SEC Form 4 · accession 0001213900-26-100280
Horizon Quantum Holdings Ltd. · HQ
Statement of changes in beneficial ownership, as filed. Original on EDGAR ↗
Reporting owner
Si-Hui Tan
Officer — Chief Science Officer
Period of report
Mar 19, 2026
Accepted (ET)
Sep 15, 2026 · 9:31 pm EDT
Rule 10b5-1 plan
box not checked
Issuer CIK
0002088256
Table I — non-derivative securities
| Security | Date | Code | Shares | Price | A/D | Owned after | D/I | Nature of ownership |
|---|---|---|---|---|---|---|---|---|
| Class A Ordinary SharesF1,F2 | Aug 20, 2026 | A | 3,600 | $0.00 | A | 3,600 | I | By Spouse |
| Class A Ordinary SharesF3,F4 | Sep 12, 2026 | M | 5,728 | $0.00 | A | 5,728 | D | |
| Class A Ordinary SharesF5 | Sep 12, 2026 | D | 2,991 | $15.22 | D | 2,737 | D |
Table II — derivative securities
| Security | Conv. / exercise price | Date | Code | Shares | A/D | Exercisable | Expires | Underlying | Underlying shares | Owned after | D/I |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Stock Option (Right to Buy)F7,F8,F6 | $2.88 | Mar 19, 2026 | A | 55,000 | A | — | Feb 1, 2035 | Class A Ordinary Shares | 133,924 | 55,000 | I |
| Restricted Stock UnitF4,F2 | $0.00 | Jun 12, 2026 | A | 91,659 | A | — | — | Class A Ordinary Shares | 91,659 | 91,659 | D |
| Restricted Stock UnitF3,F2,F4 | $0.00 | Sep 12, 2026 | M | 5,728 | A | — | — | Class A Ordinary Shares | 5,728 | 85,931 | D |
Explanation of responses
- F1On August 20, 2026 (the "August Grant Date"), Dr. Tan's spouse was granted a total of unvested 3,600 RSUs. The RSUs granted to Dr. Tan's spouse are subject to his continued employment with the Company and vest in accordance with the following schedule: One quarter (1/4) of the total number of RSUs vest on the first anniversary of the August Grant Date with the remaining three quarters (3/4) vesting in twelve approximately equal quarterly installments on 20th day of each fiscal quarter.
- F2Each restricted stock unit ("RSU") represents a contingent right to receive one Class A ordinary share, with no par value ("Class A Ordinary Share"), of Horizon Quantum Holdings Ltd. (the "Company") upon vesting, for no consideration.
- F3On September 12, 2026, 5,728 of Dr. Tan's RSU's vested.
- F4On June 12, 2026 (the "June Grant Date"), Dr. Tan was granted a total of 91,659 unvested RSUs. The RSUs granted to Dr. Tan vest in sixteen approximately equal installments on successive quarterly anniversaries of the June Grant Date and are subject to Dr. Tan's continued employment with the Company through each applicable vesting date.
- F5The reported disposition to the Company reflects the settlement in cash of a portion of the RSUs which vested on September 12, 2026, at a price per ordinary share of $15.22, the last reported sales price of the Company's Class A Ordinary Shares on September 11, 2026.
- F6Each stock option has an exercise price of $2.88 and is exercisable for approximately 2.43499 Class A Ordinary Shares of the Company. In aggregate, Dr. Tan's spouse's stock options, once fully vested, are exercisable for 133,924 Class A Ordinary Shares of the Company.
- F7Of the 55,000 stock options, 37,811 stock options are currently fully vested and exercisable. The remaining stock options vest in five approximately equal quarterly installments beginning on November 20, 2026, subject to Dr. Tan's spouse's continued employment with the Company.
- F8As a result of the closing of the Company's business combination on March 19, 2026, Dr. Tan's spouse's 55,000 Legacy Horizon stock options were exchanged for 55,000 stock options of the Company of an equivalent economic value, with an exercise price per Class A Ordinary Share of $2.88.