RNAi-based small molecule repositioning reveals clinically approved urea-based kinase inhibitors as broadly active antivirals.

Influenza viruses (IVs) tend to rapidly develop resistance to virus-directed vaccines and common antivirals targeting pathogen determinants, but novel host-directed approaches might preclude resistance development. To identify the most promising cellular targets for a host-directed approach against influenza, we performed a comparative small interfering RNA (siRNA) loss-of-function screen of IV replication in A549 cells. Analysis of four different IV strains including a highly pathogenic avian H5N1 strain, an influenza B virus (IBV) and two human influenza A viruses (IAVs) revealed 133 genes required by all four IV strains. According to gene enrichment analyses, these strain-independent host genes were particularly enriched for nucleocytoplasmic trafficking. In addition, 360 strain-specific genes were identified with distinct patterns of usage for IAVs versus IBV and human versus avian IVs. The strain-independent host genes served to define 43 experimental and otherwise clinically approved drugs, targeting reportedly fourteen of the encoded host factors. Amongst the approved drugs, the urea-based kinase inhibitors (UBKIs) regorafenib and sorafenib exhibited a superior therapeutic window of high IV antiviral activity and low cytotoxicity. Both UBKIs appeared to block a cell signaling pathway involved in IV replication after internalization, yet prior to vRNP uncoating. Interestingly, both compounds were active also against unrelated viruses including cowpox virus (CPXV), hantavirus (HTV), herpes simplex virus 1 (HSV1) and vesicular stomatitis virus (VSV) and showed antiviral efficacy in human primary respiratory cells. An in vitro resistance development analysis for regorafenib failed to detect IV resistance development against this drug. Taken together, the otherwise clinically approved UBKIs regorafenib and sorafenib possess high and broad-spectrum antiviral activity along with substantial robustness against resistance development and thus constitute attractive host-directed drug candidates against a range of viral infections including influenza.

Combined Human Genome-wide RNAi and Metabolite Analyses Identify IMPDH as a Host-Directed Target against Chlamydia Infection.

Chlamydia trachomatis (Ctr) accounts for >130 million human infections annually. Since chronic Ctr infections are extremely difficult to treat, there is an urgent need for more effective therapeutics. As an obligate intracellular bacterium, Ctr strictly depends on the functional contribution of the host cell. Here, we combined a human genome-wide RNA interference screen with metabolic profiling to obtain detailed understanding of changes in the infected cell and identify druggable pathways essential for Ctr growth. We demonstrate that Ctr shifts the host metabolism toward aerobic glycolysis, consistent with increased biomass requirement. We identify key regulator complexes of glucose and nucleotide metabolism that govern Ctr infection processes. Pharmacological targeting of inosine-5'-monophosphate dehydrogenase (IMPDH), the rate-limiting enzyme in guanine nucleotide biosynthesis, efficiently inhibits Ctr growth both in vitro and in vivo. These results highlight the potency of genome-scale functional screening for the discovery of drug targets against bacterial infections.