Sierra Oncology to Present at ASCO Annual Meeting

SAREUM HOLDINGS PLC

("Sareum" or "the Company")

Sierra Oncology to Present Chk1 Clinical Trial Enhancementsat ASCO Annual Meeting

Sareum Holdings plc (AIM:SAR), the specialist cancer drug discovery and development company, notes an announcement made by Sierra Oncology, Inc. yesterday stating that it will be presenting two Trials in Progress posters describing the innovative Phase 1 clinical designs for its Chk1 inhibitor, SRA737, at the 2017 American Society of Clinical Oncology (ASCO) Annual Meeting, being held in Chicago on June 5th.

These ongoing trials were recently amended to include cohort expansions of prospectively selected patients with tumors identified to have genetic abnormalities that are thought to confer sensitivity to Chk1 therapy.

The full announcement can be found on Sierra Oncology's IR website*.

Dr Tim Mitchell, CEO of Sareum, commented: "This announcement shows the interest by the scientific community in Sierra's leading-edge strategy that builds on Chk1's specific biological role in cancer, which has been made possible by recent developments in genetic analysis and is part of the progress towards personalised anti-cancer therapies. We look forward to keeping investors abreast of Sierra's progress and we can expect a further update from Sierra in early 2018."

Sierra Oncology holds exclusive and worldwide rights for the Chk1 inhibitor, SRA737, having licensed the programme from Sareum's co-investment partner, the CRT Pioneer Fund in September 2016. This announcement does not trigger any milestone payments under the terms of the agreement.

*http://investor.sierraoncology.com/2017-05-24-Sierra-Oncology-to-Present-Innovative-Clinical-Trial-Enhancements-Leveraging-Chk1-Synthetic-Lethality-in-Two-Posters-at-ASCO-Annual-Meeting

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Notes for editors:

Sareum is a drug discovery and development company delivering targeted small molecule therapeutics, focusing on cancer and autoimmune disease, and licensing them to pharmaceutical and biotechnology companies at the preclinical or early clinical trials stage.

Sareum operates an outsourced research model, working with international collaborators and a world-wide network of research providers. Its most advanced programme (Chk1) commenced clinical trials in May 2016 and was licensed to NASDAQ-listed Sierra Oncology in September 2016.

SKIL® (Sareum Kinase Inhibitor Library) is Sareum's drug discovery technology platform that has so far produced the Company's Aurora+FLT3 and TYK2 kinase cancer and autoimmune disease research programmes, which are in the IND-enabling preclinical and lead optimisation stages respectively. SKIL® can also generate drug research programmes against other kinase targets.

Sareum Holdings plc is listed on the AIM market of the London Stock Exchange, trading under the symbol SAR. For further information, please visit www.sareum.co.uk

ASCO 2017 Poster Presentations

Title: A phase I study of SRA737 (formerly known as CCT245737) administered orally in patients with advanced cancer.Trials in Progress Abstract: #TPS2607Poster: #93bPoster Session: Developmental Therapeutics - Clinical Pharmacology and Experimental TherapeuticsDate and Time: Monday, June 5, 2017, 8:00 - 11:30am CTLocation: McCormick Place, Event room: Hall A, 2301 S King Dr., Chicago, Illinois

Title: A phase I study of oral SRA737 (formerly CCT245737) given in combination with gemcitabine plus cisplatin or gemcitabine alone in patients with advanced cancer.Trials in Progress Abstract: #TPS2613Poster: #96bPoster Session: Developmental Therapeutics - Clinical Pharmacology and Experimental TherapeuticsDate and Time: Monday, June 5, 2017, 8:00 - 11:30am CTLocation: McCormick Place, Event room: Hall A, 2301 S King Dr., Chicago, Illinois

The posters will be available on June 5, 2017 on the company's website at www.sierraoncology.com

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