The purpose of this study is to determine the effectiveness and safety of efalizumab in treating hydradenitis suppurativa, and to evaluate the duration of the benefit seen in people who respond to treatment with efalizumab, after the medication is stopped.

The primary objective of this study is to assess the efficacy of subcutaneously administered efalizumab in the treatment of refractory, severe hydradenitis suppurativa. The secondary objectives of this study are to assess the ability to re-establish disease control after discontinuation of drug and allowance for relapse of disease, as well as to assess the safety of subcutaneously administered efalizumab in the treatment of refractory, severe hydradenitis suppurativa.

Inclusion Criteria:

• Female between 18-65 years of age
• Has Hydradenitis Suppurativa (HS) involving at least 1 area of the body with greater than or equal to 12 lesions; onset of disease is 6 months and greater.
• Failed at least 3 months of standard conventional therapies such as antibiotics and/or systemic retinoids
• Willing to use contraception unless not of childbearing potential
• Able to comply with protocol requirements

Exclusion Criteria:

• Received within 4 weeks prior immunosuppressive medication
• Received treatment within 3 months prior with systemic retinoids (acitretin or isotretinoin)
• Received high potency (class I or II) topical corticoid steroids, topical antibiotics, systemic antibiotics, or topical immunomodulators (tacrolimus or pimecrolimus) within 2 weeks prior to baseline visit
• Received intralesional injections of corticosteroids within 4 weeks prior
• Received surgical intervention for the treatment of HS
• Known history of HIV seropositivity
• History of untreated or active tuberculosis
• Active infection requiring systemic antibiotics within 4 weeks of baseline visit
• History of recurrent/chronic infections
• History of malignancy within 5 years of baseline visit (except for squamous cell carcinoma or basal cell carcinoma; may enroll if treated and assessed as cured).
• Pregnant or breastfeeding
• Immunocompromised due to a medical condition
• Has any significant laboratory abnormalities
• Has any medical condition that may interfere with evaluation of the safety and efficacy of efalizumab
• Received efalizumab or any other biologic within the last 6 months
• Taken or used any investigational drug or device within 30 days prior