Johnson & Johnson (NYSE:JNJ) today announced preliminary results from a Phase 1b study evaluating pasritamig (JNJ-78278343), a first-in-class bispecific T-cell engaging antibody, in combination with docetaxel in patients with metastatic castration-resistant prostate cancer. The combination demonstrated a safety profile consistent with docetaxel alone, with no new or unexpected safety signals observed. The regimen also showed clinically meaningful efficacy, including high rates of prostate-specific antigen (PSA) responses and sustained PSA reductions, supporting continued development and advancement into Phase 3 studies. The results were presented for the first time at the 2026 American Society of Clinical Oncology (ASCO) Genitourinary Cancers Symposium.

Pasritamig is designed to engage the immune system through a novel mechanism of action, binding CD3 on T cells and human kallikrein 2 (KLK2). KLK2 is a novel, highly specific prostate cancer target with minimal expression outside prostate tissue. By both activating and directing T cells to KLK2-expressing tumor cells, pasritamig enables targeted immune engagement. This differentiated, prostate-specific approach was intentionally built to focus immune activity on prostate cancer cells, which may help limit effects on healthy tissue, and supports administration in a doctor's office rather than hospital setting.