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.