Company: NCNA
Filing Date: 2025-09-05
Form Type: 6-K
Source: 0001193125-25-196589
Chunk: 1

Company: NuCana plc
Filing Date: 2025-09-05
Form: 6-K
Chunk 1
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 that the Company is in compliance with Nasdaq’s Listing Rules. The information contained in the second and third paragraphs of this Form 6-K ishereby incorporated by reference into the Company’s Registration Statement on Form F-3, asamended (File No. 333-281576), RegistrationStatement on Form S-8 (File No. 333-223476) andRegistration Statement on Form S-8 (File No. 333-248135). The information in the attached Exhibit 99.1 is being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that Section, nor shall it be deemed incorporated by reference in any filing made by the Company under the Securities Act of 1933, as amended, or the Exchange Act, except as otherwise set forth herein or as shall be expressly set forth by specific reference in such a filing.

SIGNATURES 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.

| NuCana plc |     |                                                                              |
| By:        |     | /s/ Ian Webster                                                              |
| Name:      |     | Ian Webster                                                                  |
| Title:     |     | Interim Chief Financial Officer (Principal Financial and Accounting Officer) |

Date: September 5, 2025