# Type 3 secretion system inhibitors to treat Pseudomonas aeruginosa keratitis

> **NIH NIH R43** · MICROBIOTIX, INC · 2022 · $300,156

## Abstract

Contact lens-associated bacterial keratitis is a serious infection of the eye that can result in blindness if treatment
is not effective. The opportunistic Gram-negative pathogen Pseudomonas aeruginosa is the most common
pathogen associated with contact lens use, and multi-drug resistant strains are increasing in prevalence. P.
aeruginosa forms biofilms on the corneal epithelium, resulting in increased resistance to antibiotics and killing
by neutrophils, further complicating the treatment of these infections. Most clinical isolates from these infections
are cytotoxic strains that express ExoU, a potent cytotoxin that is injected into host cells by the type 3 secretion
system (T3SS), which is associated with increased virulence, antibiotic resistance, and greater morbidity.
Clearly, novel approaches to treating these infections are needed. The T3SS of P. aeruginosa is a virulence
factor that is essential for this organism to establish infection in the eye. The overall goal of this proposal is to
develop a novel topical therapy for the treatment of contact lens-associated keratitis that targets the T3SS of P.
aeruginosa. In an ongoing program at Microbiotix (MBX), we discovered and chemically optimized a novel
phenoxyacetamide (PhA) chemical series of potent inhibitors of the T3SS of P. aeruginosa, resulting in the
zwitterionic (ZW) analog sub-series of PhAs with excellent in vitro potency and ADM E properties. Several ZW
analogs were efficacious in a murine non-neutropenic pneumonia model with P. aeruginosa infection consistent
with their efficacy in in vitro assays and in murine models of infection. Our strategy for developing novel
treatments for P. aeruginosa keratitis is to evaluate a select set of these ZW PhA T3SS inhibitors using in vitro
and in vivo assays designed to identify a lead candidate suitable for further development as a topical adjunctive
therapy to anti-pseudomonal antibiotics for P. aeruginosa keratitis. In this Phase I proposal, we will prioritize
members of a library of ZW analogs for T3SS inhibitory activity and cytotoxicity using a panel of in vitro cellbased
assays and keratitis clinical isolates with human corneal epithelial cell lines. Based on the results of these
studies, we will identify up to 6 analogs for evaluation of tolerability and efficacy in a murine P. aeruginosa
keratitis model as an adjunctive therapy with an ophthalmic antibiotic, with the goal of selecting a lead candidate
that is suitable for further development in a follow-on Phase II proposal. The Phase 11 research will comprise
lead optimization for an ophthalmic indication, evaluation of ophthalmic antibiotic combinations, formulation, and
pre-clinical studies that are required for an IND application to the FDA.
We will accomplish the goals of Phase I by completing the following Specific Aims: Aim 1. Prioritize select PhA
T3SS inhibitors using in vitro assays relevant to ophthalmic infection. Aim 2. Identify a lead candidate based
on in vivo effica...

## Key facts

- **NIH application ID:** 10484345
- **Project number:** 1R43EY033246-01A1
- **Recipient organization:** MICROBIOTIX, INC
- **Principal Investigator:** TIMOTHY J. OPPERMAN
- **Activity code:** R43 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $300,156
- **Award type:** 1
- **Project period:** 2022-07-01 → 2023-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10484345

## Citation

> US National Institutes of Health, RePORTER application 10484345, Type 3 secretion system inhibitors to treat Pseudomonas aeruginosa keratitis (1R43EY033246-01A1). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10484345. Licensed CC0.

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