Company: NCNA
Filing Date: 2025-06-30
Form Type: 6-K
Source: 0001193125-25-151990
Chunk: 2

Company: NuCana plc
Filing Date: 2025-06-30
Form: 6-K
Chunk 2
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side Way, Edinburgh, EH12 9DT, United
Kingdom. All of the resolutions set out in the Company’s notice of the AGM dated June 5, 2025 and furnished on Form 6-K with the SEC on June 5, 2025 were duly proposed and passed.

The information in this Form 6-K shall be deemed to be incorporated by reference into the registration statements on
Form F-3, as amended (File Number 333-281576) and Form S-8 (File Number 333-223476 and
File Number 333-248135), and related prospectuses, as such registration statements and prospectuses may be amended from time to time, and to be a part thereof from the date on which this report is filed, to
the extent not superseded by documents or reports subsequently filed or furnished.

Exhibits

| Exhibit 
 1.1     |     | Description                                                                                                                     
 Sales Agreement, dated June 27, 2025, by and among the Company, A.G.P./Alliance Global Partners and Laidlaw & Company (UK) Ltd. |
|:--------|:----|:--------------------------------------------------------------------------------------------------------------------------------|
| 5.1     |     | Opinion of Bristows LLP                                                                                                         |
| 23.1    |     | Consent of Bristows LLP (included in Exhibit 5.1)                                                                               |

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, thereto duly authorized.

| NuCana plc |     |                                 |
| By:        |     | /s/ Ian Webster                 |
| Name:      |     | Ian Webster                     |
| Title:     |     | Interim Chief Financial Officer |

Date: June 30, 2025