BioCryst has successfully completed in vitro and in vivo studies in which BCX5191 exhibited potent and selective pan-genotypic antiviral activity against the hepatitis C polymerase enzyme. BCX5191 showed no inhibition of human RNA polymerase and no evidence of toxicity from standard in vitro screens.
Human liver cells rapidly and efficiently convert BCX5191 into its active triphosphate form. BCX5191 does not require prodrug technology to achieve bioavailability. BCX5191 inhibits the viral RNA polymerase enzyme across genotypes 1-4 at sub-micromolar concentrations (0.05-0.36 µM) and is active in replicon cell assays for genotypes 1a and 1b.
In preclinical models, BCX5191 demonstrates high oral bioavailability, and the drug is actively transported into the liver. Following a single oral dose in rats, liver BCX5191 triphosphate levels exceed the IC50 values for genotypes 1-4 through 24 hours. At Cmax, the drug triphosphate level is more than 100 times the IC50. This pharmacokinetic profile is expected to support once-daily dosing in clinical studies.
“BCX5191 has met stringent preclinical criteria to advance to IND-enabling studies. We expect this program to be ready to file for first-in-human studies during the fourth quarter of 2012,” said Dr. William P. Sheridan, Senior Vice President & Chief Medical Officer of BioCryst Pharmaceuticals. “Based on our internal comparative preclinical studies of BCX5191 with the most advanced nucleotide analog in clinical development, GS-7977, we believe BCX5191 has the potential to be the backbone of best-in-class oral treatment regimens for hepatitis C patients.”
Additional BCX5191 non-clinical experiments are ongoing or planned, including Good Laboratory Practices (GLP) non-clinical safety studies and in vitro evaluation of BCX5191 in combination with ribavirin.