Company Announcements

Sareum Holdings PLC

("Sareum" or the "Company")

Sareum notes publication of Phase I/2 clinical data on SRA737 as a combination treatment for advanced cancers in Clinical Cancer Research

·    First peer-reviewed data of Phase I/2 Trial of Oral SRA737 (a Chk1 Inhibitor) in Combination with Low-Dose Gemcitabine in Patients with Advanced Cancer

Cambridge, UK, 21 November 2022 - Sareum Holdings plc (AIM: SAR), a biotechnology company developing next generation kinase inhibitors for autoimmune disease and cancer, notes the publication of data from a Phase I/2 trial of SRA737, a clinical-stage oral, selective small molecule Checkpoint kinase 1 (Chk1) inhibitor, in combination with widely used chemotherapeutic agent gemcitabine, in the November 15 edition of Clinical Cancer Research.

The paper can be accessed here.

Sareum retains a 27.5% economic interest in SRA737 arising from its collaboration in the discovery and early development of the molecule. Following the October 2022 notification that Sierra Oncology will return the rights, Sareum is evaluating potential development opportunities alongside co-development partner the CRT Pioneer Fund LP ("CPF").

This is the first peer-reviewed publication of clinical data on trials conducted using a Chk1 inhibitor in combination with a novel, lower dose of gemcitabine compared to standard of care, and the first clinical report of SRA737 used as a combination treatment. This dataset was initially published at the American Society of Clinical Oncology (ASCO) meeting in 2019.

The objectives of the trial were to establish the safety profile, recommended Phase 2 dose, pharmacokinetics profile, and clinical activity of SRA737.

Treatment of patients with SRA737 in combination with low-dose gemcitabine was found to be well tolerated and resulted in lower myelotoxicity compared to standard doses of gemcitabine alone or in combination with other Chk1 inhibitors. Tumour responses were observed in anogenital and other solid tumours.

The objective response rate (ORR) in anogenital cancer was 25%. Partial tumour responses were observed in anogenital cancer, cervical cancer, high-grade serous ovarian cancer, rectal cancer, and small cell lung cancer. Toxicities observed were primarily mild to moderate, and rarely led to treatment discontinuation.

Dr Tim Mitchell, Chief Executive Officer of Sareum, commented: "We are pleased to see the data from the Phase I/2 trial of SRA737 published in the peer-reviewed journal Clinical Cancer Research, demonstrating SRA737's anti-cancer activity in multiple indications.

"As we assess opportunities to further develop this asset, subject to discussions with our partners, this is an encouraging development which reinforces our confidence in the potential of SRA737."

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About SRA737

SRA737, a clinical-stage oral, selective Checkpoint kinase 1 inhibitor that targets cancer cell replication and DNA damage repair mechanisms, was discovered and initially developed by scientists at The Institute of Cancer Research in collaboration with Sareum, with funding from Sareum and Cancer Research UK.

The CRT Pioneer Fund acquired worldwide commercial rights to the programme in 2013 as part of a co-development agreement with Sareum. SRA737 was licensed by CPF to Sierra Oncology in 2016. Sierra progressed SRA737 through Phase 1/2 clinical development and, at the 2019 ASCO Annual meeting, reported positive preliminary efficacy and safety data from two clinical trials evaluating SRA737 as a monotherapy and in combination with chemotherapy.

Sareum was informed by Sierra Oncology (now a subsidiary of GSK plc "GSK") in October 2022 that Sierra intends to return the rights for SRA737 to the CRT Pioneer Fund LP. Sareum will discuss actively with CPF the potential options for future development opportunities for SRA737 and evaluate its next steps accordingly.

Sierra was acquired by GSK in July 2022.

About Sareum

Sareum Holdings (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. SDC1801 is a potential treatment for a range of autoimmune diseases. Sareum is also developing SDC1802, a TYK2/JAK1 inhibitor with a potential application for cancer immunotherapy.

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