Bristol Myers Cancer Drug Slows Progression of Rare Tumours in Phase 3 Trial
Bristol Myers Squibb has revealed encouraging findings from a late-stage study involving its new cancer treatment, RYZ101. It proved to be quite effective in extending progression-free survival of patients with GEP-NETs that have worsened despite previous treatment with Lu-177-based drug therapy.
The findings, which were revealed on 12 October, represent a significant breakthrough for the treatment of patients with no many treatment alternatives available. It is also an important milestone for Bristol Myers Squibb's radiopharmaceuticals. The company has not yet released detailed information on the treatment's benefits.
Phase 3 trial meets its primary endpoint
The ACTION-1 trial was a Phase 3 test of RYZ101 versus available standard therapies. The subjects were patients with somatostatin receptor-positive GEP-NETs who had progressed despite previous treatment with lutetium-177.
According to Bristol Myers, the interim analysis met the study's primary goal. The independent central assessment found a statistically significant and clinically relevant increase in progression-free survival. The safety data were also consistent with the therapy's known safety profile.
Progression-free survival refers to the period during which patients survive without worsening of their condition. It is an essential metric in advanced cancer studies, especially where patients are being tested on therapies for cancers that have recurred or grown after previous therapy.
However, the results need more evaluation. Bristol Myers has not provided numbers such as median progression-free survival and hazard ratio.
The company expects to present detailed findings at a future medical meeting. Patients enrolled in ACTION-1 will continue to receive care under the study protocol. Researchers will also continue monitoring overall survival.
How RYZ101 targets cancer cells
RYZ101 uses a targeted radiopharmaceutical approach. It combines DOTATATE, a tumour-targeting peptide, with actinium-225, a radioactive isotope that emits high-energy alpha particles.
The drug is designed to bind to somatostatin receptors expressed on cancer cells. Once delivered to the targeted tissue, actinium-225 releases radiation over a short distance. This can cause severe DNA damage in cancer cells and potentially destroy them.
The approach differs from conventional chemotherapy. Rather than relying on drugs that circulate through the body to disrupt cell growth, targeted radiopharmaceuticals carry radiation towards specific tumour cells.
This distinction matters because radiation can damage healthy tissue as well as cancer cells. The short range of alpha particles offers the potential to concentrate their effects near the target. However, targeted delivery does not eliminate the risk of side effects.
Why patients need another treatment option
GEP-NETs develop in neuroendocrine cells in the gastrointestinal tract and pancreas. These cells share characteristics of both nerve cells and hormone-producing cells.
The tumours can behave unpredictably. Some grow slowly, while others progress aggressively or spread to distant organs. Their symptoms can also vary, depending on the tumour's location and whether it produces hormones.
Bristol Myers estimates that approximately 18,000 people in the United States are diagnosed with GEP-NETs annually. The company also reports that most patients with these tumours have metastatic disease at diagnosis.
Lutetium-177-based radiopharmaceutical therapy has become an important treatment for patients with somatostatin receptor-positive disease. However, many patients eventually experience progression. Finding an effective next-line treatment remains a major clinical challenge.
ACTION-1 addresses this gap by studying RYZ101 after lutetium-177 treatment no longer controls the disease. Its positive results could help establish an evidence-based option for this difficult treatment stage.
A milestone for alpha-based radiopharmaceuticals
The findings also matter beyond Bristol Myers. According to RayzeBio, the company developing RYZ101, ACTION-1 is the first Phase 3 trial of an alpha-isotope-based targeted radiopharmaceutical to report results in any indication.
Bristol Myers acquired RayzeBio in a deal valued at approximately $4.1 billion. The acquisition gave the pharmaceutical group access to a pipeline of targeted radiopharmaceutical candidates.
The company is now seeking to advance RYZ101 towards potential regulatory submission. The US Food and Drug Administration granted the treatment orphan drug designation for GEP-NETs in August 2026. This designation recognises the need for treatments targeting rare diseases. It does not constitute marketing approval.
Actinium-225 also presents a practical challenge for the wider field. Demand for this isotope is growing as researchers investigate alpha-emitting therapies. Limited supply has complicated development efforts across the sector.
The treatment's future will therefore depend on more than its initial trial success. Regulators will need to assess the full efficacy and safety data. Manufacturing capacity and isotope availability could also affect its eventual commercial reach.
RYZ101 is additionally being studied in earlier-stage trials for hormone receptor-positive metastatic breast cancer.
For now, the ACTION-1 results offer a promising signal for patients whose GEP-NETs progress after existing radiopharmaceutical treatment. The next key test will be whether the complete data confirm a meaningful clinical benefit and support regulatory approval.
