A Clinical Trial to Evaluate the Efficacy of Abatacept in Moderate to Severe Alopecia Areata

Inclusion Criteria: * Signed Written Informed Consent * Must be between 18 and 75 years of age. * Must have a diagnosis of moderate to severe AA - defined as the presence of equal to or more than 40% and equal to or less than 95% total scalp hair loss at baseline as measured using the SALT score. * Duration of hair loss must be between 3 to 12 months. * There may be no evidence of regrowth present at baseline. * Subjects may be naïve to treatment or unresponsive to intralesional (IL) steroids or other treatments for AA. * Must be willing to avoid live vaccines while on the study medication, and within 3 months of its discontinuation. * Women of childbearing potential must use highly effective methods of birth control \[for up to 12 weeks after the last dose of investigational product\] to minimize the risk of pregnancy\]. * Women of childbearing potential must follow instructions for birth control for the entire duration of the study including a minimum of 90 days after dosing has been completed. * Women must have a negative serum or urine pregnancy test (minimum sensitivity 25 IU/L or equivalent units of HCG) within 24 hours prior to the start of investigational product. * Women must not be breastfeeding * Sexually active fertile men must use highly effective birth control if their partners are women of childbearing potential. * Men that are sexually active with women of childbearing potential must follow instructions for birth control for the entire duration of the study and a minimum of 90 days after dosing has been completed. Exclusion Criteria: * Women of childbearing potential who are unwilling or unable to use an acceptable method to avoid pregnancy for the entire study period and for up to 10 weeks after the last dose of study drug. * Women of childbearing potential using a prohibited contraceptive method. * Women who are pregnant or breastfeeding. * Women with a positive pregnancy test on enrollment or before administration of abatacept. * Sexually active fertile men not using effective birth control if their partners are women of childbearing potential. * Patients with alopecia totalis/universalis * Patients with a history of or active skin disease on the scalp such as psoriasis or seborrheic dermatitis. * Patients in whom the diagnosis of alopecia areata is in question. * Patients with active medical conditions or malignancies (except adequately treated basal or squamous cell carcinoma) that in the opinion of the investigator would increase the risks associated with study participation, including patients with a history of recurrent infections. * Patients with COPD * Patients known to be HIV or hepatitis B or C positive. * Patients with history or evidence of hematopoietic abnormality. * Patients with history of immunosuppression or history of recurrent serious infections. * Patients unwilling or unable to discontinue treatments known to affect hair regrowth in AA * Patients taking TNF antagonists or other biological therapy such as anakinra. * Patients known to be HIV or hepatitis B or C positive. * Patients with evidence of infection or active/untreated skin cancer. * Patients who have been treated with intralesional steroids, systemic steroids, anthralin, squaric acid, DPCP (diphenylcycloprophenone), protopic, minoxidil or other medication which in the opinion of the investigator may affect hair regrowth within one month of the baseline visit. * Subjects who are impaired, incapacitated, or incapable of completing study-related assessments. * Subjects with current symptoms of severe, progressive, or uncontrolled renal, hepatic, hematologic, gastrointestinal, pulmonary, cardiac, neurologic, or cerebral disease, which, in the opinion of the investigator, might place a subject at unacceptable risk for participation in the study. * Female subjects who have had a breast cancer screening that is suspicious for malignancy and in whom the possibility of malignancy cannot be reasonably excluded by additional clinical, laboratory, or other diagnostic evaluations. * Subjects with a history of cancer in the last 5 years, other than non-melanoma skin cell cancers cured by local resection or carcinoma in situ. Existing non-melanoma skin cell cancers should be removed, the lesion site healed, and residual cancer ruled out before administration of the study drug. * Subjects who currently abuse drugs or alcohol. * Subjects with evidence (as assessed by the investigator) of active or latent bacterial or viral infections at the time of potential enrollment, including subjects with evidence of human immunodeficiency virus (HIV) detected during screening. * Subjects with herpes zoster or cytomegalovirus (CMV) that resolved less than 2 months before the informed consent document was signed. * Subjects who have received any live vaccines within 3 months of the anticipated first dose of study medication. * Subjects with any serious bacterial infection within the last 3 months, unless treated and resolved with antibiotics, or any chronic bacterial infection (e.g., chronic pyelonephritis, osteomyelitis, or bronchiectasis). * Subjects at risk for tuberculosis (TB). Specifically excluded from this study will be subjects with a history of active TB within the last 3 years, even if it was treated; a history of active TB greater than 3 years ago, unless there is documentation that the prior anti-TB treatment was appropriate in duration and type; current clinical, radiographic, or laboratory evidence of active TB; and latent TB that was not successfully treated (≥ 4 weeks). * Subjects must not be positive for HIV, Hepatitis B or C. * Subjects who are positive for hepatitis C antibody * Subjects who have at any time received treatment with any investigational drug within 28 days * Any concomitant biologic Disease Modifying Anti-Rheumatic Drugs (DMARDS), such as anakinra. * Subjects who have been treated with intralesional steroids, systemic steroids, anthralin, squaric acid, DPCP (diphenylcycloprophenone), protopic, minoxidil or other medication which in the opinion of the investigator may affect hair regrowth within one month of the baseline visit. OTHER EXCLUSION CRITERIA * Prisoners or subjects who are involuntarily incarcerated. * Subjects who are compulsorily detained for treatment of either a psychiatric or physical (e.g., infectious disease) illness.