One-pot, multicomponent synthesis of 2,3-disubstituted quinazolin-ones with potent and selective activity against Toxoplasma gondii.

The discovery of two quinazolinones with selective, single-digit micromolar activity (IC50 = 6-7 µM) against the tachyzoites of the apicomplexan parasite Toxoplasma gondii is reported. These potent and selective third generation derivatives contain a benzyloxybenzyl substituent at C2 and a bulky aliphatic moiety at N3. Here we show that these quinazolinones inhibit T. gondii tachyzoite replication in an established infection, but do not significantly affect host cell invasion by the tachyzoites.

Synthesis and biological evaluation of anti-Toxoplasma gondii activity of a novel scaffold of thiazolidinone derivatives.

We designed and synthesised novel N-substituted 1,3-thiazolidin-4-one derivatives for the evaluation of their anti-Toxoplasma gondii efficacy. This scaffold was functionalised both at the N1-hydrazine portion with three structurally different moieties and at the lactam nitrogen with substituted benzyl groups selected on the basis of our previous structure-activity relationships studies. Using three different assay methods, the compounds were assessed in vitro to determine both the levels of efficacy against the tachyzoites of T. gondii (IC50 = 5-148 µM), as well as any evidence of cytotoxicity towards human host cells (TD50 = 68 to ≥320 µM). Results revealed that ferrocene-based thiazolidinones can possess potent anti-tachyzoite activity (TI =2-64).

Enol ethers as carbonyl surrogates in a modification of the Povarov synthesis of 3-aryl quinolines and their anti-Toxoplasma activity.

A novel method for the preparation of 2-carboxyl-3-aryl quinoline derivatives from anilines, ethyl glyoxalate and enol ethers as phenylacetaldehyde surrogates is reported. The three-component coupling reaction occurs rapidly under mild conditions in dichloromethane catalysed by TFA. The method allows a more direct access to 3-aryl quinolines, sidestepping issues encountered with phenylacetaldehyde derivatives. This chemistry was used to prepare quinolines with 3-diarylether functionality that showed low micromolar efficacy (IC50 range: 5-26 µM) against in vitro Toxoplasma gondii coupled with little or no cytotoxicity (TD50≥ 320 µM) towards the host cells.

Synthesis of the cyanobacterial metabolite nostodione A, structural studies and potent antiparasitic activity against Toxoplasma gondii.

A total synthesis of the cyanobacterial natural product nostodione A is reported involving a convergent, diversity-oriented route, enabling the assembly of a mini-library of structural analogues. The first single crystal X-ray structural determination on a member of this series is reported along with SAR studies identifying potent inhibitors of invasion and replication of the parasitic protozoan Toxoplasma gondii.

Endochin-like quinolones are highly efficacious against acute and latent experimental toxoplasmosis.

Toxoplasma gondii is a widely distributed protozoan pathogen that causes devastating ocular and central nervous system disease. We show that the endochin-like quinolone (ELQ) class of compounds contains extremely potent inhibitors of T. gondii growth in vitro and is effective against acute and latent toxoplasmosis in mice. We screened 50 ELQs against T. gondii and selected two lead compounds, ELQ-271 and ELQ-316, for evaluation. ELQ-271 and ELQ-316, have in vitro IC(50) values of 0.1 nM and 0.007 nM, respectively. ELQ-271 and ELQ-316 have ED(50) values of 0.14 mg/kg and 0.08 mg/kg when administered orally to mice with acute toxoplasmosis. Moreover, ELQ-271 and ELQ-316 are highly active against the cyst form of T. gondii in mice at low doses, reducing cyst burden by 76-88% after 16 d of treatment. To investigate the ELQ mechanism of action against T. gondii, we demonstrate that endochin and ELQ-271 inhibit cytochrome c reduction by the T. gondii cytochrome bc(1) complex at 8 nM and 31 nM, respectively. We also show that ELQ-271 inhibits the Saccharomyces cerevisiae cytochrome bc(1) complex, and an M221Q amino acid substitution in the Q(i) site of the protein leads to >100-fold resistance. We conclude that ELQ-271 and ELQ-316 are orally bioavailable drugs that are effective against acute and latent toxoplasmosis, likely acting as inhibitors of the Q(i) site of the T. gondii cytochrome bc(1) complex.

Synthesis and anti-toxoplasmosis activity of 4-arylquinoline-2-carboxylate derivatives.

A one-step synthesis of 4-arylquinoline-2-carboxylates along with their antiprotozoal activity against the pathogenic parasite Toxoplasma gondii is reported. Mechanistic insights into the role of Lewis acid (silver triflate) versus Bronsted acid (triflic acid) catalysis are revealed clarifying aspects of the mechanism of the quinoline synthesis.

Artemisinin derivatives inhibit Toxoplasma gondii in vitro at multiple steps in the lytic cycle.

OBJECTIVES: We sought to improve upon the usefulness of artemisinins as anti-Toxoplasma agents by synthesizing new unsaturated, carba derivatives and then testing them for in vitro efficacy against three steps of the lytic cycle of Toxoplasma gondii tachyzoites. METHODS: Novel derivatives of ART were synthesized and then tested for in vitro antiparasitic activity using T. gondii tachyzoites constitutively expressing beta-galactosidase and human fibroblast host cells. Compounds were evaluated for parasite growth inhibition and cytotoxicity, inhibition of replication and inhibition of parasite invasion of host cells. RESULTS: Five of the seven new derivatives, 3a-c, 3e and 3f, effectively inhibited T. gondii growth (IC50=1.0-4.4 microM); however, only three of these proved to be relatively non-cytotoxic (TD50>or=200 microM). The same five derivatives also inhibited tachyzoite replication, and attachment to and invasion of host cells as effectively as or better than the parent compound ART. In addition, one of the derivatives incapable of inhibiting growth, deoxy-3a, was found to inhibit parasite invasion. CONCLUSIONS: These new artemisinin derivatives have the ability to inhibit multiple steps of T. gondii's lytic cycle. Synthetic unsaturated, carba derivatives of ART have potential as therapeutic agents for the prevention and treatment of toxoplasmosis in humans.

Infection and characterization of Toxoplasma gondii in human induced neurons from patients with brain disorders and healthy controls.

Toxoplasma gondii is a protozoan parasite capable of establishing persistent infection within the brain. Serological studies in humans have linked exposure to Toxoplasma to neuropsychiatric disorders. However, serological studies have not elucidated the related molecular mechanisms within neuronal cells. To address this question, we used human induced neuronal cells derived from peripheral fibroblasts of healthy individuals and patients with genetically-defined brain disorders (i.e. childhood-onset schizophrenia with disease-associated copy number variations). Parasite infection was characterized by differential detection of tachyzoites and tissue cysts in induced neuronal cells. This approach may aid study of molecular mechanisms underlying individual predisposition to Toxoplasma infection linked to neuropathology of brain disorders.

Design, synthesis and biological characterization of thiazolidin-4-one derivatives as promising inhibitors of Toxoplasma gondii.

We designed and synthesized a large number of novel thiazolidin-4-one derivatives for the evaluation of their anti-Toxoplasma gondii activity. This scaffold was functionalized at the N1-hydrazine portion with aliphatic, cycloaliphatic and (hetero)aromatic moieties. Then, a benzyl pendant was introduced at the lactamic NH of the core nucleus to evaluate the influence of this chemical modification on biological activity. The compounds were subjected to several in vitro assays to assess their anti-parasitic efficacy, cytotoxicity on fibroblasts, inhibition of tachyzoite invasion/attachment and replication after treatment. Results showed that fourteen of these thiazole-based compounds compare favorably to control compound trimethoprim in terms of parasite growth inhibition.

Thiazole, oxadiazole, and carboxamide derivatives of artemisinin are highly selective and potent inhibitors of Toxoplasma gondii.

We have prepared 23 new dehydroartemisinin (DART) trioxane derivatives (11 thiazoles, 2 oxadiazoles, and 10 carboxamides) and have screened them for in vitro activity in the Toxoplasma lytic cycle. Fifteen (65%) of the derivatives were noncytotoxic to host cells (TD(50) > or = 320 microM). Eight thiazole derivatives and two carboxamide derivatives displayed effective inhibition of Toxoplasma growth (IC(50) = 0.25-0.42 microM), comparable in potency to artemether (IC(50) = 0.31 microM) and >100 times more inhibitory than the currently employed front-line drug trimethoprim (IC(50) = 46 microM). The thiazoles as a group were more effective than the other derivatives at inhibiting growth of extracellular as well as intracellular parasites. Unexpectedly, two thiazole trioxanes (5 and 6) were parasiticidal; both inhibited parasite replication irreversibly after parasite exposure to 10 microM of drug for 24 h, whereas the standard trioxane drugs artemisinin and artemether were not parasiticidal. Some of the new derivatives of artemisinin described here represent effective anti-Toxoplasma trioxanes as well as molecular probes for elucidating the mechanism of action of the DART class of artemisinin derivatives.

Synthesis and evaluation of 4-acyl-2-thiazolylhydrazone derivatives for anti-Toxoplasma efficacy in vitro.

A new series of 4-acyl-2-thiazolylhydrazone derivatives was synthesized and screened for its in vitro activity against Toxoplasma gondii. We evaluated parasite growth inhibition and cytotoxicity, inhibition of replication, and inhibition of parasite invasion of host cells. The biological results indicated that some substances had an antiproliferative effect against intracellular T. gondii tachyzoites cultivated in vitro.