Shanghai-based biotech Abbisko Therapeutics Co., Ltd (HKG: 2256) and its US partner X4 Pharmaceuticals Inc. have announced positive top-line data from a pivotal Phase III clinical study for the once-daily, oral CXCR4 antagonist mavorixafor. The trial is assessing the molecule as a treatment for WHIM syndrome (warts, hypogammaglobulinemia, infections, and myelokathexis), a rare, inherited, combined immunodeficiency disease caused by reduced mobilization and trafficking of white blood cells from the bone marrow due to over-signaling of the CXCR4/CXCL12 pathway.
Mavorixafor’s Mechanism and Development
Mavorixafor is an investigational small-molecule antagonist of CXCR4 being developed as a once-daily oral therapy to correct the dysfunction resulting from the underlying causes of WHIM. Abbisko struck a licensing deal with X4 in July 2019, taking rights to the drug in Greater China (China mainland, Hong Kong, Macau, and Taiwan) for WHIM and oncology indications.
Phase III Clinical Study Results
During the study, mavorixafor treatment resulted in a statistically significant reduction (~60%) in annualized infection rate versus placebo (p<0.01). Of those on placebo, 29% (5 of 17) experienced Grade 3 or higher infections, compared with only 7% (1 of 14) for patients on mavorixafor, equating to a 75% reduction in the number of individuals experiencing severe infections.
Regulatory Progress and Designations
X4 recently completed a pre-NDA meeting with the FDA and remains on track for a full NDA filing for mavorixafor in WHIM syndrome during H2 2023. For the WHIM indication, mavorixafor has been granted Breakthrough Therapy Designation, Fast Track Designation, and Rare Pediatric Designation in the US, and Orphan Drug Status in both the US and EU. Should mavorixafor be approved in the US for the indication of WHIM syndrome, X4 could be eligible to receive a Priority Review Voucher (PRV).-Fineline Info & Tech
