Increase of BookBuild Offer

Poolbeg Pharma plc (AIM: POLB, 'Poolbeg Pharma' or the 'Company'), a clinical-stage biopharmaceutical company focussed on the development of innovative medicines to address unmet medical needs, announces that, further to the announcement made on 20 May 2025 regarding the proposed BookBuild Offer (the "BookBuild Offer Announcement"), the BookBuild Offer is significantly oversubscribed and therefore the Company is increasing the number of BookBuild Offer Shares made available at the Issue Price to 6,000,000, which, if fully subscribed, would raise gross proceeds of £150,000.

A separate announcement was released by the Company on 20 May 2025 which sets out the terms of the BookBuild Offer. The Company will use the net proceeds of the BookBuild Offer, the Placing and Subscription to realise the following meaningful expected value inflection points whilst, together with the Company's existing resources, providing financial runway into 2027:

· POLB 001's Phase 2a trial: First patient dosed is expected in H2 2025 and Phase 2a topline data is expected in H2 2026, including interim analysis in H1 2026. POLB 001 is a potentially breakthrough, orally delivered p38 MAPK inhibitor designed to prevent cancer immunotherapy-induced Cytokine Release Syndrome ("CRS"), a severe, potentially life-threatening side effect of cancer immunotherapies. Poolbeg's decision to expand into oncology with POLB 001 has unlocked a significant market opportunity expected to exceed US$10 billion, as confirmed by independent research commissioned by Poolbeg. There are strong indications from Big Pharma to provide the necessary bispecific antibody, free of charge, to support the Phase 2a trial which represents a significant validation as to the industry interest in POLB 001 and its potential. The Company sees potential for partnering on positive data from this trial.

• Oral GLP-1 proof of concept trial: The trial expected to start in the coming months and topline proof of concept data expected H1 2026. The oral GLP-1 programme is comprised of a proprietary encapsulation technology to potentially offer an effective oral GLP-1 alternative for the growing obesity market and overcome oral delivery challenges of peptide-based biologicals. The Company believes that successful results from the trial may support partnering and multiple opportunities for value creation.

The BookBuild Offer is open to eligible investors in the United Kingdom and is expected to close at 4.30 p.m. today, 22 May 2025. Investors should note that Intermediaries may have earlier closing times. For further information in relation to the BookBuild Offer, please refer to the BookBuild Offer Announcement.

The New Ordinary Shares to be issued pursuant to the Fundraising (including the BookBuild Offer Shares), remain subject to the passing of certain resolutions at a general meeting of the Company to be held at the offices of DAC Beachcroft LLP at The Walbrook Building, 25 Walbrook, London, England, EC4N 8AF, UK at 2.00 p.m. on 23 June 2025.

For the avoidance of doubt, the BookBuild Offer is not part of the Placing or Subscription. Completion of the Placing is not conditional on the completion of the BookBuild Offer but completion of the BookBuild Offer is conditional, inter alia, upon the completion of the Placing and the New Ordinary Shares being admitted to trading on the AIM market ("AIM") operated by London Stock Exchange plc (the "London Stock Exchange") ("Admission").

Admission, settlement and dealings

Application will be made to the London Stock Exchange for the New Ordinary Shares (including the BookBuild Offer Shares) to be admitted to trading on AIM. Admission is expected to take place at 8.00 a.m. on 25 June 2025 and dealings in the New Ordinary Shares are expected to commence at 8.00 a.m. on 25 June 2025 or, in each case, such later time and/or date as Shore Capital and the Company agree (being in any event no later than 8.00 a.m. on 23 July 2025).

Certain terms used in this announcement but not defined in it shall, unless the context otherwise requires, have the meaning given to them in the Company's announcement of 7:01 a.m. on 20 May 2025 relating to the Fundraising.

UK Product Governance Requirements

Solely for the purposes of the product governance requirements of Chapter 3 of the FCA Handbook Product Intervention and Product Governance Sourcebook (the "UK MiFIR Product Governance Requirements"), and disclaiming all and any liability, whether arising in tort, contract or otherwise, which any "manufacturer" (for the purposes of the UK MiFIR Product Governance Requirements) may otherwise have with respect thereto, the BookBuild Offer Shares have been subject to a product approval process, which has determined that the BookBuild Offer Shares are: (i) compatible with an end target market of investors who meet the criteria of retail investors and investors who meet the criteria of professional clients and eligible counterparties, each as defined in paragraphs

3.5 and 3.6 of COBS; and (ii) eligible for distribution through all permitted distribution channels (the "Target Market Assessment"). Notwithstanding the Target Market Assessment, distributors should note that: the price of the BookBuild Offer Shares may decline and investors could lose all or part of their investment; the BookBuild Offer Shares offer no guaranteed income and no capital protection; and an investment in the BookBuild Offer Shares is compatible only with investors who do not need a guaranteed income or capital protection, who (either alone or in conjunction with an appropriate financial or other adviser) are capable of evaluating the merits and risks of such an investment and who have sufficient resources to be able to bear any losses that may result therefrom. The Target Market Assessment is without prejudice to any contractual, legal or regulatory selling restrictions in relation to the BookBuild Offer.

For the avoidance of doubt, the Target Market Assessment does not constitute: (a) an assessment of suitability or appropriateness for the purposes of Chapters 9A or 10A respectively of COBS; or (b) a recommendation to any investor or group of investors to invest in, or purchase, or take any other action whatsoever with respect to the BookBuild Offer Shares. Each distributor is responsible for undertaking its own target market assessment in respect of the BookBuild Offer Shares and determining appropriate distribution channels.

EU Product Governance Requirements

Solely for the purposes of the product governance requirements contained within: (a) EU Directive 2014/65/EU on markets in financial instruments, as amended ("MiFID II"); (b) Articles 9 and 10 of Commission Delegated Directive (EU) 2017/593 supplementing MiFID II; and (c) local implementing measures (together, the "MiFID II Product Governance Requirements"), and disclaiming all and any liability, whether arising in tort, contract or otherwise, which any "manufacturer" (for the purposes of the MiFID II Product Governance Requirements) may otherwise have with respect thereto, the BookBuild Offer Shares have been subject to a product approval process, which has determined that the BookBuild Offer Shares are: (i) compatible with an end target market of retail investors and investors who meet the criteria of professional clients and eligible counterparties, each as defined in MiFID II; and (ii) eligible for distribution through all distribution channels as are permitted by MiFID II (the "EU Target Market Assessment"). Notwithstanding the EU Target Market Assessment, distributors should note that: the price of the BookBuild Offer Shares may decline and investors could lose all or part of their investment; the BookBuild Offer Shares offer no guaranteed income and no capital protection; and an investment in the BookBuild Offer Shares is compatible only with investors who do not need a guaranteed income or capital protection, who (either alone or in conjunction with an appropriate financial or other adviser) are capable of evaluating the merits and risks of such an investment and who have sufficient resources to be able to bear any losses that may result therefrom. The EU Target Market Assessment is without prejudice to the requirements of any contractual, legal or regulatory selling restrictions in relation to the BookBuild Offer.

For the avoidance of doubt, the EU Target Market Assessment does not constitute: (a) an assessment of suitability or appropriateness for the purposes of MiFID II; or (b) a recommendation to any investor or group of investors to invest in, or purchase or take any other action whatsoever with respect to the BookBuild Offer Shares. Each distributor is responsible for undertaking its own target market assessment in respect of the BookBuild Offer Shares and determining appropriate distribution channels.