A year after paying over $3 billion for Halda Therapeutics, Johnson & Johnson has unveiled the first data from its shiny new RIPTAC pipeline that it believes could sustain its leading role in prostate cancer.
J&J bought Halda in November 2025 to get its hands on the biotech’s regulated induced proximity targeting chimera (RIPTAC) platform. The platform is intended to produce bifunctional small molecules that simultaneously bind a tumor-specific protein and a protein with essential function to cell survival in efforts to induce cancer cell death.
The idea is that this novel “hold and kill” mechanism could address cancer’s ability to develop resistance by evolving bypass mechanisms—a key challenge for next-gen oncology drugs.
Ahead of the acquisition, Halda had reported early phase 1 data for its lead asset HLD-0915—which targets androgen receptor and bromodomain 4 (BRD4)—in patients with metastatic prostate cancer who had progressed on prior therapies. The readout showed that among 22 patients who completed at least two cycles of the once-daily oral drug at various doses, 59% achieved a greater than 50% reduction in the prostate-specific antigen.
A year later, J&J has arrived at the European Society for Medical Oncology (ESMO) conference in Madrid armed with its own data from that ongoing study. The findings covered patients with metastatic castration-resistant prostate cancer (mCRPC), an advanced form of prostate cancer that continues to progress despite treatments that target the androgen receptor pathway.
Median overall survival (OS) for these patients typically ranges from around 13.5 to 31.6 months depending on the site of metastasis, J&J noted in its release.
The company’s latest data showed that 75% of patients had now experienced a confirmed complete or partial response.
When zooming in on the 38 patients who received the 50 mg dose, 77% achieved a confirmed reduction in prostate-specific antigen (PSA) levels of at least 50%, with 48% seeing a reduction of 90% of more.
J&J is already a key player in the prostate cancer space, marketing the blockbusters Zytiga and Erleada.
“At a certain point of time, honestly, there was a feeling that there’s nothing more we could do in that space because the drugs are very good,” Yusri Elsayed, M.D., Ph.D., global oncology therapeutic area head at Johnson & Johnson Innovation, told Fierce in an interview at the conference.
But the data at ESMO has been “proof of concept” for the RIPTAC mechanism, persuading J&J that there are fresh ways to treat these cancers, Elsayed explained.
“Given the fact that it kills the cell, regardless of mutations [or] any other resistance mechanism, and it's an oral drug, it’s become like opening the door to say this could be a very foundational medicine,” he said.
“We have been in prostate cancer for almost 20 years, with three drugs in the market,” Elsayed added. “[These are] the best data we have ever seen.”
When it came to treatment-related adverse events, 19% of patients experienced nausea, while 16% experienced fatigue and 13% saw elevated triglyceride levels. All of those were Grade 1 or 2, with only one Grade 3 event and only one patient discontinued treatment due to a side effect.
Because androgen is expressed to some degree in a number of organs, J&J had been prepared to see some adverse events related to this, Elsayed explained.
“We are so happy that it didn't materialize,” he said, suggesting this may be because of the need have a balanced ratio between androgen and BRD4.
The Big Pharma has already launched a phase 2 trial of JNJ-6143 at a 50 mg daily dose in around 100 patients with metastatic androgen pathway modulation-resistant prostate cancer (mAPMR), an advanced form of prostate cancer that has spread and no longer responds to hormone therapy. A phase 3 is also set to kick off next week.
While we’ll have to wait for those studies to get some data on survival, Elsayed said the PSA reductions reported at ESMO “gives some confidence that this will translate hopefully in much bigger survival. Some of the patients had what we call measurable disease or metastases in the liver or lymph node,” he pointed out. “For these patients, usually you don't see any response with Zytiga or Erleada, and we have seen very significant [PSA] reduction.”
Meanwhile, J&J has already taken another RIPTAC with the same concept as JNJ-6143 into the clinic earlier this year. And there are plenty more where that comes from.
“The good thing about it is it’s a platform,” Elsayed said. “So there are probably 20 other programs that are moving very quickly in discovery. Some of them will move quicker than others, but as soon as they progress, then they will enter the clinic in different tumor types.”