Pharmacokinetics and Pharmacodynamics of Burixafor Hydrobromide (GPC-100), a Novel C-X-C Chemokine Receptor 4 Antagonist and Mobilizer of Hematopoietic Stem/Progenitor Cells, in Mice and Healthy Subjects.

Adequate mobilization of hematopoietic stem cells (HSCs), especially CD34 cells, is necessary for stem cell transplantation in patients with hematological malignancies or autoimmune diseases. Burixafor is an inhibitor of the C-X-C Chemokine Receptor 4 that disrupts the C-X-C motif chemokine 12 (CXCL12)/CXCR4 axis in the bone marrow, releasing HSCs into circulation. In mice, a single intravenous dose of burixafor was rapidly absorbed (time to maximum concentration, 5 minutes) and increased peripheral white blood cell counts within 30 minutes. Additionally, burixafor was administered to 64 healthy subjects in a randomized, double-blind, placebo-controlled, single-ascending-dose study to evaluate safety, pharmacokinetics, and pharmacodynamics. Subjects received burixafor intravenous doses ranging from 0.10 to 4.40 mg/kg in 8 cohorts. Single doses were generally safe and well tolerated. Gastrointestinal events were reported at doses of 2.24 mg/kg or greater. Exposure (maximum concentration and area under the concentration-time curve) increased in an approximately dose-proportional manner. Time to maximum concentration occurred with a median of 0.26-0.30 hours that was not dose proportional. As expected, white blood cell, CD133 cell, and CD34 cell concentrations generally increased with the increases in burixafor dose from 0.10 to 3.14 mg/kg. At maximal levels, the CD34 cell counts increased 3- to 14-fold from baseline levels. These results provide support for continued clinical development of burixafor.