Radiopharm Theranostics Clears Safety Review to Open 180 mCi Cohort in 177Lu-RAD202 HER2 Radioligand Trial

A safety review with no patient numbers attached

The release describes the DSMC as a multidisciplinary group that "conducts detailed reviews of study data, discusses potential safety events and provides recommendations regarding trial continuation." It does not say how many patients were treated at 130 mCi, what adverse events were seen there, or whether any tumor responses have been recorded above the first dose level.

"The DSMC's recommendation supports the favorable safety profile observed to date and allows us to continue evaluating higher dose levels in patients with HER2-positive advanced solid tumors," said Riccardo Canevari, chief executive officer and managing director.

The agent and the trial design

RAD202 is a proprietary single-domain antibody, a format the company says allows deep tumor penetration and fast systemic clearance, carrying the beta emitter lutetium-177. A prior diagnostic study in ten HER2-positive breast cancer patients is the company's proof-of-concept. HEAT, short for HER2-Antibody Therapy with Lutetium-177, pairs a Phase 0 imaging-dose stage that measures biodistribution and dosimetry with a Phase 1 escalation aimed at a recommended Phase 2 dose.

The only clinical results disclosed so far come from the 30 mCi cohort, presented as a poster at the American Association for Cancer Research annual meeting on April 20, 2026. Three heavily pretreated patients with HER2-positive breast and urothelial cancers showed what the company called meaningful tumor uptake, particularly in breast lesions, with mostly Grade 1 to 2 adverse events. Chief Medical Officer Dimitris Voliotis, M.D., said then that the team expected "to see signs of antitumor activity at higher, more therapeutic dose levels."

Neither release defines HER2-positive for enrollment, so the immunohistochemistry or in situ hybridization threshold used to admit patients, and whether HER2-low tumors qualify, remains unstated.

Why This Matters to the APO|APE Reader

Enhertu's HER2-low and ultralow breast cancer labels have already turned the HER2 IHC score from a binary into a continuum, and a lutetium-177 HER2 radioligand would add another way to read the same slide, since a beta emitter's bystander effect can reach antigen-poor cells the antibody never binds. Radiopharm's own medical officer tied efficacy expectations to the higher dose levels, so the 180 mCi cohort is where the program starts to answer that question, and the HER2 cut-off the sponsor eventually writes into a Phase 2 protocol is what a lab will need to know.