Sareum Holdings PLC

("Sareum" or the "Company")

Completion of Dosing in Phase 2-Enabling Toxicology Programme for SDC-1801

·    Phase 2-enabling programme on track for year-end completion in line with Company expectations

Cambridge, UK, 20 July 2026 -- Sareum Holdings plc (AIM: SAR), a clinical-stage biotechnology company developing next-generation kinase inhibitors for autoimmune disease and cancer, is pleased to announce that dosing has been completed in the Phase 2-enabling toxicology programme for SDC-1801, a selective oral TYK2/JAK1 inhibitor being developed as a potential treatment for a range of autoimmune diseases, with an initial focus on psoriasis.

Following the restart of the programme in February 2026, dosing has been completed in line with the Company's expectations. Using existing cash resources, Sareum is now analysing the resulting data and pursuing necessary chemistry, manufacturing and controls (CMC) and formulation development activities, aimed towards completion of the full Phase 2-enabling regulatory package by Q4 2026.

Dr John Reader, Chief Scientific Officer of Sareum, said: "The completion of dosing in this toxicology programme is an important milestone towards completing the full Phase 2-enabling regulatory package, building on the encouraging Phase 1 results, which showed a pharmacokinetic profile consistent with once-daily dosing and no safety concerns. We look forward to progressing the data analysis as we move closer to advancing SDC-1801 into the clinic for patients with autoimmune diseases."

Dr Stephen Parker, Executive Chairman of Sareum, added: "I am pleased to see the Phase 2-enabling toxicology programme completed on schedule, using existing cash resources and keeping us firmly on track towards our Phase 2-enabling milestones."

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About Sareum

Sareum (AIM: SAR) is a biotechnology company developing next generation kinase inhibitors for autoimmune disease and cancer.

The Company is focused on developing next generation small molecules which modify the activity of the JAK kinase family and have best-in-class potential. Its lead candidate, SDC-1801, simultaneously inhibits TYK2 and JAK1. SDC-1801 is a potential treatment for a range of autoimmune diseases, with a planned initial focus on psoriasis.

Sareum is also developing SDC-1802, a TYK2/JAK1 inhibitor with a potential application for certain haematological cancers and has recently initiated a preclinical programme to develop TYK2/JAK1 inhibitors for neuroinflammatory diseases such as multiple sclerosis and Parkinson's disease

The Company holds the license for SRA737, a clinical-stage Checkpoint kinase 1 inhibitor that targets cancer cell replication and DNA damage repair mechanisms.

Sareum Holdings plc is based in Cambridge, UK, and is quoted on the AIM market of the London Stock Exchange, trading under the ticker SAR. For further information, please visit the Company's website at www.sareum.com