Optimization of Tacrolimus Serum Levels When Combined with Post-Transplant Cyclophosphamide As Graft-Versus-Host Disease Prophylaxis after Hematopoietic Cell Transplantation: Outcome Data Analysis

Post-transplant cyclophosphamide (PTCy) in combination with tacrolimus and mycophenolate mofetil (MMF) has been used increasingly in recent years to prevent graft-versus-host disease (GvHD) in patients undergoing hematopoietic cell transplantation (HCT), and has been proven safe and effective regardless of HLA matching criteria. Historically, the therapeutic dose level recommended for tacrolimus has ranged from 10 to 15 ng/mL, when combined with methotrexate, and between 5-10 ng/mL when combined with sirolimus. However, data on the optimal starting dose and serum level of tacrolimus when combined with PTCy does not exist. Given tacrolimus's broad inhibition on T-cells activation and the PTCy's selective inhibition on alloreactive T-cells, we hypothesized that lower serum levels of tacrolimus could suffice to achieve optimal transplant outcomes. We retrospectively identified a consecutive case series of 219 patients who received HCT with PTCy (50 mg/kg on days +3 and +4) in combination with tacrolimus and MMF (day +5) as GvHD prophylaxis at City of Hope from January 2011 to June 2018. Tacrolimus was delivered with continuous intravenous infusion until engraftment, then switched to equivalent oral dose. Tacrolimus dosing was weight-based (WBD) in 80 patients and fixed dose (FD) of 1 mg in 139 patients. We captured Tacrolimus levels at two different time points: 1. the initial steady state (ISS) and 2. at engraftment level (EL) to identify which time point will correlate with better HCT outcomes. At each time point, transplant outcomes were compared between patients with serum levels ≥10 ng/mL and Patients received HCT either from a haploidentical (n=175), matched (n=6), or mismatched donor (n= 38). Tacrolimus levels at the ISS (median: day +9 of HCT, range 8-16) was At ISS, 18 months OS, PFS, relapse rate were 64%, 58% and 19%, respectively, in patients with tacrolimus level In conclusion, tacrolimus dosing at a FD was more likely resulting in ISS of 4-10 ng/mL (86% of patients in Download : Download high-res image (688KB) Download : Download full-size image Figure 1 . Disclosures Salhotra: Celgene: Other: Research Support; Kadmon Corporation: Other: Non paid consultant. Aldoss: Helocyte: Consultancy, Honoraria, Other: travel/accommodation/expenses; Jazz Pharmaceuticals: Honoraria, Other: travel/accommodation/expenses, Speakers Bureau; Agios: Consultancy, Honoraria; AUTO1: Consultancy. Stein: Amgen: Consultancy, Speakers Bureau; Celgene: Speakers Bureau; Stemline: Speakers Bureau. Nakamura: Alexion: Other: support to a lecture at a Japan Society of Transfusion/Cellular Therapy meeting ; Merck: Membership on an entity's Board of Directors or advisory committees; Celgene: Other: support for an academic seminar in a university in Japan; Kirin Kyowa: Other: support for an academic seminar in a university in Japan.