Enhancing the Antiviral Efficacy of RNA-Dependent RNA Polymerase Inhibition by Combination with Modulators of Pyrimidine Metabolism

Qi Liu; Amita Gupta; Ayse Okesli-Armlovich; Wenjie Qiao; Curt R. Fischer; Mark Smith; Jan E. Carette; Michael C. Bassik; Chaitan Khosla

To test whether a combination therapy approach could improve the efficacy of R1479, we treated cells with R1479 in combination with GSK983 and CPU. As expected, R1479 showed dosedependent inhibition of dengue virus replication with an EC50 ~32 µM ( Figure S6A ). Inhibition of either de novo or salvage pyrimidine biosynthesis alone did not potentiate the antiviral activity of R1479 or cause additional cytotoxicity ( Figure S6A ). In contrast, inhibition of both the de novo and salvage pathways markedly enhanced the potency of R1479 ( Figure 6A ). In the presence of 250 µM CPU, the EC50 of R1479 was lowered to ~12 µM. Notably, such a 3-component regimen had minimal impact on the cytotoxicity profile of R1479 ( Figure 6B ). Regarding other analogues, 5-F-CPU-GSK983 was able to slightly potentiate the antiviral activity of R1479 whereas 5'-F-CPU appeared to actually decrease antiviral efficacy of R1479 ( Figure S6B and S6C).