Immunological analyses from the FORTE trial that compared 20 versus 40 mg dose of glatiramer acetate in multiple sclerosis

OBJECTIVE: To determine whether leukocytes alter their proliferative, cytokine and growth factor profiles dependent on the dose of glatiramer acetate (GA) that patients receive, and whether these are altered by intervals of treatment. BACKGROUND: The availability of leukocytes from patients enrolled in the FORTE Phase III trial that compared 40 versus 20 mg GA provided the opportunity to address whether the higher dose would produce a greater change in some of the immunologic parameters elicited by the standard dose of GA (20 mg) in MS. Mechanisms of interest include the shift in cytokines from a pro-inflammatory (e,g, IFN-g) to an antiinflammatory (e.g. IL-5) bias, and the production of growth factors by leukocytes. METHODS: Blood samples were collected from 20 patients at baseline, and at 1, 2, 3, 6 and 12 months of treatment for peripheral blood mononuclear cells (PBMCs). The PBMCs were left unstimulated or were stimulated ex vivo with 10, 25, 40 and 100 ug/ml GA. Proliferation rate was measured after 7 days of culture and expressed as counts per minute (cpm); the stimulation index was calculated as the ratio of cpm in the GA-stimulated culture to that of unstimulated controls. Levels of IFN-g, IL-5 and brain-derived neurotrophic factor (BDNF) were measured in the 7 day cell-conditioned media using ELISA. RESULTS: Ex vivo, PBMCs proliferated proportionally to increasing concentrations of GA. The peak stimulation index to GA in culture occurred in cells collected from 1 to 2 months of in vivo GA treatment, and it then declined to baseline levels in samples from 3-12 months of therapy. The peak stimulation index to GA in culture appears to be reached earlier in PBMCs from patients on the higher versus lower dose groups. Despite the lack of a measurable proliferative response to ex vivo GA with increasing periods of GA therapy, cells retained the ability to produce IL-5 and BDNF in both dose groups. A greater change in favor of a particular dose could not be strongly detected. CONCLUSIONS/RELEVANCE: The results demonstrate immunological alterations to both doses of GA and suggest a higher and more rapid induction response in the higher dose group. This research was supported by Teva Pharmaceuticals, Israel.