Letermovir coadministration and tacrolimus concentration-to-dose ratios before and after intravenous-to-oral conversion in allogeneic hematopoietic stem cell transplant recipients receiving isavuconazole.

Authors

Toshihisa Nakashima, Yoshihiro Inamoto, Ayumu Ito, Takahiro Fukuda, Hironobu Hashimoto

Published in

Japanese journal of clinical oncology. Aug 18, 2026. Epub Aug 18, 2026.

Abstract

Letermovir is used for cytomegalovirus prophylaxis after allogeneic hematopoietic cell transplantation (HCT) and reportedly increases tacrolimus exposure. Isavuconazole, a mold-active triazole antifungal, also inhibits cytochrome P450 3A and may affect tacrolimus pharmacokinetics. This retrospective study evaluated tacrolimus concentration-to-dose (C/D) ratios pre- and post-conversion from continuous intravenous infusion to oral administration in allogeneic HCT recipients receiving isavuconazole. Forty-five patients were stratified according to letermovir coadministration into the isavuconazole-alone group (ISCZ-alone; n = 9) and the isavuconazole with letermovir group (ISCZ + LMV; n = 36). The median C/Dciv ratios were 17.00 and 16.40 (ng/ml)/(mg/day), respectively (P = 0.81); the median C/Dpo ratios were 3.25 and 2.60 (ng/ml)/(mg/day), respectively (P = 0.77); and the median (C/Dpo)/(C/Dciv) ratios were 0.154 and 0.173, respectively (P = 0.72). Sensitivity analyses yielded consistent findings. Letermovir coadministration was not associated with significant differences in tacrolimus C/D ratios pre- or post-conversion to oral administration in allogeneic HCT recipients receiving isavuconazole.

PMID:
42611513
Bibliographic data and abstract were imported from PubMed on 19 Aug 2026.

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