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Updated: Jun 4, 2026
Determination of Chemical Inhibitor Efficiency against Intracellular Toxoplasma Gondii Growth Using a Luciferase-Based Growth Assay
Published on: April 29, 2020
Lead Optimization of TgCDPK1 Inhibitors for the Treatment of Toxoplasmosis
Michael P Mannino1, Anusha Gokanapalle1, Shrushti Patil2
1Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110, United States.
Abstract:
Toxoplasma gondii is an important opportunistic pathogen that infects many individuals and threatens the health of those with compromised immunity. Current therapies are unable to eradicate chronic infections and pose risks of adverse reactions. Using X-ray structure-based drug design, we have developed a new series of biaryl-substituted pyrazolopyrimidine inhibitors of the essential parasite enzyme calcium-dependent protein kinase 1 (TgCDPK1). These inhibitors have excellent potency against the enzyme and in vitro antiparasitic activity. We further optimized the compounds for increased metabolic stability, lowered plasma protein binding, decreased efflux, and improved pharmacokinetics (PK). Several of the inhibitors had desirable PK with high oral bioavailability, low clearance, and extended half-life, leading to excellent compound exposure in the plasma and brain over a 24-h period. Three compounds were tested during acute infection in both immunocompetent and immunocompromised mice. We identified 16c as a promising preclinical candidate to treat toxoplasmosis.
Insights
Researchers developed novel pyrazolopyrimidine inhibitors targeting the Toxoplasma gondii enzyme TgCDPK1 to combat toxoplasmosis. Compound 16c shows promise as a preclinical candidate for treating this opportunistic infection.
Area of Science:
- Parasitology
- Medicinal Chemistry
- Drug Discovery
Background:
- Toxoplasma gondii is a significant opportunistic pathogen, particularly dangerous for immunocompromised individuals.
- Existing therapies for toxoplasmosis are limited, failing to eradicate chronic infections and carrying risks of adverse effects.
Purpose of the Study:
- To design and develop novel inhibitors targeting the essential parasite enzyme calcium-dependent protein kinase 1 (TgCDPK1).
- To optimize these inhibitors for improved metabolic stability, pharmacokinetic properties, and in vitro antiparasitic activity.
Main Methods:
- Utilized X-ray structure-based drug design to create biaryl-substituted pyrazolopyrimidine inhibitors.
- Conducted in vitro assays to assess enzyme inhibition and antiparasitic activity.
- Performed pharmacokinetic studies and in vivo testing in mouse models of acute toxoplasmosis.
Main Results:
- Developed potent TgCDPK1 inhibitors with significant in vitro antiparasitic activity.
- Optimized compounds demonstrated improved metabolic stability, reduced plasma protein binding, and favorable pharmacokinetic profiles, including high oral bioavailability and brain penetration.
- Compound 16c exhibited excellent exposure in plasma and brain over 24 hours and showed efficacy in mouse models.
Conclusions:
- Biaryl-substituted pyrazolopyrimidines are effective inhibitors of TgCDPK1.
- Compound 16c represents a promising preclinical candidate for the treatment of toxoplasmosis, offering improved drug-like properties and in vivo efficacy.
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