Khobe Chandran, Christina Guo, Simon Pacey, Guillermo Villacampa, Ruth Matthews, Toby Prout, Joan Fernandes, Alison Turner, Mona Parmar, Ruth Riisnaes, Ana Ferreira, Suzanne Carreira, Claudia Bertan, Mateus Crespo, Ines Figueiredo, Wei Yuan, Denisa Bogdan, Florence Raynaud, Ruth Ruddle, Bianca Calì, Martino Maddalena, Arianna Calcinotto, C. Yap, Adam Sharp, Andrea Alimonti, Johann De Bono, Alec Paschalis
BACKGROUND: Interleukin-23 (IL23) has been reported to drive androgen receptor (AR) and JAK2-STAT3 signaling, promoting treatment resistance and disease progression in advanced prostate cancer (PC). We evaluated the safety, tolerability, and antitumor activity of the anti-IL23 monoclonal antibody tildrakizumab in combination with the AR pathway inhibitor (ARPI) abiraterone acetate (AA) in men with ARPI-resistant metastatic castration-resistant PC (mCRPC). METHODS: mCRPC patients of ECOG performance status (PS) ≤ 2, who had previously progressed on first-line ARPI therapy, were treated with tildrakizumab (100 mg, 300 mg, 600 mg; 4-weekly) in combination with AA (YonsaTM, 500 mg daily). The primary objective was to determine the recommended phase 2 dose. Secondary endpoints were elucidation of pharmacokinetics (PK), pharmacodynamics (PD), and antitumor activity. RESULTS: No dose limiting toxicities (DLTs) were observed, nor any grade ≥ 3 adverse effects (AEs). The most common treatment-related AEs attributable to tildrakizumab were grade 1-2 fatigue (n = 3/12; 25.0%) and grade 1 nausea (n = 2/12; 16.7%). PK analyses showed no obvious drug-drug interactions. Overall, no objective responses were observed. Median progression free survival (PFS) was 3.7 months (n = 10; 95% CI 1.6-not reached) with median overall survival (OS) of 9.7 months (n = 10; 95% CI 6.9-not reached). CONCLUSIONS: Tildrakizumab and abiraterone acetate combination therapy is well tolerated but did not show clinical efficacy in this small, unselected, cohort of ARPI-resistant mCRPC patients. Further study into the causes of primary resistance to IL23 targeting in mCRPC, and development of biomarkers of downstream IL23-IL23R activity, are now needed to translate IL23 blockade into the clinic.