Radiopharm Theranostics Shares RAD101 Phase IIb Update: 90% Hit Primary Endpoint in Brain Mets Study

Key Points

• 90% interim success: in the Phase IIb interim analysis, 18 of 20 patients (90%) met the primary endpoint for RAD101 imaging of suspected post‑treatment brain metastases; enrollment is nearly complete and official study results are expected in May–June with planned FDA discussions on Phase III design in mid‑2026.
• Diagnostic value: RAD101 is a small‑molecule PET tracer targeting fatty acid synthase designed to help distinguish tumor recurrence from radiation necrosis when MRI is equivocal, and presenters cited biopsy‑confirmed PET‑positive cases that supported its clinical utility.
• Development and commercial outlook: Radiopharm aims to be ready to start a registrational Phase III (estimated ~150–200 patients) before the end of 2026, has received business development interest, and referenced an external U.S. sales potential of more than $500 million annually.

Radiopharm Theranostics NASDAQ: RADX executives and clinical investigators highlighted new interim findings from the company’s ongoing Phase IIb study of RAD101, a PET imaging tracer intended to help physicians evaluate suspected recurrent brain metastases after radiotherapy when MRI results are unclear.

Phase IIb interim analysis: 18 of 20 patients met the primary objective

During the workshop, company representatives said a second interim analysis now includes data from the first 20 patients in the 30-patient Phase IIb trial, representing about two-thirds of the planned dataset. Management said 18 of the 20 treated patients (90%) achieved the primary objective, which the company described as a strong result in a population where standard-of-care MRI is considered “suboptimal,” “equivocal,” or otherwise not definitive.

Radiopharm emphasized that the study is focused specifically on post-treatment scenarios where physicians suspect recurrence but cannot confidently distinguish tumor recurrence from radiation necrosis using MRI alone. The company argued that an additional functional imaging readout could help clinicians manage patients more effectively by supporting earlier and more confident treatment decisions.

Enrollment update and expected timing of results and FDA interactions

Radiopharm said enrollment is nearly complete, with 27 of 30 patients recruited and two additional patients already scheduled for treatment. The company expects to complete the study in April, describing a timeline of “two to three weeks” to finish enrollment and dosing.

Management said the “official results” from the Phase IIb study are expected between May and June. Based on the interim findings, Radiopharm said it is preparing for a Phase III registrational study and expects to interact with the U.S. Food and Drug Administration in mid-2026 (described as June or July by the CEO, and as July or August by the CMO), noting that a meeting request has not yet been submitted. The company framed the FDA discussions as focused on trial design details—such as patient count and endpoints—rather than whether a Phase III study is warranted.

Radiopharm also said it is working on protocol development and chemistry, manufacturing, and controls (CMC) preparation. Company leadership stated an ambition to be ready to start Phase III before the end of 2026. In discussing potential Phase III size, the CMO said the company believes it could involve roughly 150 to 200 patients, although final sizing would be part of FDA alignment.

Why the company believes RAD101 may add value beyond MRI

Chief Medical Officer Dimitris Voliotis said brain metastases represent a large clinical need, citing an estimate of approximately 300,000 new cases diagnosed annually in the U.S. He said MRI is effective for initial detection but is limited after treatments such as stereotactic radiosurgery, where radiation necrosis can appear similar to active tumor on structural imaging.

Voliotis described RAD101 (also referred to as Pivalate during the presentation) as a small-molecule imaging agent that selectively targets fatty acid synthase, which he said cancer cells use to grow in the brain’s lipid-deprived microenvironment. He said FDG PET is often less useful in the brain because of high baseline glucose metabolism, making tumor-to-background contrast challenging.

He also referenced published work from Imperial College London, which he said demonstrated tracer uptake across multiple primary tumor types and reported preliminary observations linking higher PET SUV values with shorter progression-free survival and overall survival, while MRI was described as not informative for that correlation.

Patient case examples and biopsy confirmations

Dr. Harshad Kulkarni, Chief Medical Advisor at BAMF Health and a principal investigator, reviewed multiple case examples comparing MRI findings after stereotactic radiosurgery with RAD101 PET-CT imaging. Across the examples, speakers repeatedly described MRI results as uncertain regarding whether findings represented residual/recurring tumor or radiation necrosis, while PET imaging showed focal tracer uptake interpreted as metabolically active tumor.

In two cases discussed, the presenters said biopsy results confirmed active tumor in lesions that were PET-positive. In one example involving a breast cancer patient, Kulkarni reported intense tracer uptake with an SUV max of 3.7 and said biopsy confirmed viable tumor. In another example described as potentially misleading on MRI and more consistent with necrosis by appearance, presenters said RAD101 PET showed strong uptake and biopsy subsequently confirmed active tumor.

Speakers argued that these findings could support more timely decisions—either escalation to targeted therapy when PET suggests viable tumor or avoidance of overtreatment when PET is negative.

Discordant cases and how “truth standard” will be established

Radiopharm said two patients did not show PET-MRI concordance in the interim dataset. Management attributed those cases to very small, questionable cerebellar lesions that were difficult to image and may ultimately represent false positives on MRI. The company said confirmation will depend on the study’s “truth standard,” which includes longitudinal follow-up imaging over roughly six to nine months and, when available, histopathology from biopsy.

In the Q&A, the company said it expects to approach the FDA with interim results based on the primary endpoint and partial sensitivity/specificity data, while full sensitivity and specificity assessment depends on completion of follow-up windows or biopsy confirmation.

Separately, the CEO said Radiopharm has received business development interest in RAD101 but declined to provide specifics. He also said an external commercial assessment estimated U.S. sales potential of more than $500 million annually, while noting he could not disclose additional details. On potential partnerships, management said a partner could help with resources and global rollout, but may not materially accelerate timelines if the Phase III study remains relatively small.

About Radiopharm Theranostics NASDAQ: RADX

Radiopharm Theranostics, Inc is a clinical-stage biopharmaceutical company focused on the development and commercialization of radiopharmaceutical products for both diagnostic imaging and targeted radiotherapeutic applications. By harnessing the unique properties of radioisotopes, the company aims to improve the precision of disease detection and deliver therapeutic payloads directly to diseased tissues, particularly in oncology.

The company's research and development efforts are concentrated on a pipeline of radioligand therapies and companion diagnostic agents designed to address a variety of tumor types.

This instant news alert was generated by narrative science technology and financial data from MarketBeat in order to provide readers with the fastest reporting and unbiased coverage. Please send any questions or comments about this story to contact@marketbeat.com.