Oral LGD-4665 Versus Placebo in Adults With Immune Thrombocytopenic Purpura (ITP) for 6 Weeks Plus Open Treatment Continuation

The purpose of this study is to assess the ability of LGD-4665 given daily by mouth to increase platelet counts in the treatment of patients with ITP (immune thrombocytopenic purpura). LGD-4665 increased platelet counts safely and tolerably compared to placebo in healthy volunteers. This study will examine the safety, tolerability and efficacy of 7.5 mg capsules of LGD-4665 to increase platelets compared to placebo, randomized 2:1, during blinded treatment for 6 weeks. Evaluation of platelet counts, bleeding scores and safety parameters will be done weekly. All patients are eligible to continue on active, open LGD-4665 treatment for an additional 12 weeks with optimal adjustment of dose for each patient.

This is a Phase IIA study with two parts to the design. * Part 1 is a randomized, double-blinded, placebo-controlled treatment of 7.5 mg/day LGD-4665 versus placebo in approximately 24 patients with ITP who have been treated with at least one prior therapy for ITP. Patients will be randomized in a ratio of 1:2 (placebo: 7.5 mg/day LGD-4665) for 6 weeks of treatment. Platelet counts, bleeding scores, vital signs, physical exams and laboratory tests will be assessed weekly. Treatment groups will be analyzed for efficacy by the percentage of patients with platelet counts two times baseline and ≥ 50,000/uL at 6 weeks of treatment, and for safety by adverse events, vital signs, physical exams, laboratory tests and use of ITP rescue medications or transfusions. * Part 2 is an extension of study treatment with open label LGD-4665. All patients who participate in the Part 1 randomized double-blind treatment of this Ph IIA trial are eligible to continue open label treatment with LGD-4665 for up to 3 months at an appropriate dose for the safe maintenance of platelet counts (≥ 50,000/uL to ≤ 200,000/uL). Assessments of effectiveness and safety will be made at 2 and 4 week intervals.