Abstract CT137: Efficacy and immunological outcomes of non-fucosylated anti-CTLA-4 (BMS-986218) + degarelix acetate vs. degarelix acetate alone in men with high-risk localized prostate cancer (Neo-Red-P)

Abstract Background: Men with high-risk localized prostate cancer are at significant risk for disease recurrence and there is currently no role for neoadjuvant therapy. Although androgen deprivation therapy (ADT) is immunomodulatory and can increase CD8 T cell infiltration, these effects are counterbalanced by the expansion of suppressive regulatory T cells (Tregs). We therefore designed a correlative-rich clinical trial for men with high-risk localized prostate cancer to test whether BMS-986218 - a novel afucosylated anti-CTLA-4 antibody optimized for antibody-dependent cell-mediated cytotoxicity (ADCC) - depletes Tregs and augments response to ADT. Methods: Neo-Red-P is a single-center, two-arm, open-label pilot study assessing degarelix (ADT) versus ADT + anti-CTLA-4-NF (BMS-986218) in patients with treatment naïve high-risk localized prostate cancer. Key eligibility criteria included histologically confirmed adenocarcinoma with Gleason sum of ≥4+3 and clinical stage T1c-T3bN0M0. All patients received degarelix (ADT; 240mg SQ) 2 weeks before radical prostatectomy (RP). Patients were randomized to Arm A (ADT only), or Arm B (ADT + BMS-986218 20mg IV 2 doses Q2w starting 3 weeks before RP). The primary endpoint was the safety and feasibility of neoadjuvant BMS-986218 in prostate cancer. Secondary endpoints included the pathologic complete response rate, rate of undetectable PSA at 12 months, PSA response rate (50% decrease pre-RP), and time-to-PSA recurrence. Fresh tumor specimens were collected at RP for single-cell RNA-sequencing, cytometry by time-of-flight, next-generation sequencing, and multiplex immunofluorescence. A treatment naïve cohort of matching demographic and pathological characteristics was collected for comparative analysis (n=14). Results: Between February 26, 2020, and November 15, 2022, 24 patients were enrolled. Severe treatment-related adverse events (TRAE; Grade ≥ 3) were rare in both arms; 0% in the ADT alone arm and 4% in the combination arm, suggesting a tolerable safety profile with the addition of BMS-986218. In the combination arm, 54% of subjects achieved a 50% reduction in PSA versus 33% in the ADT alone arm. In the ADT alone arm, 80% of patients had an undetectable PSA at 12 months, with a median recurrence-free survival of 1. 61 years (IQR: 1. 50-1. 99 years). In the combination group, 75% had an undetectable PSA at 12 months, with a median recurrence-free survival of 1. 82 years (IQR: 0. 89-2. 07 years). The overall recurrence rate in patients treated with combination therapy was 25% (3 of 12 patients) versus 20% (2 of 10 patients) in the ADT alone arm. Correlative studies suggest that aCTLA4-NF mitigates ADT-induced Treg accumulation through enhanced Fc receptor activity and augmented CTL activation, indicating an enhanced anti-tumor response with combination therapy. Conclusions: The neoadjuvant combination of ADT + aCTLA-4-NF (BMS-986218) is feasible, well tolerated, and induces significant remodeling of the immune TME through enhanced Fc receptor and CTL activity. Rates of disease recurrence following surgery were low in this high-risk population, warranting further investigation of combination immuno-hormonal therapy in the neoadjuvant setting for high-risk prostate cancer. Clinical Trial Information: NCT04301414 Citation Format: Patrick J. McCann, Casey R. Ager, Aleksandar Z. Obradovic, Matthew G. Chaimowitz, Samuel Pan, Caroline J. Laplaca, Parin Shah, Renu K. Virk, Christopher B. Anderson, Catherine S. Spina, Karie D. Runcie, Mark N. Stein, Charles G. Drake, Matthew C. Dallos. Efficacy and immunological outcomes of non-fucosylated anti-CTLA-4 (BMS-986218) + degarelix acetate vs. degarelix acetate alone in men with high-risk localized prostate cancer (Neo-Red-P) abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (7Suppl): Abstract nr CT137.