5 June 2017


("Sareum" or "the Company")

Chk1 Clinical Trials Update

Sierra Oncology Reports Encouraging Initial Progress from Ongoing Phase 1 Clinical Trials

Sareum Holdings plc (AIM:SAR), the specialist cancer drug discovery and development company, notes an announcement made today by Sierra Oncology, Inc. reporting on the initial progress of the two ongoing Phase 1 trials of the Chk1 inhibitor, SRA737. The full announcement can be found on Sierra Oncology's IR website*.

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

The SRA737 Phase 1 monotherapy trial has advanced through six single patient dose cohorts of 20, 40, 80, 160, 300 and 600 mg/day, administered under a continuous daily oral dosing regimen in 28-day cycles. Dose escalation will continue until a maximum tolerated dose (MTD) is reached, in parallel with ongoing Cohort Expansion enrolment. 

Preliminary observations from the ongoing monotherapy study are as follows: 

• SRA737 has been very well-tolerated to date: No Grade 2 or higher SRA737-related adverse events have been reported. No dose-limiting toxicities have been observed and an MTD has not been reached. 

• Dose-proportional exposure: Pharmacokinetic (PK) parameters for SRA737 have been generally linear across the dose range tested to date. 

• Plasma concentrations of SRA737 exceeding the proposed minimum efficacious threshold (Cmin) of 100 nM were maintained for 24 hours post-dose at the 160 mg/day dose level and above. 

Having successfully surpassed the proposed minimum efficacious exposure threshold, the Cohort Expansion Phase of the trial has commenced and is enrolling patients with tumours identified to have genetic aberrations hypothesized to confer sensitivity to Chk1 inhibition via synthetic lethality into five indication-specific cohorts: colorectal, head and neck, non-small cell lung, ovarian, and prostate cancers. 

For the Phase 1 Chemotherapy Combination study, Stage 1, which is evaluating SRA737 in combination with gemcitabine and cisplatin, has concluded enrolment and the study has transitioned to Stage 2. This stage is seeking to establish the safety profile, determine the MTD and propose a recommended dose for further development of SRA737 in combination with low-dose gemcitabine. Once an MTD and dosing schedule have been determined, the study will also evaluate the preliminary efficacy of SRA737 in combination with low-dose gemcitabine in indication-specific cohorts of prospectively-selected, genetically-defined subjects with bladder or pancreatic cancer. 

Gemcitabine is a potent inducer of replication stress and DNA damage via multiple mechanisms, and represents a rational drug combination for SRA737, given Chk1’s fundamental biological role in responding to such stressors. The preclinical modelling demonstrates robust synergistic anti-tumour activity of SRA737 in combination with low-dose gemcitabine.

Dr Tim Mitchell, CEO of Sareum, commented: "We are very pleased with the amount of progress that has been made in both clinical trials of SRA737 and that the trial data is consistent with preclinical studies. In particular we are pleased to note that SRA737 has been very well tolerated in the monotherapy trial and that there have been no dose limiting toxicities observed so far.

"We look forward to the next update from these studies, which Sierra has indicated could potentially include preliminary activity data, 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.

As previously announced, Sierra is today presenting two posters describing the innovative designs of these clinical trials at the 2017 American Society of Clinical Oncology (ASCO) Annual Meeting, being held in Chicago. Copies of the posters are available on Sierra’s website at www.sierraoncology.com.



For further information, please contact: 

Sareum Holdings plc


Tim Mitchell

01223 497 700

WH Ireland Limited (Nominated Adviser and Co-Broker)

Chris Fielding / Nick Prowting

020 7220 1666

Hybridan LLP (Co-Broker)


Claire Noyce

020 3764 2341

The Communications Portfolio (Sareum Media enquiries)


Ariane Comstive

07785 922 354

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

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