X4 Pharmaceuticals Advances Mavorixafor Phase 3 Trial in Chronic Neutropenia, Cuts Costs

X4 Pharmaceuticals is prioritizing completion of the Phase 3 4WARD trial for mavorixafor in chronic neutropenia, with enrollment on track to finish by the end of Q3 2026. The company has also received European Commission marketing approval for XOLREMDI® (mavorixafor) as the first authorized treatment for WHIM syndrome in the EU.

The 4WARD Phase 3 trial is enrolling 176 patients in a 1:1 randomization versus placebo, with co-primary endpoints of absolute neutrophil count (ANC) increase and infection reduction. The company has implemented operational fixes to boost recruitment and aims for a 2028 launch in chronic neutropenia.

The European Commission has granted marketing approval for XOLREMDI® (mavorixafor) for WHIM syndrome in the European Union. Commercialization in Europe will be led by Norgine later this year.

X4 has reduced costs and headcount over the past six months, with the management team focusing the company on completing the Phase 3 program successfully. The company has deprioritized active commercialization of mavorixafor in WHIM syndrome in the U.S., describing the indication as "ultra-rare" and noting that the company "was spending more than it was bringing in revenue." The company will continue to provide the drug to patients who require it but said it is "not feasible" to spend more commercial dollars than the revenue coming in for that indication.

Mavorixafor is an oral CXCR4 inhibitor positioned as an alternative to injectable G-CSF, which is used by about 40% of chronic neutropenia patients but has drawbacks including subcutaneous administration, bone pain, and a risk of long-term transformation to leukemia. X4 estimates a symptomatic chronic neutropenia population of approximately 15,000 patients in the U.S., with a base case assumption of treating about one-third — around 5,000 patients — initially as monotherapy. The company expects pricing below the current WHIM level (~$500,000) but still potentially premium for a rare-disease therapy.

Financially, X4 reported a cash position of $233.7 million as of March 31, 2026, providing a financial runway through 2028. In the first quarter of 2026, revenue decreased to $2.7 million from $28.8 million in Q1 2025 due to prior license revenue, resulting in a net loss of $20.2 million compared to a net income of $0.3 million in Q1 2025.