Low Dose Azacitidine Maintenance Therapy Following Allogeneic Stem Cell Transplantation for MDS/AML Does Not Interact with Tacrolimus Dosing or Serum Levels

Recurrence of disease remains a significant cause of morbidity and mortality in patients who undergo allogeneic SCT for AML and MDS. Low-dose azacitidine is currently under investigation in the post-transplant setting with the goal of prolonging disease-free survival and decreasing relapse rates. It is unclear if there is potential pharmacologic interaction between azacitidine and dose-adjusted tacrolimus used to prevent post-transplant graft-versus-host disease (GVHD), a clinically relevant question since any resultant tacrolimus under- or over-dosing may lead to increased risk of GVHD or drug toxicity, respectively. We hypothesized that azacitidine does not significantly interact with tacrolimus levels and performed a retrospective analysis to test this hypothesis.

We reviewed tacrolimus daily doses and serum drug levels of 62 AML and MDS patients who received azacitidine maintenance therapy (n=30) or no maintenance therapy (n=32) following allogeneic stem cell transplantation at MD Anderson Cancer Center between 2008–2012. Patient characteristics are summarized in the Table. Patients in the maintenance cohort received subcutaneous azacitidine at 32 mg/m² on days 1–5 repeated every 28 days starting at a median time of post-transplant day +65 (range 43–100). Tacrolimus doses and serum levels were averaged for 28 days for each patient before and after initiation of azacitidine maintenance and at day +66 in the non-maintenance cohort. Differences between the two cohorts in their mean change of tacrolimus doses and serum drug levels were assessed using a Student's t-test.

Mean (SD) oral tacrolimus doses pre- and post-maintenance therapy were 2.61 (2.13) mg daily and 2.44 (2.15) mg daily in the azacitidine group and 2.54 (1.86) mg and 2.23 (1.39) mg daily in the non-azacitidine cohort. This resulted in a mean change in tacrolimus dosing of -0.17 (1.16) mg daily in the azacitidine patients and -0.31 (1.10) mg daily in the non-maintenance group (p=0.62). Mean (SD) serum tacrolimus levels pre- and post-maintenance therapy were 8.07 (1.16) ng/mL and 7.58 (2.32) ng/mL in the azacitidine group and 8.23 (1.49) ng/mL and 7.10 (1.69) ng/mL in patients on no maintenance therapy. This resulted in a mean change in serum tacrolimus levels of -0.49 (2.75) ng/mL in the azacitidine cohort and -1.13 (2.04) ng/mL in the non-maintenance group (p=0.30).

Maintenance azacitidine therapy following allo-SCT for AML and MDS does not appear to affect concurrent tacrolimus dosing or serum drug levels.

Off Label Use: azacitidine: off-label use as maintenance therapy following allogeneic stem cell transplant for MDS/AML. Champlin:Otsuka: Research Funding. De Lima:Celgene: Research Funding.