Enhancing Oral Azacitidine Efficacy with Cedazuridine in a Mouse Model: Bridging the Gap to Intravenous Therapy

DNA methyltransferase inhibitors (DNMTi) are crucial for treating MDS and AML patients who cannot undergo traditional chemotherapy, forming the foundation of standard of care (SOC) treatment. However, the standard administration of DNMTi, such as azacitidine (AZA) or decitabine (DAC), via subcutaneous (SQ) or intravenous (IV) routes is inconvenient and can impact patients' quality of life (QOL). Oral administration has been challenging due to the rapid clearance by cytidine deaminase (CDA) present in the gut and liver.

A recent development combined DAC with cedazuridine (CDZ), an oral CDA inhibitor, in a fixed-dose combination tablet (ASTX727) to mimic the pharmacokinetics of IV DAC, as reported in Lancet Haematology 2019. To explore a similar approach with AZA, researchers investigated the possibility of enhancing the bioavailability of oral AZA with CDZ in a mouse tumor model.

The study involved measuring GI50 in AML cell lines treated with AZA, CDZ, or their combination. Despite cancer cell lines producing CDA, the levels are minimal compared to those in the gut and liver. Therefore, a systemic model of AML in immunodeficient mice was used, where mice were irradiated and injected with MOLM-13 AML cells. The mice were then randomly assigned to receive AZA via intraperitoneal (i.p.) injection, oral AZA, CDZ plus oral AZA, or CDZ alone. The treatments were administered daily for seven days.

The study found no significant difference in cell viability between AZA and the AZA/CDZ combination in vitro. However, in the xenograft model, i.p. AZA significantly reduced leukemic expansion in the bone marrow and spleen, while CDZ alone had no effect. Notably, oral AZA alone did not decrease AML expansion, but when combined with CDZ, it significantly reduced AML in both bone marrow and spleen. Importantly, the combination of CDZ and oral AZA was as effective as traditional i.p. AZA dosing in bone marrow and splenic tissue.

Survival analysis showed that mice treated with CDZ alone died within 21 days post-transplant, whereas those treated with i.p. AZA or oral AZA plus CDZ had a 50% extended survival, with no significant difference between the two treatment groups. H&E staining indicated no significant bone marrow toxicity, suggesting AZA's selective effect on transplanted MOLM-13 AML cells.

These findings support the potential of oral AZA combined with CDA-inhibitor CDZ as a viable alternative to traditional AZA treatment, providing a basis for the development of a fixed-dose combination therapy (ASTX030) for myeloid diseases. Clinical trials for ASTX030 are in the planning stages.