# Small molecule inhibitors and degraders of picornavirus 2A proteases as direct-acting antivirals

> **NIH NIH U19** · STANFORD UNIVERSITY · 2022 · $3,728,844

## Abstract

ABSTRACT – Project 2: Small molecule inhibitors and degraders of picornavirus 2A proteases
Traditional direct-acting antivirals (DAAs) target a viral protein by occupying an enzymatic pocket; dissociation
of the drug leads to immediate regain of function. Consequently, most antivirals must have high-affinity,
stoichiometric binding to be effective, and point mutations that reduce affinity can rapidly give rise to antiviral
resistance. The established method to prevent resistance is the use of combinations of direct-acting antivirals
that act via independent targets and mechanisms. In this project, we will pursue two innovative approaches to
develop DAAs targeting the enterovirus (EV) 2A protease, a viral protein with at least two essential functions: (1)
it catalyzes a required cleavage of the viral polyprotein and (2) it mediates a protein-protein interaction that is
essential for replication. First, we will pursue targeted protein degradation (TPD) against 2A as an antiviral
strategy. TPD is a new paradigm in drug development in which a small molecule that binds the target of interest
is conjugated to an E3 ligase ligand resulting in protein degradation. This approach allows a wider range of
protein targets because its event-driven pharmacology does not require stoichiometric inhibition of the viral
protein and because the affinity required for effective protein degradation is generally lower. We previously
developed the first small molecule antiviral degrader by coupling telaprevir, an FDA-approved inhibitor of the
hepatitis C virus NS3-4A protease, to a ligand of the CRBNCRL E3 ubiquitin ligase. The resulting NS3 degraders
inhibit HCV in vitro, including point mutants that are known to be telaprevir-resistant. Since telaprevir was recently
shown to have broad-spectrum activity against enterovirus 2A proteins, we will build upon our prior work to
develop telaprevir-based degraders of 2A that remove the protein from the cell and ablate all of 2A’s functions.
Second, we will perform high-throughput screens for DAAs that bind to 2A and inhibit its function as a mediator
of essential protein-protein interactions. Compounds discovered in these screens will be validated as 2A ligands
and tested for antiviral activity, with validated ligands advanced as leads for degrader development and
compounds with antiviral activity advanced as lead compounds for development of DAAs. We will also undertake
screening of DNA-encoded libraries to more broadly sample chemical space and to discover additional chemical
matter suitable for inhibitor and degrader development. We will also determine if DAAs targeting the active site
(Aim 1) and the 2A interacting site (Aim 2) can be combined for superior efficacy and resistance profile. This
work leverages the innovative discoveries made by our labs in the areas of TPD and 2A biology along with the
collective expertise of our groups and the AViDD in virology, medicinal chemistry, chemical biology biochemistry,
structural...

## Key facts

- **NIH application ID:** 10514272
- **Project number:** 1U19AI171421-01
- **Recipient organization:** STANFORD UNIVERSITY
- **Principal Investigator:** Priscilla Li-ning Yang
- **Activity code:** U19 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $3,728,844
- **Award type:** 1
- **Project period:** 2022-05-16 → 2026-10-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10514272

## Citation

> US National Institutes of Health, RePORTER application 10514272, Small molecule inhibitors and degraders of picornavirus 2A proteases as direct-acting antivirals (1U19AI171421-01). Retrieved via AI Analytics 2026-05-27 from https://api.ai-analytics.org/grant/nih/10514272. Licensed CC0.

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