Sareum Regulatory News (SAR)

SAREUM HOLDINGS PLC

("Sareum" or "the Company")

Milestone Payment from Chk1 Licence Agreement

Sareum Holdings plc (AIM:SAR), the specialist cancer drug discovery and development company, is pleased to announce the attainment of a US$2.0 million success milestone payment as part of the Chk1 licence agreement between its co-investment partner, the CRT Pioneer Fund, and Sierra Oncology, Inc. (NASDAQ: SRRA), formerly, until today, ProNAi Therapeutics, Inc.

Under the terms of the agreement, first announced on 27 September 2016, the fee has become payable as a result of the successful transfer of the two ongoing Phase 1 clinical trials to Sierra Oncology. Further payments in the aggregate amount of up to US$319.5 million may additionally become payable upon achievement of certain development, regulatory and commercial milestones. Sierra Oncology will also pay high single to low double digit royalties on the net sales of any product successfully developed.

Under Sareum's agreements with Cancer Research Technology and the CRT Pioneer Fund, Sareum is entitled to 27.5% of all payments arising from the Chk1 licence agreeement. Therefore, Sareum will receive $550,000 as its financial share of this milestone event.

Furthermore, the unspent balance, now estimated at c£200,000, of the financial commitment to the trial funding of £797,500 made by Sareum in December 2015 will be returned to the Company in due course.

Dr Tim Mitchell, CEO of Sareum commented, "We are delighted that the first milestone event from this agreement has been reached. This is a useful addition to our cash position, following the receipt of £1.5 million as our share of the $7 million up-front payment announced in September."

This announcement contains inside information for the purposes of Article 7 of Regulation 596/2014.

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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, for licensing 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 (previously ProNAi Therapeutics) 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

Checkpoint Kinase 1 (Chk1) and SRA737 (formerly PNT737 and CCT245737):

SRA737 is a highly selective, orally available, small molecule inhibitor of Checkpoint kinase 1 (Chk1).

DNA is continuously subject to damage through a variety of endogenous and exogenous mechanisms and, in turn, cells have developed complex processes to resolve this DNA damage. Chk1 is a central regulator in the DNA Damage Repair ("DDR") network of cellular pathways that detect and repair DNA damage. Chk1 impacts multiple cell-cycle checkpoints, temporarily inhibiting the progression of cell replication and division in order for DNA repair processes to be undertaken.

Malignant cells tolerate substantially greater levels of DNA damage than would be acceptable in healthy cells. Cancer cells survive and replicate, despite accumulating DNA damage due to replicative stress, via an over-reliance on select components of the DDR network including Chk1. As such, inhibition of Chk1 by SRA737 may be synthetically lethal to cancer cells and of potential benefit in the treatment of certain cancers.

Certain standard chemotherapeutic agents and radiotherapy also induce DNA damage in order to kill cancer cells. There exists potential for synergy between these standard therapies and Chk1 inhibitors such as SRA737.

SRA737737 was discovered and initially developed by scientists in the Cancer Research UK Cancer Therapeutics Unit at The Institute of Cancer Research (ICR) in collaboration with Sareum, with funding provided by Cancer Research UK, the ICR and Sareum. The program was licensed by CRT and the ICR to the CRT Pioneer Fund, a specialist cancer investment fund established by Sixth Element Capital LLP (6EC), Cancer Research Technology (CRT) and the European Investment Fund (EIF) and managed by 6EC, in September 2013 and a co-investment partnership with Sareum was formed to progress the candidate drug through clinical trials.

About Sierra Oncology

Sierra Oncology is a clinical stage drug development company advancing next generation DDR therapeutics for the treatment of patients with cancer. Its lead drug candidate, SRA737, is a highly selective, orally bioavailable small molecule inhibitor of Checkpoint kinase 1 (Chk1), a key cell cycle checkpoint and central regulator of the DNA Damage Response (DDR) network. In cancer cells, replication stress induced by oncogenes (e.g., MYC and RAS) combined with loss of function in tumor suppressors (e.g., p53 and ATM) results in persistent DNA damage and genomic instability. Targeted inhibition of the remaining components of the DDR network such as by SRA737 may be synthetically lethal to cancer cells and have utility as a monotherapy in a range of tumor indications. Chk1 is also believed to facilitate tumor cell resistance to chemotherapy or radiation-induced DNA damage and the combination of SRA737 with these standards-of-care may provide synergistic anti-tumor activity. SRA737 is currently being investigated in two Phase 1 clinical trials in patients with advanced cancer.

Sierra Oncology is also advancing SRA141, a potent, selective and orally bioavailable small molecule inhibitor of the Cdc7 kinase undergoing preclinical development. Cdc7 is a key regulator of both DNA replication and the DDR network, making it a compelling emerging target for the potential treatment of a broad range of tumor types.

Sierra Oncology retains the global commercialization rights to both SRA737 and SRA141. For more information, please visit www.sierraoncology.com.

About the CRT Pioneer Fund

SRA737 is the lead asset in the CRT Pioneer Fund, a specialist oncology investment fund established in 2012 by Sixth Element Capital LLP (6EC), CRT, BACIT and the European Investment Fund and managed by 6EC. The CRT Pioneer Fund is dedicated to investment in oncology development programs in Europe. The focus for investment is pre-lead optimization through to early clinical trials in man. The Fund is dedicated to asset financing projects emanating from Europe and expects to commit two-thirds of its investment to projects derived from Cancer Research UK's oncology drug discovery portfolio with the remainder being invested in projects from outside Cancer Research UK.

About Cancer Research Technology

Cancer Research Technology (CRT) is a specialist commercialisation and development company, which aims to develop new discoveries in cancer research for the benefit of cancer patients. CRT works closely with leading international cancer scientists and their institutes to protect intellectual property arising from their research and to establish links with commercial partners. CRT facilitates the discovery, development and marketing of new cancer therapeutics, vaccines, diagnostics and enabling technologies. CRT is a wholly owned subsidiary of Cancer Research UK, the world's leading cancer charity dedicated to saving lives through research. Further information about CRT can be found at www.cancertechnology.com and about Cancer Research UK at www.cancerresearchuk.org.