Study of ATI-450 in Patients With Cryopyrin-Associated Periodic Syndrome (CAPS)

Inclusion Criteria: * Diagnosis of Familial Cold Autoinflammatory Syndrome, Muckle-Wells Syndrome, or Neonatal Onset Multisystem Inflammatory Disease. Prior agreement between the Investigator and Aclaris for study eligibility is required for patients who do not have a molecular diagnosis of NALP3 mutations available (either testing not performed, or testing performed, but negative) upon study entry. For those patients who have not been molecularly tested for NALP3 mutations, molecular testing should be performed during the study. * Patients with a PGA score of "minimal" or less and hsCRP and SAA values within the normal range (≤10mg/L), and who are considered to have achieved that response as a result of successful anti-IL-1 therapy. * Continuous Treatment with anti-IL1 therapy for at least 6 months. * Able to understand and comply with study procedures and able to provide informed consent. * Male or non-pregnant, non-nursing female patients at least 18 years of age, inclusive. * Female patients who are of childbearing potential must use 2 methods of highly effective contraception\* - one of which must be a physical barrier- for the duration of the study and for 30 days after the last dose. * Male patients of childbearing potential with a female partner of childbearing potential must agree to use a condom plus another highly effective form of birth control for the duration of the study and for 90 days after the last dose. * Female patients must have a negative serum pre…