Structural Studies of Inhibitors with Clinically Relevant Influenza Endonuclease Variants
Alysia J Kohlbrand1, Ryjul W Stokes1, Banumathi Sankaran2
1Department of Chemistry and Biochemistry, University of California, La Jolla, California 92093, United States.
Abstract:
Vital to the treatment of influenza is the use of antivirals such as Oseltamivir (Tamiflu) and Zanamivir (Relenza); however, antiviral resistance is becoming an increasing problem for these therapeutics. The RNA-dependent RNA polymerase acidic N-terminal (PAN) endonuclease, a critical component of influenza viral replication machinery, is an antiviral target that was recently validated with the approval of Baloxavir Marboxil (BXM). Despite its clinical success, BXM has demonstrated susceptibility to resistance mutations, specifically the I38T, E23K, and A36 V mutants of PAN. To better understand the effects of these mutations on BXM resistance and improve the design of more robust therapeutics, this study examines key differences in protein-inhibitor interactions with two inhibitors and the I38T, E23K, and A36 V mutants. Differences in inhibitor binding were evaluated by measuring changes in binding to PAN using two biophysical methods. The binding mode of two distinct inhibitors was determined crystallographically with both wild-type and mutant forms of PAN. Collectively, these studies give some insight into the mechanism of antiviral resistance of these mutants.
Insights
Baloxavir Marboxil (BXM) resistance in influenza is linked to PAN mutations. This study reveals how these mutations alter protein-inhibitor interactions, offering insights for developing new antiviral drugs.
Area of Science:
- Virology
- Biochemistry
- Drug Discovery
Background:
- Antiviral resistance to influenza therapeutics like Oseltamivir and Zanamivir is a growing concern.
- Baloxavir Marboxil (BXM) targets the influenza PAN endonuclease, a key viral replication enzyme, but resistance mutations have emerged.
Purpose of the Study:
- To investigate the impact of PAN resistance mutations (I38T, E23K, A36V) on Baloxavir Marboxil (BXM) binding.
- To understand the molecular mechanisms underlying BXM resistance for improved antiviral drug design.
Main Methods:
- Utilized two biophysical methods to measure changes in inhibitor binding to wild-type and mutant PAN.
- Determined the crystallographic binding modes of two distinct inhibitors with both wild-type and mutant PAN.
Main Results:
- Identified key differences in protein-inhibitor interactions caused by PAN resistance mutations.
- Characterized the structural basis for reduced BXM efficacy against specific PAN mutants.
Conclusions:
- The study provides crucial insights into the mechanisms of antiviral resistance mediated by PAN mutations.
- Findings can inform the development of next-generation influenza antivirals that overcome existing resistance pathways.
