Phase 1 Trials of Gatralimab, a Next-Generation Humanized Anti-CD52 Monoclonal Antibody, in Participants with Progressive Multiple Sclerosis.

introductionLymphocyte depletion via anti-CD52 monoclonal antibody (mAb) therapy is an effective treatment strategy for relapsing-remitting multiple sclerosis (MS) but is associated with infusion/injection-associated reactions (IARs) and autoimmune-related adverse events (AEs). Gatralimab is a next-generation humanized anti-CD52 mAb.

methodsTwo first-in-human trials were conducted in participants with progressive MS to assess the pharmacodynamics, pharmacokinetics, and safety of gatralimab administered via subcutaneous (SC) and intravenous (IV) routes, and to determine the effect of different comedication regimes on IARs to SC gatralimab. A Phase 1 trial (NCT02282826) included double-blind, placebo-controlled sequential ascending single IV (1, 3.5, and 12 mg) and SC (12, 36, and 60 mg) dose groups. A Phase 1b trial (NCT02977533) involved five groups who received SC gatralimab (36, 48, or 60 mg) and different comedications. A long-term safety (LTS) study (NCT02313285) examined safety and pharmacodynamics over 4 years.

resultsGatralimab produced depletion of lymphocytes (dose-dependently) and CD4+ regulatory T cells, with partial repopulation to normal values by approximately 12 months. Peak serum gatralimab concentrations followed dose-proportionality and were delayed by 6.0-7.5 days following SC administration. Treatment-emergent AEs, including IARs, were reported for most participants but were generally of mild or moderate severity, and treatment-emergent serious AEs were mostly MS-related. Methylprednisolone and antihistamine comedications were associated with reduced incidence of fevers and skin and subcutaneous tissue AEs, respectively. During the LTS study, one participant (3.0%) experienced an autoimmune-related AE (Basedow's disease), and subsequently died from pulmonary sepsis deemed unrelated to gatralimab by the investigator.

conclusionsThese data show that gatralimab achieves the desired pharmacodynamic effect of lymphocyte depletion followed by repopulation, and has an acceptable safety profile, including low risk of non-MS autoimmunity. Although gatralimab is no longer in development for MS, insights from these trials may inform the development of comedication regimes of future anti-CD52 mAbs and subcutaneous formulations of other lymphocyte-depleting mAbs.

trial registrationNCT02282826, NCT02977533, NCT02313285.