An Open-label, Time-lagged, Dose-escalation Study to Evalaute the Safety and Efficacy of Subcutaneous Siplizumab in the Treatment of Hidradenitis Suppurativa.

Subjects will be assigned to receive seven subcutaneous doses of siplizumab over an 8 week period. The study will include up to 3 investigational treatment cohorts, 10 mg, 20 mg and a 40 mg cohort. Each cohort will contain from 3-6 subjects. The cohort will be administered either 10 mg, 20mg, or 40mg siplizumab SC weekly from baseline (week 0) to week 4 and a dose at weeks 6 and 8. Assessments will be performed weekly from baseline (week 0) through week 6 and biweekly through week 12 (weeks 8, 10 \& 12) by an investigator. Weeks 5 and 10 will be telephone visits and will not include physician HS assessments. All other visits will be conducted in person. During all visits, subjects will also be asked to complete a quality of life questionnaire (DLQI) and Visual Analog Scale (VAS) for pain assessment.

A total enrollment of 12 subjects is anticipated in this pilot study; however, up to 18 patients may be enrolled.