PAR-2

↵ Dr. Anthony Johnson, President and Chief Executive Officer of Domain Therapeutics, and Sean A. MacDonald, Chief Business Officer to engage in key industry events in Q2 2024 Domain’s leadership will provide a corporate overview including advancements of key drug candidates in immuno-oncology: DT-9081 currently in Phase I ascending dose, as well as DT-7012 and DT-9045 in IND-enabling studies STRASBOURG, France & MONTREAL & BOSTON--(BUSINESS WIRE)-- Domain Therapeutics (“Domain” or “the Company”), a global clinical-stage biopharmaceutical company developing innovative drug candidates in immuno-oncology targeting G Protein-Coupled Receptors (GPCRs), today announced its President and Chief Executive Officer, Anthony Johnson, M.D., and its Chief Business Officer, Sean A. MacDonald, will participate in the following investor, partnering and healthcare industry conferences in April-May, 2024: This press release features multimedia. View the full release here: ​ Anthony Johnson & Sean A. MacDonald (Photo: Domain Therapeutics) Bloom Burton & Co. Healthcare Investor Conference – April 16-17 Location: Metro Toronto Convention Centre (North Building), Toronto, Canada Presentation slot: Wednesday, April 17, 3:30 PM ET, Room 104 A LSX World Congress – April 29-30 Location: Business Design Centre, London, UK Bio€quity Europe – May 12-14 Location: Kursaal Elkargunea Center, San Sebastián, Spain Presentation slot: to be announced at a later date The portfolio currently boasts the following novel drug candidates in the rapidly evolving cancer field of resistance in the tumor micro-environment: DT-7012, a best-in-class Treg-depleting anti-CCR8 monoclonal antibody DT-9045, a first-in-class, PAR2 biased ligand Negative Allosteric Modulator, small molecule DT-9081, an EP4R antagonist program, small molecule currently in Phase I ascending dose study About Domain Therapeutics For more information, please visit: ​ View source version on businesswire.com: Contacts For more information or to schedule a meeting with Dr. Tony Johnson: ICR Consilium Amber Fennell, Namrata Taak, Andrew Stern Email: DomainTherapeutics@consilium-comms.com Tel: +44 (0)20 3709 5813 Source: Domain Therapeutics Smart Multimedia Gallery ​ ​ Photo Anthony Johnson & Sean A. MacDonald (Photo: Domain Therapeutics) ​ ​ Logo ​ View this news release and multimedia online at:

- DT-9045 is a game-changer in immuno-oncology with competitive pharmacological properties and unique therapeutic potential to unlock new cancer treatment possibilities - Preclinical studies highlight the efficacy of DT-9045 in overcoming resistance to EGFR-targeting therapies and immunotherapy in cancer models - IND-enabling studies are currently ongoing STRASBOURG, France & MONTREAL & BOSTON--(BUSINESS WIRE)-- Domain Therapeutics (“Domain” or “the Company”), a global clinical-stage biopharmaceutical company developing innovative drug candidates in immuno-oncology targeting G Protein-Coupled Receptors (GPCRs), today announces that latest preclinical data on DT-9045, a novel protease-activated receptor 2 (PAR2) Negative Allosteric Modulator candidate, will be presented at the American Association for Cancer Research (AACR) Annual Meeting 2024 in San Diego, California. Date/Time: 7 April 2024 1:30 PM - 5:00 PM PST – Section 27 Abstract number: 684 / 30 Poster session: PO.ET09.05 - Novel Antitumor Agents 2 Title: DT-9045, a novel PAR2 inhibitor with best-in-class properties that reduces resistance to both EGFR-targeting therapies and immunotherapy in oncology models The abstract will be made available in the online Proceedings of the AACR. PAR2 is one of the genes most significantly linked to resistance against immune checkpoint blockage (ICB) and T cells dysfunction in cancer patients. Its upregulation across a variety of cancer types and expression on diverse cells within the tumor microenvironment underscore PAR2’s critical role in cancer development. Leveraging its integrated precision research approach, backed by over 20 years of solid GPCR expertise, Domain has developed a novel highly potent and selective PAR2 inhibitor, DT-9045. This first-in-class Negative Allosteric Modulator has shown unparalleled potential in oncology and immuno-oncology. Remarkably, when compared to its most advanced competitors positioned in other therapeutic areas, this candidate has demonstrated clear differentiated features. Moreover, several proof-of-concept studies have shown strong potency in models resistant to EGFR-targeting therapies and immunotherapy opening solid perspectives of strategic clinical positioning and revenues generation in tumor types that constitute a high medical unmet need. DT-9045 is a small molecule, orally available, insurmountable, biased, and active in tumor-like conditions (high concentration of activating proteases and acidic pH). IND-enabling studies are currently ongoing to advance the candidate toward the clinic. Stephan Schann, Chief Scientific Officer of Domain Therapeutics, commented: “We are excited to present our newest findings on DT-9045 at AACR. The results not only confirm the immense potential of our PAR2 inhibitor to change the way we treat cancer, but also emphasize its high potency and efficacy against several drug resistance, offering cancer patients a clear therapeutic perspectives in immuno-oncology. More broadly, they reflect our deep commitment to precision research, pioneering innovative new GPCR targets in immunosuppression, designing clear competitive properties to deliver game-changing candidates. We eagerly anticipate advancing this groundbreaking research, with a focus on addressing a substantial unmet medical need for cancer patients.” This progress, follows the announcement in June 2023 when DT-9045 was nominated as a first-in-class clinical PAR2 antagonist. It has shown great therapeutic potential in enhancing the efficacy to immunotherapy aiming to substantially improve treatment outcomes for non-responding cancer patients. About Domain Therapeutics Domain Therapeutics, a global clinical-stage biopharmaceutical company, is developing innovative immunotherapies targeting G Protein-Coupled Receptors (GPCRs), one of the most important drug target classes, to unlock new possibilities in cancer. As the leading GPCR immuno-oncology company, Domain aims to beat resistance to immune modulation within the tumor microenvironment by unveiling therapeutic potential of GPCRs to defeat cancer. Two decades of solid GPCR expertise, validated through multiple pharma partnerships across various therapeutic areas and associated to a world-class drug discovery platform, enable the Company to deepen the understanding of cancer biology and deliver the next-generation of immunotherapies to patients. Domain’s proprietary programs include DT-7012, a Treg-depleting CCR8 antibody, DT-9045, a first-in-class PAR2 negative allosteric modulator, and DT-9081, an EP4 receptor antagonist alongside the M1069, an A2aR/A2b receptor antagonist identified in partnership with Merck KGaA. The company has also an optimized pipeline of best-in-class and first-in-class GPCR targets selected through Domain’s proprietary cross-validation drug discovery and development platform. Since 2022, the Company raised €51m ($55m) in series A to progress preclinical and clinical development of its high-value drug candidates to address GPCR-mediated immunosuppression. Domain is supported by leading international venture capital firms from Europe (3B Future Health Fund, Seventure, Schroders, Omnes, Turenne, Theodorus), Asia (Panacea and Viva) and North America (CTI Life Science, adMare). For more information, please visit:

Stephan Schann brings an outstanding track record in GPCRs, precision research and drug discovery to guide Domain’s scientific strategy in its next phase of growth His key contributions enabled Domain’s shift to immuno-oncology and the development of new cancer treatments, including DT-9081 in Phase I and DT-7012 and DT-9045 in preclinical stages STRASBOURG, France & MONTREAL & BOSTON--(BUSINESS WIRE)-- Domain Therapeutics (“Domain” or “the Company”), a clinical-stage global biopharmaceutical company developing innovative drug candidates in immuno-oncology targeting G Protein-Coupled Receptors (GPCRs), today announces the expansion of the Company’s executive management team with the appointment of Stephan Schann as Chief Scientific Officer (CSO). Stephan will oversee the development of Domain’s proprietary pipeline and its highly innovative R&D center based in Strasbourg, France. This press release features multimedia. View the full release here: (Photo: Domain Therapeutics) Stephan has been with Domain since its inception in 2008 and has been promoted from his previous role as Vice President of Research. He has been instrumental in leading and executing Domain’s research initiatives, raising funds, building its intellectual property portfolio, and advancing its proprietary R&D programs and collaborations with pharma partners. Stephan has also contributed significantly to the Company’s scientific achievements and strategic direction. With over two decades of leadership experience in the biopharmaceutical industry, Stephan has extensive expertise in biomedical research. He has successfully managed several programs from idea through to early development. In his new role, Stephan will lead Domain’s scientific strategy, coordinating with the CEO and executive management team to drive the Company’s pipeline of GPCR targeted cancer immunotherapies towards the next R&D milestones. This includes the continued development of novel drug candidates DT-7012, a best-in-class Treg-depleting anti-CCR8 monoclonal antibody and DT-9045, a first-in-class PAR2 antagonist, while advancing the EP4R program’s DT-9081, currently in its Phase I ascending dose study. Prior to his time with Domain, Stephan held several prominent roles including Head of Medicinal Chemistry at Faust Pharmaceuticals and Senior Scientist at Evotec. Stephan holds two Master’s Degrees in Organic and Medicinal Chemistry as well as a Ph.D. in Medicinal Chemistry from the University of Strasbourg, France. Dr. Tony Johnson, President and Chief Executive Officer of Domain Therapeutics, said: “We are thrilled to have Stephan be promoted into the role of Chief Scientific Officer. It has been a privilege for our teams to work with Stephan to bring our GPCR targeted immunotherapies to the clinic, backed by robust pre-clinical evidence built under his expert guidance. His visionary leadership, scientific acumen, knowledge of Domain and unwavering dedication to our shared mission make him ideal to lead our remarkable research team as we strive to progress our pipeline of first-in-class and best-in-class GPCR targeted cancer immunotherapies to deliver effective treatments to patients. Stephan’s appointment reinforces our commitment to growth, solidifying our position as the leading GPCR immuno-oncology company, now expanding our reach into the US markets.” Stephan Schann, newly appointed Chief Scientific Officer of Domain Therapeutics, commented: “I have always been deeply impressed by the commitment of Domain’s staff, scientists, management and Board of Directors to advancing its science. It is a true honor to be working with such a dynamic and driven leadership team. I look forward to continuing to support the Company and to further developing Domain’s unique precision research approach, translating our groundbreaking science into meaningful, differentiated and life-saving treatments for cancer patients. Domain is a highly innovative company built on a foundation of leading scientific expertise in pioneering GPCR in immuno-oncology that has the potential to be a game-changer in the coming years.” About Domain Therapeutics: