Methotrexate (MTX) is one of the main therapeutic agents currently used for the prophylaxis of graft-versus-host disease (GvHD) following hematopoietic stem cell transplantation. However, it is associated with significant toxicity and considerable side effects in many patients, which lead to either early withdrawal or dose reductions that may expose patients to the risk of GvHD and graft failure. Folinic acid (FA) can bypass the inhibitory effects of MTX on folate availability and control MTX toxicity. However, concerns that FA might inhibit the anti-GvHD effect of MTX and limited reports on its clinical usefulness have led to reluctance in its inclusion in standard GvHD prophylaxis regimens. Additionally, universal dosing and timing guidelines are lacking. I discuss the available literature and evaluate the evidence for the effect of FA on MTX toxicity and its safety regarding GvHD development and graft rejection in both adult and pediatric patients. Although FA administration appears to be safe, its efficacy for routine use in all types of transplants in adult patients is unproven and further research is required to confirm its MTX toxicity-lowering effect, identify the individual parameters that influence its usefulness in clinical practice, and evaluate its potential when developing a personalized prophylaxis regimen.
Keywords: Methotrexate; bone marrow transplant; clinical practice; folinic acid; graft-versus-host disease; personalized medicine; prophylaxis; toxicity.