Radiopharm posts 93% PET–MRI match in brain trial

Radiopharm Theranostics reports Phase 2b RAD101 PET data meeting its primary endpoint and prepares for an FDA meeting to plan a pivotal Phase 3 trial in brain metastases imaging.

Rhea-AI Filing Summary

Radiopharm Theranostics Limited (RADX) reported positive interim results from a U.S. Phase 2b imaging trial of its PET tracer 18F‑RAD101 in patients with suspected recurrent brain metastases. RAD101 PET showed 93% concordance with MRI across all evaluable lesions, meeting the study’s primary endpoint, and data have been selected for a late‑breaking oral presentation at the 2026 Society of Neuro‑Oncology meeting.

The company plans to meet the FDA on October 1, 2026 to align on the protocol for a pivotal, multi‑center global Phase 3 imaging trial, supported in the U.S. by a manufacturing and distribution partnership with Siemens Healthineers. Preliminary analysis in 14 patients with six‑month follow‑up and/or biopsy showed 86% sensitivity, a secondary objective, in a U.S. market the company estimates at about $600 million for brain metastases imaging with no currently approved PET products.

Filing Explained

The filing adds that RAD101’s interim results come from a 30-evaluable-person, single-arm Phase 2b trial; the data are intended to support Phase 3 initiation, but protocol alignment with the FDA remains planned for October 1, 2026.

Key Figures

PET–MRI Concordance: 93% Preliminary Sensitivity: 86% Planned Phase 2b Sample Size: 30 individuals +3 more

6 metrics

PET–MRI Concordance 93% Concordance between RAD101 PET and MRI across all evaluable lesions in the Phase 2b trial, meeting the primary endpoint

Preliminary Sensitivity 86% Sensitivity in 14 patients with six‑month follow‑up and/or biopsy data, a secondary objective of the Phase 2b trial

Planned Phase 2b Sample Size 30 individuals Number of evaluable participants targeted in the U.S. Phase 2b imaging trial of 18F‑RAD101

FDA Meeting Date October 1, 2026 Planned meeting with the FDA to align on the RAD101 Phase 3 pivotal trial protocol

Brain Metastases Imaging TAM $600 million Estimated total addressable market for brain metastases imaging with no approved PET products

Annual U.S. Cerebral Metastases Patients 300,000+ patients Patients diagnosed annually with cerebral metastases in the United States

Key Terms

Fast Track Designation, Phase 2b imaging trial, pivotal Phase 3 trial, sensitivity, +2 more

6 terms

Fast Track Designation regulatory

"RAD101 has received U.S. Food and Drug Administration (FDA) Fast Track Designation"

Fast track designation is a status the U.S. Food and Drug Administration grants to drugs intended to treat serious conditions and address an unmet medical need. It gives the developer more frequent communication with the FDA and can allow parts of the application to be reviewed on a rolling basis, and it may pave the way to priority review or accelerated approval. It can shorten development timelines, though it does not guarantee approval.

Phase 2b imaging trial medical

"positive data from an interim analysis of the Company’s Phase 2b imaging clinical trial"

pivotal Phase 3 trial medical

"used to support the initiation of a pivotal multi-center, global Phase 3 imaging trial"

A pivotal phase 3 trial is the late-stage clinical study designed to provide the decisive evidence regulators need to approve a new drug or medical treatment. Think of it as the final exam where the treatment must prove it works and is safe in a large group of people; investors watch the results closely because a positive outcome can unlock regulatory approval, sales, milestone payments and big changes in a company’s valuation.

sensitivity medical

"14 patients with evaluable six-month follow-up and/or biopsy data show preliminary 86% sensitivity"

brain metastases medical

"participants with suspected recurrent brain metastases from solid tumors"

Cancer cells that have spread from another part of the body to the brain, forming new tumors there. Think of it like weeds from one garden taking root in another; the behavior and treatment needs can change significantly once cancer reaches the brain. For investors, brain metastases matter because they often drive different clinical trial designs, higher healthcare costs, and urgent demand for effective therapies, all of which can materially affect a biotech or healthcare company’s prospects.

Intracranial Metastatic Disease (IMD) medical

"The incidence of Intracranial Metastatic Disease (IMD) continues to increase"

Intracranial metastatic disease (IMD) is cancer that has spread from another part of the body into the brain. For investors, IMD matters because it often requires costly, specialized treatments and can drive demand for new therapies, diagnostics, and medical devices; like a house fire in a distant room, it suddenly changes priorities, timelines and expenses for care and can strongly influence a healthcare company’s revenue and regulatory outlook.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What did RADX disclose about the RAD101 Phase 2b trial in this Form 6-K?

Radiopharm Theranostics reported positive interim data from a U.S. Phase 2b imaging trial of 18F‑RAD101 in suspected recurrent brain metastases, with RAD101 PET achieving 93% concordance with MRI and meeting the study’s primary endpoint, and these data were selected for a late‑breaking oral presentation at SNO26.

What key efficacy metrics for RAD101 were highlighted by RADX?

The company highlighted 93% concordance between RAD101 PET and MRI across all evaluable lesions, meeting the primary endpoint, and preliminary 86% sensitivity in 14 patients with six‑month follow‑up and/or biopsy data, a secondary objective assessing the ability to correctly identify patients with disease.

What are Radiopharm Theranostics’ next regulatory steps for RAD101?

Radiopharm Theranostics plans a meeting with the FDA on October 1, 2026 to align on the protocol for a pivotal global Phase 3 imaging trial of RAD101 in suspected recurrent brain metastases, following the positive interim Phase 2b data.

How large is the target market for RAD101 according to RADX?

The company states that brain metastases imaging has an estimated $600 million total addressable market and notes there are no currently approved PET products for this indication, with more than 300,000 patients diagnosed annually with cerebral metastases in the U.S.

What special regulatory status does RAD101 have with the FDA?

RAD101 has received U.S. FDA Fast Track Designation to distinguish between recurrent disease and treatment effect in brain metastases originating from solid tumors of different origins, including leptomeningeal disease, supporting its further development in this high‑unmet‑need indication.

What partnership supports RAD101’s planned Phase 3 trial mentioned by RADX?

Radiopharm Theranostics disclosed a partnership with Siemens Healthineers, under which Siemens will manufacture and distribute 18F‑RAD101 doses in the U.S. to support the company’s planned pivotal Phase 3 imaging trial.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Available on EDGAR 09/14/2026 - 06:11 AM Accepted by SEC EDGAR 09/14/2026 - 06:11 AM Learn about SEC filing dates

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 6-K

REPORT OF FOREIGN PRIVATE ISSUER

PURSUANT TO RULE 13a-16 OR 15d-16 UNDER

THE SECURITIES EXCHANGE ACT OF 1934

For the Month of September 2026

Commission File Number: 001-41621

RADIOPHARM THERANOSTICS LIMITED

(Name of Registrant)

Level 3, 62 Lygon Street, Carlton South, Victoria, 3053, Australia

(Address of principal executive office)

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.

Form 20-F ☒       Form 40-F ☐

RADIOPHARM THERANOSTICS LIMITED

EXPLANATORY NOTE

Radiopharm Theranostics Limited (the “Company”) published one announcement (the “Public Notice”) to the Australian Securities Exchange on September 14, 2026 titled:

“RAD oral presentation at SNO26 on RAD101 Phase IIb data”

A copy of the Public Notice is attached as an exhibit to this report on Form 6-K.

This report on Form 6-K (including any exhibit hereto) shall not be deemed to be “filed” for purposes of the Securities Exchange Act of 1934 and shall not be incorporated by reference into any registration statement or prospectus under the Securities Act of 1933, except as shall be expressly set forth by specific reference in such registration statement or prospectus.

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EXHIBITS

Exhibit Number		Description
99.1		RAD oral presentation at SNO26 on RAD101 Phase IIb data

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SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

	RADIOPHARM THERANOSTICS LIMITED
Date: September 14, 2026	By:	/s/ Amritha Sushil
		Amritha Sushil
		Company Secretary

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Exhibit 99.1

ASX ANNOUNCEMENT
September 14, 2026

Radiopharm Theranostics Selected for Late-Breaking Oral Presentation of Positive Data from Interim Analysis of U.S. Phase 2b Imaging Trial of RAD101 at 2026 Society of Neuro-Oncology Annual Meeting

RAD101 PET demonstrated 93% concordance with MRI across all evaluable lesions, meeting the trial’s primary endpoint

Meeting with FDA planned on October 1^st to align on RAD101Phase 3 pivotal trial protocol

Brain Metastases Imaging has ~$600 million total addressable market, and there are no currently approved PET products

Sydney, Australia – 14 September 2026 – Radiopharm Theranostics (ASX: RAD, Nasdaq: RADX, “Radiopharm” or the “Company”), a clinical-stage biopharmaceutical company focused on developing innovative oncology radiopharmaceuticals for areas of high unmet medical need, today announced that positive data from an interim analysis of the Company’s Phase 2b imaging clinical trial (NCT06777433) of 18F-RAD101 (RAD101) in participants with suspected recurrent brain metastases from solid tumors has been selected for a late-breaking oral presentation at the  31^st Annual Meeting of the Society of Neuro-Oncology (SNO26), taking place from November 12-15, 2026 in Philadelphia.

RAD101 is Radiopharm’s novel imaging small molecule targeting fatty acid synthase (FASN) radiolabelled with Fluorine-18 for the diagnosis of suspected recurrent brain metastases from solid tumors of different origins. The data from these findings will be used to support the initiation of a pivotal multi-center, global Phase 3 imaging trial.

“Having these data selected for a late-breaking oral presentation at SNO26 is a meaningful recognition of the potential clinical importance of RAD101,” said Riccardo Canevari, CEO and Managing Director of Radiopharm Theranostics. “The neuro-oncology community understands better than anyone the challenges associated with distinguishing active brain metastases from treatment effects using current imaging approaches. Knowing whether metastatic disease is present can fundamentally alter a patient’s treatment path and prognosis. We believe these data underscore RAD101’s potential to address a significant unmet need by helping physicians make more informed decisions and potentially changing the course of disease management for patients with suspected recurrent brain metastases.”

Previously reported results from the Phase 2b imaging trial of RAD101 for all assessed lesions showed 93% concordance between MRI and PET imaging of brain metastases in this patient population with suspected recurrence. The results showed substantial and selective tumor uptake of RAD101. Images confirm metabolic activity in PET compared to equivocal MRI findings. Additionally, 14 patients with evaluable six-month follow-up and/or biopsy data show preliminary 86% sensitivity, representing a strong positive trend (a secondary objective). Sensitivity measures an imaging test’s ability to correctly identify patients with disease.

Radiopharm Theranostics Limited
Suite 1, Level 3, 62 Lygon Street, Carlton South VIC 3053 Australia
ABN: 57 647 877 889

ASX ANNOUNCEMENT
September 14, 2026

In the U.S. alone, there are more than 300,000 patients diagnosed annually with cerebral metastases. The incidence of Intracranial Metastatic Disease (IMD) continues to increase, in part, due to improvements in systemic therapy resulting in a more durable control of the tumors outside of the central nervous system. Contrast-enhanced Magnetic Resonance Imaging (CE-MRI) is the preferred method for imaging IMD, but has limitations, particularly in follow-up surveillance scans to optimise patient care.¹ 

RAD101 has received U.S. Food and Drug Administration (FDA) Fast Track Designation to distinguish between recurrent disease and treatment effect of brain metastases originating from solid tumors of different origin including leptomeningeal disease. The company also recently announced a partnership with Siemens Healthineers, who will manufacture and distribute doses of 18F-labeled RAD101 to support Radiopharm’s upcoming Phase 3 pivotal trial in the U.S.

About the Phase 2b Clinical Trial of RAD101

The U.S. multi-center, open-label, single arm Phase 2b clinical trial is assessing the diagnostic performance of 18F-RAD101 in 30 evaluable individuals with suspected recurrent brain metastases from solid tumors of different origins. The primary objective of the study is concordance between 18F-RAD101 PET-positive lesions and those equivocal lesions seen in conventional imaging (MRI with gadolinium) in participants with known brain metastases and suspected relapse after stereotactic radiosurgery (SRS). Secondary endpoints are sensitivity and specificity of RAD101 in identifying tumor recurrence versus radiation-associated changes in previously SRS-treated brain metastases.

About RAD101

RAD101 is the Company’s novel imaging small molecule that selectively binds to fatty acid synthase (FASN), a multi-enzyme protein that catalyses de-novo fatty acid synthesis and is overexpressed in cerebral metastasis from solid tumors. Targeting FASN activity may allow for the more accurate detection of cancer cells in the CNS, representing a clinically relevant method for the imaging of brain metastases. Positive data from the Imperial College of London’s Phase 2a imaging trial of 18F-RAD101 in patients with brain metastases (both SRS pre-treated and treatment naïve patients) showed significant tumor uptake that was independent from the tumor of origin. The study further indicated that PET-MRI may potentially represent a non-invasive prediction of overall-survival, warranting larger studies.

About Radiopharm Theranostics

Radiopharm Theranostics is a clinical stage radiotherapeutics company developing a world-class platform of innovative radiopharmaceutical products for diagnostic and therapeutic applications in areas of high unmet medical need. Radiopharm is listed on ASX (RAD) and on NASDAQ (RADX). The company has a pipeline of distinct and highly differentiated platform technologies spanning peptides, small molecules and monoclonal antibodies for use in cancer. The clinical program includes one Phase 2 and five Phase 1 trials in a variety of solid tumor cancers including lung, breast, prostate and brain. Learn more at radiopharmtheranostics.com.

¹ A hybrid [18F]fluoropivalate PET-multiparametric MRI to detect and characterise brain tumour metastases based on a permissive environment for monocarboxylate transport | European Journal of Nuclear Medicine and Molecular Imaging

Radiopharm Theranostics Limited
Suite 1, Level 3, 62 Lygon Street, Carlton South VIC 3053 Australia
ABN: 57 647 877 889

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ASX ANNOUNCEMENT
September 14, 2026

Authorized on behalf of the Radiopharm Theranostics Board of Directors by Executive Chairman Paul Hopper.

For more information:

Investors:

Riccardo Canevari
CEO & Managing Director
P: +1 862 309 0293
E: rc@radiopharmtheranostics.com

Anne Marie Fields

Precision AQ (formerly Stern IR)

E: annemarie.fields@precisionaq.com

Media:

Matt Wright
NWR Communications
P: +61 451 896 420
E: matt@nwrcommunications.com.au

Follow Radiopharm Theranostics:

Website – https://radiopharmtheranostics.com/
X – https://x.com/TeamRadiopharm
LinkedIn – https://www.linkedin.com/company/radiopharm-theranostics/
InvestorHub – https://investorhub.radiopharmtheranostics.com/

Radiopharm Theranostics Limited
Suite 1, Level 3, 62 Lygon Street, Carlton South VIC 3053 Australia
ABN: 57 647 877 889

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Filing Exhibits & Attachments

1 document

Press Releases

• EX-99.1 RAD ORAL PRESENTATION AT SNO26 ON RAD101 PHASE IIB DATA 18.1 KB