Dosage, Safety and Efficacy of Posaconazole As Primary Antifungal Prophylaxis in High-Risk Recipients of Allogeneic Stem Cell Transplantation

Introduction: The use of anti-mold prophylaxis with anti-aspergillus activity is recommended for patients (pts) undergoing allogeneic hematopoietic stem cell transplantation (Allo-HSCT) with high risk of fungal infection (Maertens, J Antimicrob Chemother 2018). Yet, few data are available regarding the use of posaconazole.

Methods: This retrospective study included all Allo-HSCT adult recipients having benefited from posaconazole therapy in our center as a primary anti-fungal prophylaxis for high-risk of fungal infection. The latter was defined as use of i)an alternative donor, ii)sequential conditioning regimen, iii)a regimen associated with severe mucositis, iv) post-transplant cyclophosphamide (PT-Cy) or v) previous allo-HSCT. Posaconazole was programmed to be initiated at day (D) 0 or D5/6 (in case of PT-Cy) and administered up to day 100. We report here on the residual concentration of posaconazole during the neutropenic phase then on the tolerance and efficacy of such prophylaxis in this cohort.

Results: Seventy high-risk pts (males 63.3%, median age 54 years old, range 20-73) received Allo-HSCT between April 2020 and December 2021 for a myeloid (n=51), lymphoid (n=17) or non-malignant hematological (n=2) disease and received posaconazole as a primary prophylaxis. The Sorror score at transplant time was ≥ 3 for 24 pts (33.8%). Twenty-two patients had already received posaconazole as a primary prophylaxis before Allo-SCT including 26 during the neutropenic phase of their induction for AML or MDS, 3 for prolonged neutropenia, 2 during treatment with alemtuzumab for T-cell leukemia/lymphoma, and 1 during a previous AlloHCST. Four patients had also received other antifungal agentsbefore Allo-SCT (caspofongine (n=1), voriconazole (n=1) or liposomal amphotericin B (n=2)) because of a suspected mold infection which has been finally excluded. All pts had at least one high-risk criterion of fungal infection. These included the use of an alternative donor in 42 pts (haplo-identical donor n= 41, umbilical cord blood n=1), sequential conditioning regimen in 9, with PT-Cy in 57, second or third allo-HSCT in 8 and conditioning regimen associated with severe mucositis in 11 (TBI 8-12gy n=3, thiotepa-based n=8).

All but one pts received posaconazole using the gastroresistant tablet form at a dose of 300mg/day. One patient received the drinkable suspension form at a dose of 200mg 3 times a day. Following prophylaxis initiation, serum posaconazole concentrations were available in 51 and 16 patients at medians of 9 and 39 days, respectively. A protective residual level of posaconazole (> 0.5mg/L) was achieved in 57% of the patients (n=29) at first assessment and 87.5% (n=12) at second evaluation.

Posaconazole was stopped early due to related-toxicity in 9 cases (12.6%), including liver toxicity in 7 pts, QT prolongation in 1 and skin hyperesthesia in 1. Treatment was restarted without recurrence of toxicity in 2 cases. Posaconazole was stopped early in 2 patients due to non-related toxicity, including one veno-occlusive disease and one hepatic acute GVHD. Posaconazole was temporary discontinued in 4 patients due to a suspected fungal infection before being restarted.

Most patients (n=59/70, 84.2%) did not present fungal infections while being under posaconazole therapy. Only 11 cases were documented with this complication (Table 1), including 8 invasive pulmonary aspergillosis (IPA; possible n=3; probable n=5), one possible invasive fungal infection and 2 mucormycoses (1 with possible IPA). Fungal infections occurred despite documentation of a protective residual level of posaconazole (> 0.5mg/L) in 5 of 6 evaluable patients. Of note, 9/11 patients had received PTCY as GVHD prophylaxis. Posaconazole was stopped (before D7 in 3) and other antifungal drugs started (voriconazole or liposomal amphotericin B) allowing to fungal infection cure in 5 pts. However, 7 pts died including 2 of an uncontrolled fungal infection.

Conclusion: Posaconazole is a well-tolerated and efficient primary prophylaxis in recipients of Allo-HSCT at high-risk of fungal infection. As some fungal infections occured very early after D0 while prophylaxis started only a D5/6 after PTCY, our results suggests to propose posaconazole as early as the beginning of the conditionning together with dose monitoring.

Gastinne:Gilead/Kite, Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Support for attending meetings/travel, participation in a data safety monitoring board or advisory board. Chevallier:Jazz Pharmaceuticals: Honoraria; Abbvie: Honoraria; Takeda: Honoraria; Pfizer: Research Funding; Incyte: Research Funding.