# Investigation of ATV-Based Heterobifunctional Degraders to Combat Growing HIV-1 PR Inhibitor Resistance

> **NIH NIH R21** · UNIVERSITY OF ALABAMA IN TUSCALOOSA · 2022 · $227,034

## Abstract

PROJECT SUMMARY/ABSTRACT
Heterobifunctional targeted protein degraders (TPDs) offer advantages over traditional occupancy-based
inhibitors including a unique catalytic mechanism of action (MOA), greater target selectivity, and a reduced
probability for resistance development. TPDs are known to effectively target not only cytosolic proteins, but also
nuclear and membrane-bound proteins. This therapeutic modality shows great promise for treating drug-resistant
cancers and autoimmune diseases but has seen only limited application in antiviral drug discovery. HIV-1
protease (PR) is essential for proteolytic cleavage of Gag and Gag-Pol polyproteins and, thus, virion maturation
and infectivity. Gag-Pol forms dynamic dimers at plasma membrane assembly/budding sites, allowing the
embedded precursor PR to dimerize as a prerequisite for auto-processing. We identified precursor PR/Gag-Pol
as a promising target for protease inhibitor (PI)-based TPDs. The widely used HIV-1 PI, Atazanavir (ATV), is
amenable to conjugation with linkers and ubiquitin E3 ligase recruiting ligands to serve as prototype HIV-1 TPDs.
Importantly, ATV inhibits activity of mature PR as well as autoprocessing of precursor PR/Gag-Pol during the
assembly and budding processes. The OBJECTIVE of this study is to show proof-of-concept that HIV-1 Gag-
Pol assembling on the inner leaflet of the plasma membrane can be targeted for aberrant ubiquitination,
degradation, and/or inhibition, thereby impairing HIV infectivity. Importantly, due to TPDs’ established MOA, even
low-affinity Gag-Pol/TPD interactions are likely to lead to impaired Gag-Pol function. Thus, we pose the
HYPOTHESIS that novel ATV-based TPDs will not only augment the inhibition of ATV-sensitive HIV-1 strains
compared to ATV, but also exhibit increased and broader biological activity against drug-resistant variants.
The objective of AIM 1 is to design and synthesize ATV-based TPDs built on state-of-the-art computational
methods and predictive physicochemical properties currently accepted for in vivo active TPDs. Our approach
will feature a modular TPD design to establish the appropriate ATV attachment point, E3 ligase recruiter, and
length and composition of linker required for HIV-1 Gag-Pol ubiquitination/proteasomal degradation. The goal
of AIM 2 is to provide proof-of-concept that ATV-TPDs exert superior activity versus ATV against wild type and
PI-resistant HIV-1 strains. We will systematically screen four series of novel ATV-TPD for activity in vitro, in
single-round infectivity, and in multi-round replication assays to identify the most promising ATV-TPD candidates.
The latter will be tested in complementary limited-scope mechanistic studies, including comparing ATV-TPDs
with analogs bearing inactive E3-ligase ligands, to probe if antiviral activity is consistent with the proposed MOA.
The IMPACT will be TPDs targeting HIV-1 Gag-Pol and precursor PR that limit infectivity and replication through
a mechanism distinct from oc...

## Key facts

- **NIH application ID:** 10484347
- **Project number:** 1R21AI170213-01
- **Recipient organization:** UNIVERSITY OF ALABAMA IN TUSCALOOSA
- **Principal Investigator:** CHRISTINA OCHSENBAUER
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $227,034
- **Award type:** 1
- **Project period:** 2022-08-04 → 2024-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10484347

## Citation

> US National Institutes of Health, RePORTER application 10484347, Investigation of ATV-Based Heterobifunctional Degraders to Combat Growing HIV-1 PR Inhibitor Resistance (1R21AI170213-01). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10484347. Licensed CC0.

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