Background: DNA methyltransferase inhibitors (DNMTis) improve survival for patients with myelodysplastic syndromes (MDS) and those with acute myeloid leukemia (AML) unable to receive standard cytotoxic chemotherapy and are, accordingly, the backbone of standard-of-care treatment for these conditions. Standard regimens with DNMTIs, decitabine (DEC) or azacitidine (AZA) include daily subcutaneous (s.c.) or intravenous (i.v.) administration for 5-7 consecutive days. Attempts to provide the therapy orally have been limited given rapid clearance of the agents by the enzyme cytidine deaminase (CDA), which is ubiquitous in the gut and liver as part of first-pass metabolism. Recently, cedazuridine (CDZ), an oral inhibitor of CDA, was successfully combined with DEC to approximate the pharmacokinetics of i.v. DEC in patients.
Objective: To determine if an oral dosing strategy might be feasible in the clinic with AZA, we attempted to increase the bioavailability of oral AZA through the use of CDZ, in a murine model.
Methods: Following pharmacokinetic and pharmacodynamic assessment of oral AZA dosed with CDZ in murine and monkey models, we tested this regimen in vivo with a human cell line-derived xenograft transplantation experiment (CDX). Following this we combined the regimen with venetoclax (VEN) to test the efficacy of an all-oral regimen in a patient-derived xenograft (PDX) model.
Results: Parenteral AZA and oral AZA + CDZ exhibited similar pharmacokinetic profiles, and efficacy against human AML cells. Tumor regression was seen with AZA + CDZ in MOLM-13 CDX and PDX models.
Conclusions: We conclude that oral AZA when combined with CDZ achieves successful tumor regression in both CDX and PDX models. Furthermore, the combination of AZA + CDZ with VEN in a PDX model emulated responses seen with VEN + AZA in the clinic, implying a potential all-oral VEN-based therapy opportunity in myeloid diseases.