Phase 1 study of JNJ-69086420, an actinium-225-labeled antibody targeting human kallikrein-2, for advanced prostate cancer.

Abstract

TPS206 Background: Radioligand therapy for metastatic castration resistant prostate cancer (mCRPC) has been shown to prolong survival, delay disease progression, and improve quality of life, raising hopes that these gains will be amplified with even more cancer-specific targets and more powerful radioligands. Human kallikrein-related peptidase 2 (hK2) is a tumor-associated member of the kallikrein family that shares significant homology to prostate-specific antigen and is minimally expressed in normal non-prostate tissues. JNJ-69086420 (JNJ-420; 225Ac-DOTA-h11B6 [1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid]), is a first-in-class radioimmunotherapy targeted to hK2 antigen. In a phase 0 study of [111In]-DOTA-h11B6, patients (pts) with mCRPC (progressed on standard therapies), treatment with a single dose of [111In]-DOTA-h11B6 (2 mg) with/without 8 mg h11B6, demonstrated safety, good tumor localization, nominal normal-organ uptake, and no difference in PK between 2 and 10 mg antibody mass (Morris et al. J Clin Oncol. 2021 39:6 suppl, 122). We have initiated the first-in-human study to assess the safety, pharmacokinetics (PK), pharmacodynamic (PD), and clinical activity of Ac-225 radiolabeled JNJ-420, to determine its recommended phase 2 dose (RP2D) in adults with advanced PC. Methods: This open-label, multicenter, phase 1 study will recruit approximately 50 men (aged ≥18 years) with advanced PC across dose escalation (Part 1) and expansion (Part 2) parts. Key eligibility criteria: mCRPC with histologic confirmation of adenocarcinoma, Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1, adequate organ function based on hematology and serum chemistry, and 1 or more prior novel androgen receptor-targeted therapies (prior chemotherapy acceptable). Key exclusion criteria: prior treatment with radium/strontium/samarium/radioconjugate therapy, superscan findings as protocol defined, active central nervous system metastases. In Part 1, men will receive intravenous (IV) injection of 50 μCi/ 2 mg JNJ-420 (once every 8 weeks) with one or multiple doses; escalation of dose levels to be based on dose limiting toxicities (DLTs) evaluation, until RP2D identification. In Part 2, JNJ-420 is to be given at one of the RP2D(s) determined in Part 1. Primary endpoint is safety (incidence and severity [grading per NCI-CTCAE V5.0] of AEs including DLTs). Secondary endpoints include prostate specific antigen response rate, overall response rate (PCWG3 modified RECIST 1.1 criteria), PK, PD, immunogenicity, and biomarker analyses. Enrollment began in Dec 2020; as of Sep 2021, 4 sites have been initiated and 14 pts enrolled; currently, dose escalation is ongoing. Clinical trial information: NCT04644770.