Company: NCNA
Filing Date: 2025-06-18
Form Type: F-3/A
Source: 0001193125-25-142565
Chunk: 38

Company: NuCana plc
Filing Date: 2025-06-18
Form: F-3/A
Chunk 38
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 to institute a proceeding under the indentures or to appoint a receiver or trustee, or to seek other remedies if:

| • |     | these limitations do not apply to a suit instituted by a holder of debt securities if we default in the payment 
 of the principal, premium, if any, or interest on, the debt securities;                                         |

| • |     | the holder previously has given written notice to the debenture trustee of a continuing event of default with 
 respect to that series;                                                                                       |

31

| • |     | the holders of at least a majority in aggregate principal amount of the outstanding debt securities of that                                               
 series have made written request, and such holders have offered reasonable indemnity to the debenture trustee to institute the proceeding as trustee; and |

| • |     | the debenture trustee does not institute the proceeding, and does not receive from the holders of a majority in                                                                                                                                          
 aggregate principal amount of the outstanding debt securities of that series (or at a meeting of holders of such series at which a quorum is present, the holders of a majority in principal amount of the debt securities of such series represented at 
 such meeting) other conflicting directions within 60 days after the notice, request and offer.                                                                                                                                                           |

We will periodically file statements with the applicable debenture trustee regarding our compliance with specified covenants in the applicable indenture. Modification of Indenture; Waiver The debenture trustee and we may change the applicable indenture without the consent of any holders with respect to specific matters, including:

| • |     | to fix any ambiguity, defect or inconsistency in the indenture; and |

| • |     | to change anything that does not materially adversely affect the interests of any holder of debt securities of 
 any series issued pursuant to such indenture.                                                                  |

In addition, under the indentures, the rights of holders of a series of debt securities may be changed by us and the debenture trustee with the written consent of the holders of at least a majority in aggregate principal amount of the outstanding debt securities of each series (or, at a meeting of holders of such series at which a quorum is present, the holders of a majority in principal amount of the debt securities of such series represented at such meeting) that is affected. However, the debenture trustee and we may make the following changes only with the consent of each holder of any outstanding debt securities affected:

| • |     | extending the fixed maturity of the series of debt securities;