Allogeneic stem cell transplantation compared to conservative management in adults with inborn errors of immunity.

Allogeneic hematopoietic stem cell transplantation (alloSCT) is curative for severe inborn errors of immunity (IEI), with recent data suggesting alloSCT in adulthood is safe and effective in selected patients. However, questions remain regarding the indications for and optimal timing of transplant. We retrospectively compared outcomes of transplanted with matched non-transplanted adults with severe IEI. Seventy-nine patients (aged ≥15 years) underwent alloSCT between 2008 and 2018 for IEI, including chronic granulomatous disease (CGD, n=20) and various combined immune deficiencies (CID, n=59). A cohort of non-transplanted patients from the French CEREDIH registry was identified blindly for case-control analysis after matching for birth decade, age at last review greater than age at alloSCT, CGD or CID, and autoimmune/lymphoproliferative complications; with ≤3 matched controls per index patient without replacement. 281 patients were included (79 transplanted, 202 non-transplanted). Median age at transplant was 21 years. Transplant indications were mainly lymphoproliferative disease (n=23) or colitis (n=15). Median follow-up was 4.8 years (IQR [2.5-7.2]). One-year TRM was 13%. Estimated DFS at 5 years was higher in transplanted patients (58% vs. 33%, p=0.007). Non-transplanted patients had an ongoing risk of severe events with an increased mean cumulative number of recurrent events compared to transplanted patients. Sensitivity analyses removing patients with CVID and their matched transplanted patients confirm these results. AlloSCT prevents progressive morbidity associated with IEI in adults, which may outweigh the negative impact of TRM.