Company: NCNA
Filing Date: 2025-06-27
Form Type: 6-K
Source: 0001193125-25-151430
Chunk: 0

Company: NuCana plc
Filing Date: 2025-06-27
Form: 6-K
Chunk 0
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### UNITED STATES

### SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

FORM 6-K

REPORT OF FOREIGN ISSUER

PURSUANT TO RULE 13a-16 OR 15d-16

OF THE SECURITIES EXCHANGE ACT OF 1934

For the month of June 2025

(Commission File No. 001-38215)

### NUCANA PLC
(Translation of registrant’s name into English)

3 Lochside Way

Edinburgh EH12 9DT

United Kingdom

(Address of registrant’s principal executive office)

Indicate by check mark whether the registrant files or will file annual reports under
cover Form 20-F or Form 40-F.

Form 20-F ☒ Form 40-F ☐

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101 (b) (1): ☐

Indicate by check mark if the registrant is
submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101 (b) (7): ☐

Warrant Cancellation Letter Agreements NuCana plc (the “Company”) has entered into letter agreements (the “Letter Agreements”), with the holders (the “Warrant Holders”) of the Company’s Series A ADS Purchase Warrants (the “Series A Warrants”) to purchase American Depositary Shares (“ADSs”), each ADS representing twenty-five (25) ordinary shares, nominal value £0.0004 per share, which Series A Warrants were previously issued in a registered offering on May 7, 2025 pursuant to that certain securities purchase agreement, dated as of May 5, 2025, by and between the Company and the Warrant Holders (the “Securities Purchase Agreement”). Pursuant to the Letter Agreements, the Warrant Holders waived certain restrictions under the Securities Purchase Agreement to permit the Company to, among other things, enter into and make sales under an at-the-market(“ATM”) offering, subject to specified conditions (the “ATM Sales Conditions”). The ATM Sales Conditions require the Company to use commercially reasonable efforts to enter into an ATM sales agreement, with a portion of the net proceeds from any sales under the ATM offering used to make pro rata cash payments to the Warrant Holders in consideration for the cancellation of their outstanding Series A Warrants (the “Warrant