Johnson & Johnson: in Phase 1, pasritamig with JNJ-9401 cut PSA by 50% or more in 11 of 15 patients

Johnson & Johnson presented early data on Monday, 9 November 2026, on a combination of two bispecific antibodies, pasritamig and JNJ-9401, in metastatic castration-resistant prostate cancer, according to ad-hoc-news.de. The results come from a Phase 1 study, and the combination is now moving into Phase 3 ad-hoc-news.dead-hoc-news.dead-hoc-news.deOpen source ↗.

Phase 1 results

Pasritamig and JNJ-9401 target the proteins KLK2 and PSMA and are intended to activate T cells against tumor cells with complementary signals. At the recommended dose, 11 of 15 patients, or 73 percent, had a decline in prostate-specific antigen (PSA) of at least 50 percent. Seven patients, or 47 percent, reached a decline of at least 90 percent, and in four patients PSA was no longer detectable. All seven patients with the deepest decline remained on treatment without disease progression for more than six months.

The data come from a small, early group of patients and are therefore not evidence of clinical benefit in a broad population. According to Johnson & Johnson, 144 patients had been enrolled in the ongoing study as of 15 June 2026. The group receiving the recommended combination had been treated with a median of four systemic therapy lines before enrolment.

Safety and next steps

At the recommended dose, the company's release of 9 November reports no treatment-related adverse events of grade 3 or higher, no dose-limiting toxicities, and no treatment-related discontinuations or deaths ad-hoc-news.dead-hoc-news.dead-hoc-news.deOpen source ↗. Cytokine release syndrome occurred in three patients, in all cases grade 1 with transient fever. No cases of immune effector cell-associated neurotoxicity were reported.

The combination will now be studied in the Phase 3 trial KLK2-comPAS. It is intended to determine whether adding JNJ-9401 to pasritamig improves treatment outcomes in metastatic castration-resistant prostate cancer. A further Phase 3 study is testing pasritamig together with docetaxel in the first-line setting. The company is also investigating pasritamig as a single agent and in other combinations.