Alemtuzumab has proven to be an effective treatment for patients with highly active multiple sclerosis (MS). However, its use has been limited by adverse events (AEs) as secondary autoimmunity, being the most frequent those involving the thyroid gland, observed in around 40% of patients.
To explore whether patient blood lymphocyte profile before alemtuzumab treatment initiation can identify patients with an increased risk of developing later autoimmunity.
A multicentre prospective longitudinal study was performed, including fifty‐four Relapsing-Remitting MS (RRMS) patients diagnosed in five Spanish hospitals. Patient blood samples were collected before initiating treatment with alemtuzumab. Autoimmune AEs were defined as the development, at any point within 2 years of follow-up, of any autoimmune thyroid-associated event, immune thrombocytopenia and/or autoimmune nephropathy. Differences were assessed using Man-Whitney U tests. Cut-off values were established using ROC curves to predict autoimmune AEs. Odds ratios were calculated by Fisher tests.
Fifty‐four RRMS patients, 36 (66.7%) women, with a median (range) age of 28 (13–67) years and median (range) follow-up of 6 (0-20) years. Fourteen patients (25.9%) experienced autoimmune AEs, and all of them were dysthyroidism. No immune thrombocytopenia or nephropathies were observed. No statistical differences were found in clinical and demographic characteristics between patients who developed autoimmune AEs and those who did not. Patients who experienced autoimmune AEs before treatment onset had a higher percentage of blood CD19+ B cells (p=0.001), with a higher relative percentage of naïve B cells and plasmablasts. When explored total cell numbers, only plasmablast levels remained significant (p=0.02). A lower risk of autoimmune AEs after alemtuzumab was observed among patients with less than 7.6% of blood CD19+ B cells [odds ratio (OR) 16, confidence interval (CI) 3.86–58.95, p<0.0001] or less than 0.13% of plasmablast cells [OR 9.33, CI 2.17–42.65, p=0.002].
A low percentages of blood CD19+ B cells or plasmablasts before Alemtuzumab treatment predicted a lower risk of autoimmune AEs.