RAD 101 Shows 90% Primary End Point Success in Brain Metastases Trial

Results from a phase 2b clinical trial (NCT06777433) evaluating 18F-fluoroethyl-L-tyrosine (RAD 101) for the detection and characterization of brain metastases revealed that the primary end point was achieved in 90% of the patient cohort, strengthening the clinical case for amino acid PET imaging in neuro-oncology.¹

The multicenter study is designed to assess the diagnostic performance of RAD 101 in patients with suspected metastatic brain tumors. Achieving the primary end point involved reaching a prespecified level of concordance between the PET imaging results and the established standard of truth, typically defined by histopathology or clinical and radiologic follow-up.

Addressing the Diagnostic Gap in Neuro-Oncology

The management of brain metastases remains a significant challenge for oncologists, particularly when attempting to differentiate between tumor recurrence and treatment-related changes. While gadolinium-enhanced MRI remains the current standard for monitoring central nervous system malignancies, it possesses inherent limitations. MRI primarily detects blood-brain barrier disruption, which can occur not only during tumor growth but also following stereotactic radiosurgery or immunotherapy, a phenomenon known as pseudoprogression.

By contrast, RAD 101 is an amino acid analog tracer that targets L-type amino acid transporters (LAT1 and LAT2), which are frequently overexpressed in neoplastic cells. Because amino acid uptake is less affected by inflammatory processes than glucose metabolism or contrast enhancement, RAD 101 offers a more specific metabolic signal. This allows clinicians to distinguish viable tumor tissue from radiation necrosis with greater accuracy than conventional imaging.

Trial Design and Interim Findings

The phase 2b trial focuses on the diagnostic accuracy of RAD 101 in patients who have previously undergone treatment for brain metastases. The primary objective is to demonstrate the tracer’s ability to correctly identify metastatic lesions as confirmed by independent central review.²

The achievement of the 90% threshold in this second interim analysis follows a positive first interim report, suggesting consistent performance across the study’s mid-point.¹ Radiopharm Theranostics, the sponsor, indicated that the imaging data were highly concordant with clinical outcomes, providing a reliable metabolic map of the disease state. The safety profile of RAD 101 remained favorable, with no drug-related serious adverse events reported during the interim period.

“The strength and consistency of these interim results further validate the potential of RAD 101 to address one of the most challenging diagnostic gaps in neuro-oncology,” said Riccardo Canevari, CEO and managing director of Radiopharm Theranostics, in a news release. “With 90% concordance demonstrated to date and encouraging early signals in sensitivity and specificity, we are increasingly confident in RAD 101’s ability to support more accurate and timely treatment decisions for patients with brain metastases. We look forward to the final data readout from the full 30-patient study by June, which will guide our path toward a pivotal trial and, ultimately, toward bringing this important imaging agent to the clinicians and patients who need it.”

Clinical Implications and Future Directions

The integration of amino acid PET tracers like RAD 101 into clinical practice aligns with current recommendations from the Response Assessment in Neuro-Oncology (RANO) working group. RANO guidelines increasingly advocate for the use of PET imaging to supplement MRI when radiographic findings are ambiguous.³

If the final data from this phase 2b study maintain these levels of sensitivity and specificity, RAD 101 may move toward a pivotal phase 3 program. For clinicians, the availability of a standardized, commercially produced amino acid tracer could streamline the decision-making process for secondary interventions, potentially sparing patients from unnecessary biopsies or preventing delays in treating confirmed recurrences.

REFERENCES

1. Radiopharm Theranostics Achieves Primary Endpoint In 90% of Patients At Second Interim Analysis of RAD 101 Phase 2b Imaging Trial in Brain Metastases. News release. Radiopharm Theranostics. March 24, 2026. Accessed March 26, 2026. https://tinyurl.com/yrf6ky98

2. Phase 2b Imaging Study of RAD101 in Participants With Suspected Recurrent Brain Metastases (RAD101). ClinicalTrials.gov. Updated November 24, 2025. Accessed March 26, 2026. https://clinicaltrials.gov/study/NCT06777433

3. Lopci E, Lowe V, McConathy J, et al. Joint EANM/EANO/RANO practice guidelines/SNMMI procedure standards for imaging of gliomas using PET with radiolabelled amino acids and [¹⁸F]FDG: version 1.0. Eur J Nucl Med Mol Imaging. 2019 Mar;46(3):540-557. doi: 10.1007/s00259-018-4207-9. Epub 2018 Dec 5. PMID: 30519867; PMCID: PMC6351513.