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Cedazuridine (E7727) is a synthetic nucleoside analog derived from tetrahydrouridine (THU) and designed as a potent inhibitor of cytidine deaminase (CDA) with improved stability over THU. It is currently being developed in combination with hypomethylating agent decitabine (ASTX727) as an oral option for treatment of MDS and CMML. Concomitant administration of cedazuridine enhances oral bioavailability of decitabine and achieves therapeutic AUC exposures in the clinic at low doses of decitabine (similar to IV dose, in mg) that are well tolerated.
Nonclinical development of cedazuridine included full toxicological and DMPK evaluation. Cedazuridine is well tolerated in mice and monkeys (tox species) over 1-cycle of 7 days dosing, (followed by recovery), with NOAEL at 1000 mg/kg and 200 mg/kg, respectively. Subchronic studies of 13-weeks duration with multi-cycles (28 days/cycle with dosing on days 1-7) resulted in NOAEL of 100/300 mg/kg in mice (females/males) and 60 mg/kg in cynomolgus monkeys. The highest non-severely toxic dose (HNSTD) in multi-cycle study was 200 mg/kg/dose in monkeys. Target organs at the NOAEL were lymph nodes in mice and GI mucosa and bone marrow (RBC parameters) in monkeys. These dose levels offer a large safety margin over the clinical dose (and systemic exposures) used for cedazuridine (100 mg fixed dose, in combination with 35 mg decitabine). Cedazuridine in mouse in vivo micronucleus study was negative at up to 2000 mg/kg and was negative in in vitro Ames and chromosome aberration tests at concentrations that were not cytotoxic.
Co-administration with decitabine in mice and monkeys resulted in significant increase in systemic exposures compared with decitabine administered alone. Cedazuridine is metabolically stable in liver microsomes and hepatocytes, does not inhibit major human CYP enzymes, and is not a substrate and/or inhibitor of major human drug transporters. It does not accumulate in tissues and is excreted mainly renally. The main metabolite was its epimer, to which it partially converts in acidic environment in the stomach prior to absorption.
In summary, cedazuridine has been well characterized in nonclinical toxicology and DMPK studies and its nonclinical data profile supports late-stage clinical development.