To report long-term results of a phase I/II study conducted in a single center in order to investigate the effect of hemopoietic stem cell transplantation (HSCT) in the treatment of multiple sclerosis (MS). Clinical and MRI outcomes of 35 patients with aggressive MS treated with HSCT are reported after a median follow-up period of 11 (range 2-15) years. Disease progression-free survival (PFS) at 15 years is 44% for patients with active CNS disease and 10% for those without (p=0.01); median time to progression was 11 (95% confidence interval 0-22) and 2 (0-6) years. Improvements by 0.5-5.5 (median 1) Expanded Disability Status Scale (EDSS) points were observed in 16 cases lasting for a median of 2 years. In 9 of these patients, EDSS scores did not progress above baseline scores. Two patients died, at 2 months and 2.5 years, from transplant-related complications. Gadolinium-enhancing lesions were significantly reduced after mobilization but were maximally and persistently diminished post-HSCT. HSCT is not a therapy for the general population of patients with MS but should be reserved for aggressive cases, still in the inflammatory phase of the disease, and for the malignant form, in which it can be life-saving. HSCT has an impressive and sustained effect in suppressing disease activity on MRI. This study provides Class IV evidence that HSCT results in PFS rates of 25%. PFS rate was significantly better in patients with active MRI lesions; HSCT also resulted in a significant reduction in the number and volume of gadolinium-enhancing lesions on MRI.

Immunotherapy with chimeric antigen receptor T (CAR-T cells) has been recently approved for patients with relapsed/refractory B-lymphoproliferative neoplasms. Along with great efficacy in patients with poor prognosis, CAR-T cells have been also linked with novel toxicities in a significant portion of patients. Cytokine release syndrome (CRS) and neurotoxicity present with unique clinical phenotypes that have not been previously observed. Nevertheless, they share similar characteristics with endothelial injury syndromes developing post hematopoietic cell transplantation (HCT). Evolution in complement therapeutics has attracted renewed interest in these life-threatening syndromes, primarily concerning transplant-associated thrombotic microangiopathy (TA-TMA). The immune system emerges as a key player not only mediating cytokine responses but potentially contributing to endothelial injury in CAR-T cell toxicity. The interplay between complement, endothelial dysfunction, hypercoagulability, and inflammation seems to be a common denominator in these syndromes. As the indications for CAR-T cells and patient populations expand, there in an unmet clinical need of better understanding of the pathophysiology of CAR-T cell toxicity. Therefore, this review aims to provide state-of-the-art knowledge on cellular therapies in clinical practice (indications and toxicities), endothelial injury syndromes and immunity, as well as potential therapeutic targets.