Company: NCNA
Filing Date: 2025-06-18
Form Type: F-3/A
Source: 0001193125-25-142565
Chunk: 8

Company: NuCana plc
Filing Date: 2025-06-18
Form: F-3/A
Chunk 8
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, if any. |

| • |     | aggregate principal amount or aggregate offering price; |

| • |     | maturity, if applicable; |

| • |     | rates and times of payment of interest or dividends, if any; |

| • |     | redemption, conversion or sinking fund terms, if any; |

| • |     | voting or other rights, if any; and |

| • |     | conversion or exercise prices, if any. |

The prospectus supplement also may add, update or change information contained in this prospectus or in documents we have incorporated by reference into this prospectus. However, no prospectus supplement will fundamentally change the terms that are set forth in this prospectus or offer a security that is not registered and described in this prospectus at the time of its effectiveness. We may sell the securities directly to investors or to or through agents, underwriters or dealers. We, and our agents or underwriters, reserve the right to accept or reject all or part of any proposed purchase of securities. If we offer securities through agents or underwriters, we will include in the applicable prospectus supplement:

| • |     | the names of those agents or underwriters; |

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| • |     | applicable fees, discounts and commissions to be paid to them; |

| • |     | details regarding over-allotment options, if any; and |

| • |     | the net proceeds to us. |

This prospectus may not be used to consummate a sale of any securities unless it is accompanied by a prospectus supplement.

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RISK FACTORS

Investing in our securities involves significant risk. The prospectus supplement applicable to each offering of our securities will contain a
discussion of the risks applicable to an investment in the company. Prior to making a decision about investing in our securities, you should carefully consider the specific factors discussed under the heading “Risk Factors” in the
applicable prospectus supplement, together with all of the other information contained or incorporated by reference in the prospectus supplement or appearing or incorporated by reference in this prospectus. You should also consider the risks,
uncertainties and assumptions discussed under the heading “Risk Factors” included in our most recent Annual Report on Form 20-F and any subsequent Annual Reports on Form 20-F we file after the date of this prospectus, and all other information contained in or incorporated by reference into this prospectus or the registration statement of which this prospectus forms a part, as
updated by our subsequent filings