A High-Throughput Radiometric Kinase Assay

Using a Single Peptide to Electrochemically Sense Multiple Kinases

Kinases are responsible for regulating cellular and physiological processes, and abnormal kinase activity is associated with various diseases. Therefore, kinases are being used as biomarkers for disease and developing methods for their sensing is highly important. Usually more than one kinase is involved in phosphorylating a target protein. However, kinase detection methods usually detect the activity of only one specific kinase. Here we describe an electrochemical kinase sensing tool for the selective detection of two kinases using the same target peptide. We demonstrate the sensing of kinases ERK2 and PKCδ. This is based on a single sensing element, a peptide that contains two distinct phosphorylation sites of these two kinases. Reversibility experiments with alkaline phosphatase and reaction with the electrochemically active ferrocene-labeled ATP showed that the mechanism of sensing is by detecting the enzymatic phosphorylation. Our approach can be further utilized to develop devices for the detection of multiple kinases and can be expanded to other types of enzymes involved in disease.

Gefitinib-Tamoxifen Hybrid Ligands as Potent Agents against Triple-Negative Breast Cancer

Anticancer drug conjugates may benefit from simultaneous action at two targets potentially overcoming the drawbacks of current cancer treatment, such as insufficient efficacy, high toxicity, and development of resistance. Compared to a combination of two single-target drugs, they may offer an advantage of pharmacokinetic simplicity and fewer drug-drug interactions. Here, we report a series of compounds connecting tamoxifen or endoxifen with the EGFR-inhibitor gefitinib via a covalent linkage. These hybrid ligands retain both ER antagonist activity and EGFR inhibition. The most potent analogues exhibited single-digit nanomolar activities at both targets. The amide-linked endoxifen-gefitinib drug conjugates 17b and 17c demonstrated the most favorable anti-cancer profile in cellular viability assays on MCF7, MDA-MB-231, MDA-MB-468, and BT-549 breast cancer cells. Most importantly, in TNBC cells 17b and 17c displayed nanomolar IC₅₀-values (380 nM - 970 nM) and were superior in their anti-cancer activity compared to their control compounds and combinations thereof.

Structural Basis for EGFR Mutant Inhibition by Trisubstituted Imidazole Inhibitors

Acquired drug resistance in epidermal growth factor receptor (EGFR) mutant non-small-cell lung cancer is a persistent challenge in cancer therapy. Previous studies of trisubstituted imidazole inhibitors led to the serendipitous discovery of inhibitors that target the drug resistant EGFR(L858R/T790M/C797S) mutant with nanomolar potencies in a reversible binding mechanism. To dissect the molecular basis for their activity, we determined the binding modes of several trisubstituted imidazole inhibitors in complex with the EGFR kinase domain with X-ray crystallography. These structures reveal that the imidazole core acts as an H-bond acceptor for the catalytic lysine (K745) in the "αC-helix out" inactive state. Selective N-methylation of the H-bond accepting nitrogen ablates inhibitor potency, confirming the role of the K745 H-bond in potent, noncovalent inhibition of the C797S variant. Insights from these studies offer new strategies for developing next generation inhibitors targeting EGFR in non-small-cell lung cancer.

Identification and characterization of the Cucurbitacins, a novel class of small-molecule inhibitors of Tropomyosin receptor kinase a

Background

NGF-TrkA is well known to play a key role in propagating and sustaining pruritogenic signals, which form the pathology of chronic pruritus. Inhibition of NGF-TrkA is a known strategy for the treatment of pruritus. In the present paper, we describe the identification, in vitro characterization, structure–activity analysis, and inhibitory evaluation of a novel TrkA inhibitory scaffold exemplified by Cucurbitacins (Cus).

Methods

Cus were identified as TrkA inhibitors in a large-scale kinase library screen. To obtain structural models of Cus as TrkA inhibitors, AutoDock was used to explore their binding to TrkA. Furthermore, PC12 cell culture systems have been used to study the effects of Cus and traditional Chinese medicinal plants (Tian Gua Di and bitter gourd leaf) extracts on the kinase activity of TrkA.

Results

Cus block the phosphorylation of TrkA on several tyrosine sites, including Tyr490, Tyr674/675, and Tyr785, and inhibit downstream Akt and MAPK phosphorylation in response to NGF in PC12 cell model systems. Furthermore, traditional Chinese medicinal plants (Tian Gua Di and bitter gourd leaf) containing Cu extracts were shown to inhibit the phosphorylation of TrkA and Akt. These data reveal mechanisms, at least partly, of the anti-pruritus bioactivity of Cus.

Conclusion

Taken together, with the recent discovery of the important role of TrkA as a therapeutic target, Cus could be the basis for the design of improved TrkA kinase inhibitors, which could someday help treat pruritus.

Synthesis and structure‑activity‑relationship of 3,4‑Diaryl‑1H‑pyrrolo[2,3‑b]pyridines as irreversible Inhibitors of mutant EGFR‑L858R/T790M

The epidermal growth factor receptor (EGFR) is a well‑validated drug target for the treatment of non‑small cell lung cancer. Here we present an optimization approach and preliminary structure‑activity relationship for 1H‑pyrrolo[2,3‑b]pyridines as covalent irreversible mutant EGFR inhibitors. We synthesized a focused library to investigate the effect of different aromatic substituents in the 4‑position of this scaffold, interacting with the gatekeeper. We determined the activity of the synthesized compounds mutant EGFR enzyme assays and determined the selectivity over the wild type.