JNJ-6143 prostate cancer: 75% tumor response in Phase 1 trial

Johnson & Johnson reported Phase 1 results for JNJ-6143 prostate cancer treatment, with a 75% tumor response rate: 12 of 16 patients with measurable disease responded. JNJ-6143 is an investigational, once-daily oral Regulated Induced Proximity Targeting Chimera (RIPTAC) molecule, and the first from that platform to enter clinical studies. The data were presented at the ESMO Congress 2026.

Patients had metastatic castration-resistant prostate cancer that progressed after one or more androgen receptor pathway inhibitors. They had received a median of four prior therapies, including chemotherapy and PSMA-targeted radioligand therapy. Among 38 patients on the 50 mg once-daily dose, 77% had a confirmed reduction of at least 50% in prostate-specific antigen (PSA), and 48% saw PSA fall by at least 90%.

JNJ-6143 prostate cancer: dose and safety

The dose-escalation portion tested once-daily doses from 12.5 mg to 150 mg. In the expansion, patients were randomized 1:1 to 25 mg or 50 mg, and 50 mg was identified as the preliminary optimal dose. At analysis, 71% of patients on 50 mg remained on treatment, with a median follow-up of 5.6 months. The most common treatment-related adverse events in this group were elevated cholesterol (18%), nausea (16%) and elevated triglycerides (16%). Four patients (11%) interrupted their dose, one (3%) reduced it and one (3%) discontinued because of adverse events. The 50 mg dose will advance into a Phase 2 study in metastatic prostate cancer (NCT07832292).

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Why it matters

The sample is small: 16 patients with measurable disease and 38 on the 50 mg dose, with a median follow-up of 5.6 months. The release does not report progression-free or overall survival, so whether the responses last is not yet known. The population was heavily pretreated, with a median of four prior therapies, so these results describe later-line use.

Source: Johnson & Johnson press release, 25 October 2026