RADX 6-K

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 August 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 August 27, 2026 titled:

“Change of Director's Interest Notices x 4”

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.

1

EXHIBITS

Exhibit<br><br>Number	Description
99.1	Change of Director's Interest Notices x 4

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: August 27, 2026	By:	/s/ Amritha Sushil
		Amritha Sushil
		Company Secretary

3

Exhibit 99.1

Appendix 3Y

Change of Director’s Interest Notice

Rule 3.19A.2

Appendix 3Y

Change of Director’s Interest Notice

Information or documents not available now must be given to ASX as soon as available. Information and documents given to ASX become ASX’s property and may be made public.

Introduced 30/9/2001. Amended 01/01/11

Name<br>of Entity:	Radiopharm<br>Theranostics Limited (ASX: RAD)
ABN:	57<br>647 877 889

We (the entity) give ASX the following information under listing rule 3.19A.2 and as agent for the director for the purposes of section 205G of the Corporations Act.

Name<br>of Director:	Riccardo<br>Canevari
Date<br>of Last Notice:	19<br>December 2025

Part 1 - Change of director’s relevant interests in securities

In the case of a trust, this includes interests in the trust made available by the responsible entity of the trust

Note: In the case of a company, interests which come within paragraph (i) of the definition of “notifiable interest of a director” should be disclosed in this part.

Direct<br>or Indirect Interest	Direct
Nature<br>of indirect interest<br><br>(including<br>registered holder)<br><br>Note:<br>Provide details of the circumstances giving rise to the relevant interest.	N/A
Date<br>of change	24<br>August 2026
No.<br>of securities held prior to change			Shares	Options
		Direct	20,029,986	185,287,299
		Indirect	2,650,000	-
		Total	22,679,986	185,287,299
Class	Listed<br>Options
Number<br>acquired	NIL
Number<br>disposed	1,875,000<br>Listed Options
Value/Consideration<br><br>Note:<br><br>If<br>consideration is non-cash, provide details and estimated valuation	N/A
+ See chapter 19 for defined terms.
---	---
01/01/2011	Appendix 3Y Page 1

Appendix 3Y

Change of Director’s Interest Notice

No. of securities held after change			Shares	Options
		Direct	20,029,986	183,412,299
		Indirect	2,650,000	-
		Total	22,679,986	183,412,299
Nature of change<br><br>Example:<br><br>on-market trade, off-market trade, exercise of options, issue of securities under dividend reinvestment plan, participation in buy-back	Expiry of Listed Options (Exp 24 Aug 2026)

Part 2 – Change of director’s interests in contracts

Note: In the case of a company, interests which come within paragraph (ii) of the definition of “notifiable interest of a director” should be disclosed in this part.

Detail of contract	N/A
Nature of interest	N/A
Name of registered holder<br><br>(if issued securities)	N/A
Date of change	N/A
No. and class of securities<br>to which interest related prior to change<br><br>Note: Details<br>are only required for a contract in relation to which the interest has changed	N/A
Interest acquired	N/A
Interest disposed	N/A
Value/Consideration<br><br>Note: If consideration is non-cash, provide details<br>and an estimated valuation	N/A
Interest after change	N/A
+ See chapter 19 for defined terms.
---	---
Appendix 3Y Page 2	01/01/2011

Appendix 3Y

Change of Director’s Interest Notice

Part 3 – Closed period

Were the interests in the securities or contracts detailed above traded during a +closed period where prior written clearance was required?	No
If so, was prior written clearance provided to allow the trade to proceed during this period?	N/A
If prior written clearance was provided, on what date was this provided?	N/A
+ See chapter 19 for defined terms.
---	---
01/01/2011	Appendix 3Y Page 3

Appendix 3Y

Change of Director’s Interest Notice

Rule 3.19A.2

Appendix 3Y

Change of Director’s Interest Notice

Information or documents not available now must be given to ASX as soon as available. Information and documents given to ASX become ASX’s property and may be made public.

Introduced 30/9/2001. Amended 01/01/11

Name of<br>Entity:	Radiopharm Theranostics Limited (ASX: RAD)
ABN:	57 647 877 889

We (the entity) give ASX the following information under listing rule 3.19A.2 and as agent for the director for the purposes of section 205G of the Corporations Act.

Name<br>of Director:	Paul<br>Hopper
Date<br>of Last Notice:	19<br>December 2025

Part 1 - Change of director’s relevant interests in securities

In the case of a trust, this includes interests in the trust made available by the responsible entity of the trust

Note: In the case of a company, interests which come within paragraph (i) of the definition of “notifiable interest of a director” should be disclosed in this part.

Direct<br>or Indirect Interest	Direct
Nature<br>of indirect interest<br><br>(including<br>registered holder)<br><br>Note:<br>Provide details of the circumstances giving rise to the relevant interest.	N/A
Date<br>of change	24<br>August 2026
No.<br>of securities held prior to change			Shares	Options
		Direct	53,900,000	53,642,000
		Indirect	93,821,428	9,017,518
		Total	147,721,428	62,659,518
Class	Listed<br>Options
Number<br>acquired	NIL
Number<br>disposed	27,500,000<br>Listed Options
Value/Consideration<br><br>Note:<br><br>If<br>consideration is non-cash, provide details and estimated valuation	N/A
+ See chapter 19 for defined terms.
---	---
01/01/2011	Appendix 3Y Page 1

Appendix 3Y

Change of Director’s Interest Notice

No. of securities held after change			Shares	Options
		Direct	53,900,000	26,142,000
		Indirect	93,821,428	9,017,518
		Total	147,721,428	35,159,518
Nature of change<br><br>Example:<br><br>on-market trade, off-market trade, exercise<br>of options, issue of securities under dividend reinvestment plan, participation in buy-back	Expiry of Listed Options (Exp 24 Aug 2026)

Part 2 – Change of director’s interests in contracts

Note: In the case of a company, interests which come within paragraph (ii) of the definition of “notifiable interest of a director” should be disclosed in this part.

Detail of contract	N/A
Nature of interest	N/A
Name of registered holder<br><br>(if<br>issued securities)	N/A
Date of change	N/A
No. and class of securities<br>to which interest related prior to change<br><br>Note: Details<br>are only required for a contract in relation to which the interest has changed	N/A
Interest acquired	N/A
Interest disposed	N/A
Value/Consideration<br><br>Note: If consideration is non-cash, provide details<br>and an estimated valuation	N/A
Interest after change	N/A
+ See chapter 19 for defined terms.
---	---
Appendix 3Y Page 2	01/01/2011

Appendix 3Y

Change of Director’s Interest Notice

Part 3 – Closed period

Were the interests<br>in the securities or contracts detailed above traded during a +closed period where prior written clearance was required?	No
If so, was prior written clearance provided to allow the trade to proceed during this period?	N/A
If prior written clearance was provided, on what date was this provided?	N/A
+ See chapter 19 for defined terms.
---	---
01/01/2011	Appendix 3Y Page 3

Appendix 3Y

Change of Director’s Interest Notice

Rule 3.19A.2

Appendix 3Y

Change of Director’s Interest Notice

Information or documents not available now must be given to ASX as soon as available. Information and documents given to ASX become ASX’s property and may be made public.

Introduced 30/9/2001. Amended 01/01/11

Name of Entity:	Radiopharm Theranostics Limited (ASX: RAD)
ABN:	57 647 877 889

We (the entity) give ASX the following information under listing rule 3.19A.2 and as agent for the director for the purposes of section 205G of the Corporations Act.

Name<br>of Director:	Ian<br>Turner
Date<br>of Last Notice:	31<br>March 2026

Part 1 - Change of director’s relevant interests in securities

In the case of a trust, this includes interests in the trust made available by the responsible entity of the trust

Note: In the case of a company, interests which come within paragraph (i) of the definition of “notifiable interest of a director” should be disclosed in this part.

Direct<br>or Indirect Interest	Direct<br>and indirect
Nature<br>of indirect interest<br><br>(including<br>registered holder)<br><br>Note:<br>Provide details of the circumstances giving rise to the relevant interest.	Superannuation<br>fund
Date<br>of change	24<br>August 2026
No.<br>of securities held prior to change			Shares	Options
		Direct	2,530,595	23,081,926
		Indirect	7,454,697	820,422
		Total	9,985,292	23,902,348
Class	Listed<br>Options
Number<br>acquired	NIL
Number<br>disposed	Direct
	1,125 000<br>Listed Options
	Indirect
	750,000<br>Listed Options
Value/Consideration<br><br>Note:<br><br>If<br>consideration is non-cash, provide details and estimated valuation	N/A
+ See chapter 19 for defined terms.
---	---
01/01/2011	Appendix 3Y Page 1

Appendix 3Y

Change of Director’s Interest Notice

No.<br>of securities held after change			Shares	Options
		Direct	2,530,595	21,956,926
		Indirect	7,454,697	70,422
		Total	9,985,292	22,027,348
Nature<br>of change<br><br>Example:<br><br><br>on-market trade, off-market trade, exercise of options, issue of securities under dividend<br>reinvestment plan, participation in buy-back	Expiry<br>of Listed Options (Exp 24 Aug 2026)

Part 2 – Change of director’s interests in contracts

Note: In the case of a company, interests which come within paragraph (ii) of the definition of “notifiable interest of a director” should be disclosed in this part.

Detail of contract	N/A
Nature of interest	N/A
Name of registered holder<br><br>(if issued securities)	N/A
Date of change	N/A
No. and class of securities<br>to which interest related prior to change<br><br>Note: Details<br>are only required for a contract in relation to which the interest has changed	N/A
Interest acquired	N/A
Interest disposed	N/A
Value/Consideration<br><br>Note: If consideration is non-cash, provide details<br>and an estimated valuation	N/A
Interest after change	N/A
+ See chapter 19 for defined terms.
---	---
Appendix 3Y Page 2	01/01/2011

Appendix 3Y

Change of Director’s Interest Notice

Part 3 – Closed period

Were the interests in the securities or contracts detailed above traded during a +closed period where prior written clearance was required?	No
If so, was prior written clearance provided to allow the trade to proceed during this period?	N/A
If prior written clearance was provided, on what date was this provided?	N/A
+ See chapter 19 for defined terms.
---	---
01/01/2011	Appendix 3Y Page 3
Appendix 3Y
---
Change of Director’s Interest Notice

Rule 3.19A.2

Appendix 3Y

Change of Director’s Interest Notice

Information or documents not available now must be given to ASX as soon as available. Information and documents given to ASX become ASX’s property and may be made public.

Introduced 30/9/2001. Amended 01/01/11

Name<br>of Entity:	Radiopharm<br>Theranostics Limited (ASX: RAD)
ABN:	57<br>647 877 889

We (the entity) give ASX the following information under listing rule 3.19A.2 and as agent for the director for the purposes of section 205G of the Corporations Act.

Name<br>of Director:	Hester<br>Larkin
Date<br>of Last Notice:	18<br>December 2024

Part 1 - Change of director’s relevant interests in securities

In the case of a trust, this includes interests in the trust made available by the responsible entity of the trust

Note: In the case of a company, interests which come within paragraph (i) of the definition of “notifiable interest of a director” should be disclosed in this part.

Direct or Indirect Interest	Direct and indirect
Nature of indirect interest<br><br>(including registered<br>holder)<br><br>Note: Provide details of the circumstances<br>giving rise to the relevant interest.	N/A
Date of change	24 August 2026
No. of securities held prior to change			Shares	Options
		Direct	550,000	10,175,002
		Indirect	94,247	-
		Total	644,247	10,175,002
Class	Listed Options
Number<br>acquired		NIL
Number disposed		275,000 Listed Options
Value/Consideration<br><br>Note:<br><br>If consideration is non-cash, provide details<br>and estimated valuation	NIL
+ See chapter 19 for defined terms.
---	---
01/01/2011	Appendix 3Y Page 1
Appendix 3Y
---
Change of Director’s Interest Notice
No. of securities held after change			Shares	Options
---	---	---	---	---
		Direct	550,000	9,900,002
		Indirect	94,247	-
		Total	644,247	9,900,002
Nature of change<br><br>Example:<br><br>on-market trade, off-market trade, exercise<br>of options, issue of securities under dividend reinvestment plan, participation in buy-back	Expiry<br>of Listed Options (Exp 24 Aug 2026)

Part 2 – Change of director’s interests in contracts

Note: In the case of a company, interests which come within paragraph (ii) of the definition of “notifiable interest of a director” should be disclosed in this part.

Detail of contract	N/A
Nature of interest	N/A
Name of registered holder<br><br>(if issued securities)	N/A
Date of change	N/A
No. and class of securities<br>to which interest related prior to change<br><br>Note: Details<br>are only required for a contract in relation to which the interest has changed	N/A
Interest acquired	N/A
Interest disposed	N/A
Value/Consideration<br><br>Note: If consideration is non-cash, provide details<br>and an estimated valuation	N/A
Interest after change	N/A
+ See chapter 19 for defined terms.
---	---
Appendix 3Y Page 2	01/01/2011

Appendix 3Y

Change of Director’s Interest Notice

Part 3 – Closed period

Were the interests<br>in the securities or contracts detailed above traded during a +closed period where prior written clearance was required?	No
If so, was prior written clearance provided to allow the trade to proceed during this period?	N/A
If prior written clearance was provided, on what date was this provided?	N/A
+ See chapter 19 for defined terms.
---	---
01/01/2011	Appendix 3Y Page 3