V-domain immunoglobulin suppressor of T-cell activation (VISTA) is an emerging immune checkpoint with distinctive structural and functional features distinct from PD-1/PD-L1 and CTLA-4. Constitutively expressed on naïve T cells and myeloid cells, VISTA functions as a master regulator of immune quiescence while being co-opted by tumors for immune evasion. VISTA engages multiple ligands, including PSGL-1, VSIG-3, VSIG-8, and LRIG-1, to suppress T-cell responses and mediate immunosuppression, thereby contributing to resistance to PD-1/PD-L1 blockade. Consequently, VISTA has emerged as a promising target for cancer immunotherapy. However, first-generation pH-independent antibodies encountered cytokine release syndrome and rapid clearance, spurring the development of pH-selective, Fc-engineered, and non-depleting antibody strategies. Concurrently, small-molecule VISTA inhibitors have advanced from controversial compounds to validated chemical matter across multiple scaffolds, with representative candidates demonstrating oral bioavailability, antitumor efficacy, and synergy with anti-PD-L1. Nevertheless, most small-molecule inhibitors remain preclinical, and a critical bottleneck persists. All reported small-molecule binding poses for VISTA are derived from molecular docking and require experimental validation by mutagenesis or co-crystallization. The absence of co-crystal structures continues to limit structure-based optimization. Here, we review VISTA biology from a medicinal chemistry perspective, covering its unique structural features, ligand interactions, and the landscape of antibody and small-molecule inhibitors. Finally, we discuss current challenges and future opportunities, with the aim of guiding the discovery of next-generation VISTA-targeted therapeutics for cancer immunotherapy and autoimmune diseases.

O-alkylated gentamicin C1a analogs were prepared in 3-5 steps from gentamicin C1a using phase transfer-catalyzed O-alkylation. The O-alkylated gentamicin C1a analogs lost their standalone antibacterial activity but instead synergized the outer membrane-impermeable antibiotic rifampicin. 5,2''-di-O-alkylated-gentamicin C1a analogs 4 and 6 bearing biphenyl- or octyl- but not phenyl-substituents synergized rifampicin against a panel of Gram-negative bacteria. At concentrations of 8 μg/mL of 4 or 6 (~ 6 mmol), Gram-positive-selective antibiotic rifampicin was 32- to 512-fold potentiated against Gram-negative pathogens including multidrug-resistant Acinetobacter baumannii, Escherichia coli, and Pseudomonas aeruginosa isolates. Time-kill studies elucidated that the dual combination of 4 and rifampicin was bacteriostatic in A. baumannii AB031. The proposed mechanism of outer membrane permeabilization was verified by the reduced rifampicin potentiation in the presence of Mg[2+], as well as the absence of activity and synergy with rifampicin in Gram-positive bacteria. These findings indicate that di-O-alkylated gentamicin C1a analogs 4 and 6 are two new members of aminoglycoside-based outer membrane permeabilizers capable of potentiating rifampicin against Gram-negative pathogens.

Chagas disease, which is transmitted by Trypanosoma cruzi parasites, remains a major neglected tropical disease for which there are limited treatment choices. In this study, we present the in vitro evaluation of 31 tizoxanide (TIZ) derivatives against the Y strain of T. cruzi bloodstream trypomastigotes. Several of the compounds exhibited significantly enhanced trypanocidal activity compared to benznidazole (BZ), the reference drug. At 4 °C, eight derivatives demonstrated IC50 values ranging from 25 to 50 μM, up to four times more active than BZ. At physiological temperature (37 °C), these compounds exhibited enhanced potency, with IC50 values as low as 1.9 μM and selectivity indices (SIs) of up to 77, indicating low cytotoxicity to host macrophages. The most promising of these compounds, 13, 19 and 21 exhibited superior efficacy to both BZ and TIZ, the key active metabolite of nitazoxanide (NTZ). In vitro DMPK analyses of selected front runner compounds reveal that halogenation of the phenyl ring provides analogues with significantly increased metabolic stability. Our in vitro findings demonstrate that analogues in this series are potent, metabolically stable and represent potential T. cruzi drug lead candidates, warranting further mechanistic and in vivo evaluation.

A process for the synthesis of aminated pyrimidinyl hydrazones (APH) designed to accumulate in acidic vesicles was developed and 8 examples were prepared. The APH were able to complex metal ions at pH levels characteristic of both cytosolic and lysosomal environments. Key members of the series showed no toxicity against non-cancer fibroblasts at 25 μM while showing potent cytotoxicity against a variety of cancer cell lines (average IC50 of 300 nM against 5 cell-lines) thus demonstrating selectivity towards cancerous cells. The basicity of the aliphatic amine in the side chain of the APH appears to be a major determinant of cytotoxicity against cancer cells - aliphatic amines being preferred to anilines. Partition experiments suggest that the APH are likely to accumulate in acidic vesicles such as the lysosome, this potentially being a rationale for the potency and selectivity. The APH show great promise as a class of metal-chelating anti-cancer agents and are an evolution of our earlier pyrimidinyl hydrazone (PH) series with broader applicability.

The rise of multi-drug-resistant bacteria highlights the need for antibiotics that act through novel mechanisms of action. The Na[+]-pumping NADH-Ubiquinone (UQ) oxidoreductase (NQR) is a respiratory enzyme found in many pathogenic bacteria including Vibrio cholerae and plays a central role in energy production and redox balance. This enzyme is essential to the virulence of V. cholerae and structural motifs that are unique to NQR are not found in the humans, making it an excellent target for antibiotic drug design. Herein we report the synthesis and biological evaluation of 2-substituted heterocyclic quinolones designed to target the ubiquinone binding site of NQR. The most potent quinolone derivative exhibits 45% inhibition at 50 μM and docking studies indicate that it overlaps with the surrogate ubiquinone substrate within the binding pocket. These compounds also show inhibition of NQR while maintaining low toxicity in mammalian HeLa and HFF-1 cells, expanding the chemical space of bacterial respiratory enzyme inhibitors and supporting their development as a potential class of bacteriostatic antibiotics.

A quinoxaline benzothiazole PAR4 antagonist chemotype has been optimized by investigating aza substitutions in the benzothiazole ring. The 7'-azabenzothiazole, when combined with extended side chains discovered in previous studies, generated advanced leads with significantly improved potency, reduced cLogP, and favorable pharmacokinetic properties.

A novel series of quinoline-based PAR4 antagonists with single digit nanomolar potency has been discovered through iterative structure-activity relationship optimization. This series of quinoline antagonists demonstrates excellent rat pharmacokinetic properties with favorable oral exposure and Cmax.

Drug-repurposing strategies have been widely explored to accelerate the development of new treatments for Chagas disease, leveraging compounds with previously established safety profiles. Among these, azole antifungals have attracted attention due to their inhibitory activity against 14-α-lanosterol demethylase (CYP51), an enzyme also present in Trypanosoma cruzi and essential for its ergosterol biosynthesis. Inhibition of this pathway compromises parasite membrane integrity and function and several azoles, including posaconazole, ravuconazole, and miconazole, have demonstrated significant in vitro trypanocidal activity. In this work, we have synthesized new 1,2,3-triazoles as miconazole analogues using eugenol and its analogues as scaffolds. These compounds were initially evaluated against epimastigote forms of T. cruzi and a benzoyl eugenol-derived triazole 16 (IC50 = 37.1 μM) shown trypanocidal potential close to benznidazole (IC50 = 32.3 μM). This compound was further evaluated against trypomastigote and amastigote forms of T. cruzi, displaying IC50 values of 1.4 μM and 2.9 μM, respectively, whereas benznidazole presented IC50 values of 4.09 μM and 3.07 μM, with selectivity indexes of 110 and 53, respectively, considering healthy neonatal rat cardiomyoblast cell line (H9c2 cells). Docking studies suggested CYP51 as a putative molecular target, with compound 16 adopting a binding mode similar to known azole inhibitors. DFT calculations indicated weaker Fe-heme coordination for the 1,2,3-triazole moiety compared to classical azoles, suggesting that inhibition may depend on additional interactions within the binding site. Consistently, the compounds were inactive against Candida species. This finding suggests a degree of selectivity toward the target pathogens evaluated in this study, however additional investigations are required to confirm this selectivity profile. Given the known risk of human CYP inhibition associated with azole derivatives, this observation may be particularly relevant.

This study addresses persistent androgen receptor signaling in castration-resistant prostate cancer by developing novel CYP11A1-directed compounds that target the first step of steroid hormone biosynthesis. Based on the clinical-stage inhibitor Opevesostat, 26 analogues were designed and synthesized by modifying the aromatic or pyranone core, cyclic amine linker, sulfonyl substituent, and hydrophobic fragment. Compound IIA-1 showed 96.2% inhibition at 500 nM and an estimated IC50 of 25.2 nM (95% CI, 9.0-41.4 nM) in the KGN cell-based assay; Opevesostat gave an IC50 of 20.4 nM (95% CI, 12.3-28.5 nM) under the same assay conditions. The docking protocol reproduced the crystallographic cholesterol pose with an RMSD of 0.45 Å. Using this docking setup, molecular docking generated a predicted binding pose for IIA-1, with hydrogen-bonding, π-π, and hydrophobic contacts that provide a structural hypothesis for the observed activity. In a preliminary single-concentration screen against five major drug-metabolizing CYP isoforms, I-8 showed low numerical inhibition across the panel; these data do not establish CYP isoform selectivity. The results define preliminary structure-activity relationships and identify IIA-1 as a preliminary hit for further direct biochemical, selectivity, pharmacokinetic, and in vivo evaluation.

In this study, a series of quinoxaline derivatives were designed and evaluated for activity against Mycobacterium tuberculosis (H37Rv strain). Several compounds displayed promising antimycobacterial activity, with multiple derivatives showing minimum inhibitory concentration (MIC90) values in the low micromolar (<10 μM) range. Among these, compounds 4d and 3b were the most active in the series, with MIC values of 0.97 μM and 0.94 μM, respectively. Structure activity relationship (SAR) analysis revealed that the 6-nitroquinoxaline core is essential for activity, while the alkynyl linker plays a critical role in maintaining antimycobacterial potency. The presence and positioning of a hydroxyl group on the alkynyl side chain influenced activity, with tertiary alcohol derivatives generally providing improved potency. Among the synthesized compounds, compound 4h exhibited a comparatively favorable in vitro selectivity index but was limited by low aqueous solubility. These findings highlight key structural characteristics within this scaffold and offer valuable insight for the further optimization of quinoxaline-based anti-tuberculosis agents.

The present study describes the design and synthesis of twenty novel tolmetin-hydrazones (3a-t). The structures of the synthesized compounds were elucidated using FT-IR, 1H NMR, 13C NMR, and HR-MS (ESI+) spectroscopy techniques. The cytotoxic potential of all synthesized compounds was evaluated against HCT-116 human colon cancer cells and CCD-18Co normal colon fibroblasts using the CCK-8 colorimetric assay. Based on their IC50 and selectivity index (SI) values, 2-[1-methyl-5-(4-methylbenzoyl)-1H-pyrrol-2-yl]-N'-(thiophen-2-ylmethylene) acetohydrazide (3h) (IC50 = 10.93 ± 0.07 μM / SI = 4.01) and N'-(2,3-dichlorobenzylidene)-2-[1-methyl-5-(4-methylbenzoyl)-1H-pyrrol-2-yl] acetohydrazide (3q) (IC50 = 21.41 ± 0.13 μM / SI = 2.76) were selected as the most active compounds for further mechanistic investigations. To elucidate the underlying cytotoxic mechanisms, mitochondrial membrane potential (MMP) assessment via JC-1 staining, apoptosis detection through Annexin V/PI double staining, and quantitative evaluation of COX-2 enzyme activity and PGE2 levels were performed on HCT-116 cells. Compound 3h selectively induced mitochondrial membrane potential depolarization, triggered apoptosis, exhibited dose-dependent COX-2 inhibition, and decreased prostaglandin levels. Furthermore, detailed molecular docking simulations of all compounds were performed against human COX-1 (PDB ID: 6Y3C) and COX-2 (PDB ID: 5KIR) enzymes to calculate their binding energies and identify the structural basis of their selectivity. In silico analysis revealed favorable binding orientations for compound 3h (-10.1 kcal/mol), including hydrogen-bonding interactions with key active-site and gating residues such as HIS90. Collectively, compound 3h exhibits selective anticancer activity and represents a promising hit compound for the development of COX-2-targeted anticancer agents.

Primary hyperparathyroidism (PHPT) is caused by the enlargement and overactivation of one or more of the parathyroid glands, via parathyroid adenomas or hyperplasia. This results in over-secretion of PTH hormone, which results in agonism of PTH1R and subsequent hypercalcemia. Blocking PTH action via an oral, small-molecule PTH1R antagonist may provide a convenient and improved therapy for PHPT. Herein, we report the discovery, optimization and characterization of a highly potent, bioavailable and efficacious series represented by 9c (hPTH1R IC50 = 5.2 nM), which based on pharmacokinetics and biological activity, represents a significant preclinical advancement in the development of small-molecule PTH antagonists.

The human epidermal growth factor receptor 2 (HER2) plays an important role as a transmembrane receptor, contributing to signaling activities implicated in cellular proliferation, differentiation, and survival. Across select tumor types, HER2 is pro-oncogenic, facilitating cancer initiation, progression and metastatic spread, leading towards treatment resistance. Further, cell surface presentation and signaling activity of HER2 has led to the development of precision oncology therapeutic approaches. In this study, a HER2-targeting DNA aptamer was modified into a novel chimeric sequence with an RNA sense strand that was hybridized with a complementary antisense RNA or DNA sequence for aptamer-mediated HER2 cellular uptake in a representative HER2 positive (+) SKBR3 breast cancer cell line. The incorporation of antisense oligonucleotide (ASO) and short interfering (si) RNA within the chimeric HER2-aptamer elicited favorable hybrid duplex secondary structures and thermal stability profiles for biological activity. Enzymatic (Ribonuclease H, RNase H) digestion of the RNA sense strand made the chimeric HER2-aptamer:ASO hybrid applicable for antisense and with siRNA for RNA interference (RNAi) gene silencing activities against the stress-inducible oncoprotein, Glucose Regulated Protein 78, GRP78, as a key regulator of cancer cell survival and apoptosis. The chimeric ASO and siRNA conjugated aptamer demonstrated cellular binding and uptake activities directly in the HER2 presenting SKBR3 cell line and downstream GRP78 silencing (siRNA) activity that was dependent on a Lipofectamine-based formulation, underscoring the importance of the transfection agent for cellular delivery of genetic therapies.

We here report the discovery of a series of fluoro-substituted 3-phenoxy-azetidines useful for modulating levels of monoamines in cerebral cortical areas of the brain. The compounds were characterized by in vivo studies using, in particular, behavioural, and microdialysis methods. Furthermore, the compounds were tested in binding assays for the human serotonin (5-HT), noradrenaline (NA), and dopamine (DA) transporters in order to assess the risk for addiction/dependency. Optimization of this class of compounds for improving cognitive functions while minimizing the effect on monoamine transporters resulted in the selection of a candidate drug 1 (IRL757). After 1 was successfully assessed in different animal models for motivation/goal-directed behaviour (unpublished data), it is currently being evaluated in humans for the treatment of apathy in neurological disorders in general, and in particular in Parkinson's disease (PD).

GPR120 is expressed in the tongue and plays an important role in fatty acid taste perception. Natural polyunsaturated fatty acids, including α-linolenic acid and linoleic acid, are found in various edible oils such as soybean, rapeseed, and safflower oils. These fatty acids activate GPR120 but are susceptible to oxidation during storage and heating. To address these limitations while retaining GPR120 activity, a series of conformationally restricted, aliphatic side-chain-conjugated aryl short-chain fatty acid derivatives was synthesized. Several compounds exhibited potent GPR120-mediated activity. Compound 20, one of the most active compounds, enhanced fatty orosensation in a preliminary sensory evaluation.