Machine learning prioritizes synthesis of primaquine ureidoamides with high antimalarial activity and attenuated cytotoxicity

Quinoline derivatives volunteering against antimicrobial resistance: rational approaches, design strategies, structure activity relationship and mechanistic insights

Emergence of antimicrobial resistance has become a great threat to human species as there is shortage of development of new antimicrobial agents. So, its mandatary to combat AMR by initiating research and developing new novel antimicrobial agents. Among phytoconstituents, Quinoline (nitrogen containing heterocyclic) have played a wide role in providing new bioactive molecules. So, this review provides rational approaches, design strategies, structure activity relationship and mechanistic insights of newly developed quinoline derivatives as antimicrobial agents.

Application of Artificial Intelligence in Pharmaceutical and Biomedical Studies

BACKGROUND

Artificial intelligence (AI) is the way to model human intelligence to accomplish certain tasks without much intervention of human beings. The term AI was first used in 1956 with The Logic Theorist program, which was designed to simulate problem-solving ability of human beings. There have been a significant amount of research works using AI in order to determine the advantages and disadvantages of its applicabication and, future perspectives that impact different areas of society. Even the remarkable impact of AI can be transferred to the field of healthcare with its use in pharmaceutical and biomedical studies crucial for the socioeconomic development of the population in general within different studies, we can highlight those that have been conducted with the objective of treating diseases, such as cancer, neurodegenerative diseases, among others. In parallel, the long process of drug development also requires the application of AI to accelerate research in medical care.

METHODS

This review is based on research material obtained from PubMed up to Jan 2020. The search terms include "artificial intelligence", "machine learning" in the context of research on pharmaceutical and biomedical applications.

RESULTS

This study aimed to highlight the importance of AI in the biomedical research and also recent studies that support the use of AI to generate tools using patient data to improve outcomes. Other studies have demonstrated the use of AI to create prediction models to determine response to cancer treatment.

CONCLUSION

The application of AI in the field of pharmaceutical and biomedical studies has been extensive, including cancer research, for diagnosis as well as prognosis of the disease state. It has become a tool for researchers in the management of complex data, ranging from obtaining complementary results to conventional statistical analyses. AI increases the precision in the estimation of treatment effect in cancer patients and determines prediction outcomes.

Antiproliferative evaluation of various aminoquinoline derivatives

Four classes of aminoquinoline derivatives were prepared: primaquine ureas 1a-f, primaquine bis-ureas 2a-f, chloroquine fumardiamides 3a-f and mefloquine fumardiamides 4a-f. Their antiproliferative activities against breast adeno-carcinoma (MCF-7), lung carcinoma (H460) and colon carcinoma (HCT 116 and SW620) cell lines were evaluated in vitro, using MTT cell proliferation assay. The results revealed a low activity of primaquine urea and bis-urea derivatives and high activity of all fumardiamides, with IC50 values in low micromolar range against all tested cancer cell lines.

Primaquine derivatives: Modifications of the terminal amino group

Numerous modifications of the well-known antimalarial drug primaquine, both at the quinoline ring and at the primary amino group, have been reported, mostly to obtain antimalarial agents with improved bioavailability, reduced toxicity and/or prolonged activity. Modifications of the terminal amino group were made with the main idea to prevent the metabolic pathway leading to inactive and toxic carboxyprimaquine (follow-on strategy), but also to get compounds with different activity (repurposing strategy). The modifications undertaken until 2009 were included in a review published in the same year. The present review covers various classes of primaquine N-derivatives with diverse biological profiles, prepared in the last decade by our research group as well as the others. We have summarized the synthetic procedures applied for their preparation and discussed the main biological results. Several hits for the development of novel antiplasmodial, anticancer, antimycobacterial and antibiofilm agents were identified.

Primaquine homodimers as potential antiplasmodial and anticancer agents

Primaquine homodimers, e.g. symmetric PQ-diamides of dicarboxylic acids containing 4 to 8 carbon atoms, were evaluated against Plasmodium berghei hepatic stages and P. falciparum blood stages, as well as against three cancer cell lines. Novel PQ-homodimers exerted much higher activity against hepatic stages, but less pronounced activity against blood stages in comparison to the parent drug. The submicromolar activity of succinic, fumaric and maleic derivatives against P. berghei was determined (IC₅₀ values: 726.2, 198.1 and 358.4 nM, respectively). Our results indicated that the length and type of spacer between two PQ moieties highly modified the antiproliferative activities of PQ-homodimers. The general antiproliferative activity of the adipic and mesaconic derivatives against three cancer cell lines (MCF-7, HCT116, H 460) was observed (GI₅₀ = 1.78-13.7 and 2.36-4.31 µM, respectively), but adipic derivative was less toxic to human embryonic kidney cells (HEK 293). High selectivity of fumaric and suberic derivatives against breast adenocarcinoma cell line MCF-7 was detected. These two compounds have shown no antiproliferative activity against other tumor cells and HEK 293.

Primaquine and Chloroquine Fumardiamides as Promising Antiplasmodial Agents

This paper describes a continuation of our efforts in the pursuit of novel antiplasmodial agents with optimized properties. Following our previous discovery of biologically potent asymmetric primaquine (PQ) and halogenaniline fumardiamides (1-6), we now report their significant in vitro activity against the hepatic stages of Plasmodium parasites. Furthermore, we successfully prepared chloroquine (CQ) analogue derivatives (11-16) and evaluated their activity against both the hepatic and erythrocytic stages of Plasmodium. Our results have shown that PQ fumardiamides (1-6) exert both higher activity against P. berghei hepatic stages and lower toxicity against human hepatoma cells than the parent drug and CQ derivatives (11-16). The favourable cytotoxicity profile of the most active compounds, 5 and 6, was corroborated by assays performed on human cells (human breast adenocarcinoma (MCF-7) and non-tumour embryonic kidney cells (HEK293T)), even when glucose-6-phosphate dehydrogenase (G6PD) was inhibited. The activity of CQ fumardiamides on P. falciparum erythrocytic stages was higher than that of PQ derivatives, comparable to CQ against CQ-resistant strain PfDd2, but lower than CQ when tested on the CQ-sensitive strain Pf3D7. In addition, both sets of compounds showed favourable drug-like properties. Hence, quinoline fumardiamides could serve as a starting point towards the development of safer and more effective antiplasmodial agents.

Synthesis and antiplasmodial evaluation of novel mefloquine-based fumardiamides

The paper is focused on the synthesis and screening of the antiplasmodial activity of novel fumardiamides 5-10 with the mefloquine pharmacophore and a Michael acceptor motif. Multi-step reactions leading to the title compounds included two amide bond formations. The first amide bond was achieved by the reaction of (E)-ethyl 4-chloro-4-oxobut-2-enoate (1) and N1-(2,8-bis(trifluoromethyl)quinolin-4-yl) butane-1,4-diamine (2). The obtained ester 3 was hydrolyzed and gave acid 4, which then reacted with the selected halogenanilines in the presence of HATU/DIEA and formed products 5-10. Title compounds showed marked, dose dependent activity in vitro against hepatic stages of Plasmodium berghei. IC50 values of the most active compounds 5, 7 and 9 bearing 3-fluoro, 3-chloro and 3-trifluoromethyl substituents were 3.04-4.16 µmol L-1, respectively. On the other hand, the compounds exerted only weak activity against the erythrocytic stages of two P. falciparum strains (Pf3D7 and PfDd2) in vitro, with the exception of compound 5 (IC50 = 2.9 µmol L-1).

Second generation of primaquine ureas and bis-ureas as potential antimycobacterial agents

Here, we describe design and synthesis of twelve novel compounds bearing primaquine motif and hydroxy- or halogenamine linked by an urea or bis-urea spacer. Preparation of ureas 3a-f started with the conversion of primaquine to benzotriazolide 2 and aminolysis of the later compound by 4-(2-aminoethyl)phenol or amino alcohols bearing fluorine atom, cycloalkyl or trifluoromethyl group under microwave irradiation. The four-step sequence leading to bis-ureas 6a-f included preparation of benzotriazolide 2 and two intermediates, semicarbazide 4 and benzotriazole bis-urea 5, which upon aminolysis with the same aminophenol or amino alcohols gave the title compounds. Antimycobacterial screening detected three active compounds against Mycobacterium marinum and M. tuberculosis, namely 3b, 3f and 6f, derived from cyclobutyl amino alcohol or amino phenol.

A review on diverse heterocyclic compounds as the privileged scaffolds in antimalarial drug discovery

The upward extend of malaria collectively with the emergence of resistance against predictable drugs has put enormous pressure on public health systems to introduce new malaria treatments. Heterocycles play an important role in the design and discovery of new malaria active compounds. Heterocyclic compounds have attracted significant attention for malaria treatment because of simplicity of parallelization and the examining power with regard to chemical space. Introduction of a variety of heterocyclic compounds have enabled to maintain the high levels of antimalarial potency observed for other more lipophilic analogues whilst improving the solubility and the oral bioavailability in pre-clinical species. In this review, we present an overview of recent literature to provide imminent into the applications of different heterocyclic scaffolds in fighting against malaria.

Asymmetric Primaquine and Halogenaniline Fumardiamides as Novel Biologically Active Michael Acceptors

Novel primaquine (PQ) and halogenaniline asymmetric fumardiamides 4a⁻f, potential Michael acceptors, and their reduced analogues succindiamides 5a⁻f were prepared by simple three-step reactions: coupling reaction between PQ and mono-ethyl fumarate (1a) or mono-methyl succinate (1b), hydrolysis of PQ-dicarboxylic acid mono-ester conjugates 2a,b to corresponding acids 3a,b, and a coupling reaction with halogenanilines. 1-[bis(Dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium 3-oxide hexafluorophosphate (HATU) was used as a coupling reagent along with Hünig's base. Compounds 4 and 5 were evaluated against a panel of bacteria, several Mycobacterium strains, fungi, a set of viruses, and nine different human tumor cell lines. p-Chlorofumardiamide 4d showed significant activity against Staphylococcus aureus,Streptococcus pneumoniae and Acinetobacter baumannii, but also against Candida albicans (minimum inhibitory concentration (MIC) 6.1⁻12.5 µg/mL). Together with p-fluoro and p-CF₃ fumardiamides 4b,f, compound 4d showed activity against Mycobacterium marinum and 4b,f against M. tuberculosis. In biofilm eradication assay, most of the bacteria, particularly S. aureus, showed susceptibility to fumardiamides. m-CF₃ and m-chloroaniline fumardiamides 4e and 4c showed significant antiviral activity against reovirus-1, sindbis virus and Punta Toro virus (EC50 = 3.1⁻5.5 µM), while 4e was active against coxsackie virus B4 (EC50 = 3.1 µM). m-Fluoro derivative 4a exerted significant cytostatic activity (IC50 = 5.7⁻31.2 μM). Acute lymphoblastic leukemia cells were highly susceptible towards m-substituted derivatives 4a,c,e (IC50 = 6.7⁻8.9 μM). Biological evaluations revealed that fumardiamides 4 were more active than succindiamides 5 indicating importance of Michael conjugated system.