Company: NCNA
Filing Date: 2025-06-18
Form Type: 6-K
Source: 0001193125-25-142535
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Company: NuCana plc
Filing Date: 2025-06-18
Form: 6-K
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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): ☐

Other Events

Effective June 18, 2025, Hugh S. Griffith, the Chief Executive Officer of NuCana plc (the “Company”), will be taking a leave of
absence due to health reasons. Mr. Griffith is expected to return to his duties as Chief Executive Officer later in the year. In addition, the Company announced that (i) Andrew Kay, the Chairman of the Company’s Board of Directors
(the “Board”), has been appointed Executive Chairman by the Board and, during the pendency of Mr. Griffith’s leave, will act as the Company’s principal executive officer and (ii) Ian Webster, the Company’s Director
of Finance, has been appointed Interim Chief Financial Officer by the Board. Mr. Webster will continue to serve as the Company’s principal financial officer.

Supplemental Risk Factors

The following risk factors are provided to supplement the Company’s risk factors previously disclosed under the heading “Risk
Factors” in the Company’s Annual Report on Form 20-F for the year ended December 31, 2024.

The May 2025 offering may result in an immediate trading halt or delisting of our ADSs from The Nasdaq Capital Market due to public interest concerns.

Under Nasdaq Listing Rule 5101, The Nasdaq Stock Market has broad discretionary authority to terminate the
listing of