US-based pharmaceutical firm G1 Therapeutics has started a randomized, placebo-controlled, single ascending dose Phase I clinical trial of G1T28-1, a highly potent and selective CDK4/6 inhibitor with broad potential in multiple oncology indications. The trial is designed to evaluate the safety, pharmacokinetics and pharmacodynamics of G1T28-1 in healthy volunteers, who are currently being enrolled in the Netherlands. G1T28-1 is a first-in-class therapy for protecting the bone marrow from chemotherapy-induced myelosuppression in patients with CDK4/6-independent tumors, and has the potential to be best-in-class as an antineoplastic agent in patients with CDK4/6-dependent tumors. Preclinical data suggests that G1T28-1 is differentiated from currently available therapies for myelosuppression in that it protects all hematopoietic lineages, including red cells, platelets, granulocytes and lymphocytes, before damage is done by chemotherapy.