Scala: a randomized phase I trial comparing subcutaneous and intravenous alemtuzumab in patients with progressive multiple sclerosis

BACKGROUND: Alemtuzumab is administered intravenously (IV) for relapsing-remitting multiple sclerosis (RRMS), with limited studies of subcutaneous (SC) treatment.

OBJECTIVES: We sought to evaluate the pharmacodynamics (PD), pharmacokinetics (PK), and safety profile of SC-administered alemtuzumab in people with progressive multiple sclerosis (PMS).

DESIGN: SCALA was a phase I, open-label, randomized, parallel-group study with two 12-month periods and a safety monitoring phase to 60 months.

METHODS: Of 29 screened participants, 24 were enrolled and randomized 2:1 to two 12 mg/day alemtuzumab treatments (60 and 36 mg total; SC:IV). Key inclusion criteria: ⩾18 years with a PMS diagnosis. Key exclusion criteria included RRMS diagnosis and prior treatment with anti-CD52 antibodies. Primary endpoint: CD3 + lymphocyte count. Secondary endpoints: PD and PK parameters.

RESULTS: Demographics were broadly similar for participants in the SC (16) and IV (8) arms; more participants with primary PMS received SC (44%) versus IV (25%) treatment. After the first course, the mean CD3 + cell count/µL was reduced at month 1 in both arms (SC: baseline (BL) 1326 to 48 vs IV: BL 1155 to 84). Lymphocyte counts partially repopulated by month 12, with mean CD3 + cell counts/µL of SC 599 versus IV 528. The mean lymphocyte counts/µL decreased again after the second course at month 13 in both arms (SC: 90 vs IV: 129), with partial repopulation by month 24. Alemtuzumab serum concentrations were lower following SC administration relative to IV, with 32% bioavailability. There were no adverse events leading to permanent treatment discontinuation or death.

CONCLUSION: In SCALA, there were similar patterns of lymphocyte depletion and repopulation for participants receiving SC or IV alemtuzumab. In both arms, alemtuzumab had a manageable safety profile, with no emerging safety concerns. The general stabilization of neurological outcomes observed over 60 months underscores the potential long-term benefits of alemtuzumab treatment.