Background:
Tenofovir (TFV) prodrugs [TFV disoproxil-/TFV alafenamide- fumarates (TDF/TAF)] are recommended daily oral treatments for chronic hepatitis B (HBV) infection. Given the growing popularity of long-acting (LA) therapies for treatment of chronic viral infections, an ever increasing number of potent medicines will come available. One, developed in our own laboratories, is a lipophilic ProTide of TFV called M1TFV that exhibited sustained suppression of HBV DNA in mouse models of human disease [Sci. Adv.8,eade9582(2022)]. However, like other ProTide prodrugs, the reported chemical synthesis of M1TFV necessitates costly chiral catalysts and time-consuming separation of the Sp and Rp diastereomers generated at the phosphorous atom. To overcome these limitations we developed alternative amino acid free hydrophobic and lipophilic double ester crystalline TFV prodrugs. Two nanoformulated diester candidates elicited enhanced and sustained HBV DNA suppression in transgenic C57BL/6 Tg05 mice compared to limited efficacy for TAF ProTide.
Methods:
Three amino acid free lipophilic double ester prodrugs of TFV were synthesized through a non-catalytic esterification of TFV monophenyl ester with either an aryl substituted lipid (M4TFV), octadecanol (M5TFV) or docosanol (M6TFV). The synthesized prodrugs were characterized and nano-formulated using biocompatible surfactants to produce stable aqueous solid drug nanosuspenisons (NM4TFV, NM5TFV and NM6TFV). Control treatment consisted of TFV alafenamide solid drug nanosuspensions (NTAF). Additional controls were infected, untreated animals. Antiviral efficacy was tested in HBV Tg05 mice. Drug formulations were administered as single intramuscular injections at 168 mg/kg TFV equivalents. HBV DNA viral load in blood was measured every other week.
Results:
Three diester prodrugs of TFV were synthesized in high chemical yields and formed predominantly one of the two stereoisomers at the phosphorous chiral center. These prodrugs were crystalline and compatible with scalable formulation approaches for producing surfactant stabilized aqueos nanosuspenisons. Notably, a single IM injection of NM5TFV or NM6TFV diester prodrug nanosuspensions in Tg05 mice demonstrated enhanced and sustained efficacy compared to limited anti-HBV activity for TAF ProTide or arylated NM4TFV diester prodrug (Figure 1).
Conclusions:
NM5TFV and NM6TFV diester prodrug formulations produced sustained monthslong suppression of HBV DNA in Tg05 mice without recorded adverse events.
