Alemtuzumab-related thyroid dysfunction in a phase 2 trial of patients with relapsing-remitting multiple sclerosis.

Context: Alemtuzumab, an anti-CD52 monoclonal antibody, increased the risk of thyroid dysfunction in CAMMS223, a phase 2 trial in relapsing-remitting multiple sclerosis.

Objective: The objective of the study was a detailed description of thyroid dysfunction in CAMMS223.

Design: Relapsing-remitting multiple sclerosis patients (n=334) were randomized 1:1:1 to 44 μg sc interferon-β-1a (SC IFNB-1a, Rebif) or annual courses of 12 or 24 mg iv alemtuzumab. Thyroid function tests (TSH, free T3, free T4) and thyrotropin-binding inhibitory immunoglobulin (TBII) were assessed at screening, month 1, and quarterly thereafter; antithyroid peroxidase antibodies were assessed at screening and every 6 months. Thyroid dysfunction episodes were categorized post hoc by an endocrinologist.

Results: During a median follow-up of 57.3 months, 34% of alemtuzumab and 6.5% of SC IFNB-1a patients had thyroid dysfunction (P<.0001). Ten percent of alemtuzumab and 3% of SC IFNB-1a patients had more than one episode of thyroid dysfunction. With alemtuzumab, Graves' hyperthyroidism occurred in 22%, hypothyroidism in 7%, and subacute thyroiditis in 4%. Of patients with overt Graves' hyperthyroidism, 23% spontaneously became euthyroid and an additional 15% spontaneously developed hypothyroidism. Of patients with overt hypothyroidism, 74% were TBII positive. The annual incidence of a first episode of thyroid dysfunction increased each year through year 3 and then decreased each subsequent study year.

Conclusions: Thyroid dysfunction was more common with alemtuzumab than with SC IFNB-1a. There were few serious episodes. Regular monitoring facilitated early detection. Unique features of this population included high prevalence of Graves' hyperthyroidism, multiple episodes of thyroid dysfunction in individual patients, spontaneous hypothyroidism after overt Graves' hyperthyroidism, and a high prevalence of TBII-positive overt hypothyroidism.