In a 3-day replicon assay, the interaction between MK-5172 www.selleckchem.com/products/epz-6438.html and MK-8408 was demonstrated to be additive to synergistic with no evidence of antagonism. Colony formation assays showed that the combination of MK-5172 and MK-8408 suppressed
robustly the emergence of resistant colonies at low multiples of their EC90 values. A combination of 10X EC90 of each compound was sufficient to suppress resistant colony formation in Gts 1 and 3. The MK-5172/MK-8408 combination presented a higher genetic barrier to resistance and was more effective in suppressing resistant colony formation compared to combinations of MK-5172 and other NS5A compounds in development. Linked mutations from previously described RAVs at position 168 in NS3 and positions BGB324 clinical trial 30 and 31 (plus 28 and 93 to a lesser extent) in NS5A were required to elicit resistance. Conclusions: MK-5172 and MK-8408 are potent DAAs for HCV infection. The compounds are neither cross-resistant nor antagonistic
in their interactions. In combination, they suppress effectively the emergence of resistance by exerting a high genetic barrier in the difficult-to-treat HCV Gts. Disclosures: Frederick Lahser – Employment: Merck Stephanie Curry – Employment: Merck Patricia McMonagle – Employment: Merck and Co. Robert Chase – Employment: Merck, Inc Stuart Black – Employment: Merck Eric B. Ferrari – Employment: Merck Wensheng Yu – Employment: Merck Joseph Kozlowski – Employment: Merck Ernest Asante-Appiah – Employment: Merck The following people have nothing to disclose: Karin Bystol, Rong Liu, Ellen Xia, Ling Tong Background: Nucleotide analogs have emerged as an important component of interferon (IFN)-free combination therapies for the treatment of chronic hepatitis C (CHC) based on their potent activity and high barrier to
the generation of viral resistance. AL-335, a novel monophosphate prodrug of a uridine-based nucleotide analog, has been identified as a potent inhibitor of NS5B-directed HCV RNA replication in the cell based replicon system. In this study, inhibition of the HCV replicon by AL-335 was examined in pairwise combinations with other direct-acting antiviral agents (DAAs) either registered for the medchemexpress treatment of CHC or currently in clinical development. Methods: Studies were performed using a Huh-7 cell line expressing a Firefly luciferase-encoding HCV 1b subgenomic replicon. Compounds were added to cells in a checkerboard fashion and inhibition of HCV replication measured by luminescence. Data were analyzed using two drug interaction models; Isobologram analysis using the Loewe additivity model and the Bliss-Independence model using Pritchard’s MacSynergy II software. Results: In the HCV 1b replicon, AL-335 exhibited potent antiviral activity with an EC50 of 75 nM.