Johnson & Johnson reports 75% RECIST response for JNJ-6143 in advanced prostate cancer

Phase 1 efficacy

In a Phase 1 dose-escalation and expansion study of JNJ-6143, an investigational oral RIPTAC molecule, 75% (12/16) of patients with measurable disease had a confirmed complete or partial response by RECIST. Among 38 patients treated at the 50 mg once-daily dose, 77% had a confirmed ≥50% PSA reduction and 48% had ≥90% PSA reductions. Patients had received a median of four prior therapies, including chemotherapy and PSMA-targeted radioligand therapy.

Mechanism

JNJ-6143 is the first clinical candidate from the RIPTAC platform; the molecule is designed to bring together BRD4, an essential cell survival protein, and the androgen receptor (AR), a tumor-selective protein highly expressed in prostate cancer, to disrupt cancer cell function and trigger cancer cell death.

Safety and dose selection

Most treatment-related adverse events were reported as mild to moderate. The most common events were elevated cholesterol (18%), nausea (16%), and elevated triglycerides (16%). Four patients (11%) interrupted dosing, one (3%) reduced dose, and one (3%) discontinued due to adverse events. At analysis, median follow-up for the 50 mg cohort was 5.6 months with 71% still on treatment.

Next steps and context

Based on clinical activity, safety and pharmacokinetics, the 50 mg once-daily dose was chosen to advance into further development, including a planned Phase 2 study (NCT07832292). The program was added to Johnson & Johnson’s portfolio following its December 2025 acquisition of Halda Therapeutics. The company notes ongoing unmet need in metastatic androgen pathway modulation-resistant prostate cancer, where median overall survival is approximately two to three years.