P155 | DANAZOL TREATMENT FOR POOR GRAFT FUNCTION AFTER HEMATOPOIETIC STEM CELL TRANSPLANTATION: A SINGLE-CENTRE EXPERIENCE.

Poor graft function (PGF) is a rare but serious complication following allogeneic hematopoietic stem cell transplantation (alloHCT), defined by persistent cytopenia despite full donor chimerism. Its multifactorial pathogenesis includes intrinsic stem cell defects, bone marrow microenvironment damage and immune dysregulation, leading to increased morbidity, transfusion burden and infection risk. Current treatments (e.g. mesenchymal cell infusions, CD34+ boosts, TPO mimetics) are often limited by cost and availability. Androgens like danazol, have shown effectiveness in stimulating hematopoiesis in others haematologic disorders, but their role in PGF remains unexplored. We retrospectively analysed six male patients with PGF treated with danazol between February 2020 and March 2025. Median age was 61 years (range 59–64). Underlying diseases included myeloid (2 myelodisplastic syndromes, 1 acute myeloid leukemia and 1 myelofibrosis) and lymphoid malignancies (1 acute lymphoid leukemia and 1 cutaneous T-cell lymphoma). All underwent PBSC alloHCT from haploidentical (n=3), matched (n=1) or mismatched (n=2) unrelated donors, and all but one received reduced-intensity conditioning. Two patients had a major AB0 mismatch and two a minor one. All met EBMT PGF diagnostic criteria. The median number of transfusions before danazol were 25 units (6–49) for platelets and 39 units (21–75) for red blood cells. Before danazol, two patients had GvHD resolved with systemic steroids, and two underwent CMV reactivation successfully treated with valganciclovir. Danazol (200–400 mg/day) was started after a median of 19 weeks post-transplant due to persistent cytopenias. Four patients achieved sustained platelet recovery and transfusion independence after a median of 13 days. Hb levels improved in four cases after a median of 46 days. Two previously G-CSF–dependent patients normalized neutrophil counts, while others showed only transient responses. Danazol was stopped upon achieving response, after a median of 71 days, maintaining a stable engraftment in 3 patients. Another developed liver failure likely due to pre-existing risk factors. No other major toxicities were observed. Danazol appears feasible, accessible, and well-tolerated in PGF patients, particularly in resource-limited settings. It demonstrated efficacy in promoting trilineage recovery, with the most rapid effect on platelets. Larger studies are needed to confirm these findings and better define its therapeutic role.