Antimalarial activity of 4-amidinoquinoline and 10-amidinobenzonaphthyridine derivatives

Discovery and Optimization of Tambjamines as a Novel Class of Antileishmanial Agents

Leishmaniasis is a neglected tropical disease that is estimated to afflict over 12 million people. Current drugs for leishmaniasis suffer from serious deficiencies, including toxicity, high cost, modest efficacy, primarily parenteral delivery, and emergence of widespread resistance. We have discovered and developed a natural product-inspired tambjamine chemotype, known to be effective against Plasmodium spp, as a novel class of antileishmanial agents. Herein, we report in vitro and in vivo antileishmanial activities, detailed structure-activity relationships, and metabolic/pharmacokinetic profiles of a large library of tambjamines. A number of tambjamines exhibited excellent potency against both Leishmania mexicana and Leishmania donovani parasites with good safety and metabolic profiles. Notably, tambjamine 110 offered excellent potency and provided partial protection to leishmania-infected mice at 40 and/or 60 mg/kg/10 days of oral treatment. This study presents the first account of antileishmanial activity in the tambjamine family and paves the way for the generation of new oral antileishmanial drugs.

Lead Optimization of Second-Generation Acridones as Broad-Spectrum Antimalarials

The global impact of malaria remains staggering despite extensive efforts to eradicate the disease. With increasing drug resistance and the absence of a clinically available vaccine, there is an urgent need for novel, affordable, and safe drugs for prevention and treatment of malaria. Previously, we described a novel antimalarial acridone chemotype that is potent against both blood-stage and liver-stage malaria parasites. Here, we describe an optimization process that has produced a second-generation acridone series with significant improvements in efficacy, metabolic stability, pharmacokinetics, and safety profiles. These findings highlight the therapeutic potential of dual-stage targeting acridones as novel drug candidates for further preclinical development.

Derivatives of the Antimalarial Drug Mefloquine Are Broad-Spectrum Antifungal Molecules with Activity against Drug-Resistant Clinical Isolates

The antifungal pharmacopeia is critically small, particularly in light of the recent emergence of multidrug-resistant pathogens, such as Candida auris Here, we report that derivatives of the antimalarial drug mefloquine have broad-spectrum antifungal activity against pathogenic yeasts and molds. In addition, the mefloquine derivatives have activity against clinical isolates that are resistant to one or more of the three classes of antifungal drugs currently used to treat invasive fungal infections, indicating that they have a novel mechanism of action. Importantly, the in vitro toxicity profiles obtained using human cell lines indicated that the toxicity profiles of the mefloquine derivatives are very similar to those of the parent mefloquine, despite being up to 64-fold more active against fungal cells. In addition to direct antifungal activity, subinhibitory concentrations of the mefloquine derivatives inhibited the expression of virulence traits, including filamentation in Candida albicans and capsule formation/melanization in Cryptococcus neoformans Mode/mechanism-of-action experiments indicated that the mefloquine derivatives interfere with both mitochondrial and vacuolar function as part of a multitarget mechanism of action. The broad-spectrum scope of activity, blood-brain barrier penetration, and large number of previously synthesized analogs available combine to support the further optimization and development of the antifungal activity of this general class of drug-like molecules.

Discovery and Structural Optimization of Acridones as Broad-Spectrum Antimalarials

Malaria remains one of the deadliest diseases in the world today. Novel chemoprophylactic and chemotherapeutic antimalarials are needed to support the renewed eradication agenda. We have discovered a novel antimalarial acridone chemotype with dual-stage activity against both liver-stage and blood-stage malaria. Several lead compounds generated from structural optimization of a large library of novel acridones exhibit efficacy in the following systems: (1) picomolar inhibition of in vitro Plasmodium falciparum blood-stage growth against multidrug-resistant parasites; (2) curative efficacy after oral administration in an erythrocytic Plasmodium yoelii murine malaria model; (3) prevention of in vitro Plasmodium berghei sporozoite-induced development in human hepatocytes; and (4) protection of in vivo P. berghei sporozoite-induced infection in mice. This study offers the first account of liver-stage antimalarial activity in an acridone chemotype. Details of the design, chemistry, structure-activity relationships, safety, metabolic/pharmacokinetic studies, and mechanistic investigation are presented herein.

Improving Relative Bioavailability of Oral Imidazolidinedione by Reducing Particle Size Using Homogenization and Ultra-Sonication

Particle size is an important determinant of gastrointestinal absorption of compounds administrated orally. The present study evaluates the effect of a reduction in particle size assessed by homogenization, sonication, and homogenization plus sonication on the bioavailability of imidazolidinedione (IZ), an antimalarial compound with known causal prophylactic activity and radical cure of relapsing malaria. Formulations were administrated intragastrically to mice, and blood samples were collected for LC-MS/MS analysis. The homogenization method manually decreased particle size with minimal variance, resulting in a mean particle diameter of 42.22 μm, whereas the probe sonication method evenly distributed pulses of sound to break apart particles, resulting in a mean diameter of 1.50 μm. Homogenization plus sonication resulted in a mean particle diameter of 1.44 μm, which was similar to that of the sonication method alone. The compound suspensions did not show a significant difference in mean particle size between the different vehicles. The sonically engineered microparticle delivers high sonic energy to the suspension leads to faster breakdown and stabilizing of the micronized particles when compared with homogenizer. The bioavailability of the small particle IZ formulation was 100%, compared to the 55.79% relative bioavailability of IZ with larger particle size. These initial data clearly show that a reduction in particle size of orally administered IZ with probe sonication could significantly increase bioavailability in rodent animals that is affected by a high first-pass effect.

Quinolines and Quinolones as Antibacterial, Antifungal, Anti-virulence, Antiviral and Anti-parasitic Agents

Infective diseases have become health threat of a global proportion due to appearance and spread of microorganisms resistant to majority of therapeutics currently used for their treatment. Therefore, there is a constant need for development of new antimicrobial agents, as well as novel therapeutic strategies. Quinolines and quinolones, isolated from plants, animals, and microorganisms, have demonstrated numerous biological activities such as antimicrobial, insecticidal, anti-inflammatory, antiplatelet, and antitumor. For more than two centuries quinoline/quinolone moiety has been used as a scaffold for drug development and even today it represents an inexhaustible inspiration for design and development of novel semi-synthetic or synthetic agents exhibiting broad spectrum of bioactivities. The structural diversity of synthetized compounds provides high and selective activity attained through different mechanisms of action, as well as low toxicity on human cells. This review describes quinoline and quinolone derivatives with antibacterial, antifungal, anti-virulent, antiviral, and anti-parasitic activities with the focus on the last 10 years literature.

Novel Aminoquinoline Derivatives Significantly Reduce Parasite Load in Leishmania infantum Infected Mice

In this Letter, a detailed analysis of 30 4-aminoquinoline-based compounds with regard to their potential as antileishmanial drugs has been carried out. Ten compounds demonstrated IC₅₀ < 1 μM against promastigote stages of L. infantum and L. tropica, and five compounds showed IC₅₀ < 1 μM against intramacrophage L. infantum amastigotes. Two compounds showed dose-dependent enhancement of NO and ROS production by bone marrow-derived macrophages and remarkable reduction of parasite load in vivo, with advantage of being short-term and orally active. To the best of our knowledge, this is the first example of 4-amino-7-chloroquinoline derivatives active in Leishmania infantum infected mice.

Copper-catalyzed synthesis of quinoline derivatives via tandem Knoevenagel condensation, amination and cyclization

A novel regioselective synthesis of 2-aminoquinolines and 2-arylquinoline-3-carbonitriles is described via copper-mediated tandem reaction.