A Phase I/II Trial of Intravenous Azacitidine for Acute Gvhd Prophylaxis in Patients Undergoing Matched Unrelated Stem Cell Transplantation: Phase I Results

Background

The negative impact of acute graft-versus-host disease (GvHD) on morbidity and mortality after allogeneic transplant is significant; thus, finding a means to harness the beneficial Graft versus tumor effect (GVT) while reducing or eliminating GvHD is a major goal of transplant trials. Alterations in immune subsets present after transplant can work to suppress allo-reactive T-cell responses by increasing regulatory T-cells and suppressing allo-reactive T-cell proliferation. Azacitidine (AZA) treatment in pre-clincal models resulted in an increase in regulatory T-cells, a decrease in allo-reactive T-cell proliferation and prevention of acute GvHD while preserving GVT effects. (Choi et al. Blood 2010). Based on these results a phase I/II study was designed to test the safety and efficacy of AZA administered shortly after transplant for the prevention/prophylaxis of acute GvHD and relapse in subjects receiving transplants from matched unrelated stem cell donors.  We report the results for the Phase I portion of this trial.

Methods

Patients with hematologic malignancies in remission age 18 – 70 were eligible. Myeloablative or reduced intensity conditioning without antithymocyte globulin was used. All recipients were required to receive at least 2 x 10⁶ CD34/kg and have at least 1 x 10⁶ CD34/kg cryopreserved as back up in case of primary graft failure. AZA was administered intravenously on day +7 for five consecutive days and repeated every 28 days for a total of 4 cycles after allogeneic transplant from a 10/10 HLA matched unrelated donor.  Standard GvHD prophylaxis with mini-methotrexate and tacrolimus was given.  A Phase I, 3+3 dose escalation design of 4 cohorts (AZA dose levels 15, 30, 37.5, and 45 mg/m²) was used to determine toxicity and recommended phase II dose. The primary outcome for phase II is the rate of grade II – IV acute GvHD at day 180 after transplant.

Results

We have transplanted 16 subjects on trial, 15 have received study drug. Recipient characteristics include: median age 57, 67% male, and diagnoses of AML in CR (9), ALL in CR (2), or MDS (4). One DLT was observed in the final cohort of 6 subjects. The DLT experienced in the final cohort was primary graft failure. The subject had developed Clostridium difficile colitis during conditioning and fungemia shortly after transplant. A total CD34 dose of 2 x 10⁶/kg was infused after myeloablative conditioning of Busulfan and Cytoxan. The subject received the cryopreserved back up donor leukocyte infusion at day +28 but died at day 29 of sepsis without evidence of neutrophil engraftment. Contributing causes to the DLT were thought to be the CD34 dose infused, sepsis, severe colitis and possibly AZA administration. For the remainder of subjects treated in phase I the median CD34 dose infused was 5 x 10⁶ /kg (range 2 – 5), median ANC engraftment was 14 days (range 10 – 22 days).  Median platelet engraftment was 22 days (range 14 – 70). No grade III/IV acute GvHD has been observed.  Grades 1 and 2 skin and gut GvHD have been observed, and all cases have responded to steroids except one case of steroid refractory GvHD in cohort 1 (15mg/m² AZA). At the recommended phase 2 dose of 45mg/m² AZA, 3 cases of skin GvHD were observed occurring just prior to or at the time of cycle 2 of treatment.  All responded to steroids.  With a median follow up of 233 days (range 29 – 784), only 2 subjects have relapsed and 11 (73%) remain alive.  The most common non-hematologic grade 3 or 4 AEs were gastrointestinal toxicity (mucositis, nausea and diarrhea), electrolyte abnormalities, and infections.

In conclusion, AZA can be given safely starting at day +7 after MUD transplant up to a dose of 45mg/m² tested. Phase II is currently enrolling subjects. Because of the DLT experienced in phase I, the infused CD34 dose will be increased to a minimum of 4 x 10⁶ CD34/kg with 1 x 10⁶ CD34/kg cryopreserved in backup. Correlative studies from banked Phase I biospecimens evaluating dynamics of regulatory T-cells, T-cell subsets and methylation before and after treatment are being analyzed and will be reported.