New Delhi: Johnson & Johnson’s experimental prostate cancer drug JNJ-6143 has shown promising anti-tumour activity in an early-stage clinical trial involving patients with advanced prostate cancer who had already undergone multiple treatments. The once-daily oral medicine produced substantial reductions in prostate-specific antigen (PSA) levels and measurable tumour responses in patients receiving a 50-milligram dose.
The findings were presented at the 2026 European Society for Medical Oncology (ESMO) Congress. They offer early evidence that the drug’s novel approach to targeting cancer cells could provide another treatment option for patients with difficult-to-treat prostate cancer.
According to a report by Reuters published by NDTV Profit on October 24, 2026, 77% of 31 evaluable patients receiving the 50-milligram dose experienced a PSA decline of at least 50%. Nearly half, or 48%, recorded a decline of at least 90%.
Imaging assessments also found a confirmed complete or partial tumour response in 69% of patients whose tumours could be measured. However, the medicine remains under clinical investigation, and further trials are needed to establish its safety and effectiveness in larger patient populations.
What the early clinical trial found
The trial evaluated JNJ-6143 in patients with advanced prostate cancer who had received several previous treatments. This is an important aspect of the research because treatment options can become more limited when the disease progresses despite earlier therapies.
The reported findings included two key measurements: changes in PSA levels and tumour responses observed through imaging.
PSA is a protein produced by cells in the prostate. Its level in the blood is commonly used to help monitor prostate cancer and assess how a patient responds to treatment. A substantial fall in PSA can indicate that a treatment is having an effect, although PSA changes alone do not establish whether a medicine improves survival or provides lasting disease control.
In the 50-milligram group, 77% of the 31 evaluable patients recorded a PSA reduction of at least 50%, while 48% experienced a decline of at least 90%.
Separately, imaging assessments showed a confirmed complete or partial response in 69% of patients whose tumours were measurable. A complete response means the measurable signs of cancer have disappeared under the assessment criteria, while a partial response indicates that tumours have decreased sufficiently to meet those criteria.
These outcomes are encouraging, particularly given the patients’ previous treatment histories. Nevertheless, the results come from an early-stage study and should not be interpreted as proof that the drug will work for every patient or provide a long-term survival benefit.
How JNJ-6143 is designed to attack cancer cells
JNJ-6143 uses a new approach known as Regulated Induced Proximity Targeting Chimera, or RIPTAC. Rather than working solely through conventional hormone-blocking mechanisms, the experimental medicine is designed to bring two proteins together inside cancer cells in a way that disrupts their function.
The drug targets the androgen receptor, a protein highly expressed in many prostate cancer cells, and BRD4, a protein involved in processes that help cells survive and function.
By bringing these proteins together, JNJ-6143 is designed to interfere with BRD4’s normal activity in cells expressing the targeted androgen receptor. The intended result is disruption of essential cancer-cell functions, ultimately triggering cell death.
This mechanism differs from treatments that primarily block androgen signalling. Androgens, including testosterone, can support the growth of prostate cancer, which is why hormone-directed treatments play an important role in managing the disease.
The RIPTAC approach is intended to exploit characteristics of cancer cells to produce a more targeted effect. However, the proposed mechanism and early clinical responses do not yet establish how well the medicine will perform across different forms of prostate cancer or how it will compare with existing treatments.
JNJ-6143 was previously known as HLD-0915 and originated from the research programme of Halda Therapeutics.
Side effects and safety remain under evaluation
The reported trial findings also identified side effects that researchers will need to monitor as development continues.
Commonly reported adverse effects included nausea and elevated cholesterol and triglyceride levels. One patient discontinued treatment because of adverse effects, according to Reuters.
Changes in cholesterol and triglycerides are relevant because these blood fats can affect cardiovascular health, depending on their severity, duration and the patient’s broader medical circumstances. Further clinical evaluation will help researchers understand the frequency and seriousness of these effects, as well as whether additional risks emerge with longer treatment.
The available findings do not establish that the drug is suitable for all patients with prostate cancer. Its safety profile will need to be assessed across a larger group of participants and over a longer period.
Patients should not interpret the early results as a reason to discontinue or replace existing treatment. Decisions about prostate cancer therapy require an assessment by qualified healthcare professionals based on the patient’s diagnosis, disease stage, previous treatments and overall health.
J&J expands its cancer drug research portfolio
Johnson & Johnson gained access to JNJ-6143 through its acquisition of Halda Therapeutics, a transaction valued at approximately $3.05 billion that was completed in December 2025.
The acquisition brought Halda’s RIPTAC technology platform into J&J’s oncology research portfolio. JNJ-6143 is the first investigational compound from this platform to advance into clinical studies, according to the company’s announcement.
J&J has said the drug adds a new mechanism of action to its prostate cancer portfolio. The company is evaluating the medicine through Phase 1 and Phase 2 clinical studies involving patients with metastatic prostate cancer.
The company also presented other cancer research findings at the 2026 ESMO Congress, reflecting its broader efforts to develop treatments for solid tumours.
The acquisition demonstrates how pharmaceutical companies are seeking new approaches to cancer treatment through research partnerships and purchases of biotechnology businesses. For J&J, the longer-term value of the Halda transaction will depend on whether its experimental medicines can demonstrate meaningful clinical benefits and progress through the regulatory process.
What happens next?
JNJ-6143 will require further clinical evaluation before its potential role in prostate cancer treatment can be determined. Researchers will need to assess the consistency of tumour responses, how long those responses last, the medicine’s effects on disease progression and survival, and its safety at different doses.
The early results are notable because they show activity in patients with advanced disease who had already received multiple treatments. However, small early-stage studies cannot establish the full balance of benefits and risks or determine whether the drug will be more effective than existing options.
For now, JNJ-6143 represents an investigational approach that could broaden the range of treatments available for advanced prostate cancer if subsequent studies confirm its promise. The next stages of research will be crucial in determining whether the encouraging initial responses translate into sustained benefits for patients.