J&J prostate cancer drug shows strong early data

Johnson & Johnson (JNJ) reported that its investigational oral prostate cancer therapy JNJ-6143 achieved substantial antitumor activity in an early-stage trial of previously treated advanced disease. In the Phase 1 study’s 50 mg once-daily cohort, 12 of 16 patients with measurable tumors had a confirmed complete or partial response, corresponding to a 75% tumor response rate. In a group of 31 evaluable patients at the same dose, 69% of those with measurable tumors achieved confirmed complete or partial responses, indicating that their tumors either disappeared or shrank in size. The study enrolled patients with metastatic prostate cancer whose disease had progressed after one or more androgen receptor pathway inhibitors and who had received a median of four prior therapies.

JNJ-6143 is described as a first-in-class RIPTAC molecule that uses a novel mechanism intended to selectively eliminate prostate cancer cells by targeting a protein critical for their survival. Dose escalation in the Phase 1 trial ranged from 12.5 mg to 150 mg once daily, followed by a dose-expansion phase that randomized participants to receive 25 mg or 50 mg once daily. Based on the emerging data, Johnson & Johnson plans further development of the 50 mg once-daily dose, including a Phase 2 study in metastatic prostate cancer.

Beyond radiographic tumor responses, JNJ-6143 produced marked reductions in prostate-specific antigen, a blood marker commonly used to monitor prostate cancer. Among 38 patients receiving the 50 mg once-daily dose, 77% achieved a confirmed PSA decline of at least 50%. Within this group, 48% recorded PSA reductions of at least 90%, underscoring the depth of biomarker response in many participants.

At the time of analysis, the median follow-up for patients in the 50 mg cohort was 5.6 months, and 71% of patients remained on treatment. The findings were presented at the European Society for Medical Oncology Congress, highlighting the early but notable activity of JNJ-6143 in a heavily pretreated, metastatic population.

Most treatment-related adverse events observed with JNJ-6143 in the Phase 1 trial were mild to moderate. Frequently reported side effects included elevated cholesterol in 18% of patients, nausea in 16%, and elevated triglycerides in 16%. Adverse events led to four dose interruptions, one dose reduction, and one treatment discontinuation at the 50 mg dose. One patient discontinued treatment because of adverse effects.

JNJ-6143 was added to Johnson & Johnson’s pipeline through its $3.05 billion acquisition of Halda Therapeutics. The drug introduces a new mechanism of action within the company’s prostate cancer portfolio, distinct from its existing therapies. While the current data come from a relatively small, early-stage study that does not establish effects on long-term survival, they support continued clinical development of the 50 mg once-daily regimen into Phase 2 trials in metastatic prostate cancer.