A Treatment Study of ACH-0144471 in Patients With Paroxysmal Nocturnal Hemoglobinuria (PNH) With Inadequate Response to Eculizumab

The purpose of this study is to determine the effectiveness of ACH-0144471 in improving
anemia, as measured by increased blood hemoglobin, when given with eculizumab (a drug
commonly used for treatment of PNH) for 24 weeks in patients with PNH.

Key Inclusion Criteria:

- Diagnosed with PNH

- 18 to 65 years of age

- Have received at least one RBC transfusion within last 12 weeks

- Anemia with adequate reticulocytosis

- Must be on a stable regimen of eculizumab

- Platelet count ≥ 40,000/μL without the need for platelet transfusions

- Documentation of vaccination for N. meningitidis, H. influenza, and S. pneumoniae or
willingness to receive vaccinations based on local guidelines

- Willingness to receive antibiotic prophylaxis

- Female participants must use highly effective birth control to prevent pregnancy
during the clinical trial and for 30 days after their last dose of study drug.

- Male participants must use a highly effective birth control with a female partner to
prevent pregnancy during the clinical trial and for 90 days after the last dose of
study drug.

Key Exclusion Criteria:

- Current evidence of bone marrow failure or aplastic anemia requiring treatment

- History of a major organ transplant or hematopoietic stem cell/marrow transplant

- Received another investigational agent within 30 days or 5 half-lives of the
investigational agent prior to study entry, whichever is greater

- Documented C5 mutations

- Known or suspected complement deficiency

- Contraindication to any of the required vaccinations

- Active bacterial infection or clinically significant active viral infection, a body
temperature >38°C, or other evidence of infection

- History of meningococcal infection, or a first-degree relative or household contact
with a history of meningococcal infection

- History of hypersensitivity reactions to commonly used antibacterial agents

NOTE: Additional inclusion/exclusion criteria may apply, per protocol.