X4 Pharmaceuticals, Inc. (Nasdaq: XFOR) announced on September 8, 2026, that it has received a positive outcome from a Type C meeting with the U.S. Food and Drug Administration (FDA) regarding the global 4WARD Phase 3 clinical trial. The meeting focused on the design of the trial for the company's drug candidate, mavorixafor, specifically concerning a revised sample size and associated statistical power.
The FDA agreed with X4’s analysis that the sample size for the 4WARD trial can be reduced from 176 to 126 participants. The agency determined that this reduction maintains adequate overall power for the study's co-primary endpoints: the reduction in annualized infection rate and positive absolute neutrophil count (ANC) response. Additionally, the FDA indicated that the proposed safety database would be acceptable to support a potential supplemental new drug application (sNDA) for the treatment of chronic neutropenia.
The 4WARD trial is a randomized, double-blind, placebo-controlled, multicenter study designed to enroll 126 patients aged 12 years and older. Participants must have confirmed trough absolute neutrophil count levels less than 1,000 cells per microliter at baseline screening and a history of two or more serious and/or recurrent infections in the prior year. The trial is a 52-week study evaluating the efficacy, safety, and tolerability of oral, once-daily mavorixafor, with or without G-CSF, in patients with congenital, acquired primary autoimmune, or idiopathic chronic neutropenia.
According to the press release, X4 expects to complete the enrollment of the 4WARD trial by the end of 2026 and report topline data in the first half of 2028. The company noted that the FDA has granted Fast Track designation to mavorixafor for the treatment of chronic neutropenia.
