A Phase I Biological Study of Azacitidine (Vidaza) to Determine the Optimal Biological Dose and Route of Administration.
Authors: Bernstein Ilan , Byun Hyang-Min , Mohrbacher Ann , Douer Dan , Gorospe Gerry , Yang Allen S. , O'Connell Casey L 
Published: October 2019

Abstract
Abstract 1753
Poster Board I-779

Background
Azacitidine (5-azacytidine, Vidaza) is a DNA methylation inhibitor with used to treat myelodysplastic syndrome (MDS). The studies which led to FDA approval based dosing and administration guidelines on clinical response. In vitro studies have demonstrated that azacitidine exerts its effect by inhibiting DNA methyltransferase in hypermethylated tumor suppressor genes in malignant cells. Research to date has not linked azacitidine dosing with biochemical and clinical response in vivo. The degree of DNA repetitive element sequence methylation (such as LINE-1) has been demonstrated to correlate with global DNA methylation and may be used to determine DNA methylation changes after treatment with azacitidine. We have conducted a phase I study to link clinical and biologic response to azacitidine. This study aims to determine the optimal dose and route of administration for azacitidine to inhibit global DNA methylation levels in the peripheral blood of patients with hematologic malignancies.

Methods
Patients with hematologic malignancy who provided informed consent were eligible for study inclusion, with enrollment criteria based on the specific malignancy. Patients were enrolled into one of five dose level treatment groups (25mg, 50mg, 75mg, 100mg or 150mg IV per m2 per day for 5 days) for the first course of therapy. On day 28, all patients received a course of 75mg/m2/day IV for 5 days. Subcutaneous dosing of 75mg/m2/day for 5 days was used for course three. Patients received 75mg/m2/day either SQ or IV x 5 days every 4 weeks for course four and beyond. Peripheral blood was collected on days 1, 3, and 5 during each course, and global DNA methylation was measured using bisulfite-PCR Pyrosequencing of the 6 DNA repetitive elements (LINE1, AluYb8, AluSq, Sat-alpha, D4Z4, NBL-2). Additionally, gene promoter specific DNA methylation was assessed in a subset of patients using the Illumina GoldenGate Bead Array DNA Methylation Assay which measures DNA methylation of 1505 CpG sites (807 genes).

Results
Seventeen patients were treated (3 at 25mg, 4 at 50mg, 4 at 75mg, 3 at 100mg, and 3 at 150mg/m2). Diagnosis included 5 patients with MDS, 10 patients with AML (2 untreated older patients, 7 relapsed or refractory patients), 1 patient with CML (Imatinib refractory), and 1 patient with non-Hodgkin's lymphoma (relapsed disease). At the time of submission, 14 patients were evaluable for response with 4 CR (1 mCr, 1 CRp), 1 PR, 6 SD and 3 PD reported. The median number of cycles given was 3 (range 1-14+). LINE1 DNA methylation decreased by 1.4, 2.3, 4.8, 1.9 and 4.0% on day 5 for the 25mg, 50mg, 75mg, 100mg, and 150mg/m2 course one dose levels respectively. Mean decrease in LINE1 DNA methylation with 75mg/m2 IV was 3.7% and only 2.6% by 75mg/m2 of azacitidine SQ. There was a large amount of inter-patient variability but less intra-patient variability in DNA methylation response to azacitidine.

Conclusion
Azacitidine is effective at inhibiting DNA methylation at multiple dose levels for both IV and SQ routes of administration. There is a high degree of patient-to-patient variability in DNA methylation changes, although 75mg/m2 lead to the greatest mean decrease in DNA methylation by a 5 day IV regimen. Measurement of DNA methylation of LINE1 and AluYb8 repetitive elements were the best surrogate markers for measuring overall changes in gene specific promoter DNA methylation when compared with 807 genes assessed by the Illumina GoldenGate platform. High-throughput gene promoter DNA methylation analysis revealed subtle changes in DNA methylation, though gene specific changes could not be linked to therapeutic activity.

Disclosures
Off Label Use: Azacitidine in hematologic malignancies other than MDS. Mohrbacher:Celgene: Honoraria, Speakers Bureau. Gorospe:Novartis: Honoraria, Speakers Bureau. Yang:Celgene: Honoraria, Research Funding, Speakers Bureau.