A Study of Mavorixafor in Participants With Congenital and Acquired Primary Autoimmune and Idiopathic Chronic Neutropenic Disorders Who Are Experiencing Recurrent and/or Serious Infections

Key Inclusion Criteria: Diagnosis of congenital or acquired primary autoimmune and idiopathic chronic neutropenic disorder ≥6 months prior to the screening visit that is not attributable to medications, active or recent infections or malignancy. Have a confirmed trough ANC <1500 cells/µL during the screening visit (single ANC measurement) and at baseline visit (mean ANC over 6 hours) held at least 2 weeks prior to Day 1 dosing, with no clinical evidence of infection. Participants who are on G-CSF or other active SoC must have been receiving these therapies for ≥12 months, be on a stable dose and dosing schedule for ≥4 weeks prior to screening visit and remain on this dose and dosing schedule throughout the study (unless ANC >10,000 cells/µL for ≥4 weeks). Participants must be willing to keep their G-CSF doses/regimens stable (other than for safety reasons) for the duration of the trial. Key Exclusion Criteria: A diagnosis of secondary neutropenia including those due to: Hypersplenism Infection Malignancy Autoimmune disease, for example, systemic lupus erythematosus, rheumatoid arthritis, irritable bowel disease, graft-versus-host disease, thyroid disease Nutritional deficiency, for example, vitamin B12, folic acid, copper, caloric malnutrition Drug-induced cause, for example, chemotherapy, clozapine, antiretrovirals, antibiotics, monoclonal antibodies. A diagnosis of any of the following: Aplastic anemia Warts, hypogammaglobulinemia, infections, and myelokathexis (WHIM) syndrome Certain Congenital Neutropenias, including but not limited to these classifications are excluded: Isolated with a cyclic presentation, for example, elastase, neutrophil expressed (ELANE) Associated with immune dysregulation, for example, autoimmune lymphoproliferative syndrome, Familial hemophagocytic lymphohistiocytosis, Chédiak-Higashi syndrome Associated with bone marrow failure, for example, Fanconi Anemia, Diamond-Blackfan anemia, Telomere diseases c. Neutropenia associated with a Duffy-null phenotype (formerly known as benign ethnic neutropenia). Known active COVID-19 infection or a positive test within the local accepted clinical and governmental guidelines for a communicable window. A medical or personal condition that may potentially compromise the safety of the participant, may preclude the participant's successful completion of the clinical study, or could, in the opinion of the Investigator or the Sponsor, interfere with the objectives of the study. Received more than 1 dose of mavorixafor in the past. Received C-X-C chemokine receptor 4 (CXCR4) antagonist (other than mavorixafor) in the past 6 months. Participants taking pegylated-G-CSF unless they have a diagnosis of congenital neutropenia confirmed at screening. Participant is currently taking or have taken other investigational drug at least <30 days prior to the screening visit. Note: Other protocol-defined inclusion and exclusion criteria may apply.