Jaiswal SR, et al. – A pilot study employing extended T cell costimulation blockade (COSBL) with Abatacept along with sirolimus and post–transplantation cyclophosphamide (PTCy) in patients (median age 12) with severe aplastic anemia (SAA), was conducted. Probably due to synergistic effect on early recovery of Tregs, COSBL in combination with PTCy and sirolimus appeared to augment transplantation tolerance in children with SAA.