Exhibit 99.1

ASX ANNOUNCEMENT 28 OCTOBER 2025

QUARTERLY ACTIVITIES AND CASH FLOW REPORT
QUARTER ENDED 30 SEPTEMBER 2025

Sydney, Australia – 28 October 2025 – Radiopharm Theranostics (ASX:RAD, “Radiopharm” or the “Company”), a developer of a world-class platform of radiopharmaceutical products for both diagnostic and therapeutic uses, is pleased to provide a summary of its activities for the quarter ended 30 September 2025.

Subsequent to the end of the period the Company also announced:

Program Updates

RADIOPHARM THERANOSTICS PROVIDES POSITIVE CLINICAL UPDATES ACROSS FOUR PROGRAMS

Following the quarter’s conclusion, the Company announced an update on its pipeline of clinical programs and outlined expected milestones through the end of 2025 and into 2026.

The RAD 101 Phase 2b imaging study, evaluating a Fluorine-18 labelled small molecule targeting fatty acid synthase for brain metastases, continues to show encouraging results. Twelve patients have been enrolled in the US trial, with data from the first three demonstrating strong and selective tumour uptake in brain metastases, confirming metabolic activity where MRI findings were inconclusive. These early results are consistent with prior Phase 2a findings and further validate proof-of-concept for the molecule. The program holds FDA Fast Track designation and aims to complete enrolment in the first quarter of 2026, with topline data expected in the first half of the year. If outcomes remain consistent, Radiopharm plans to initiate a multicentre Phase 3 registrational study to address the significant population of patients diagnosed annually in the US with cerebral metastases.

The RAD 202 Phase 1 ‘HEAT’ trial, assessing a Lutetium-177 labelled HER2-targeting nanobody in advanced solid tumours, has reported higher-than-expected tumour uptake in the first cohort. Dosing at the initial 30mCi level has been completed, and following a recommendation from the independent Data Safety and Monitoring Committee (see ASX announcement 1/10/25), the trial has progressed to the 75mCi dose level. The therapy has shown a favourable safety profile with no drug-related adverse events reported. Enrolment in the higher-dose second cohort is expected to be completed by the end of 2025, with data from both cohorts to be released around that time. These findings further support the clinical potential of RAD 202 as a novel HER2-directed radiotherapeutic.

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

ASX ANNOUNCEMENT 28 OCTOBER 2025

The RAD 204 Phase 1 study, which uses a Lutetium-177 labelled nanobody targeting PD-L1, continues to generate promising data in patients with PD-L1-positive solid tumours, including lung, breast, and melanoma cancers. At the first 30mCi dose level, two of three patients with late-stage metastatic non-small cell lung cancer achieved stable disease for 5.5 months—considerably longer than the 3.5 months typically observed with standard of care in similar settings. Tumour uptake was evident across the first six patients dosed at the initial and second (60mCi) levels, and the safety profile remained favourable with no dose-limiting toxicities. A meeting with the Data Safety and Monitoring Committee is planned to consider dose escalation to the third level.

The RAD 301 program, a Gallium-68 peptide imaging agent targeting αvβ6-integrin, has produced data supporting its advancement into a Phase 2 trial in patients with loco-regional pancreatic cancer. The αvβ6-integrin biomarker is associated with tumour invasion and poor prognosis in pancreatic ductal adenocarcinoma, and RAD 301 has previously received Orphan Drug Designation from the FDA. In the current Phase 1 trial, six of nine planned subjects have been dosed, with data confirming both strong uptake in αvβ6-positive lesions and a favourable safety profile. The Company will now shift its focus to evaluating the candidate in earlier-stage pancreatic cancer, where improved imaging accuracy can significantly inform surgical decision-making and outcomes.

IND APPROVAL RECEIVED FROM US FDA TO INITIATE PHASE I THERAPEUTIC CLINICAL STUDY TO TARGET B7H3 WITH BETABART (RV-01)

Radiopharm received Investigational New Drug (IND) approval from the US Food and Drug Administration to begin a Phase I clinical trial of Betabart (RV-01), a first-in-class radiopharmaceutical therapy targeting the 4Ig isoform of B7-H3. The company plans to initiate the first-in-human study for solid tumours in the fourth quarter of 2025.

RV-01 is a lutetium-177–conjugated monoclonal antibody designed to selectively bind the 4Ig isoform of B7-H3, which is highly expressed in tumours but largely absent from healthy tissue. Preclinical studies have shown that RV-01 demonstrates hepatic clearance, enabling effective tumour targeting while potentially reducing blood-related side effects compared with other radiotherapeutics cleared through the kidneys. The molecule’s short half-life and high binding affinity further enhance its therapeutic potential.

Developed under Radiopharm’s joint venture with MD Anderson Cancer Center, RV-01 has exhibited tumour shrinkage and extended survival in animal models. The Company believes its selectivity for B7-H3 offers a new approach for treating refractory and high-risk cancers, as overexpression of this immune-checkpoint protein is linked to tumour aggressiveness and poor prognosis.

Corporate Updates

DR OLIVER SARTOR APPOINTED TO SCIENTIFIC ADVISORY BOARD

In July, the Company announced the appointment of Dr Oliver Sartor, MD to the Company’s Scientific Advisory Board (SAB).

Dr Sartor is an internationally recognised medical oncologist and scientist specialising in prostate cancer and radiopharmaceutical therapies. He currently serves as Director of Radiopharmaceutical Clinical Trials and Chair of the Genitourinary Cancer Disease Group at the world-renowned Mayo Clinic, in Rochester, Minnesota. He was previously Laborde Professor of Medicine and Urology and Medical Director of Tulane Cancer Center in New Orleans under Tulane University School of Medicine.

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

ASX ANNOUNCEMENT 28 OCTOBER 2025

Dr Sartor has also held senior roles at LSU Health Sciences Center, Dana-Farber/Harvard Medical School, and as Medical Oncology Co-Chair of the GU Committee of NRG Oncology. Dr Sartor received his MD with honours from Tulane University School of Medicine in 1982, completed internal medicine residency at Tulane, and a medical oncology fellowship at the National Cancer Institute (NCI).

Since 1990 he has focused on prostate cancer clinical research, authoring more than 500 peer-reviewed publications and leading multiple pivotal Phase 3 trials that resulted in FDA approvals for therapies including samarium-153 EDTMP, cabazitaxel, radium-223, and PSMA-targeted radioligand therapy.

KEY OPINION LEADER WEBINARS

During the quarter, the Company held three key opinion leader webinars discussing the use of the radiopharmaceutical therapies in oncology and for the treatment of prostate cancer.

Click here to view recordings of each webinar.

Financial Updates

COMPLETION OF A$35 MILLION PLACEMENT AND LAUNCH OF A$5 MILLION SHARE PURCHASE PLAN

Subsequent to the end of the quarter, Radiopharm completed a A$35 million institutional placement and launched a A$5 million Share Purchase Plan (SPP) to strengthen its financial position and support ongoing clinical and operational initiatives. The placement, priced at $0.03 per share, received strong backing from new and existing Australian and international institutional investors, including strategic investor and existing shareholder Lantheus Holdings, who contributed A$7.6 million (US$5 million) to lift its shareholding to 14.5 per cent. Participants in both the placement and SPP will receive one free attaching option for every new share issued, exercisable at $0.039 and expiring on 31 October 2027, subject to shareholder approval.

Together with Radiopharm’s unaudited cash balance of A$19 million as at 30 September 2025, the proceeds will extend the company’s funding runway into 2027. The funds will be used to advance drug manufacturing, progress multiple clinical trials across its six active programs, and cover working capital and corporate costs. This strengthened capital position will enable the company to pursue key clinical milestones and maintain development momentum across its diagnostic and therapeutic radiopharmaceutical portfolio.

The SPP, open to eligible shareholders in Australia and New Zealand, provides an opportunity for retail investors to participate on the same terms as the institutional placement. Eligible shareholders will be able to apply for up to A$30,000 in new shares at the same $0.03 issue price, with one attaching option per share on identical terms. While the company aims to raise approximately A$5 million through the SPP, it retains the right to vary the final amount depending on demand.

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

ASX ANNOUNCEMENT 28 OCTOBER 2025

An Extraordinary General Meeting is expected to be held on 4 December 2025 to approve the second tranche of shares and attaching options, with allotment anticipated on 10 December 2025. Bell Potter Securities acted as lead manager to the capital raising, while Leerink Partners LLC and B. Riley Securities Inc served as US placement agents.

R&D TAX REFUND

In July, Radiopharm received its research and development (R&D) tax refund for the 2024 financial year, totalling A$4,485,434, including A$94,559 interest. The refund is received as part of the Australian Government’s R&D tax incentive, which provides companies engaging in appropriate and eligible activities with a refundable tax offset of up to 43.5%.

QUARTERLY RESULTS

The following is a summary of the Appendix 4C Cash Flow Report:

In compliance with Listing Rule 4.7C, payments to related parties and their associates, as detailed in item 6.1 of Appendix 4C, encompass remuneration for director fees to executive and non-executive directors, conducted in the ordinary course of business at commercial rates, excluding reimbursements for out-of-pocket expenses.

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 three Phase 1 trials in a variety of solid tumor cancers including lung, breast, and brain metastases. Learn more at radiopharmtheranostics.com.

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

ASX ANNOUNCEMENT 28 OCTOBER 2025

Authorised 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/
Twitter – https://twitter.com/TeamRadiopharm

Linked In – 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 

Rule 4.7B 

Appendix 4C

Quarterly cash flow report for entities
subject to Listing Rule 4.7B

Appendix 4C

Quarterly cash flow report for entities subject to Listing Rule 4.7B

Appendix 4C

Quarterly cash flow report for entities subject to Listing Rule 4.7B

Note: if any amounts are shown in items 6.1 or 6.2, your quarterly activity report must include a description of, and an explanation for, such payments.

In accordance with Listing Rule 4.7C, payments made to related parties and their associates included in items 6.1 of the Appendix 4C includes compensation and director fee related payments in the normal course of business at commercial rates, excluding reimbursements of out-of-pocket expenses.

Appendix 4C

Quarterly cash flow report for entities subject to Listing Rule 4.7B

Appendix 4C

Quarterly cash flow report for entities subject to Listing Rule 4.7B

Compliance statement

(Name of body or officer authorising release – see note 4)

Notes