Pasritamig is a bispecific antibody designed to engage both T cells and prostate cancer cells by binding CD3 on T cells and the kallikrein-related peptidase 2 (KLK2) protein, which is largely restricted to prostate tissue. This mechanism allows circulating T cells to be redirected toward prostate cancer cells, triggering targeted immune-mediated killing. KLK2 has been pursued as a prostate-specific antigen with the potential to minimize off-tumor toxicity that can arise when more broadly expressed targets are chosen.

The first-in-human evaluation of pasritamig has recently been reported in metastatic castration-resistant prostate cancer after multiple prior treatments. In that trial, step-up dosing strategies were applied to control cytokine release, and intravenous dosing schedules were developed that made outpatient administration feasible, including an every-six-week regimen.  No treatment discontinuations due to adverse events were reported at this dose level.

Clinical activity was observed despite the late-line setting. In the recommended dose expansion group, nearly half of patients achieved a reduction of prostate-specific antigen by at least 50%, and over a third had these declines confirmed. Among patients with measurable disease, radiographic responses were modest but durable when they occurred. Median radiographic progression-free survival was close to eight months, with several patients remaining on therapy at the time of data cutoff.

On the basis of these findings, a phase 3 trial known as KLK2-comPAS has been initiated. The study is a randomized, double-blind, placebo-controlled investigation comparing pasritamig with best supportive care against placebo with best supportive care in late-line metastatic castration-resistant prostate cancer. Its primary goal is to evaluate whether the agent can extend overall survival.

Clinical trial.