RAD101 brain metastasis imaging pact supports Phase 3 plans for Radiopharm (NASDAQ: RADX)

Rhea-AI Filing Summary

Radiopharm Theranostics Limited filed a Form 6-K to furnish an announcement that it has signed a clinical supply agreement with Siemens Healthineers for RAD101 in the U.S. Siemens will radiolabel and distribute 18F-labeled RAD101 to support a planned multi-center global Phase 3 registrational trial.

Interim data from a Phase 2b trial showed 90% concordance (18 of 20 patients) between RAD101 PET imaging and MRI, the study’s primary endpoint, with significant and selective tumor uptake in brain metastases. Early six-month follow-up in five evaluable patients indicates a positive trend for sensitivity and specificity. RAD101 has received U.S. FDA Fast Track Designation for distinguishing recurrent brain metastases from treatment effects, and topline Phase 2b data are expected in the first half of 2026.

Insights

Biopharma & Clinical Trials Analyst

Supply deal enables late-stage trials for Fast Track RAD101 with encouraging Phase 2b imaging data.

Radiopharm Theranostics has secured Siemens Healthineers to manufacture and distribute 18F-labeled RAD101 for a planned U.S. Phase 3 registrational trial in recurrent brain metastases. This arrangement addresses the complex logistics of PET tracer production and nationwide delivery.

Phase 2b interim data reported 90% concordance (18/20 patients) between RAD101 PET scans and MRI, the primary endpoint, with selective tumor uptake. Early six‑month and biopsy data from five patients show a positive trend in sensitivity and specificity, supporting progression to Phase 3.

RAD101 already has U.S. FDA Fast Track Designation for differentiating recurrent disease from treatment effects in brain metastases of various solid tumors. Actual impact will depend on final Phase 2b topline results in the first half of 2026 and execution of the subsequent global Phase 3 trial.

Key Figures

Primary endpoint concordance: 90% (18/20 patients) Early follow-up set: 5 patients Regulatory status: Fast Track Designation +2 more

5 metrics

Primary endpoint concordance 90% (18/20 patients) Phase 2b trial PET–MRI concordance in brain metastases

Early follow-up set 5 patients First patients with six‑month follow-up and/or biopsy data

Regulatory status Fast Track Designation U.S. FDA status for RAD101 in recurrent brain metastases

Annual U.S. incidence 300,000 people Individuals diagnosed with brain metastases each year in the U.S.

Topline Phase 2b data timing First half 2026 Expected readout guiding initiation of Phase 3 trial

Key Terms

Fast Track Designation, Phase 2b trial, Phase 3 registrational trial, PET imaging, +1 more

5 terms

Fast Track Designation regulatory

"The company has received U.S. Food and Drug Administration (FDA) Fast Track Designation to distinguish between recurrent disease and the treatment effect"

A "fast track designation" is a process that speeds up the review and approval of a product or project, allowing it to reach the market or be completed more quickly than usual. For investors, it can signal that a product may become available sooner, potentially leading to earlier revenue or benefits, and indicating a priority status that might influence company performance and market opportunities.

Phase 2b trial clinical

"Data from the interim analysis in Phase 2b trial of RAD101 showed significant and selective tumor uptake"

A phase 2b trial is a mid-stage clinical study that tests whether a new drug or therapy is effective at specific doses and helps determine the optimal amount and schedule for treatment. For investors it matters because convincing phase 2b results lower the chance of failure in later, larger trials—like a prototype consistently meeting performance targets before mass production—making the program more likely to advance and increasing its potential commercial value.

Phase 3 registrational trial clinical

"Partnership ensures sufficient supply of RAD 101 in Phase 3 registrational trial in the U.S."

A phase 3 registrational trial is a large, late-stage clinical study designed to produce the definitive safety and effectiveness data regulators need to decide whether to approve a new medical product. For investors, its results are critical because positive findings greatly increase the chance of market authorization and future sales, while negative or ambiguous results can sharply reduce expected value—think of it as the product’s final exam before getting a license to sell.

PET imaging technical

"90% (18/20) of the patients dosed with RAD101 achieved concordance between PET imaging and MRI"

PET imaging is a noninvasive medical scan that works like a molecular camera, using tiny radioactive tracers to reveal biological activity inside the body—for example metabolism, blood flow, or the presence of specific proteins. It matters to investors because PET results guide diagnosis, show whether a drug reaches its intended target and how patients respond, and therefore affect clinical trial success, regulatory approval, reimbursement decisions and demand for scanners, tracers and related services.

radiopharmaceuticals technical

"a clinical-stage biopharmaceutical company focused on developing innovative oncology radiopharmaceuticals for areas of high unmet medical need"

Radiopharmaceuticals are medicines that carry tiny amounts of radioactive material to help doctors see or treat disease inside the body, acting like a tracer dye for imaging or a microscopic guided missile for targeted therapy. They matter to investors because their safety, regulatory approval, production complexity, short shelf life and hospital reimbursement determine how quickly they can reach patients and generate revenue, affecting a company’s sales potential and risk profile.

Form 6-K: How Foreign Companies Report to the SEC →

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 April 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 ☐

Indicate by check mark whether by furnishing the information contained in this Form, the registrant is also thereby furnishing the information to the Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934.

Yes ☐       No ☒

If “Yes” is marked, indicate below the file number assigned to the registrant in connection with Rule 12g3-2(b): 82-

RADIOPHARM THERANOSTICS LIMITED

EXPLANATORY NOTE

Radiopharm Theranostics Limited (the “Company”) published one announcement (the “Public Notice”) to the Australian Securities Exchange on April 7, 2026 titled:

“RAD and Siemens Sign Clinical Supply Agreement for RAD101 ”

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 the exhibit hereto) shall not be deemed to be “filed” for purposes of the Securities Exchange Act of 1934, as amended (the “Exchange Act”) and shall not be incorporated by reference into any filing under the Securities Act of 1933, as amended, except as shall be expressly set forth by specific reference in such filing.

1

EXHIBITS

Exhibit Number		Description
99.1		RAD and Siemens Sign Clinical Supply Agreement for RAD101

2

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: April 7, 2026	By:	/s/ Phillip Hains
		Phillip Hains
		Company Secretary

3

Exhibit 99.1

ASX ANNOUNCEMENT
7 April 2026

Radiopharm Theranostics and Siemens Healthineers Sign Clinical Supply Agreement for RAD101 in the U.S.

Data from the interim analysis in Phase 2b trial of RAD101 showed significant and selective tumor uptake in brain metastases,
with 90% concordance (Primary Endpoint) with MRI.

Partnership ensures sufficient supply of RAD 101 in Phase 3 registrational trial in the U.S.

Sydney, Australia. – 7 April 2026 – Radiopharm Theranostics (ASX:RAD, “Radiopharm” or the “Company”), a clinical-stage biopharmaceutical company focused on developing innovative oncology radiopharmaceuticals for areas of high unmet medical need, and Siemens Healthineers, today announced the signing of a supply agreement in which Siemens Healthineers will radiolabel and distribute RAD101 with Fluorine-18 (¹⁸F). 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.

“This partnership marks a milestone for Radiopharm, as we bring RAD101 closer to improving diagnostic precision for brain metastases,” said Riccardo Canevari, CEO and Managing Director of Radiopharm Theranostics. “We have made considerable progress advancing RAD101 through the clinic, and the second interim analysis showed 90% (18/20) of the patients dosed with RAD101 achieved concordance between PET imaging and MRI (the primary endpoint). The results showed significant and selective tumor uptake in the brain metastases. Images confirm metabolic activity in brain metastases compared to equivocal MRI findings. In addition, the first five patients with evaluable six-month follow-up and/or biopsy data show a positive trend for sensitivity and specificity (the secondary objectives). This partnership ensures our supply of ¹⁸F-labeled RAD101 in the U.S. for the initiation of the multi-center global Phase 3 registrational trial following our readout of topline data in the Phase 2b trial in the first half of 2026.”

The company has received U.S. Food and Drug Administration (FDA) Fast Track Designation to distinguish between recurrent disease and the treatment effect of brain metastases originating from solid tumors of different origins, including leptomeningeal disease.

Under the terms of the agreement, Siemens Healthineers will manufacture and distribute doses of ¹⁸F-labeled RAD101 to support Radiopharm’s upcoming Phase 3 registrational trial in the U.S.

“As the leader in PET imaging solutions, we are pleased to partner with Radiopharm Theranostics to provide our reliable and specialized manufacturing capabilities,” said Barry Scott, Head of Radiopharma at Siemens Healthineers. “With our large national network of radiopharmacies in the U.S., we are uniquely qualified and well-equipped to deliver RAD101 as well as other novel PET biomarkers to assist in the fight against challenging diseases such as brain metastases, a condition that more than 300,000 people are diagnosed with in the U.S. each year.”

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

ASX ANNOUNCEMENT
7 April 2026

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, and brain metastases. Learn more at radiopharmtheranostics.com.

Authorised on behalf of the Radiopharm Theranostics board of directors by Chairman Paul Hopper.

For more information:

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

Paul Hopper
Executive Chairman
P: +61 406 671 515
E: paulhopper@lifescienceportfolio.com

Media

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

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

FAQ

What did Radiopharm Theranostics (RADX) announce in this Form 6-K?

Radiopharm Theranostics reported a new clinical supply agreement with Siemens Healthineers for 18F-labeled RAD101. Siemens will manufacture and distribute doses in the U.S. to support Radiopharm’s planned multi-center global Phase 3 registrational trial in recurrent brain metastases.

What are the key Phase 2b results for Radiopharm Theranostics’ RAD101?

Interim Phase 2b data showed RAD101 achieved 90% concordance, or 18 of 20 patients, between PET imaging and MRI, meeting the primary endpoint. The images demonstrated significant, selective tumor uptake in brain metastases and helped clarify equivocal MRI findings in suspected recurrent disease.

What U.S. FDA status does RAD101 have according to Radiopharm Theranostics (RADX)?

RAD101 has received U.S. FDA Fast Track Designation to distinguish recurrent disease from treatment effects in brain metastases from solid tumors, including leptomeningeal disease. This designation is intended to facilitate development of imaging agents addressing serious conditions with unmet medical need.

How will Siemens Healthineers support Radiopharm Theranostics’ RAD101 Phase 3 trial?

Under the agreement, Siemens Healthineers will radiolabel RAD101 with Fluorine-18 and distribute doses across its large U.S. radiopharmacy network. This support is intended to ensure sufficient supply of 18F-labeled RAD101 for Radiopharm’s planned Phase 3 registrational trial in the United States.

When does Radiopharm Theranostics expect topline Phase 2b data for RAD101?

Radiopharm Theranostics expects to read out topline data from the Phase 2b trial of RAD101 in the first half of 2026. The company indicates that initiation of the multi-center global Phase 3 registrational trial will follow this Phase 2b topline data readout.

What medical need is Radiopharm Theranostics’ RAD101 designed to address?

RAD101 targets fatty acid synthase to image suspected recurrent brain metastases from various solid tumors. It aims to distinguish recurrent disease from treatment-related effects, improving diagnostic precision where MRI alone may be equivocal, in a condition affecting more than 300,000 people annually in the U.S.

Filing Exhibits & Attachments

1 document

Press Releases

• EX-99.1 RAD AND SIEMENS SIGN CLINICAL SUPPLY AGREEMENT FOR RAD101 11.0 KB