Derivatives of a benzoquinone acyl hydrazone with activity against Toxoplasma gondii

TZD-Based Hybrid Molecules Act as Dual Anti-Mycobacterium tuberculosis and Anti-Toxoplasma gondii Agents

Two distinct intracellular pathogens, namely Mycobacterium tuberculosis (Mtb) and Toxoplasma gondii (Tg), cause major public health problems worldwide. In addition, serious and challenging health problems of co-infections of Tg with Mtb have been recorded, especially in developing countries. Due to this fact, as well as the frequent cases of resistance to the current drugs, novel anti-infectious therapeutics, especially those with dual (anti-Tg and anti-Mtb) modes of action, are needed. To address this issue, we explored the anti-Tg potential of thiazolidinedione-based (TZD-based) hybrid molecules with proven anti-Mtb potency. Several TZD hybrids with pyridine-4-carbohydrazone (PCH) or thiosemicarbazone (TSC) structural scaffolds were more effective and more selective than sulfadiazine (SDZ) and trimethoprim (TRI). Furthermore, all of these molecules were more selective than pyrimethamine (PYR). Further studies for the most potent TZD-TSC hybrids 7, 8 and 10 and TZD-PCH hybrid molecule 2 proved that these compounds are non-cytotoxic, non-genotoxic and non-hemolytic. Moreover, they could cross the blood-brain barrier (BBB), which is a critical factor linked with ideal anti-Tg drug development. Finally, since a possible link between Tg infection and the risk of glioblastoma has recently been reported, the cytotoxic potential of TZD hybrids against human glioblastoma cells was also evaluated. TZD-PCH hybrid molecule 2 was found to be the most effective, with an IC50 of 19.36 ± 1.13 µg/mL against T98G cells.

In vitro anti-Toxoplasma gondii efficacy of synthesised benzyltriazole derivatives

Toxoplasma gondii, an obligate intracellular parasite, is the aetiological agent of toxoplasmosis, a disease that affects approximately 25% – 30% of the world’s population. At present, no safe and effective vaccine exists for the prevention of toxoplasmosis. Current treatment options for toxoplasmosis are active only against tachyzoites and may also cause bone marrow toxicity. To contribute to the global search for novel agents for the treatment of toxoplasmosis, we herein report the in vitro activities of previously synthesised benzyltriazole derivatives. The effects of these compounds against T. gondii in vitro were evaluated by using a expressing green fluorescent protein (GFP) type I strain parasite (RH-GFP) and a type II cyst-forming strain of parasite (PruΔku80Δhxgprt). The frontline antitubercular drug isoniazid, designated as Frans J. Smit -isoniazid (FJS-INH), was also included in the screening as a preliminary test in view of future repurposing of this agent. Of the compounds screened, FJS-302, FJS-303, FJS-403 and FJS-INH demonstrated > 80% parasite growth inhibition with IC₅₀ values of 5.6 µg/mL, 6.8 µg/µL, 7.0 µg/mL and 19.8 µg/mL, respectively. FJS-302, FJS-303 and FJS-403 inhibited parasite invasion and replication, whereas, sulphadiazine (SFZ), the positive control, was only effective against parasite replication. In addition, SFZ induced bradyzoite differentiation in vitro, whilst FJS-302, FJS-303 and FJS-403 did not increase the bradyzoite number. These results indicate that FJS-302, FJS-303 and FJS-403 have the potential to act as a viable source of antiparasitic therapeutic agents.

In Vitro Selection Implicates ROP1 as a Resistance Gene for an Experimental Therapeutic Benzoquinone Acyl Hydrazone in Toxoplasma gondii

Toxoplasma gondii is a globally distributed apicomplexan parasite and the causative agent of toxoplasmosis in humans. While pharmaceuticals exist to combat acute infection, they can produce serious adverse reactions, demonstrating a need for enhanced therapies. KG8 is a benzoquinone acyl hydrazone chemotype identified from a previous chemical screen for which we previously showed in vitro and in vivo efficacy against T. gondii However, the genetic target and mechanism of action of KG8 remain unknown. To investigate potential targets, we generated resistant T. gondii lines by chemical mutagenesis followed by in vitro selection. Whole-genome sequencing of resistant clones revealed a P207S mutation in the gene encoding rhoptry organelle protein 1 (ROP1) in addition to two lesser resistance-conferring mutations in the genes for rhoptry organelle protein 8 (ROP8) and a putative ADP/ATP carrier protein (TGGT1_237700). Expressing ROP1^P207S in parental parasites was sufficient to confer significant (10.3-fold increased half-maximal effective concentration [EC₅₀]) KG8 resistance. After generating a library of mutants carrying hypermutated rop1 alleles followed by KG8 pressure, we sequenced the most resistant clonal isolate (>16.9-fold increased EC₅₀) and found independent recapitulation of the P207S mutation, along with three additional mutations in the same region. We also demonstrate that a rop1 knockout strain is insensitive to KG8. These data implicate ROP1 as a putative resistance gene of KG8. This work further identifies a compound that can be used in future studies to better understand ROP1 function and highlights this novel chemotype as a potential scaffold for the development of improved T. gondii therapeutics.

Activity of diphenyl ether benzyl amines against Human African Trypanosomiasis

Insect-borne parasite Trypanosoma brucei plagues humans and other animals, eliciting the disease Human African trypanosomiasis, also known as African sleeping sickness. This disease poses the biggest threat to the people in Sub-Saharan Africa. Given the high toxicity and difficulties with administration of currently available drugs, a novel treatment is needed. Building on known Human African trypanosomiasis structure-activity relationship (SAR), we now describe a number of functionally simple diphenyl ether analogs which give low micromolar activity (IC₅₀ = 0.16-0.96 μM) against T. b. rhodesiense. The best compound shows favorable selectivity against the L6 cell line (SI = 750) and even greater selectivity (SI = 1200) against four human cell lines. The data herein provides direction for the ongoing optimization of antitrypanosomal diphenyl ethers.

Recent progress on anti-Toxoplasma drugs discovery: Design, synthesis and screening

Toxoplasma gondii severely threaten the health of immunocompromised patients and pregnant women as this parasite can cause several disease, including brain and eye disease. Current treatment for toxoplasmosis commonly have high cytotoxic side effects on host and require long durations ranging from one week to more than one year. The regiments lack efficacy to eradicate T. gondii tissue cysts to cure chromic infection results in the needs for long treatment and relapsing disease. In addition, there has not been approved drugs for treating the pregnant women infected by T. gondii. Moreover, Toxoplasma vaccine researches face a wide variety of challenges. Developing high efficient and low toxic agents against T. gondii is urgent and important. Over the last decade, tremendous progress have been made in identifying and developing novel compounds for the treatment of toxoplasmosis. This review summarized and discussed recent advances between 2009 and 2019 in exploring effective agents against T. gondii from five aspects of drug discovery.