• 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.

• Congenital Neutropenia, including but not limited to these classifications:

‣ Isolated with a permanent (non-cyclic) presentation, for example, elastase, neutrophil expressed (ELANE), colony stimulating factor 3 receptor (CSF3R), C-X-C chemokine receptor 2 (CXCR2), Wiskott-Aldrich syndrome (WAS)

⁃ Associated with extra-hematologic manifestations, for example, Barth syndrome, Cohen syndrome, glucose-6-phosphatase catalytic subunit 3 (G6PC3), Kostmann disease

⁃ Associated with metabolic disorders, for example, glycogen storage disease 1b (GSD1b)

⁃ Shwachman-Diamond syndrome

• Acquired Primary Neutropenia

‣ Chronic idiopathic neutropenia

⁃ Primary autoimmune neutropenia. Other chronic neutropenia (CN) disorders that may be eligible for enrollment can be clarified and approved upon discussion with study Medical Monitor and Sponsor.

• Have an ANC \<1000 cells/µL during screening (single ANC value from hematology) and confirmed trough mean ANC (mean value of multiple ANC measurements over 6 hours) at baseline visit, with no clinical evidence of systemic infection.

• Prior history of recurrent and/or serious infections during the 12 months preceding the screening visit (that is, suffering sequelae of chronic neutropenia), as defined by having at least 2 infections in the last 12 months that meet the following criteria:

• Infection requiring the use of antibiotics (intravenous \[IV\]/oral); OR

• Infection requiring a visit to healthcare facility (including but not limited to emergency room visit, urgent care facility, primary care physician's office, or in-patient hospitalization);

∙ AND for all potential participants:

• Infections considered by the Investigator to be likely related to the potential participant's CN disorder.

• Participants who are on G-CSF or other active background therapy must have been receiving these therapies during the previous 12 months while continuing to suffer from infections, 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 or other background therapy doses/regimens stable (other than for safety reasons) for the duration of the study.