Johnson & Johnson (NYSE:JNJ) has presented Phase 1 clinical trial results for JNJ-6143, an investigational oral treatment for advanced prostate cancer, at the European Society for Medical Oncology (ESMO) Congress 2026 in Madrid.
The company reported tumour responses and reductions in prostate-specific antigen (PSA) levels among patients who had previously received multiple treatments for the disease.
In the 50 mg dose group, 75% of patients with measurable disease achieved a confirmed complete or partial tumour response, while 77% of patients receiving the same daily dose recorded a confirmed PSA reduction of at least 50%.
The results come from an early-stage clinical study, with Johnson & Johnson selecting the 50 mg once-daily dose for further investigation, including a planned Phase 2 trial in metastatic prostate cancer.
Johnson & Johnson reported that 12 of 16 patients with measurable disease in the 50 mg dose cohort achieved a confirmed complete or partial tumour response.
This represented a response rate of 75%, assessed using the Response Evaluation Criteria in Solid Tumors (RECIST), a standardised framework for measuring changes in tumour size during cancer treatment.
The findings were reported in patients with advanced prostate cancer who had previously undergone several lines of therapy.
Participants had received a median of four prior treatments before entering the study.
The company also evaluated changes in PSA levels, a biomarker commonly used to monitor prostate cancer activity and treatment response.
Among 38 patients treated with JNJ-6143 at a dose of 50 mg once daily, 77% experienced a confirmed reduction in PSA levels of at least 50%.
Additionally, 48% of patients in the same group achieved PSA reductions of 90% or more.
These measurements provide preliminary evidence of the drug’s biological and antitumour activity, although PSA reductions do not independently establish improvements in survival or other long-term clinical outcomes.
At the time of the analysis, 71% of patients in the 50 mg cohort were continuing treatment with JNJ-6143.
The median follow-up period was 5.6 months.
The proportion of patients remaining on treatment provides information about treatment continuation during the observation period, but the relatively short follow-up limits conclusions about the durability of responses.
The Phase 1 study involved patients with advanced disease who had received a median of four previous therapies.
This treatment history is relevant when interpreting the findings because the study population had already undergone multiple therapeutic interventions.
Further clinical investigation will be needed to determine whether the responses observed during the initial study are maintained over longer periods.
Johnson & Johnson also presented preliminary safety findings from the study.
The most frequently reported treatment-related adverse events were elevated cholesterol levels, affecting 18% of patients, nausea in 16%, and increased triglyceride levels in 16%.
One patient discontinued treatment because of adverse events.
The reported findings provide an initial assessment of the tolerability of JNJ-6143 in patients with advanced prostate cancer.
However, the early stage of development and limited follow-up mean that additional studies will be required to characterise the drug’s safety profile more fully.
Longer-term research will also help establish whether adverse events change with treatment duration or exposure in larger patient populations.
JNJ-6143 is an investigational oral small molecule developed using a mechanism known as Regulated Induced Proximity Targeting Chimera, or RIPTAC.
The technology is designed to bring two proteins into close proximity within cancer cells, disrupting functions required for their survival.
In the case of JNJ-6143, the treatment is intended to connect BRD4, a protein involved in cell survival, with the androgen receptor.
The androgen receptor is highly expressed in prostate cancer cells and plays a role in the biological processes associated with the disease.
By bringing these proteins together, the investigational treatment is designed to interfere with cancer cell function.
The mechanism differs from approaches that act solely by blocking androgen receptor signalling.
The clinical results presented at ESMO provide early information about the activity of this investigational mechanism in patients with advanced prostate cancer.
Johnson & Johnson obtained JNJ-6143 and the underlying RIPTAC technology platform through its acquisition of Halda Therapeutics in December 2025.
The acquisition added the investigational treatment and its associated drug development technology to Johnson & Johnson’s oncology research portfolio.
The company has subsequently advanced clinical development of JNJ-6143, including evaluation of different dosing levels in patients with advanced prostate cancer.
The Phase 1 results presented at ESMO represent an update on the programme following the acquisition.
Johnson & Johnson has not disclosed a commercial launch timetable for the treatment.
Following its assessment of the Phase 1 findings, Johnson & Johnson selected the 50 mg once-daily dose for continued clinical development.
The next stages include a Phase 2 study involving patients with metastatic prostate cancer.
Further research will be intended to evaluate the treatment’s antitumour activity, safety and durability of response in a larger clinical setting.
The initial results are based on relatively small patient groups, including 16 participants assessed for measurable tumour responses and 38 assessed for PSA reductions at the selected dose.
The study also had a median follow-up of 5.6 months at the time of analysis.
These factors limit the conclusions that can be drawn about long-term effectiveness and safety.
JNJ-6143 remains an investigational medicine, and the reported Phase 1 findings do not establish regulatory approval or clinical effectiveness in a broader patient population.
The Phase 1 data presented at ESMO 2026 provide preliminary clinical information about JNJ-6143 and its RIPTAC mechanism in previously treated advanced prostate cancer.
The reported findings include a 75% confirmed tumour response rate among patients with measurable disease in the 50 mg cohort and a confirmed PSA reduction of at least 50% in 77% of patients receiving the selected daily dose.
Johnson & Johnson also reported that 71% of patients remained on treatment at the time of analysis, with elevated cholesterol, nausea and increased triglycerides among the most common treatment-related adverse events.
The company’s decision to advance the 50 mg dose into further development will allow additional investigation of the treatment’s efficacy and safety.
Future clinical data will be needed to determine whether the early responses translate into sustained benefits for patients with metastatic prostate cancer.
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