X4 Pharmaceuticals Reaches FDA Agreement on Revised Phase 3 Trial for Chronic Neutropenia Treatment

08:18 AM EDT, 09/08/2026 (MT Newswires) -- X4 Pharmaceuticals (XFOR) and the US Food and Drug Administration reached agreement on the design of a Phase 3 clinical trial for mavorixafor as a potential treatment for chronic neutropenia, the company said Tuesday. The purpose of the meeting was to reach agreement on a revised sample size, associated statistical power, and the size of the safety database to support a supplemental new drug application, the company said. The FDA agreed with the company's proposed reduction in sample size to 126 from 176, saying the revised enrollment target maintains adequate overall power for the trial's co-primary endpoints, the company said. Chronic neutropenia is a rare blood condition that can lead to life-threatening infections. Shares of the company were up 1% in recent premarket trading.