Seeking to improve graft-versus-host disease (GVHD) prophylaxis in haploidentical (HI) hematopoietic stem cell transplant (HSCT), researchers investigated a regimen of post-transplant cyclophosphamide (PTCy), abatacept (A), and a short course of tacrolimus (CAST). In a presentation of the findings at the Transplantation & Cellular Therapy 2022 Tandem Meetings, A. Samer Al-Homsi and colleagues suggested that “CAST with shortened course of T is feasible and offers promising outcomes with low rates of acute GVHD.”
In this clinical trial of 23 patients, GVHD prevention after HI HSCT consisted of intravenous (IV) PTCy 50 mg/kg on days three and four post-transplantation; IV A 10 mg/kg on days five, 14, and 28; and tacrolimus starting on day five at 0.02 mg/kg/day. The dose of T was adjusted to sustain a trough level of 5-12 ng/mL and then tapered starting at day 60 for 30 days.
According to the authors, the median time to absolute neutrophil count (ANC) engraftment was 18 days (range: 14–30). In 21 patients who were evaluable for platelet engraftment, the median time to engraftment was 26 days (range: 16–61). Notably, “all 23 patients achieved full whole blood donor chimerism by day ?30.” Over a median follow-up of 137 days (range: 18–362), three patients developed grade II to IV acute GVHD and one patient developed grade III to IV acute GVHD. The authors also stated that two patients developed chronic GVHD of the skin, which were reportedly both limited and moderate. Except for one patient with adult T-cell leukemia/lymphoma who experienced relapse and died, all patients remained disease-free at the time of the abstract’s writing.
The study is still enrolling participants, and data from a larger cohort with a longer follow-up duration is forthcoming, according to the authors. In closing, they wrote that “if confirmed, this regimen may further address a health care disparity issue by improving the results of HI HSCT, thus offering almost every patient in need of allogeneic stem cell transplantation an alternative donor option with equal outcomes.”