4 April 2025

4basebio PLC

("4basebio" or the "Company")

Director Dealing

Cambridge, UK, 4 April 2025 – 4basebio PLC (AIM: 4BB), an innovation-led provider of novel synthetic DNA products and a non-viral, thermostable nucleic acid delivery platform, announces that it was informed by Dr. Heikki Lanckriet, CEO of the Company, that on 2 April 2025 he made the following purchases in ordinary shares in the capital of the Company through the market, on behalf of his three children.

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

                                                              Shareholding
                  Number of                      Shareholding Following
Director / PCA    Ordinary Shares Purchase Price Following    Acquisition as a
                  Acquired        (p)            Acquisition  Percentage of
                                                              Issued Share
                                                              Capital

Heikki Lanckriet* 2,400           1,205          1,117,688    7.21%

*Refers to Heikki Lanckriet and persons closely associated with him.

The 2,400 additional shares purchased represent approximately 0.02 per cent. of the Company's issued share capital. The issued share capital of the Company comprises 15,496,393 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
                                             +44 (0)1223 967 943
Dr. Heikki Lanckriet, CEO

Nominated Adviser

Cairn Financial Advisers LLP                 +44 (0)20 7213 0880

Jo Tuner / Sandy Jamieson / Ed Downes

Joint Broker

RBC Capital Markets                          +44 (0)20 7653 4000

Rupert Walford / Max Avison / Kathryn Deegan

Joint Broker

Cavendish Capital Markets Limited            +44 (0)20 7220 0500

Geoff Nash / Nigel Birks

Notes to Editors

About 4basebio

4basebio (AIM: 4BB) is an innovation driven life biotechnology company focused on accelerating the development of advanced therapy medicinal products (ATMPs) through its high-performance synthetic DNA products and non-viral, cell targeting nucleic acid delivery platform. The Company’s objective is to become a market leader in the manufacture and supply of high-quality synthetic DNA products for research, therapeutic and pharmacological use as well as development of target specific non-viral vectors for the efficient delivery of payloads in patients.

Forward-looking statements

This announcement may contain certain statements about the future outlook for 4basebio.  Although the directors believe their expectations are based on reasonable assumptions, any statements about future outlook may be influenced by factors that could cause actual outcomes and results to be materially different.

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) NameHeikki Lanckriet

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

   Details of the transaction(s): section to be repeated for (i) each type of
4  instrument; (ii) each type of transaction; (iii) each date; and (iv) each
   place where transactions have been conducted

   Description of the financialinstrument, type Ordinary Shares
a) ofinstrumentIdentification code
                                                ISIN: GB00BMCLYF79

b) Nature of the transaction                    Acquisition of ordinary shares


                                                Date       Price(s) Volume(s)
c) Price(s) and volume(s)
                                                02/04/2025 1,205p   2,400


d) Aggregated information- Aggregated volume-   2,4001,205p
   Price

e) Date of transaction                          02 April 2025

f) Place of transaction                         London Stock Exchange