Grant of Options & Director/PDMR Dealing

4basebio PLC

("4basebio" or the "Company")

Grant of Options

Director/PDMR Dealing

Cambridge, UK – 22 July 2026   –   4basebio PLC (AIM: 4BB), a company pioneering an enzymatically-produced DNA technology serving the next generation genetic medicines markets, announces that it has granted in aggregate 684,872 options over ordinary shares of the Company, (the “ Share Options ") to certain Directors and a PDMR of the Company.

634,872 of the Share Options granted to Dr. Amy Walker, Dr. Manja Boerman and Dr. Heikki Lanckriet have an exercise price of £5.05 per ordinary share (breakdown below), being the closing mid-market price on 1 May 2026, and the remaining 50,000 Share Options granted to Richard Bungay have an exercise price of £5.25 per ordinary share, being the closing mid-market price on 21 July 2026.

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

	Number of Share Options Granted	Resultant Number of Share Options Held	As a % of Current Issued Share Capital
Dr. Amy Walker	387,872	430,000	2.77%
Dr. Manja Boerman	172,000	172,000	1.11%
Dr. Heikki Lanckriet	75,000	101,137	0.65%
Richard Bungay	50,000	50,000	0.32%
Total	684,872	753,127	4.85%

Certain amounts of the Share Options have been granted to Dr. Amy Walker and Dr. Manja Boerman pursuant to delayed option grants that were agreed in 2024 and 2025.

301,872 of the Share Options granted to Dr. Amy Walker and all of the Share Options granted to Dr. Manja Boerman vest annually in equal tranches over four years from 1 May 2026. 86,000 of the Share Options granted to Dr. Amy Walker will become exercisable if the volume-weighted average share price of the Company exceeds £15.00 for 30 consecutive trading days. The Share Options granted to Richard Bungay vest annually in equal tranches over four years from 21 July 2026. The Share Options granted to Dr. Heikki Lanckriet vest in full immediately on grant.

The issued share capital of the Company is 15,538,518 ordinary shares. Following the grant of the Share Options, the Company will have 1,354,024 options over ordinary shares in issue representing approximately 8.71 per cent. of the Company’s current issued share capital

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	1)       Dr. Amy Walker 2)       Dr. Manja Boerman 3)       Dr. Heikki Lanckriet 4)       Richard Bungay
2	Reason for the notification
a)	Position/Status	1)       Chief Executive Officer 2)       Executive Chair 3)       Non-executive Director 4)       PDMR
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	Options over Ordinary Shares   ISIN: GB00BMCLYF79
b)	Nature of the transaction	Grant of Options over Ordinary Shares
c)	Price(s) and volume(s)	Price(s) per share (p) Volume(s) i)                      505p ii)                    505p iii)                  505p iv)                  525p i)                      387,872 ii)                    172,000 iii)                  75,000 iv)                  50,000
d)	Aggregated information -             Aggregated volume -             Aggregated Price	See above
e)	Date of transaction	21 July 2026
f)	Place of transaction	Outside a trading venue

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