Here is a summary of the press release:

**Overview**
Johnson & Johnson announced promising preliminary results from a Phase 1b study evaluating its investigational drug **pasritamig** (JNJ-78278343) in combination with the chemotherapy drug **docetaxel** for patients with metastatic castration-resistant prostate cancer (mCRPC). The findings were presented at the 2026 ASCO Genitourinary Cancers Symposium.

**How Pasritamig Works**
Pasritamig is a first-in-class bispecific T-cell engaging antibody. It works by binding to CD3 on T cells and human kallikrein 2 (KLK2)—a target highly specific to prostate tissue—on cancer cells. This redirects the body’s immune system to specifically attack the prostate cancer cells while minimizing damage to healthy tissues.

**Key Efficacy Results**
The combination showed deep and sustained clinical activity, particularly in reducing prostate-specific antigen (PSA) levels:

* **Overall Patients:** 64.7% achieved a PSA reduction of 50% or more, and 39.2% achieved a reduction of 90% or more.
* **Taxane-Naïve Patients:** Efficacy was even higher, with 75% achieving a ≥50% PSA reduction and 53.6% achieving a ≥90% reduction.
* **Taxane-Naïve Patients with Bone-Only Disease:** Showed the strongest response, with 88.2% achieving a ≥50% PSA reduction and 76.5% achieving a ≥90% reduction.

**Safety Profile**
The safety profile of the combination was favorable and consistent with what is typically seen with docetaxel alone. There were no new or unexpected safety signals.

* Grade 3 or higher treatment-related adverse events were primarily attributed to docetaxel (29.4%) rather than pasritamig (2%).
* No patients experienced cytokine release syndrome (CRS) or treatment-related deaths.

**Next Steps**
Because of these encouraging results—combining immunotherapy with chemotherapy where previous approaches have fallen short—J&J is advancing pasritamig into two Phase 3 trials. The drug has also already received Breakthrough Therapy Designation in China and Fast Track designation from the U.S. FDA.