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# X4 Pharma Gets Rare Pediatric Disease Status
- URL: https://www.fdaweb.com/x4-pharma-gets-rare-pediatric-disease-status/
- Published: 2020-12-10T12:00:00.000Z
- Updated: 2026-09-14T16:39:40.000Z
- Author: David McFarland
- Tags: Drugs, #legacy-id-D5148276

FDA has granted X4 Pharmaceuticals a rare pediatric disease designation for mavorixafor for treating WHIM (Warts, Hypogammaglobulinemia, Infections, and Myelokathexis) syndrome, a rare, inherited, primary immunodeficiency disease caused by genetic mutations in the CXCR4 receptor gene. The company says the drug is currently being investigated in a global pivotal Phase 3 clinical trial called [4WHIM](https://www.globenewswire.com/Tracker?data=xyQOPkp7HCZQJYDYiSUqXq-%5Fe-eG%5Fpg4piotNS2OjJIGIW6tYpJSrOEhsRI7cJd7&ref=fdaweb.com). Mavorixafor had previously been granted fast track, breakthrough therapy and orphan drug designations by the agency.

Mavorixafor is described as a potent, selective and bioavailable CXCR4 chemokine receptor allosteric antagonist. It was originally developed for HIV treatment, and is now being repurposed by X4 Pharmaceuticals for treating WHIM syndrome.