Radiopharm Theranostics (NASDAQ: RADX) reports strong RAD204 and RAD101 trial results

Rhea-AI Filing Summary

Radiopharm Theranostics Limited reported encouraging clinical data for two key radiopharmaceutical programs. In an ongoing Phase 1 trial of RAD204, a PD-L1-targeted lutetium-177 nanobody for advanced solid tumors post-immunotherapy, the first patient in cohort 3 at the highest dose level #3 (90 mCi) achieved a RECIST-confirmed durable Partial Response, remaining progression-free for beyond seven months. A second patient in the same cohort remains on treatment with early tumor shrinkage, and RAD204 has been generally well-tolerated with no dose-limiting toxicities across dosing cohorts.

In a Phase 2b imaging trial of RAD101 for suspected recurrent brain metastases after radiotherapy, PET imaging with 18F-RAD101 achieved 93% concordance with MRI across all evaluable lesions, meeting the primary endpoint. Among 14 patients with six-month follow-up and/or biopsy, preliminary sensitivity was 86% (12/14), with specificity data expected in Q4 2026. Radiopharm plans to advance RAD101 into a U.S. Phase 3 pivotal trial in Q4 2026. RAD101 holds U.S. FDA Fast Track Designation, and the brain metastases imaging market is estimated at approximately $600+m, with more than 300,000 patients diagnosed annually in the U.S. with cerebral metastases.

Positive

• RAD204 showed a RECIST-confirmed durable Partial Response at the highest dose 90 mCi, with the first patient remaining progression-free beyond seven months and no dose-limiting toxicities reported.
• RAD101 met its Phase 2b primary endpoint with 93% concordance versus MRI and preliminary 86% sensitivity (12/14), supporting plans for a U.S. Phase 3 pivotal trial in Q4 2026.
• RAD101 holds U.S. FDA Fast Track Designation for brain metastases imaging in a total addressable market of approximately $600+m, targeting more than 300,000 U.S. patients annually with cerebral metastases.

Negative

• None.

Filing Explained

This July 22, 2026 Form 6-K furnishes two company announcements and incorporates them by reference into the existing Form F-3 registration statement, making the announcements part of that registration record to the extent they are not later superseded.

Key Figures

RAD204 dose level: 90 mCi RAD204 progression-free duration: beyond seven months RAD101 concordance with MRI: 93% +5 more

8 metrics

RAD204 dose level 90 mCi Current highest dose level #3 in the Phase 1 trial cohort

RAD204 progression-free duration beyond seven months First cohort 3 patient with RECIST-confirmed durable Partial Response

RAD101 concordance with MRI 93% Concordance between RAD101 PET and MRI across all evaluable lesions, primary endpoint

RAD101 sensitivity 86% (12/14) Preliminary sensitivity in 14 patients with six-month follow-up and/or biopsy data

RAD101 Phase 2b patients 30 Number of evaluable participants in the Phase 2b imaging trial

Brain metastases imaging TAM $600+m Estimated total addressable market for brain metastases imaging

Annual cerebral metastases cases (U.S.) more than 300,000 Number of patients diagnosed annually with cerebral metastases in the U.S.

RAD101 Phase 3 timing Q4 2026 Planned start of U.S. Phase 3 pivotal trial for RAD101

Key Terms

RECIST, Partial Response, dose-limiting toxicities, Fast Track Designation, +2 more

6 terms

RECIST medical

"first patient has achieved a durable confirmed RECIST Partial Response"

RECIST (Response Evaluation Criteria In Solid Tumors) is a standardized set of rules doctors and researchers use to measure how solid tumors change over time on medical scans, categorizing whether a tumor shrinks, grows, or stays the same. Investors pay attention because RECIST-based results often serve as clear, comparable trial endpoints that influence drug approvals, market expectations and company valuations—like using a reliable ruler to track progress in a development program.

Partial Response medical

"first patient has achieved a durable confirmed RECIST Partial Response"

A partial response is a clinical outcome where a treatment produces a clear, measurable improvement in a disease — for example a substantial shrinkage of a tumor or reduction in symptom measures — but does not eliminate the disease entirely. For investors it signals meaningful efficacy that can support regulatory progress, further trials, or commercial potential, like seeing a product gain market traction even though it hasn’t achieved a complete cure.

dose-limiting toxicities medical

"RAD204 is generally well-tolerated with no dose-limiting toxicities observed"

Dose-limiting toxicities are the harmful side effects seen in early clinical trials that are severe enough to stop researchers from raising a drug’s dose. Like a car’s speed limiter marking the safe top speed, DLTs define the maximum tolerable dose, and they matter to investors because they determine whether a medicine can reach effective levels, influence development timelines, costs, and regulatory chances, and thus affect a drug’s commercial prospects.

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.

stereotactic radiosurgery (SRS) medical

"suspected relapse after stereotactic radiosurgery (SRS)"

dosimetry medical

"evaluating the safety, tolerability, dosimetry, pharmacokinetics and preliminary anti-tumor activity"

Dosimetry is the measurement and calculation of how much ionizing radiation is absorbed by people, tissues, or devices, similar to a thermostat tracking temperature in different rooms to know where and how much heat is present. Investors should care because accurate dosimetry underpins safety, treatment effectiveness, regulatory approval, and liability for products and services that use radiation—affecting market access, costs, and commercial risk.

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FAQ

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

Radiopharm Theranostics reported positive clinical data for two programs: RAD204 in a Phase 1 trial for advanced solid tumors and RAD101 in a Phase 2b imaging trial for suspected recurrent brain metastases, including progression-free response and strong imaging concordance metrics.

What are the latest Phase 1 results for RAD204 reported by RADX?

In cohort 3 at 90 mCi, the first patient achieved a RECIST-confirmed durable Partial Response and remained progression-free beyond seven months. A second patient showed early tumor shrinkage, and RAD204 has been generally well-tolerated with no dose-limiting toxicities so far.

How did RAD101 perform in the Phase 2b brain metastases trial for RADX?

RAD101 PET imaging achieved 93% concordance with MRI across all evaluable lesions, meeting the primary endpoint. Among 14 patients with follow-up or biopsy, preliminary 86% sensitivity (12/14) was observed for detecting recurrent brain metastases after radiotherapy.

What are the next development steps for RAD101 according to Radiopharm (RADX)?

Radiopharm plans to advance RAD101 into a U.S. Phase 3 pivotal trial in Q4 2026. The company is continuing discussions with the U.S. FDA and has partnered with Siemens Healthineers to manufacture and distribute 18F-RAD101 doses for the trial.

What regulatory status does RAD101 have and what market is RADX targeting?

RAD101 has U.S. FDA Fast Track Designation for distinguishing recurrent brain metastases from treatment effects. The total addressable imaging market for brain metastases is estimated at approximately $600+m, with over 300,000 U.S. patients diagnosed annually with cerebral metastases.

What is the goal of the ongoing Phase 1 trial of RAD204 at Radiopharm (RADX)?

The Phase 1 trial of RAD204 aims to establish the recommended Phase 2 dose and characterize safety, including dosimetry and pharmacokinetics. Secondary objectives include measuring anti-tumor activity such as tumor responses and duration of response in advanced solid tumors post-standard therapies.

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 July 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 two announcements (the “Public Notice”) to the Australian Securities Exchange on July 22, 2026 titled:

“RAD Achieves Partial Response in Phase 1 Trial of RAD204”

“RAD Announces Positive Phase 2b Trial Results of RAD 101”

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

This Form 6-K, including the exhibits hereto, is incorporated by reference into the registration statement of the Company on Form F-3 (File No. 333-292178) and forms part thereof to the extent not superseded by documents or reports subsequently filed by the Company under the Securities Act of 1933 or the Securities Exchange Act of 1934. 

1

EXHIBITS

Exhibit Number		Description
99.1		RAD Achieves Partial Response in Phase 1 Trial of RAD204
99.2		RAD Announces Positive Phase 2b Trial Results of RAD 101

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: July 22, 2026	By:	/s/ Nathan Jong
		Nathan Jong
		Company Secretary

3

Exhibit 99.1

ASX ANNOUNCEMENT
22 July 2026  

Radiopharm Theranostics Achieves Confirmed Durable Partial Response in Ongoing Phase 1 Trial of RAD204 in Patients with Advanced Solid Tumors Post-Immunotherapy

First RECIST-confirmed durable Partial Response at current highest dose level #3 (90mCi) with the patient remaining progression free beyond seven months

Second patient dosed remains progression free on treatment with RAD204 with early tumor shrinkage observed after first treatment

RAD204 is generally well-tolerated with no dose-limiting toxicities observed in any of the dosing cohorts thus far

Sydney, Australia and MALVERN, Pa. – 22 July 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 updated clinical results from the first two patients in the third cohort of RAD204, the Company’s investigational PD-L1-targeted lutetium-177 nanobody radiotherapeutic being evaluated in a Phase 1 clinical trial in patients with advanced solid tumors in a post-immunotherapy setting.

Radiopharm previously received positive recommendations from the Data and Safety Monitoring Committee, allowing the Company to proceed with enrolling patients in the Phase 1 treatment study after completion of cohorts # 1 and #2 to the current highest dose level #3 (90 mCi). Initial data from all cohorts of the Phase 1 treatment study demonstrated tumor uptake in the PD-L1-positive lesions, which is in line with published results from the previously completed imaging study.

“We are excited to announce positive initial data from the first two patients treated with RAD204 in the third dosing cohort, which showed favorable tolerability and tumor reduction in target lesions, with both patients remaining on treatment,” said Riccardo Canevari, CEO and Managing Director of Radiopharm Theranostics. “Importantly, the first patient has achieved a durable confirmed RECIST Partial Response lasting through four treatment cycles and has remained progression-free beyond seven months. The combined preliminary results indicate the broad therapeutic potential of RAD204 in PD-L1-associated malignancies. Additionally, the data demonstrated that RAD204 was generally well-tolerated, reinforcing the safety profile of RAD204 at the highest dose level evaluated and supporting continued dose escalation.”

“We remain laser-focused on advancing the Phase 1 study and anticipate releasing additional data that will support the therapeutic potential of RAD204 to treat PD-L1 associated malignancies. The totality of data across our multiple dose cohorts supports our confidence in this program and are expected to inform the recommended dose for our planned Phase 2 clinical trial,” concluded Mr. Canevari.

Radiopharm Theranostics Limited

Suite 1, Level 3, 62 Lygon Street, Carlton South VIC 3053 Australia

ABN: 57 647 877 889

ASX ANNOUNCEMENT
22 July 2026  

Initial Clinical Results from Cohort 3 of the Phase 1 Trial of RAD204

Thus far, two patients have been dosed with RAD204 in the third cohort of the Phase 1 treatment study, with the third patient under screening evaluation. Both patients remain on treatment, and initial clinical observations from the ongoing study support the potential of repeated administration of RAD204.

Patient 1

● Patient 1 has achieved a RECIST-confirmed Partial Response after the second treatment cycle, which has been maintained during continued therapy:

o 19% reduction in target lesions from baseline, observed after Dose 1.

o 43% reduction after Dose 2, which meets the RECIST criteria for a Partial Response.

o 43% reduction maintained after Dose 3, i.e., a confirmed Partial response per RECIST

o 35% reduction after Dose 4, while continuing to meet RECIST criteria for a Partial Response.

● The patient remains progression-free beyond seven months with continued follow-up.

Patient 2

● Patient 2 has demonstrated an early 7% reduction in target lesions following the first treatment cycle. The patient remains on treatment and is progression-free with continued follow up for additional efficacy and safety assessments.

Safety and Tolerability

● In all patients dosed to date across dose levels 1 to 3, RAD204 has continued to demonstrate a favorable safety and tolerability profile. There have been no dose-limiting toxicities observed in any of the cohorts thus far. Kidney uptake has been limited (cumulative 8.1 Gy across the four cycles, in Patient 1) and does not represent a potential obstacle for escalation to the next higher dose level (Dose level #4).

About the Phase 1 Study

The ongoing first-in-human Phase 1 study is evaluating the safety, tolerability, dosimetry, pharmacokinetics and preliminary anti-tumor activity of RAD204 in patients with advanced solid tumors following progression on standard therapies. The primary objectives are to establish the recommended Phase 2 dose and characterize safety, while secondary endpoints include anti-tumor activity, eg., tumor responses and duration of responses.

About RAD204

RAD204 is a single-domain monoclonal antibody (sdAb) that targets PD-L1, a protein that regulates the immune system’s response to malignant tumors and is overexpressed in many cancers, making it an attractive therapeutic target in multiple tumor types, including NSCLC, SCLC, TNBC, Cutaneous Melanoma, HNSCC, and Endometrial Cancer. Previously published Phase I imaging data of 16 NSCLC patients with 99Tc-RAD204 demonstrated positive tumor targeting, favorable biodistribution and image characteristics correlating with PD-L1 immunohistochemistry results in cancer patients². Tumor targeting with radioimmunotherapies such as 177Lu-RAD204 has the potential to address resistance mechanisms to current standard-of-care treatment options. The platform is designed to provide hidden epitope access, exceptional stability, rapid tumor penetration, favorable pharmacokinetics and the potential for repeat dosing.

Radiopharm Theranostics Limited

Suite 1, Level 3, 62 Lygon Street, Carlton South VIC 3053

Australia ABN: 57 647 877 889 

2

ASX ANNOUNCEMENT
22 July 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

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

3

Exhibit 99.2

ASX ANNOUNCEMENT
22 July 2026  

Radiopharm Theranostics Announces Positive Phase 2b Trial Results of RAD 101 for Diagnosis of Brain Metastases

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

14 patients with available data from six-month follow-up and biopsy show preliminary 86% (12/14) Sensitivity (secondary objective). Specificity data will be available in Q4 2026.

The Company plans to advance RAD101 into a U.S. Phase 3 pivotal trial in Q4 2026

The imaging Brain Metastases total addressable market is ~$600+m for which there is no currently approved PET product

Sydney, Australia – 22 July 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, today announced positive data from all thirty evaluable patients in the Phase 2b trial of RAD101 in participants with suspected recurrence of brain metastases after radiotherapy. 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.

The analysis of the imaging data 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.

“The entirety of this dataset captures the strength and potential of RAD101 to address a difficult diagnostic challenge in neuro-oncology,” said Riccardo Canevari, CEO and Managing Director of Radiopharm Theranostics. “Achieving the primary endpoint provides strong validation of our approach and supports the advancement of RAD101 into an intended registrational Phase 3 program. We look forward to continuing our discussions with the U.S. FDA as we finalize the study design and work toward bringing a more precise diagnostic tool to patients and clinicians. With this positive data in hand, we have a strong foundation from which to launch our pivotal trial.”

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.

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

ASX ANNOUNCEMENT
22 July 2026  

About the Phase 2b Clinical Trial of RAD101

The U.S. multicenter, 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 2b 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

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

Filing Exhibits & Attachments

2 documents

Press Releases

• EX-99.1 RAD ACHIEVES PARTIAL RESPONSE IN PHASE 1 TRIAL OF RAD204 19.6 KB
• EX-99.2 RAD ANNOUNCES POSITIVE PHASE 2B TRIAL RESULTS OF RAD 101 14.6 KB