Threshold Pharmaceuticals Announces Promising Phase 1 Clinical Trial Results in Patients With Advanced Leukemias

Threshold Pharmaceuticals, Inc. THLD today announced clinical trial results of the Phase 1 study of TH-302 in patients with advanced leukemias conducted at MD Anderson's Cancer Center in Houston, Texas. Thirty-two patients with either acute myelogenous leukemia or acute lymphoblastic leukemia have been enrolled in the trial to date. The starting dose in the trial was 120mg/m2 daily for 5 days of a 21-day cycle and the highest dose investigated in the study was 550 mg/m2. At this dose two patients developed dose limiting mucosal toxicity. The maximum tolerated daily dose of TH-302 was established at 460 mg/m2. Efficacy assessments have demonstrated TH-302 activity in multiple subjects with relapsed/refractory AML and ALL as evidenced by stabilization or reduction of bone marrow and peripheral blast counts. One patient had a complete response with incomplete platelet recovery with resolution of leukemia cutis. A dose expansion with 10 additional evaluable patients is ongoing at the MTD. "With the establishment of the MTD, we look forward to better defining the safety and efficacy of single agent TH-302 in patients with advanced leukemias," said Dr. Marina Konopleva, M.D., Associate Professor in the Department of Leukemia at MD Anderson Cancer Center. "The accumulating evidence of the importance of hypoxia in advanced leukemias and our initial findings that TH-302 can reduce blasts in patients with refractory advanced leukemias are promising. Ongoing preclinical investigations have demonstrated that TH-302 is active as a monotherapy and demonstrate synergistic activity in combination with multiple chemotherapies. We are excited to continue further clinical investigations." Clinical Trial Design The objectives of the Phase 1 trial are to determine the maximum tolerated dose, dose limiting toxicity, safety, tolerability, clinical activity and pharmacokinetics of TH-302 in patients with advanced leukemia. Approximately 50 patients with advanced leukemias or other severe hematologic disorders affecting the marrow are planned to enroll in the clinical trial that is solely conducted at the MD Anderson Cancer Center. Patients with relapsed/refractory chronic lymphocytic leukemia, ALL, AML, advanced phase chronic myelogenous leukemia, high risk myelodysplastic syndrome or advanced myelofibrosis are eligible for the trial.