Treatment of progressive multiple sclerosis with high-dose all-trans retinoic acid – no clear evidence of positive disease modifying effects

BACKGROUND: All-trans retinoic acid (ATRA) is an acid derivative of vitamin A which is discussed as a promising candidate to ameliorate the disease course of multiple sclerosis (MS) by immunomodulation or even by promoting regeneration in progressive MS. Here we report a patient who significantly improved for MS related disability following administration of chemotherapy including ATRA for mitoxantrone-related acute promyelocytic leukemia and assess the effect of high-dose ATRA in three additional patients with progressive MS. METHODS: Patients with progressive MS who had failed previous therapies were treated with high-dose ATRA. Patients underwent clinical and routine laboratory monitoring. Additionally, PBMCs were analyzed by flow cytometry for lymphocyte subsets. RESULTS: ATRA was well tolerated and no pathological laboratory abnormalities were observed. After initial mild (not statistically significant) improvement of EDSS and mean MSFC z-score, ongoing disease progression was observed. One patient subacutely experienced severe cognitive and motor worsening. Cerebral MRI revealed persistent gadolinium-enhancing lesions. Flow cytometric alterations of peripheral blood naïve, central memory and effector memory CD4 and CD8 T cells, B lymphocytes, plasma cells, memory B cells, plasmablasts and natural killer (NK) cells did not reach statistical significance. CONCLUSIONS: Stand-alone therapy with ATRA did not ameliorate progressive MS in our limited cohort and we did not observe consistent alterations of T and B cell subsets. Intriguingly, application of ATRA may have caused marked disease exacerbation in one patient. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s42466-021-00121-4.