X4 Pharmaceuticals, Inc. is hosting a webinar highlighting new data from its global, pivotal, 4WHIM Phase 3 clinical trial of once-daily, oral mavorixafor in individuals with WHIM syndrome. Following the announcement of positive top-line data from the 4WHIM trial in November 2022, event focuses on the impact of mavorixafor on the rate, severity, and duration of infections in trial participants. Key highlights: Rate of Infections: In the trial, mavorixafor treatment resulted in a statistically significant reduction (~60%) in annualized infection rate versus placebo (p<0.01).

In addition, the data showed that the reduction was greater with time on treatment, with participants on mavorixafor experiencing less than one infection per year versus 4.5 for those on placebo; during the second 6 months of the trial, the difference also achieved statistical significance (p<0.005). Severity of Infections: During the trial, 29% (5 of 17) of those on placebo experienced Grade 3 or higher infections, whereas only 7%, (1 of 14) of those on mavorixafor experienced a Grade 3 or higher infection, equating to a 75% reduction in the number of individuals experiencing severe infections. Importantly, the single Grade 3 infection in the mavorixafor treatment arm occurred during the first 3 months of the trial; after 3 months of treatment, there were no serious infections in the mavorixafor-arm, whereas the frequency of severe infections in those on placebo remained unchanged over the 52-week trial period.

Duration of Infections: In the trial, mavorixafor treatment reduced the total duration (in days) of infections by more than 70% as compared to placebo, with those on placebo experiencing a mean of 7 weeks (49.1 days) with infections over the 52-week trial period versus a mean of only 2 weeks (14.1 days) with infections for those treated with mavorixafor. Other Infection Metrics: Mavorixafor treatment resulted in a 40% lower total infection score, a metric that combines infection number and severity (LS mean [95% CI]: mavorixafor, 7.41 [1.64–13.19]; placebo, 12.27 [7.24–17.30]). Treatment with mavorixafor also resulted in reductions in upper and lower respiratory tract and skin infections compared with those on placebo; participants on placebo required greater medical intervention, with 10 of the 17 participants on placebo requiring treatment with antibiotics over the course of the study, versus 3 of the 14 receiving mavorixafor; and slight improvements in warts were demonstrated both in the mavorixafor and placebo arms (no difference between arms).

Safety and Tolerability: As reported previously, mavorixafor was generally well tolerated in the 4WHIM trial, with no drug-related serious adverse events, no treatment limiting toxicities, and no discontinuations due to safety. Approximately 90% of participants in the trial continued on to receive mavorixafor treatment in the ongoing open-label extension study. A late-breaking abstract of these data was accepted for oral presentation at the annual meeting of the Clinical Immunology Society (CIS) taking place May 18-21, 2023 in St.

Louis, MO. Dr. Raffaele Badolato, Professor of Pediatrics at the University of Brescia (Italy) and an investigator in the 4WHIM clinical trial, will present at 11:30 am CT on Sunday, May 21st. Although the session is only accessible live to conference attendees, the company will post the presentation slides to its website concurrent with the presentation.

In addition, X4 is also announcing that its submitted abstract of these data was accepted for oral presentation at the annual meeting of the European Hematology Association (EHA), taking place June 8-15, 2023 in Frankfurt, Germany. Dr. Jean Donadieu, Pediatrician in the Hemato Oncologic Department of Trousseau Hospital (Paris), Coordinator of the French Histiocytosis Registry, Coordinator of the pediatric branch of the French Histiocytosis Reference Center, and also an investigator in the 4WHIM clinical trial, will be delivering an encore oral presentation of the results being presented at CIS.