CHEK1 and neutropenia: Thus, the toxicity profile of SRA737 as a single agent has differences and similarities with other Chk1 inhibitors; though neutropenia was seen at the non-tolerated dose of 1300 mg SRA737, and treatment-related neutropenia occurred in 16% of overall patients receiving SRA737, it was less frequently observed than with other oral or intravenous Chk1 inhibitors.