NOTICE OF 2023 ANNUAL GENERAL MEETING NuCana plc 77-78 Cannon Street, London, England, EC4N 6AF Company number: 03308778 NOTICE OF 2023 ANNUAL GENERAL MEETING NOTICE is hereby given that the 2023 annual general meeting o

77-78 Cannon Street, London, England, EC4N 6AF

Company number: 03308778

NOTICE OF 2023 ANNUAL

NOTICE is hereby given that the 2023 annual general meeting of NuCana plc (the Company ) will be held on 15 June 2023

at 11.00am at Lochside House, 3 Lochside Way, Edinburgh EH12 9DT, U.K. for transaction of the following business:

Ordinary Resolutions

To consider and, if thought fit, pass the following resolutions (1 to 10 inclusive), which will be proposed as ordinary resolutions:

To consider and, if thought fit, pass the following resolutions 11 and 12, which will be proposed as special resolutions:

The directors of the Company consider that all the proposals to be considered at the AGM are in the best interests of the Company and its shareholders as a

whole and are most likely to promote the success of the Company. The directors unanimously recommend that you vote in favour of all the proposed resolutions as they intend to do in respect of their own beneficial holdings.

YOUR VOTE IS IMPORTANT. Members will be

able to attend the AGM in person however you are strongly encouraged to vote on all resolutions in advance of the AGM by appointing the Chair of the meeting as your proxy. Further details on how shareholders can appoint the Chair of the meeting as

their proxy are set out in this document.

The following notes explain your general rights as a member and your right to attend and vote at the annual general meeting or to appoint someone else to vote

CREST members and, where applicable, their CREST sponsors or voting service providers should note that EUI does not make

available special procedures for any particular messages. Normal system timings and limitations will therefore apply in relation to the input of CREST proxy instructions. It is the responsibility of the CREST member concerned to take (or, if the

CREST member is a CREST personal member or sponsored member or has appointed a voting service provider, to procure that his CREST sponsor or voting service provider takes) such action as shall be necessary to ensure that a message is transmitted by

any particular time. Reference should be made to those sections of the CREST Manual concerning practical limitations of the CREST system and timings.

The Company may treat as invalid a CREST proxy instruction in the circumstances set out in Regulation 35(5)(a) of the Uncertificated Securities

EXPLANATORY NOTES TO THE RESOLUTIONS PROPOSED AT THE ANNUAL GENERAL MEETING

The resolutions to be proposed at the AGM of the Company to be held on 15 June 2023 at 11.00am are set out in this Notice of AGM. The following notes

provide an explanation to the resolutions being put to shareholders.

Ordinary Resolutions

Resolutions 1 to 10 are proposed as ordinary resolutions. Assuming that a quorum is present, an ordinary resolution is passed on a show of hands if it is

approved by a simple majority (more than 50%) of the votes cast by shareholders present (in person or by proxy) at the meeting and entitled to vote. On a poll, an ordinary resolution is passed if it is approved by holders representing a simple

majority of the total voting rights of shareholders present (in person or by proxy) who (being entitled to vote) vote on the resolution.

1 3 Re-election of directors

Under the Company s Articles of Association there are three classes of

board members (Class I, Class II and Class III) with each class having a specified term of office. The Company s Articles of Association require the Class I directors to retire from office this year. Hugh Stephen Griffith

currently serves as a Class I director. Hugh Stephen Griffith is retiring and (being eligible) is standing for re-election as a Class I director at the AGM. Andrew Martin Kay currently serves as a

Class I director. Andrew Martin Kay is retiring and (being eligible) is standing for re-election as a Class I director at the AGM. Bali Muralidhar currently serves as a Class I director. Bali

Muralidhar is retiring and (being eligible) is standing for re-election as a Class I director at the AGM. Biographical information for each director standing for

re-election is included on page 10 of this Notice.

THE BOARD RECOMMENDS A VOTE FOR THE RE-ELECTION OF EACH OF HUGH STEPHEN GRIFFITH, ANDREW MARTIN KAY AND BALI MURALIDHAR TO THE BOARD OF DIRECTORS.

Resolution 4 Re-appointment of auditors

The Act requires that auditors be appointed at each general meeting, at which accounts are laid, to hold office until the next AGM. The appointment of

Ernst & Young LLP as auditors of the Company terminates at the conclusion of the AGM. They have indicated their willingness to stand for re-appointment as auditors of the Company until the conclusion

The Audit Committee has assessed the effectiveness, independence and objectivity of the auditors, Ernst & Young LLP, and

concluded that the auditors were in all respects effective.

THE BOARD RECOMMENDS A VOTE FOR THE

RE-APPOINTMENT OF ERNST & YOUNG LLP AS AUDITORS.

Resolution 5 Authorising and fixing the

remuneration of the auditors

This resolution gives authority to the directors to determine the auditors remuneration.

It is normal practice for shareholders to resolve at the AGM that the directors shall decide on the level of remuneration of the auditors for the audit work

to be carried out by them in the next financial year. The amount of the remuneration paid to the auditors for the next financial year will be disclosed in the next audited accounts of the Company.

THE BOARD RECOMMENDS A VOTE FOR THE AUTHORISATION OF THE DIRECTORS TO DETERMINE THE AUDITORS REMUNERATION.

Resolution 6 Laying of accounts

required to present to shareholders at the AGM, the annual accounts of the Company for the year ended 31 December 2022, the Strategic Report, the Directors Report and the Auditor s Report on the accounts.

THE BOARD RECOMMENDS A VOTE FOR THE RESOLUTION TO RECEIVE THE ANNUAL ACCOUNTS OF THE COMPANY FOR THE YEAR ENDED 31 DECEMBER 2022, THE STRATEGIC

REPORT, THE DIRECTORS REPORT AND THE AUDITOR S REPORT ON THE ACCOUNTS.

Resolution 7 Directors Remuneration Report

Shareholders are invited to cast their vote on the Directors Remuneration Report, in accordance with Section 439 of the Act. The Directors

Remuneration Report is set out on pages 17 to 24 of the Company s annual accounts and reports for the year ended 31 December 2022. The vote is advisory in nature and therefore no entitlement to remuneration is conditional on the passing of

THE BOARD RECOMMENDS A VOTE FOR THE RESOLUTION TO RECEIVE AND APPROVE THE DIRECTORS REMUNERATION REPORT FOR THE FINANCIAL

YEAR ENDED 31 DECEMBER 2022.

Resolution 8 Directors Remuneration Policy

In accordance with the requirements of the Act, as a company registered in England and Wales and listed on Nasdaq, the Company is required to establish a

Directors Remuneration Policy containing a framework of limits within which the remuneration committee are authorised by shareholders to operate. This Remuneration Policy has to be annually disclosed within the Remuneration Report contained

within the Company s annual report, and this policy is required to be approved by shareholders at least every three years, by the passing of an ordinary resolution at the AGM.

Shareholders are asked to approve the Directors Remuneration Policy which is set out in full on pages 25 to 30 of the Directors Remuneration

Report. The vote on the Directors Remuneration Policy is binding in that, once the policy is approved, the Company will not be able to make a remuneration payment to a current or prospective director or a payment for loss of office to a

current or past director, unless that payment is consistent with the policy or has been specifically approved by a resolution of the Company s shareholders. If resolution 8 is passed, the Directors Remuneration Policy will take effect

THE BOARD RECOMMENDS A VOTE FOR THE RESOLUTION TO RECEIVE AND APPROVE THE DIRECTORS REMUNERATION POLICY.

Background to Resolution 9 and Special Resolution 11

As a matter of U.K. company law, directors of a company incorporated in England must have authority from shareholders to allot or grant rights to subscribe

for, or to convert any security into, the company s shares. In addition, when an allotment of shares is for cash, the company must first offer those shares on the same terms to existing shareholders of the company on a pro-rata basis (commonly referred to as statutory pre-emption rights) unless these statutory pre-emption rights are dis-applied, by approval of the shareholders.

Resolutions 9 and 11, which we refer to as our Share Issuance

Proposals, ask our shareholders for authority for the directors to allot shares or grant rights over shares up to an aggregate nominal amount of 4,000,000 and the power for the directors to allot shares or grant rights over shares for

cash up to an aggregate nominal amount of 4,000,000 on a non-preemptive basis. This authority and power would expire at the conclusion of our 2024 AGM.

Many of our peer companies are listed and incorporated in the United States, and are thus not subject to similar share issuance restrictions. We are asking

you to approve our Share Issuance Proposals to allow us to continue to execute on our business and growth strategy in a timely and competitive manner.

Should our shareholders not approve resolutions 9 and 11, whilst we appreciate that we would still have the ability to seek shareholder approval in connection

with a specific issuance of shares on a case-by-case basis by convening general meetings from time to time, we do not believe that such an approach is a workable

alternative to obtaining approval of resolutions 9 and 11 at the AGM as we propose. The uncertainty as to whether we could obtain shareholder approval for a specific issuance, as well as the delays we would experience in seeking and obtaining such

approval, could be harmful to the terms of such a share issuance. In addition, the case-by-case approval approach ignores market windows and other deal timing and

competitive realities.

Specifically, the requirement to first offer shares that we propose to issue for cash to all of our existing shareholders in

time-consuming pro-rata rights offerings would considerably reduce the speed at which we could complete capital-raising activities undertaken in furtherance of our growth strategy, would increase our costs,

might otherwise make it difficult or impossible for us to complete such transactions, and could put us at a distinct competitive disadvantage relative to our peer companies.

Access to capital and the ability to raise equity capital at short notice have been important factors that have contributed to our ability to execute our

long-term growth strategy. In practice, offering shares to existing shareholders in accordance with U.K. statutory pre-emption rights can be time-consuming, so U.K. market practice for listed companies is to

annually seek a shareholder resolution waiving or dis-applying pre-emption rights over new share issuances for cash, up to an agreed limit. We fully appreciate that our

proposals are in excess of the investment advisory guidance in this regard and for this reason, our proposals may attract a negative voting recommendation from certain proxy advisory firms. However, we have an established track record since our IPO

in October 2017 of securing annual shareholder support for a resolution dis-applying pre-emption rights over amounts of share capital in excess of the investment

advisory guidance. Using these authorities, we have responsibly raised capital in order to execute our business plan.

We believe the request for

authorisation and disapplication of pre-emption rights sought will provide us with the continued flexibility to raise equity capital that we believe we may require at this stage of development of the Company.

This recognises the fact that as a development-stage business, we have needed access to equity capital to ensure that we can maintain the business appropriately capitalised to expedite our development programs. We have publicly stated that we

believe our existing cash resources will be sufficient to fund the Company into 2025. We believe it is in the interests of all shareholders to ensure that we retain the ability to raise equity capital on reasonably short notice if advisable. We

propose to seek an authority (to expire at the 2024 AGM) to allot shares or grant rights over shares and under this authority to seek the power to allot shares or grant rights over shares for cash on a non-preemptive basis over a maximum of

100 million ordinary shares.

The Share Issuance Proposals are consistent with U.S. capital markets practice and U.S. governance standards, and, if

approved, will keep us on an equal footing with our peer companies who are incorporated and listed in the United States. We believe that the Share Issuance Proposals are appropriate to the needs of the Company and in the best interests of

shareholders. We are therefore asking you to approve the Share Issuance Proposals to allow us to continue to execute our business and growth strategy in a timely and competitive manner.

The Share Issuance Proposals, if approved, will

allow our Board of Directors continued flexibility to issue shares subject to other requirements of Nasdaq Stock Market and the Securities and Exchange Commission. The Share Issuance Proposals, as proposed:

Resolution 9 Authority to allot sharess

directors may only allot shares or grant rights over shares if authorised to do so by shareholders.