Synthesis and biological evaluation of orally active prodrugs and analogs of para-aminosalicylic acid (PAS)

Medoxomil Prodrug Strategies

Drug discovery campaigns often face biopharmaceutical challenges, some of which can be solved by a prodrug approach. Prodrugs are enzymatically or chemically transformed in vivo to produce active drugs. Among these, medoxomil promoieties have been judiciously employed in multiple drug discovery campaigns, leading to three prodrugs gaining FDA approval: azilsartan medoxomil (6), olmesartan medoxomil (20), and ceftobiprole medocaril (29), and one approval in Japan: prulifloxacin (35). The promoiety can be easily appended to mask carboxylic acids, amines, zwitterionic compounds, and other polar groups, imparting lipophilicity to the parent compound. The promoiety has the added advantage of rapid and complete conversion to the parent drug by multiple enzymatic pathways across different tissues. The approach has been used for drugs spanning multiple classes to improve oral bioavailability, solubility, tissue localization, efflux, and side effect profiles. This Perspective analyzes the history and application of medoxomil prodrugs and discusses their potential for drug development.

Dopamine-based selective spectrophotometry p-aminosalicylic acid assay by hydrolyzate-triggered formation of azamonardine-like products

BACKGROUND

The selective recognition of drugs and its metabolism or decomposition products is significant to drug development and drug resistance research. Fluorescence-based techniques provide satisfying sensitivity by target-triggered chemical reaction. However, the interference from the matrix or additives usually restricts the specific detection. It is highly desirable to explore specific chemical reactions for achieving selective perception of these species.

RESULTS

We report a specific m-aminophenol (MAP)-dopamine (DA) reaction, which generates highly fluorescent azamonardine-like products. Based on this reaction, fluorometric and indirect detection of p-aminosalicylic acid (typical antituberculosis drug, PAS) can be realized using the DA-based probe with high sensitivity. The acid induces the decarboxylation of PAS and produces MAP, which reacts with DA and generates fluorescent azamonardine-like products. The practical application of the proposed method is validated by the accurate PAS analysis in urine samples and Pasinazid tablets. Interestingly, none of additives in the Pasinazid tablets contribute comparable fluorescence variation.

SIGNIFICANCE

This work discovers a new MAP-DA reaction for the first time, it not only explores sensitive PAS drug detection probe, but also demonstrates the feasibility of the development of novel drug analysis platform by recognizing decomposition product with specific reaction. Thus, new avenues for the exploration of simple and rapid spectrophotometric probes toward various drug analytes with high specify and sensitivity based on this tactic might be possible in analytical and drug-related fields.

New nitazoxanide derivatives: design, synthesis, biological evaluation, and molecular docking studies as antibacterial and antimycobacterial agents

A new series inspired by combining fragments from nitazoxanide (NTZ) and 4-aminosalicylic acid (4-ASA) was synthesized and screened for in vitro antibacterial and antimycobacterial activities. The majority showed higher antibacterial potency than NTZ against all the screened strains, notably, 5f, 5j, 5n and 5o with MICs of 0.87-9.00 μM. Compounds 5c, 5n and 5o revealed higher potency than ciprofloxacin against K. pneumoniae, while 5i was equipotent. For E. faecalis, 3b, 5j, and 5k showed higher potency than ciprofloxacin. 5j was more potent against P. aeruginosa than ciprofloxacin, while 5n was more potent against S. aureus with an MIC of 0.87 μM. 5f showed equipotency to ciprofloxacin against H. pylori with an MIC of 1.74 μM. Compounds 3a and 3b (4-azidoNTZ, MIC 4.47 μM) are 2 and 5-fold more potent against Mycobacterium tuberculosis (Mtb H37Rv) than NTZ (MIC 20.23 μM) and safer. 4-Azidation and/or acetylation of NTZ improve both activities, while introducing 1,2,3-triazoles improves the antibacterial activity. Molecular docking studies within pyruvate ferredoxin oxidoreductase (PFOR), glucosamine-6-phosphate synthase (G6PS) and dihydrofolate reductase (DHFR) active sites were performed to explore the possible molecular mechanisms of actions. Acceptable drug-likeness properties were found. This study may shed light on further rational design of substituted NTZ as broad-spectrum more potent antimicrobial candidates.

Synthesis, biological evaluation and molecular docking study of some new 4-aminosalicylic acid derivatives as anti-inflammatory and antimycobacterial agents

In this study, new derivatives of the antitubercular and anti-inflammatory drug, 4-aminosaliclic acids (4-ASA) were synthesized, characterized, and evaluated for these activities. In vivo and in viro evaluation of anti-inflammatory activity revealed that compounds 10, 19 and 20 are the most active with potent cyclooxygenase-2 (COX-2) and 5-lipooxgenase (5-LOX) inhibition and without causing gasric lesions. The minimum inhibitory concentrations (MIC) of the newly synthesized compound were, also, measured against Mycobacterium tuberculosis H37RV. Among the tested compounds 17, 19 and 20 exhibited significant activities against the growth of M. tuberculosis. 20 is the most potent with (MIC 1.04 µM) 2.5 folds more potent than the parent drug 4-ASA. 20 displayed low cytotoxicity against normal cell providing a high therapeutic index. Important structure features were analyzed by docking and structure-activity relationship analysis to give better insights into the structural determinants for predicting the anti-inflammatory and anti-TB activities. Our results indicated that compounds 19 and 20 are potential lead compounds for the discovery of dual anti-inflammatory and anti-TB drug candidates.

Hybridization Approach Toward Novel Antituberculars: Design, Synthesis, and Biological Evaluation of Compounds Combining Pyrazinamide and 4-Aminosalicylic Acid

Apart from the SARS-CoV-2 virus, tuberculosis remains the leading cause of death from a single infectious agent according to the World Health Organization. As part of our long-term research, we prepared a series of hybrid compounds combining pyrazinamide, a first-line antitubercular agent, and 4-aminosalicylic acid (PAS), a second-line agent. Compound 11 was found to be the most potent, with a broad spectrum of antimycobacterial activity and selectivity toward mycobacterial strains over other pathogens. It also retained its in vitro activity against multiple-drug-resistant mycobacterial strains. Several structural modifications were attempted to improve the in vitro antimycobacterial activity. The δ-lactone form of compound 11 (11') had more potent in vitro antimycobacterial activity against Mycobacterium tuberculosis H37Rv. Compound 11 was advanced for in vivo studies, where it was proved to be nontoxic in Galleria mellonella and zebrafish models, and it reduced the number of colony-forming units in spleens in the murine model of tuberculosis. Biochemical studies showed that compound 11 targets mycobacterial dihydrofolate reductases (DHFR). An in silico docking study combined with molecular dynamics identified a viable binding mode of compound 11 in mycobacterial DHFR. The lactone 11' opens in human plasma to its parent compound 11 (t_1/2 = 21.4 min). Compound 11 was metabolized by human liver fraction by slow hydrolysis of the amidic bond (t_1/2 = 187 min) to yield PAS and its starting 6-chloropyrazinoic acid. The long t_1/2 of compound 11 overcomes the main drawback of PAS (short t_1/2 necessitating frequent administration of high doses of PAS).