X4 Pharmaceuticals provided a summary of its chronic neutropenia-related presentations at this year's annual meeting of the American Society of Hematology (ASH), taking place December 10-13, 2022 in New Orleans. In an oral presentation entitled “Mavorixafor for Patients With Chronic Neutropenic Disorders: Results From a Phase 1b, Open-Label, Multicenter Study,” Julia T. Warren, M.D., Ph.D., Hematologist at Children's Hospital of Philadelphia and Assistant Professor of Pediatrics at the Perlman School of Medicine at the University of Pennsylvania, presented positive data from a Phase 1b clinical trial evaluating the ability of X4's lead clinical candidate, mavorixafor, to increase absolute neutrophil count (ANC) in people with idiopathic, cyclic, or congenital chronic neutropenia as monotherapy or concurrently with injectable granulocyte colony-stimulating factor (G-CSF). Data analyses continue to show that a single dose of oral mavorixafor effected meaningful increases in ANC across all participants, regardless of disease etiology or use of G-CSF.

Mavorixafor was well tolerated overall in the trial. The Phase 1b clinical trial has now been amended and a Phase 2 trial (NCT04154488) is being initiated by X4 to assess the durability, safety, and tolerability of the chronic use of once-daily, oral mavorixafor in a larger chronic neutropenia patient population. Poster #2407, entitled “Prevalence of Chronic Neutropenic Disorders in the United States: A Retrospective Analysis of a Large Claims Database,” estimated that in 2021, between 37,000–48,000 people in the United States were living with a diagnosis of idiopathic, cyclic, or congenital neutropenia.

The study was a retrospective analysis designed to project the prevalence of chronic neutropenia disorders based on U.S. claims data for people with a diagnosis code for neutropenia during the calendar years 2018, 2019, and 2021. (The year 2020 was excluded from this analysis owing to anticipated reduced claims during the COVID-19 pandemic.). People diagnosed with chronic idiopathic, cyclic, or congenital neutropenia were identified using the earliest relevant diagnosis claim based on International Classification of Disease 10th Revision, Clinical Modification (ICD-10-CM) codes in the calendar year of interest.

Poster #3575, entitled “Patient and Health Care Professional Perspectives on Quality of Life and Unmet Needs of People With Chronic Neutropenia: A Survey-Based Assessment,” highlighted responses of 100 patients/caregivers and 10 healthcare professionals (HCPs) to a survey on the experiences of people living with chronic neutropenia. Survey results demonstrate the considerable impact of chronic neutropenic disorders on the lives of people diagnosed. Results also describe the potential burdens related to the existing treatment paradigm, injectable G-CSF, and its limitations to improving physical health and quality of life.

While patients/caregivers cited fatigue as the most impactful symptom and fatigue reduction as a priority treatment need, HCPs ranked fewer and/or less frequent severe infections requiring hospitalization, how medication is administered, and fewer and/or less frequent long-term side effects as the priority treatment needs. The clinical trial was a proof-of-concept Phase 1b open-label, multicenter study designed to assess the safety and tolerability of oral mavorixafor, with or without G-CSF, in participants with chronic neutropenic disorders, including severe idiopathic, cyclic, and congenital neutropenia. Participants were dosed with a single dose of 400 mg oral mavorixafor to assess the magnitude of treatment response.

The Phase 1b clinical trial has now been amended to continue as a Phase 2 clinical trial aiming to evaluate the use of daily oral mavorixafor with or without G-CSF for 6 months in participants with chronic neutropenic disorders.