May 10 (Reuters) - Sierra Oncology Inc SRRA.O :
* Says received clearance from regulators in UK to amend two ongoing phase 1 trials for its CHK1 inhibitor, SRA737
* Sierra Oncology Receives clearance to enhance ongoing clinical trials for SRA737
* Says amended trials will include cohort expansions of prospectively selected patients with tumors
* Says an initial update from these trials is anticipated in early 2018
* Says study will now consist of two phases, a dose escalation phase and a cohort expansion phase, being run concurrently Source text for Eikon: ID:nCNWJM530a Further company coverage: SRRA.O