The importance of being profiled: improving drug candidate safety and efficacy using ion channel profiling

Isolation and Identification of Endophytic Fungi from Syzygium cumini Linn and Investigation of Their Pharmacological Activities

This study was conducted to isolate and identify the endophytic fungi from the bark and leaves of the Syzygum cumini plant and investigate the pharmacological activities of endophytic fungi along with plant parts. After isolation, endophytic fungi were identified based on morphological characteristics and molecular identification. Antimicrobial, antioxidant, and cytotoxic activities were studied by a disc diffusion method, free radical scavenging DPPH assay, and brine shrimp lethality bioassay, respectively. A total of eight endophytic fungi were isolated and identified up to the genus level based on morphological characteristics and confirmed by molecular identification techniques. Among the eight isolates, three isolates were identified as Colletotrichum sp. (SCBE-2, SCBE-7, and SCLE-9), while the rest of the isolates belonged to Diaporthe sp. (SCBE-1), Pestalotiopsis sp. (SCBE-3), Penicillium sp. (SCBE-4), Phyllosistica sp. (SCLE-7), and Fusarium sp. (SCLE-8). The presence of flavonoids, anthraquinones, coumarins, and isocoumarins was assumed by the preliminary screening of the fungal and plant extracts by a thin-layer chromatographic technique under UV light. Fungal extracts of Pestalotiopsis sp. Penicillium sp. were found sensitive to all test bacteria, but only extracts from the leaf and bark showed significant antifungal activity along with their antimicrobial activity. Penicillium sp. The fungal extract showed the highest free radical scavenging activity (2.43 μg/mL) near that of ascorbic acid (2.42 μg/mL). Some fungal extracts showed cytotoxic activity that, in general, suggests their probable abundance of biological metabolites. This is the first approach to investigate the endophytic fungi of Syzygium cumini Linn. in Bangladesh, to find the pharmacological potential of endophytes, and to explore novel compounds from those endophytes.

Polypharmacology: The science of multi-targeting molecules

Polypharmacology is a concept where a molecule can interact with two or more targets simultaneously. It offers many advantages as compared to the conventional single-targeting molecules. A multi-targeting drug is much more efficacious due to its cumulative efficacy at all of its individual targets making it much more effective in complex and multifactorial diseases like cancer, where multiple proteins and pathways are involved in the onset and development of the disease. For a molecule to be polypharmacologic in nature, it needs to possess promiscuity which is the ability to interact with multiple targets; and at the same time avoid binding to antitargets which would otherwise result in off-target adverse effects. There are certain structural features and physicochemical properties which when present would help researchers to predict if the designed molecule would possess promiscuity or not. Promiscuity can also be identified via advanced state-of-the-art computational methods. In this review, we also elaborate on the methods by which one can intentionally incorporate promiscuity in their molecules and make them polypharmacologic. The polypharmacology paradigm of "one drug-multiple targets" has numerous applications especially in drug repurposing where an already established drug is redeveloped for a new indication. Though designing a polypharmacological drug is much more difficult than designing a single-targeting drug, with the current technologies and information regarding different diseases and chemical functional groups, it is plausible for researchers to intentionally design a polypharmacological drug and unlock its advantages.

Cardiovascular Safety Assessment in Cancer Drug Development

The development of cardiovascular toxicity attributable to anticancer drugs is a pivotal event that is associated with cardiovascular morbidity as well as with worse cancer-specific and overall outcomes. Although broad consensus exists regarding the importance of cardiovascular safety assessment in cancer drug development, real-world data suggest that cardiovascular events are significantly underestimated in oncology trials. This drug safety discrepancy has profound implications on drug development decisions, risk-benefit evaluation, formulation of surveillance and prevention protocols, and survivorship. In this article, we review the contemporary cardiovascular safety evaluation of new pharmaceuticals in hematology and oncology, spanning from in vitro pharmacodynamic testing to randomized clinical trials. We argue that cardiovascular safety assessment of anticancer drugs should be reformed and propose practical strategies, including development and validation of preclinical assays, expansion of oncology trial eligibility, incorporation of cardiovascular end points in early-phase studies, and design of longitudinal multi-institutional cardiotoxicity registries.

Machine Learning Strategies When Transitioning between Biological Assays

Machine learning is widely used in drug development to predict activity in biological assays based on chemical structure. However, the process of transitioning from one experimental setup to another for the same biological endpoint has not been extensively studied. In a retrospective study, we here explore different modeling strategies of how to combine data from the old and new assays when training conformal prediction models using data from hERG and Na_V assays. We suggest to continuously monitor the validity and efficiency of models as more data is accumulated from the new assay and select a modeling strategy based on these metrics. In order to maximize the utility of data from the old assay, we propose a strategy that augments the proper training set of an inductive conformal predictor by adding data from the old assay but only having data from the new assay in the calibration set, which results in valid (well-calibrated) models with improved efficiency compared to other strategies. We study the results for varying sizes of new and old assays, allowing for discussion of different practical scenarios. We also conclude that our proposed assay transition strategy is more beneficial, and the value of data from the new assay is higher, for the harder case of regression compared to classification problems.

Targeting the Kv11.1 (hERG) channel with allosteric modulators. Synthesis and biological evaluation of three novel series of LUF7346 derivatives

We synthesized and evaluated three novel series of substituted benzophenones for their allosteric modulation of the human K_v11.1 (hERG) channel. We compared their effects with reference compound LUF7346 previously shown to shorten the action potential of cardiomyocytes derived from human stem cells. Most compounds behaved as negative allosteric modulators (NAMs) of [³H]dofetilide binding to the channel. Compound 9i was the most potent amongst all ligands, remarkably reducing the affinity of dofetilide in competitive displacement assays. One of the other derivatives (6k) tested in a second radioligand binding set-up, displayed unusual displacement characteristics with a pseudo-Hill coefficient significantly distinct from unity, further indicative of its allosteric effects on the channel. Some compounds were evaluated in a more physiologically relevant context in beating cardiomyocytes derived from human induced pluripotent stem cells. Surprisingly, the compounds tested showed effects quite different from the reference NAM LUF7346. For instance, compound 5e prolonged, rather than shortened, the field potential duration, while it did not influence this parameter when the field potential was already prolonged by dofetilide. In subsequent patch clamp studies on HEK293 cells expressing the hERG channel the compounds behaved as channel blockers. In conclusion, we successfully synthesized and identified new allosteric modulators of the hERG channel. Unexpectedly, their effects differed from the reference compound in functional assays on hERG-HEK293 cells and human cardiomyocytes, to the extent that the compounds behaved as stand-alone channel blockers.

Evaluation of bioactive secondary metabolites from endophytic fungus Pestalotiopsis neglecta BAB-5510 isolated from leaves of Cupressus torulosa D.Don

Six endophytic fungi were isolated from Cupressus torulosa D.Don and identified phenotypically and genotypically. The fungal cultures were further grown and the culture was extracted by two organic solvents methanol and ethyl acetate. The screening was carried out using the agar well diffusion method against human pathogen such as Escherichia coli, Salmonella typhimurium, Bacillus subtilis and Staphylococcus aureus. Isolated strain of Pestalotiopsis sp. was showing prominent antibacterial activity. The crude methanol and ethyl acetate extract of Pestalotiopsis sp. showed MIC of 6.25 mg/mL for S. typhimurium and S. aureus which showed its efficacy as a potent antimicrobial. The phytochemical screening revealed the existence of a diverse group of secondary metabolites in the crude extracts of the endophytic fungi that resembled those in the host plant extracts. On the basis of phenotypic characteristics and rDNA sequencing of the ITS region of the endophyte was identified as P. neglecta which turned out to be a promising source of bioactive compounds. There is little known about endophytes from C. torulosa D.Don. In this paper we studied in detail the identification of isolated endophytic fungi P. neglecta from C. torulosa D.Don and characterization of its active metabolite compounds. The partially purified second fraction (PPF) extracted from the fungal culture supernatant was subjected to gas chromatography followed by mass spectrometry which revealed the presence of many phytochemicals. These results indicate that endophytic fungi P. neglecta isolated from medicinal plants could be a potential source for bioactive compounds and may find potential use in pharmaceutical industry.

Ion channel profiling to advance drug discovery and development

In vitro pharmacological profiling provides crucial information to eliminate drug candidates with potential toxicity early in drug discovery and reduce failure in later stages. It has become a common practice in industry to test lead compounds against a panel of ion channel targets for selectivity and safety liability at early drug discovery stages. Ion channel profiling technologies include binding assays, flux assays, fluorescent membrane potential assays, automated and conventional electrophysiology. Instead of examining compound effects on individual ion channel targets, automated current clamp, optical electrophysiology, and multi-electrode assays have evolved to investigate the integrated compound effects on cardiac myocytes. This review aims to provide an overview of ion channel profiling for cardiac safety and comparisons of various technologies.

Bioactivity of fungal endophytes as a function of endophyte taxonomy and the taxonomy and distribution of their host plants

Fungal endophytes--fungi that grow within plant tissues without causing immediate signs of disease--are abundant and diverse producers of bioactive secondary metabolites. Endophytes associated with leaves of tropical plants are an especially exciting and relatively untapped source of novel compounds. However, one major challenge in drug discovery lies in developing strategies to efficiently recover highly bioactive strains. As part of a 15-year drug discovery project, foliar endophytes were isolated from 3198 plant samples (51 orders, 105 families and at least 232 genera of angiosperms and ferns) collected in nine geographically distinct regions of Panama. Extracts from culture supernatants of >2700 isolates were tested for bioactivity (in vitro percent inhibition of growth, % IG) against a human breast cancer cell line (MCF-7) and the causative agents of malaria, leishmaniasis, and Chagas' disease. Overall, 32.7% of endophyte isolates were highly active in at least one bioassay, including representatives of diverse fungal lineages, host lineages, and collection sites. Up to 17% of isolates tested per assay were highly active. Most bioactive strains were active in only one assay. Fungal lineages differed in the incidence and degree of bioactivity, as did fungi from particular plant taxa, and greater bioactivity was observed in endophytes isolated from plants in cloud forests vs. lowland forests. Our results suggest that using host taxonomy and forest type to tailor plant collections, and selecting endophytes from specific orders or families for cultivation, will markedly increase the efficiency and efficacy of discovering bioactive metabolites for particular pharmaceutical targets.

Selective, direct activation of high-conductance, calcium-activated potassium channels causes smooth muscle relaxation

High-conductance calcium-activated potassium (Maxi-K) channels are present in smooth muscle where they regulate tone. Activation of Maxi-K channels causes smooth muscle hyperpolarization and shortening of action-potential duration, which would limit calcium entry through voltage-dependent calcium channels leading to relaxation. Although Maxi-K channels appear to indirectly mediate the relaxant effects of a number of agents, activators that bind directly to the channel with appropriate potency and pharmacological properties useful for proof-of-concept studies are not available. Most agents identified to date display significant polypharmacy that severely compromises interpretation of experimental data. In the present study, a high-throughput, functional, cell-based assay for identifying Maxi-K channel agonists was established and used to screen a large sample collection (>1.6 million compounds). On the basis of potency and selectivity, a family of tetrahydroquinolines was further characterized. Medicinal chemistry efforts afforded identification of compound X, from which its two enantiomers, Y and Z, were resolved. In in vitro assays, Z is more potent than Y as a channel activator. The same profile is observed in tissues where the ability of either agent to relax precontracted smooth muscles, via a potassium channel-dependent mechanism, is demonstrated. These data, taken together, suggest that direct activation of Maxi-K channels represents a mechanism to be explored for the potential treatment of a number of diseases associated with smooth muscle hyperexcitability.