JNJ-78278343 is a humanized immunoglobulin (Ig)G1-based bispecific antibody designed to direct T lymphocytes (T cells) to human kallikrein 2 (hK2or KLK2) positive target tumor cells. One arm of JNJ-78278343 binds to the cluster of differentiation (CD)3 receptor complex present on T cells and the other arm binds to KLK2 present on target tumor cells leading to the activation of the T cells and T-cell-mediated lysis of the KLK2 bearing tumor cells. JNJ-78278343 is being developed for the treatment of metastatic castration-resistant prostate cancer (mCRPC). KLK2 expression is highly restricted in normal tissues and highly enriched in prostate adenocarcinoma and its expression is mostly maintained throughout disease progression, making KLK2 an attractive target for therapy. This study will be conducted in 2 phases: a Screening Phase (up to 30 days), a Treatment Phase (start of study drug administration) with an end of treatment (EOT) visit (up to 30 plus 14 days after last dose of study drug or prior to the start of a new anticancer therapy), whichever comes first). The total duration of the study is up to 1 year and 10 months. Safety assessment will include adverse events (AEs) including dose-limiting toxicity (DLT), serious adverse events (SAEs), physical examination, vital signs, electrocardiogram, clinical safety laboratory assessments, Eastern Cooperative Oncology Group (ECOG) performance status, and neurologic examination.
The purpose of this study is to determine the recommended phase 2 dose(s) (RP2Ds) of JNJ-78278343 in Part 1 (Dose Escalation) and the safety at the RP2Ds in Part 2 (Dose Expansion).