Hematopoietic stem cell transplant, chimeric antigen receptor T-cells, and other cellular therapies as stepping stones toward long-term improvement in severe scleroderma and other autoimmune diseases

Preclinical models of inherited and induced autoimmune diseases (AIDs) have shown that hematopoietic stem cell transplantation (HSCT) following high-dose immunosuppressive conditioning could reverse organ damage and alter the course of AIDs. The rationale for both autologous and allogeneic HSCT has been based upon a reset of the immune system. Clinical application of HSCT was initially focused on severe systemic sclerosis (SSc) and three randomized trials comparing autologous HSCT with standard cyclophosphamide (CY) demonstrated significant improvement in SSc measured 12-54 months after transplant. Meta-analysis of the three trials showed the relative risk of all-cause mortality after HSCT was 0.5 compared to CY. More recently, clinical improvements in several AIDs have been reported with CY/fludarabine preparation followed by CD19 chimeric antigen receptor (CAR) T-cell infusion. With follow-up of 4-29 months, major disease responses and full B-cell reconstitution have been observed while side effects have been modest. Industry and academic centers are active in developing these and other cellular products for AID treatments including CAR-NK, off the shelf CAR-Ts, chimeric autoantibody receptor (CAAR-Ts), and mesenchymal stromal cells (MSCs). Clinical improvements after MSC administration have been reported, but as with the CAR-T trials, follow-up is still brief. Shared decision making with patients considering cellular therapy is perhaps easier for autologous HSCT since we have longer follow-up with many patients clinically improved and surviving off DMARDS for decades. Such individuals understandably view themselves as cured. Thus, the interest in the evolving role of cellular therapies in long-term improvement in severe AIDs.