HIT to lead drug development for acanthamoeba keratitis

The National Institute of Allergy and Infectious Diseases awarded Purdue University $248,814 on September 1, 2026, under the Allergy and Infectious Diseases Research program (CFDA 93.855) for hit-to-lead drug development targeting Acanthamoeba keratitis.

Purdue will optimize a novel chemical class of benzoxazepinoindazole inhibitors to develop potent drug candidates for treating Acanthamoeba keratitis, a difficult-to-resolve eye infection caused by free-living amoeba exposure during improper contact lens use. Current treatment involves non-specific chemotherapy lasting one to six years and multiple corneal transplantations; approximately six percent of patients require eye removal. The project applies structure-activity and structure-property relationship analysis to improve inhibitory activity against Acanthamoeba species, enhance pathogen selectivity, and optimize in vivo ocular pharmacokinetics. Purdue's approach includes bioactive-guided susceptibility screening against an Acanthamoeba keratitis clinical isolate, synthesis of novel compounds, and systematic investigation to drive medicinal chemistry optimization. The team integrates expertise in drug discovery against pathogenic amoebae, infectious disease chemotherapeutics optimization, translational pharmacology, and metabolite profiling.

Performance runs from September 1, 2026, through August 31, 2028, at Purdue's West Lafayette, Indiana location. This is a Project Grant assistance type.

Abstract

Acanthamoeba is a pathogenic free-living amoeba which causes ocular keratitis, a difficult to resolve eye infection, that leads to visual impairment and blindness from improper contact lens disinfecting practices or incorrect lens wearing (showering, swimming, bathing or incorrect storage of lenses). Acanthamoeba keratitis "AK" affects mainly healthy, immunocompetent, contact lens wearers who ~85% have had some sort of water exposure event. The major unmet medical need is the development of potent drugs to be added into the current, unoptimized, multi-drug cocktail to resolve AK. Non-specific chemotherapy can last 1-6 years and requires the need for multiple corneal transplantations (KERATOPLASTY) to resolve these infections. In ~6% of patients, enucleation of the eye is required. The goal of this proposal is to develop and optimize newly identified drug candidates with better inhibitory activity than the currently recommended disinfectants against acanthamoeba species. We propose optimizing a novel chemical class of benzoxazepinoindazole inhibitors with a focus on structure-activity (SAR) and structure-property relationships (SPR) to drive HIT-to-lead drug discovery, improving pathogen selectivity and in vivo ocular pharmacokinetics. To achieve this, we have brought together a team of complementary expertise in drug discovery and development against pathogenic amoebae (DR. Rice), optimizing chemotherapeutics for infectious diseases (DR. Ferrins), purdue university translational pharmacology core (DR. Gregory knipp) and purdue's metabolite profiling facility core (DR. Bruce cooper). For our first aim, we will use bioactive guided susceptibility screening against an AK clinical isolate, acanthamoeba castellanii (atcc 50370), to drive our HIT-to-lead medicinal chemistry optimization on the benzoxazepinoindazole chemical series. Through synthesis of novel compounds, a thorough investigation of the SAR and SPR will be performed, leading to chemical matter with improved potency and more 'drug-like' properties. We will phenotypically assess selectivity, time-kill kinetics (≤24 HR inhibition), cytopathogenicity (≥75% restriction), and cysticidal effects of compounds which display HIT activity (EC50S ≤5 ΜM). Lead-like compounds will be further assessed for their activity against a panel of acanthamoeba clinical isolates ensuring we can kill multiple genotypes and strains with minimal biological variation (≤4-fold between strains). This data will be concurrently used to down select the best drug-like candidates from our proposed target candidate profile (TCP) and go/no-go criteria, to be assessed for lead optimization. Our second aim will focus on evaluating in vitro tier 1 & 2 adme (stability in hepatocytes, aqueous solubility, permeability, and logd), drug stability, and in vivo ocular PK studies. Significance in this project is driven by the first description of potent benzoxazepinoindazole inhibitors (first-in- class) specifically developed through the first phenotypic optimization program for AK. By the end of this project, we will have optimized and identified the best compounds meeting our TCP by having lead-like biological properties for future MOA elucidation and in vivo proof-of-concept efficacy against AK infected animal models.