Johnson & Johnson (NYSE:JNJ) disclosed Phase 1 clinical results for the investigational combination of pasritamig and JNJ-9401 in metastatic castration-resistant prostate cancer, presented at the Society for Immunotherapy of Cancer 2026 Annual Meeting on November 8, 2026.

Key Highlights

  • PSA50 response rate: 73 percent (11 of 15 patients) at the recommended regimen achieved PSA reductions of at least 50 percent, according to the filing.
  • Deep PSA reductions: 47 percent (7 of 15 patients) achieved reductions of at least 90 percent, with four patients reaching undetectable PSA levels.
  • Sustained responses: All seven patients with at least 90 percent PSA reductions remained on treatment for more than six months without disease progression.
  • Safety profile: No Grade 3 or higher treatment-related adverse events, dose-limiting toxicities, or treatment-related discontinuations or deaths were reported at the recommended regimen.
  • Recommended regimen: JNJ-9401 200 mg subcutaneously every six weeks combined with pasritamig 300 mg intravenously every six weeks, following two initial weekly pasritamig step-up doses.
  • Study enrollment: As of June 15, 2026, 144 patients had enrolled in the Phase 1 study (NCT06095089).
  • Phase 3 advancement: The combination is being evaluated in the ongoing Phase 3 KLK2-comPAS study (NCT07164443) in metastatic castration-resistant prostate cancer.

Phase 1 Findings for Pasritamig and JNJ-9401 in Prostate Cancer

Johnson & Johnson disclosed preliminary Phase 1 results for the investigational combination of pasritamig and JNJ-9401 in an open-label, multicenter study evaluating safety and clinical activity in patients with metastatic castration-resistant prostate cancer (mCRPC). According to the filing, patients treated at the recommended regimen were heavily pretreated, having received a median of four prior lines of systemic therapy, with a range of two to six. The data cutoff for these findings was June 15, 2026.

The filing describes the combination as the first dual-tumor-antigen-targeted bispecific antibody regimen clinically evaluated in prostate cancer. Pasritamig is characterized as a first-in-class KLK2xCD3 bispecific antibody designed to direct T cells to prostate cancer cells, while JNJ-9401 is described as a PSMAxCD28 costimulatory bispecific antibody designed to provide an additional signal that enhances T-cell activation and function. The company noted the combination targets two prostate cancer proteins, KLK2 and PSMA, through complementary mechanisms.

Regarding the safety data at the recommended regimen, the filing reports that cytokine release syndrome (CRS) was observed in three patients (20 percent), all classified as mild Grade 1 cases presenting as temporary fever, with none requiring treatment with tocilizumab. No cases of immune effector cell-associated neurotoxicity syndrome (ICANS) were reported. The filing states the findings suggest the combination has potential for administration in an outpatient setting on the every-six-week schedule. The company noted these preliminary findings are based on a small number of patients and that "further evaluation is needed to determine the clinical benefit and safety of the combination in a larger population."

What Was Disclosed

Johnson & Johnson released Phase 1 data for the pasritamig and JNJ-9401 combination in mCRPC patients, reporting PSA response rates and a safety profile at the recommended regimen, while noting the combination has advanced into a Phase 3 study.