RADX 6-K

UNITEDSTATES

SECURITIESAND EXCHANGE COMMISSION

Washington,D.C. 20549

Form6-K

REPORTOF FOREIGN PRIVATE ISSUER

PURSUANTTO RULE 13a-16 OR 15d-16 UNDER

THESECURITIES EXCHANGE ACT OF 1934

For the Month of July 2026

Commission File Number: 001-41621

RADIOPHARMTHERANOSTICS LIMITED

(Name of Registrant)

Level3, 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 ☐

RADIOPHARMTHERANOSTICS LIMITED

EXPLANATORYNOTE

Radiopharm Theranostics Limited (the “Company”) published one announcement (the “Public Notice”) to the Australian Securities Exchange on July 31, 2026 titled:

“Quarterly Activities/Appendix 4C Cash Flow Report”

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the registration statement of the Company on Form F-3 (File No. 333-292178) and forms part thereof to the extent not superseded by documents or reports subsequently filed by the Company under the Securities Act of 1933 or the Securities Exchange Act of 1934.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<br> <br><br> Number		Description
99.1		Quarterly Activities/Appendix 4C Cash Flow Report

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:<br> July 31, 2026	By:	/s/<br> Amritha Sushil
		Amritha<br> Sushil
		Company<br> Secretary

3

Exhibit99.1

ASX ANNOUNCEMENT<br><br> <br>31 July 2026

Radiopharm Theranostics Reports Business Update

Reported positive resultsfrom the Phase 2b clinical trial of imaging agent RAD 101, showing 93% of evaluable patients treated with RAD 101 achieved the primaryendpoint

Plans to initiate Phase 3 registrationaltrial of RAD 101 in Q4 2026

Raised approximately $12.5M throughan institutional offer and launched a $6million Share Purchase Plan, post balance date

Sydney, Australia – 31 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 financial results for the quarter ended June 30, 2026, and provided a corporate update.

“We continue to make meaningful progress across our portfolio as we advance a diverse pipeline of targeted radiopharmaceutical candidates designed to address some of the most challenging cancers,” said Riccardo Canevari, CEO and Managing Director of Radiopharm Theranostics. “The positive Phase 2b results for RAD 101 represent an important milestone for Radiopharm and reinforce our confidence in the potential of our technologies. In addition, the early clinical signs in the third cohort of RAD 204, showing RECIST-confirmed Partial Response in the first patient treated at this dose, is creating a lot of excitement among the Clinical Investigators of our Phase I therapeutic trial. Across the organization, we are generating clinical data, advancing multiple development programs, and building the capabilities required to realize the full value of our platform. With six active clinical programs spanning both diagnostic and therapeutic applications, we believe Radiopharm is establishing a leading radiopharmaceutical company uniquely positioned to deliver innovative new medicines to patients while creating long-term value for shareholders. We remain focused on executing against our development priorities and advancing what we believe could become a new generation of precision cancer treatments.”

Program and Business Updates

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18F-RAD101 – Small moleculetargeting fatty acid synthase radiolabelled with Fluorine-18

RAD 101 is being evaluated in a single-arm U.S. Phase 2b clinical trial for the diagnostic performance of the molecule in 30 individuals with confirmed recurrent brain metastases from solid tumors of different origins. RAD 101 has received U.S. Food and Drug Administration (FDA) Fast Track Designation to expedite the review process and help bring the novel imaging small molecule to the over 300,000 patients diagnosed annually in the U.S. with cerebral metastases.

·	In July 2026, the Company announced that RAD 101 had met<br>its primary endpoint, with 93% of patients treated with RAD 101 achieving concordance with MRI imaging. Additionally, an interim analysis of 14 patients from six-month<br>follow-up and biopsy shows 86% (12/14) sensitivity.
●	The Company anticipates the initiation of a Phase 3, multi-center, multi-country registrational study in Q4 2026. Siemens Healthineers<br>will manufacture and distribute doses of 18F-labeled RAD-101 through a partnership to support the Phase 3 registrational trial.

Radiopharm Theranostics Limited

Suite 1, Level 3, 62 LygonStreet, Carlton South VIC 3053 Australia

ABN: 57 647 877 889

ASX ANNOUNCEMENT<br><br> <br>31 July 2026

177Lu-RAD204 – Nanobody targeting PD-L1 radiolabelledwith Lutetium 177

RAD 204 is being evaluated in a Phase 1 study in PD-L1-driven cancers, including Non-Small Cell Lung Cancer (NSCLC), Small-Cell Lung Cancer (SCLC), Triple-negative Breast Cancer (TNBC), Cutaneous Melanoma, head and neck squamous cell carcinoma (HNSCC) and Endometrial Cancer.

·	Initial data from the first six patients across the first<br>two cohorts of the Phase 1 study showed tumor uptake in the PD-L1 positive lesions, in line with the published results of the previously<br>conducted imaging study
·	Data from the third cohort (90mCi) in the Phase 1 study of<br>RAD 204 showed that the first patient dosed at this dose level achieved a durable RECIST-confirmed partial response, with tumor shrinkage<br>up to -43%, still progression free after 7+ months.
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177Lu-RAD202 – Nanobodytargeting HER2 radiolabelled with Lutetium 177

The Company continues to evaluate RAD 202 in the Phase 1 ‘HEAT’ clinical trial in patients with Human Epidermal Growth Factor Receptor 2 (HER2)-positive advanced solid tumors. HER2 is overexpressed in breast cancer and several other solid tumors and represents a validated target in oncology. RAD 202 has demonstrated clinical proof-of-concept with positive safety and biodistribution.

·	At the American Association for Cancer Research (AACR) Annual<br>Meeting 2026, the company presented initial findings from the Phase 1 first-in-human ‘HEAT’ clinical trial for RAD 202. At<br>the lowest dose level, RAD 202 showed meaningful tumor uptake and was generally well-tolerated in the first three treated patients, with<br>no dose-limiting toxicities or treatment discontinuations due to adverse events being observed. Organ-level absorbed radiation doses<br>were within expected and clinically acceptable ranges.
·	The Company previously received a positive recommendation from<br>the Data Safety and Monitoring Committee to advance RAD 202 to the next dose level of 130mCi in the Phase 1 ‘HEAT’ clinical<br>trial. The Company expects to complete enrolment of Cohort #3 in Q3 and the entire Phase 1 Dose Escalation by 1H 2027.
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Lu177-RV 01 – monoclonalantibody targeting 4Ig isoform of B7H3 radiolabelled with Lutetium 177

RV 01 (Betabart) is a monoclonal antibody targeting the 4Ig isoform of B7H3, an immune checkpoint protein that is highly expressed in tumors and not in healthy tissue. In multiple preclinical studies, RV-01 has shown tumor shrinkage and prolonged survival. This is the first radiopharmaceutical therapeutic developed by Radiopharm Ventures, a joint venture between Radiopharm Theranostics and the MD Anderson Cancer Center.

·	The Company continues to make progress advancing the first-in-human (FIH) Phase 1/2a clinical trial of RV 01, which is designed to establish<br>the safety profile, biodistribution, pharmacokinetics, and radiation dosimetry of RV 01 in various tumor types. The trial will also determine<br>the recommended dose of RV-01 for future studies.

Tb161-RAD 402 – Monoclonal antibodytargeting KLK3 radiolabelled with Terbium 161

RAD 402 is a monoclonal antibody targeting Kallikrein Related Peptidase 3 (KLK3) radiolabelled with the radionuclide 161Tb for the treatment of prostate cancer. In preclinical mouse models, RAD 402 showed strong tumor targeting, limited bone and marrow uptake, and a hepatic excretion profile consistent with expectations for a monoclonal antibody.

·	The Company continues to progress its First-In-Human (FIH) Phase 1 clinical trial of RAD 402, designed to evaluate the safety, tolerability,<br>whole-body distribution, and preliminary clinical activity of RAD 402 in patients with advanced prostate cancer. The dose escalation Phase<br>1 study is designed to determine the Maximum Tolerated Dose and recommended Phase 2 dose for expansion.

Radiopharm Theranostics Limited

Suite 1, Level 3, 62 LygonStreet, Carlton South VIC 3053 Australia

ABN: 57 647 877 889

2

ASX ANNOUNCEMENT<br><br> <br>31 July 2026

Ga68-RAD301 – Peptide targeting αvB-integrinradiolabeled with Gallium 68

RAD 301 is being evaluated in a Phase 1 imaging trial in patients with Pancreatic Ductal Adenocarcinoma (PDAC). The αvB-integrin is a cellular marker for tumor invasion and metastatic growth, which correlates with decreased survival in several carcinomas, particularly pancreatic. RAD 301 has previously received Orphan Drug Designation (ODD) from the FDA and data from the Phase 1 trial is supportive of the Company’s decision to move to a Phase 2 imaging trial in patients with loco-regional pancreatic cancer.

·	Enrollment in the Phase 1 imaging trial in metastatic pancreatic cancer continues, having dosed 8 patients out of 9, with last patient<br>expected to be dosed in 2H 2026.

Financial Update

Closing cash at the end of the quarter was $4.1 million, decreasing from $19.2 million at the end of the prior quarter. Net cash outflows from operating activities during the period was $14.97 million with direct Research and Development expenditure and staff costs accounting for 95% of the operating activities.

Following the close of the quarter, the Company received its FY25 Australian R&D Tax Incentive of $5.9 million and also completed a $12.5 million institutional offer and launched a $6 million Share Purchase Plan which is already subscribed for up to $3 million.

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

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

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Formore information:

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Investors:

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Riccardo Canevari

CEO & Managing Director

P: +1 862 309 0293

E: [email protected]

Anne Marie Fields

Precision AQ (formerly Stern IR)

E: [email protected]

Media:

Matt Wright

NWR Communications

P: +61 451 896 420

E: [email protected]

Follow Radiopharm Theranostics:

Website – https://radiopharmtheranostics.com/

X – https://x.com/TeamRadiopharm

LinkedIn – https://www.linkedin.com/company/radiopharm-theranostics/

Investor Hub – https://investorhub.radiopharmtheranostics.com/

Radiopharm Theranostics Limited

Suite 1, Level 3, 62 LygonStreet, Carlton South VIC 3053 Australia

ABN: 57 647 877 889

3

Rule 4.7B

Appendix 4C

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Quarterly cash flow reportfor entities

subject to Listing Rule 4.7B

Name of entity
Radiopharm Theranostics Limited
ABN	Quarter ended (“current quarter”)
57 647 877 889	30 June 2026
Consolidated statementof cash flows		Current quarter<br><br> <br>$A’000	Year to date (12 months)<br><br> <br>$A’000
---	---	---	---
1.	Cash flows from operating activities
1.1	Receipts from customers	93	536
1.2	Payments for
	(a)  research and development	(12,225)	(43,381)
	(b)  product manufacturing and operating costs	-	-
	(c)  advertising and marketing	(56)	(392)
	(d)  leased assets	-	-
	(e)  staff costs	(2,335)	(11,016)
	(f)  administration and corporate costs	(727)	(4,234)
1.3	Dividends received (see note 3)	-	-
1.4	Interest received	71	485
1.5	Interest and other costs of finance paid	-	-
1.6	Income taxes paid	-	-
1.7	Government grants and tax incentives	-	4,485
1.8	Other – GST refunded	207	954
1.9	Net cash from / (used in) operating activities	(14,972)	(52,563)
ASX Listing Rules Appendix 4C (17/07/20)	Page 1
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+ See chapter 19 of the ASX Listing Rules for defined terms.

Appendix 4C

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

Consolidated statement of cash flows		Current quarter<br><br> <br>$A’000	Year to date (12 months)<br><br> <br>$A’000
2.	Cash flows from investing activities
2.1	Payments to acquire or for:
	(a)  entities	-	-
	(b)  businesses	-	-
	(c)  property, plant and equipment	-	-
	(d)  investments	-	-
	(e)  intellectual property	-	-
	(f)  other non-current assets	-	-
2.2	Proceeds from disposal of:
	(a)  entities	-	-
	(b)  businesses	-	-
	(c)  property, plant and equipment	-	-
	(d)  investments	-	-
	(e)  intellectual property	-	-
	(f)  other non-current assets	-	-
2.3	Cash flows from loans to other entities	-	-
2.4	Dividends received (see note 3)	-	-
2.5	Other - payments of license fee liabilities	(109)	(5,421)
2.6	Net cash from / (used in) investing activities	(109)	(5,421)
3.	Cash flows from financing activities
3.1	Proceeds from issues of equity securities (excluding convertible debt securities)	****<br><br> <br>-	****<br><br> <br>35,263
3.2	Proceeds from issue of convertible debt securities	-	-
3.3	Proceeds from exercise of options	-	-
3.4	Transaction costs related to issues of equity securities or convertible debt securities	-	(2,109)
3.5	Proceeds from borrowings	-	-
3.6	Repayment of borrowings	-	-
3.7	Transaction costs related to loans and borrowings	-	-
3.8	Dividends paid	-	-
3.9	Other – (provide details if material)	-	-
3.10	Net cash from / (used in) financing activities	-	33,154
ASX Listing Rules Appendix 4C (17/07/20)	Page 2
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+ See chapter 19 of the ASX Listing Rules for defined terms.

Appendix 4C

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

Consolidated statement of cash flows		Current quarter<br><br> <br>$A’000	Year to date (12 months)<br><br> <br>$A’000
4.	Net increase / (decrease) in cash and cash equivalents for the period
4.1	Cash and cash equivalents at beginning of period	19,238	29,117
4.2	Net cash from / (used in) operating activities (item 1.9 above)	(14,972)	(52,563)
4.3	Net cash from / (used in) investing activities (item 2.6 above)	(109)	(5,421)
4.4	Net cash from / (used in) financing activities (item 3.10 above)	-	33,154
4.5	Effect of movement in exchange rates on cash held	(20)	(150)
4.6	Cash and cash equivalents at end of period	4,137	4,137
5.	Reconciliation of cash and cash equivalents<br><br> <br>at the end of the quarter (as shown in the consolidated statement<br> of cash flows) to the related items in the accounts	Current quarter<br><br> <br>$A’000	Previous quarter<br><br> <br>$A’000
---	---	---	---
5.1	Bank balances	4,137	19,238
5.2	Call deposits	-	-
5.3	Bank overdrafts	-	-
5.4	Other (provide details)	-	-
5.5	Cash and cash equivalents at end of quarter (should equal item 4.6 above)	4,137	19,238
6.	Paymentsto related parties of the entity and their associates	Current quarter<br><br> <br>$A’000
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6.1	Aggregate amount of payments to related parties and their associates included in item 1	443
6.2	Aggregate amount of payments to related parties and their associates included in item 2
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.

ASX Listing Rules Appendix 4C (17/07/20)	Page 3
+ See chapter 19 of the ASX Listing Rules for defined terms.

Appendix 4C

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

7.	Financing facilities<br><br> <br>Note: the term “facility’ includesall forms of financing arrangements available to the entity.<br><br> <br>Add notes as necessary for an understanding of the sources of finance available to the entity.	Total facilityamount at quarter end<br><br> <br>$A’000	Amount drawn at quarter end<br><br> <br>$A’000
7.1	Loan facilities	-	-
7.2	Credit standby arrangements	-	-
7.3	Other (please specify)	-	-
7.4	Total financing facilities	-	-
7.5	Unused financing facilities available at quarter end		-
7.6	Include in the box below a description of each facility above, including the lender, interest rate, maturity date and whether it is secured or unsecured. If any additional financing facilities have been entered into or are proposed to be entered into after quarter end, include a note providing details of those facilities as well.
	N/A
8.	Estimatedcash available for future operating activities	$A’000
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8.1	Net cash from / (used in) operating activities (item 1.9)	(14,972)
8.2	Cash and cash equivalents at quarter end (item 4.6)	4,137
8.3	Unused finance facilities available at quarter end (item 7.5)	-
8.4	Total available funding (item 8.2 + item 8.3)	4,137
8.5	Estimated quarters of funding available (item 8.4 divided by item 8.1)	0.28
Note: if the entity has reported positive net operating cash flows in item 1.9, answer item 8.5 as “N/A”. Otherwise, a figure for the estimated quarters of funding available must be included in item 8.5.
8.6	If item 8.5 is less than 2 quarters, please provide answers to the following questions:
	8.6.1 Does the entity expect that it will continue to have the current<br>level of net operating cash flows for the time being and, if not, why not?
Answer:	No. The Company does not expect the current quarter’s net operating<br>cash outflow of A$14.97 million to be representative of its go-forward burn profile. Three specific factors elevated Q4 FY2026 operating<br>outflows and are expected to moderate during Q1 FY2027 and beyond:
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1)	Accelerated clinical milestone investment. Direct research and development expenditure (A$12.23 million)<br> and staff costs (A$2.34 million) together represented 95% of operating spend. This reflects<br> deliberate, time-bound investment aligned to specific value-inflecting milestones achieved<br> during and shortly after the quarter, including:
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-	Partial Response in Phase 1 Trial of RAD204
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-	Positive Phase 2b trial results of RAD101
-	Initial Findings from Phase 1 177Lu-RAD202 Trial
ASX Listing Rules Appendix 4C (17/07/20)	Page 4
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+ See chapter 19 of the ASX Listing Rules for defined terms.

Appendix 4C

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

8.6.2	Has the entity taken any steps, or does it propose to take any<br>steps, to raise further cash to fund its operations and, if so, what are those steps and how likely does it believe that they will be<br>successful?

Answer: The Board is continuing to assess alternative capital sources, and the Directors believe that the Company can raise sufficient capital in the form of equity financing and or non-dilutive inflows. In December 2025 a At-The-Market Facility was set up to allow the company to draw upon US$18.9 million for the issue of ADR’s.

Subsequent to 30 June 2026, the Company received its FY25 Australian R&D Tax Incentive of $5.9 million and also completed a $12.5 million institutional offer and launched a $6 million Share Purchase Plan which is already subscribed for up to $3 million.

In addition, the Company has and will continue to employ cash management strategies such as delaying discretionary operating activities.

8.6.3	Does the entity expect to be able to continue its operations<br>and to meet its business objectives and, if so, on what basis?

Answer: Yes, the Board expects to be able to continue its operations and to meet its business objectives based on the responses detailed in 8.6.1 and 8.6.2.

Note: where item 8.5 is less than 2 quarters, all of questions 8.6.1,8.6.2 and 8.6.3 above must be answered.

ASX Listing Rules Appendix 4C (17/07/20)	Page 5
+ See chapter 19 of the ASX Listing Rules for defined terms.

Appendix 4C

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

Compliance statement

1	This statement has been prepared in accordance with accounting<br>standards and policies which comply with Listing Rule 19.11A.
2	This statement gives a true and fair view of the matters disclosed.
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Date:	31 July 2026
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Authorised by:	The Board
	(Name of body or officer authorising release<br> – see note 4)

Notes

1.	This quarterly cash flow report and the accompanying activity<br>report provide a basis for informing the market about the entity’s activities for the past quarter, how they have been financed<br>and the effect this has had on its cash position. An entity that wishes to disclose additional information over and above the minimum<br>required under the Listing Rules is encouraged to do so.
2.	If this quarterly cash<br> flow report has been prepared in accordance with Australian Accounting Standards, the definitions<br> in, and provisions of, AASB 107: Statement of Cash Flows apply to this report. If<br> this quarterly cash flow report has been prepared in accordance with other accounting standards<br> agreed by ASX pursuant to Listing Rule 19.11A, the corresponding equivalent standard applies<br> to this report.
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3.	Dividends received may be classified either as cash flows from<br>operating activities or cash flows from investing activities, depending on the accounting policy of the entity.
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4.	If this report has been<br> authorised for release to the market by your board of directors, you can insert here: “By<br> the board”. If it has been authorised for release to the market by a committee of your<br> board of directors, you can insert here: “By the [name of board committee – eg Audit and Risk Committee]”. If it has been authorised for release to the market<br> by a disclosure committee, you can insert here: “By the Disclosure Committee”.
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5.	If this report has been<br> authorised for release to the market by your board of directors and you wish to hold yourself<br> out as complying with recommendation 4.2 of the ASX Corporate Governance Council’s<br> Corporate Governance Principles and Recommendations, the board should have received<br> a declaration from its CEO and CFO that, in their opinion, the financial records of the entity<br> have been properly maintained, that this report complies with the appropriate accounting<br> standards and gives a true and fair view of the cash flows of the entity, and that their<br> opinion has been formed on the basis of a sound system of risk management and internal control<br> which is operating effectively.
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ASX Listing Rules Appendix 4C (17/07/20)	Page 6
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+ See chapter 19 of the ASX Listing Rules for defined terms.