maintaining a CR for 12 months is 59%, with a median duration of complete response of 19.2 (7.6, 26.4) months. Low-grade treatment related AEs include dysuria, hematuria, and pollakiurua (all 16%), urgency (14%), and bladder spasm (8%), all other AEs were seen at 6% or less. A total of 9 subjects experienced at least 1 treatment emergent SAE (Severe Adverse event), the SAE rate is 1% for any given AE. No treatment emergent SAE’s were considered treatment related. No immune related SAE’s have been seen. To date, 10/80 (12.5%) patients proceeded to cystectomy in this BCG unresponsive population. Conclusions:With a CR rate of 72%, N-803 has met its primary endpoint with 59% probability of CR patients maintaining CR for at least 12 months. With the observed strong efficacy and an SAE rate of 1%, N-803 represents a novel treatment option for BCG unresponsive CIS with a favorable benefit:risk ratio, in a therapeutically challenging disease. Clinical trial information: NCT03022825.