Company: NCNA
Filing Date: 2025-04-24
Form Type: F-1
Source: 0001193125-25-092131
Chunk: 18

Company: NuCana plc
Filing Date: 2025-04-24
Form: F-1
Chunk 18
---
 exchange or other trading market. Without a trading market, the liquidity of the Pre-Funded Warrants and Warrants will be 
 extremely limited.                                                                                                                                                                                           |

The number of our ordinary shares to be outstanding immediately after this offering is calculated by reference to our entire issued share capital of 142,037,199 ordinary shares as of December 31, 2024 and excludes as of that date:

| • |     | 17,175,304 ordinary shares issuable upon exercise of outstanding options under our equity compensation plans as 
 of December 31, 2024 at a weighted average exercise price of £2.11 per ordinary share; and                      |

| • |     | 29,123 ordinary shares issued upon exercise of options under our equity incentive plans subsequent to December 
 31, 2024 at an exercise price of £0.04 per ordinary share.                                                     |

7

RISK FACTORS

Investing in our securities involves a high degree of risk. You should carefully consider the risks described under “Risk Factors” in our Annual Report on Form 20-F forthe fiscal year ended December 31, 2024, as filed with the SEC, and all other information contained in, or incorporated by reference in, this prospectus, as updated by those subsequent filings with the SEC under the Exchange Act, before making an investment decision. The risks and uncertainties described below and incorporated by reference are not the only ones we face. Additional risks and uncertainties not presently known to us may also adversely affect our business. Our business, financial condition and/or results of operations could be materially and adversely affected if any of these risks occur, and as a result the trading price of the ADSs could decline and you could lose all or part of your investment.

This prospectus also contains forward-looking statements that involve risks and uncertainties. See “Special Note Regarding Forward-Looking Statements.” Our actual results could differ materially and adversely from those anticipated in these forward-looking statements as a result of certain factors.

Risks Related to This Offering

You may experience future dilution as a result of future equity offerings.

In order to raise additional capital, we may in the future offer additional ADSs or other securities convertible into or exchangeable for our
ADSs at prices that may not be the same as the price per ADS in this offering. We may sell ADSs or other securities in any other offering at a price per ADS that is less than the price per ADS paid by any investors in this offering, and investors
purchasing shares or