A Dose and Schedule Finding Study of Maintenance Therapy with Low-Dose 5-Azacitidine (AZA) after Allogeneic Hematopoietic Stem Cell Transplantation (HSCT) for High-Risk AML or MDS.

Disease relapse is the most frequent cause of treatment failure after HSCT in patients (pts) with refractory AML/MDS. AZA inhibits the enzyme DNA methyltransferase and leads to DNA hypomethylation. It may induce leukemic cell differentiation and increased immunogenicity, therefore potentially magnifying the graft-versus-leukemia effect. Lower doses are likely to be better tolerated after HSCT and to be as effective as larger doses in inducing hypomethylation. We hypothesized that AZA maintenance will result in lower relapse rates, and designed a phase I clinical trial to determine the safest dose and schedule combination. We also monitored global methylation post HSCT as a surrogate marker for changes in methylation status during AZA.

Methods: Pts with AML or high-risk MDS not in 1st complete remission (CR), not candidates for ablative regimens were eligible. Conditioning regimen was gemtuzumab ozogamicin 2 mg/m² (day -12), fludarabine 120mg/m², and melphalan 140mg/m². GVHD prophylaxis was tacrolimus/mini-methotrexate. ATG was administered to recipients of unrelated donor (UD) HSCT. We investigated 3 AZA doses: 8, 16, and 24 mg/m² daily × 5 starting on day +42, and given for 1–4 28-day cycles (schedule). An outcome-adaptive method was used in order to determine both dose and schedule (number of cycles): pts were assigned to a dose/schedule combination chosen on the basis of the data (toxicity) from all pts treated previously in the trial. Patients in CR on transplant day +30, without gd III/IV GVHD, platelet >10,000/mm³ and ANC >500/mm³ were eligible to receive SQ AZA. The methylation status of long interspersed nuclear elements (LINE) was analyzed by pyrosequencing and used as a surrogate marker of global DNA methylation in mononuclear cells of 22 pts(55%) that received AZA for at least 1 cycle.

Results: 40 patients were enrolled; median age was 57 years (22–72). Diagnoses were MDS with high IPSS(n=6) and AML (n=34). Disease status at HSCT: complete remission (CR), 10% (n=4); chemo-naive MDS, 2% (n=1); induction failure, 35% (n=14), 1st/2nd relapse, 42.5% (n=21). Patients had received a median of 5 courses of chemotherapy (0–23) prior to HSCT, and the median comorbidity Charlson score was 3 (0–8). Donors were related (n=23) or UD(n=17), and stem cell source was bone marrow(n=8) or peripheral blood(n=32). Median follow-up of alive pts is 11 mo (2.5–20; n=21). 49 cycles of AZA were delivered at 8 (n=7 pts), 16 (n=4) and 24 mg/m² (n=12 pts). AZA-associated toxicities were grade I/II hematologic, nausea and fatigue. There was no increase in GVHD: gd II-IV aGVHD, and chronic GVHD rates were 34% and 30%. 11 pts have relapsed, 2 while on AZA (16 and 24 mg/m²). Day +30 and +100 non-relapse mortality was 5% and 12%. Mean LINE methylation results were as follows: baseline: 43.51% (±5; n=22); on cycle 1, 5th day of AZA: 24 mg/m²=43.58% (±5; n=9); 16 mg/m²: 36.93% (±6.5; n=4); 8 mg/m²: 42.86% (±5; n=3). There were trends towards lower levels of global methylation at 16mg/m² in subsequent cycles. The trial design has reached the higher dose and the maximum number of cycles given the absence of AZA-related major toxicities.

Conclusion: AZA at 24 mg/m² is safe and can be administered for at least 4 cycles. The lack of toxicity and the methylation studies indicate that higher doses and longer periods of administration should be investigated.