Statement of Changes in Beneficial Ownership (Form 4)

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b). Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

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(Print or Type Responses)

1. Name and Address of Reporting Person * Fitzsimons Catherine Michele 2. Issuer Name and Ticker or Trading Symbol Horizon Quantum Holdings Ltd. [HQ] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner __X__ Officer (give title below) _____ Other (specify below) CLO and CCO (Last) (First) (Middle) C/O HORIZON QUANTUM HOLDINGS LTD., 29 MEDIA, CIR. #05-22 3. Date of Earliest Transaction (Month/Day/Year) 06/11/2026 (Street) SINGAPORE 138565 4. If Amendment, Date Original Filed (Month/Day/Year) 6. Individual or Joint/Group Filing (Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price

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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)

2. Conversion or Exercise Price of Derivative Security

3. Transaction Date (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

4. Transaction Code (Instr. 8)

5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)

6. Date Exercisable and Expiration Date (Month/Day/Year)

7. Title and Amount of Underlying Securities (Instr. 3 and 4)

8. Price of Derivative Security (Instr. 5)

9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)

10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)

11. Nature of Indirect Beneficial Ownership (Instr. 4)

Code

V

(A)

(D)

Date Exercisable

Expiration Date

Title

Amount or Number of Shares

Stock Option (Right to Buy)

$10.78(1)

06/11/2026(2)

A

601,932(2)

(2)

06/11/2036(2)

Class A Ordinary Shares

601,932(1)

$10.78

601,932

D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Fitzsimons Catherine Michele C/O HORIZON QUANTUM HOLDINGS LTD. 29 MEDIA, CIR. #05-22 SINGAPORE 138565			CLO and CCO

Signatures

/s/ Catherine Michele Fitzsimons		10/21/2026
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	Each stock option has an exercise price of $10.78 and is exercisable for one Class A Ordinary Share of Horizon Quantum Holdings Ltd. (the "Company"). Ms. Fitzsimons's stock options, once fully vested, will be exercisable for an aggregate of 601,932 Class A Ordinary Shares of the Company.
(2)	On June 11, 2026 (the "Grant Date"), Ms. Fitzsimons was granted a total of 601,932 unvested stock options. The unvested stock options granted to Ms. Fitzsimons vest in sixteen approximately equal quarterly installments over a four-year period beginning on August 11, 2026, with each vesting installment subject to Ms. Fitzsimons's continued employment with the Company. The unvested stock options expire ten years from the Grant Date, or June 11, 2036. Of the 601,932 unvested stock options granted to Ms. Fitzsimons, 37,620 are fully vested and exercisable as of the date hereof.

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