SAREUM HOLDINGS PLC

("Sareum" or "the Company")

Sareum notes completion of Sierra Oncology's acquisition by GSK

Cambridge, UK, 4 July 2022 - Sareum Holdings plc (AIM: SAR), the specialist drug development company, notes that GSK has completed its acquisition of Sierra Oncology, Inc ("Sierra"), the licence holder for SRA737 (a novel Chk1 inhibitor), for US$1.9 billion in cash. The acquisition was approved by Sierra's shareholders on 29 June 2022.

GSK has noted that the key driver of the acquisition was momelotinib, a drug Sierra is developing for the treatment of myelofibrosis. Sierra reported positive topline results from a Phase III study investigating momelotinib in this indication in January 2022 and submitted a New Drug Application ("NDA") to the US Food and Drug Administration ("FDA") in June 2022 for marketing approval.

Following the acquisition, GSK also now owns the licence rights to SRA737, a clinical-stage oral, selective Checkpoint kinase 1 inhibitor that targets cancer cell replication and DNA damage repair mechanisms. SRA737 was discovered and initially developed by scientists at The Institute of Cancer Research in collaboration with Sareum, and with funding from Sareum and Cancer Research UK. SRA737 was licensed to Sierra in September 2016 and has progressed through multiple preclinical and early-stage clinical trials demonstrating potential for further investigation in combination with other agents in haematologic and solid tumour indications.

Under an amended US$299m licensing deal on SRA737 between Sierra and CRT Pioneer Fund LP (announced 12 November 2020), Sareum is eligible to receive a 27.5% share of any future milestone payments as well as royalties on any future sales. The dosing of the first patient with SRA737 in any new clinical trial would result in a US$2.0m payment from Sierra (now GSK), with 27.5% of this due to Sareum.

The full announcement made by GSK can be viewed here.

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About Sareum

Sareum is a specialist drug development company delivering targeted small molecule therapeutics to improve the treatment of cancer and autoimmune diseases. The Company aims to generate value through licensing its candidates to international pharmaceutical and biotechnology companies at the preclinical or early clinical trials stage.

Sareum is advancing internal programmes focused on distinct dual tyrosine kinase 2 (TYK2) / Janus kinase 1 (JAK1) inhibitors through preclinical development as therapies for autoimmune diseases, including the 'cytokine storm' immune system overreaction to Covid-19 and other viral infections, (SDC-1801) and cancer immunotherapy (SDC-1802).

Sareum also has an economic interest in SRA737, a clinical-stage oral, selective Checkpoint kinase 1 (Chk1) inhibitor that targets cancer cell replication and DNA damage repair mechanisms. Preliminary Phase 2 and comprehensive preclinical data suggest SRA737 may have broad application in combination with other oncology and immune-oncology drugs in genetically defined patients.

SRA737 was discovered and initially developed by scientists at The Institute of Cancer Research in collaboration with Sareum, and with funding from Sareum and Cancer Research UK. SRA737 was licensed by CRT Pioneer Fund (CPF) to Sierra Oncology Inc., acquired by GSK in July 2022.

Sareum Holdings plc is listed 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

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