Director Dealing

4basebio PLC
("4basebio" or the "Company")

Director Dealing

CAMBRIDGE, UK – 22 May 2026   –   4basebio PLC (AIM: 4BB), a company pioneering an enzymatically-produced DNA technology serving the next generation genetic medicines markets, announces that on 21 May 2026 it was informed that Dr. Amy Walker, Chief Executive Officer of the Company, purchased 1,863 ordinary shares in the capital of the Company through the market.  

Further details are set out in the Notification of Dealing Form below.

Director / PCA	Number of ordinary shares urchased	Purchase price (pence)	Shareholding following purchase	Shareholding following purchase as a % of the issued share capital
Dr. Amy Walker	1,863	509.00	48,529	0.31%

The 1,863 shares purchased represent approximately 0.01 per cent. of the Company's issued share capital.

The issued share capital of the Company comprises 15,538,518 ordinary shares.

This announcement contains inside information for the purposes of Article 7 of EU Regulation 596/2014 as amended by regulation 11 of the Market Abuse (Amendment) (EU Exit) Regulations 2019/310.

For further enquiries, please contact:

4basebio PLC

Dr Amy Walker, CEO

[phone]

Cairn Financial Advisers LLP (Nominated Adviser)

Jo Turner / Sandy Jamieson / Ed Downes [phone]

Cavendish Capital Markets Limited (Joint Broker)

Geoff Nash / Nigel Birks [phone]

RBC Capital Markets (Joint Broker)

Kathryn Deegan / Matthew Coakes [phone]

ICR Healthcare (Media and Investor Relations)

Mary-Jane Elliott / Jessica Hodgson [phone]

About 4basebio

4basebio (AIM: 4BB) is a Cambridge-based biotechnology company pioneering the use of synthetic DNA to enable next-generation therapeutics and vaccines. Through its proprietary enzymatic DNA synthesis platform, 4basebio produces GMP-grade synthetic DNA and mRNA with superior speed, purity, and scalability, overcoming the limitations of plasmid-based systems. The company offers application-specific DNA constructs tailored to the diverse needs of gene therapies, genome editing, mRNA production, and DNA vaccines, helping partners accelerate proof-of-concept studies and reach clinical milestones more efficiently while maintaining the highest standards of safety and quality.

For more information, visit 4basebio.com .

Notification and public disclosure of transactions by persons discharging managerial responsibilities and persons closely associated with them

1	Details of the persons discharging managerial responsibilities / person closely associated
a)	Name	Dr. Amy Walker
2	Reason for the notification
a)	Position/Status	Chief Executive Officer
b)	Initial notification/ Amendment	Initial notification
3	Details of the issuer, emission allowance market participant, auction platform, auctioneer or auction monitor
a)	Name	4basebio plc
b)	LEI	213800E2DX9EAIUNCB30
4	Details of the transaction(s): section to be repeated for (i) each type of instrument; (ii) each type of transaction; (iii) each date; and (iv) each place where transactions have been conducted
a)	Description of the financial instrument, type of instrument Identification code	Ordinary Shares   ISIN: GB00BMCLYF79
b)	Nature of the transaction	Acquisition of ordinary shares
c)	Price(s) and volume(s)	Price: 509.00p Volume: 1,863
d)	Aggregated information -             Aggregated volume -             Aggregated Price	See above
e)	Date of transaction	21 May 2026
f)	Place of transaction	London Stock Exchange

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