Mitotic kinesin-like protein 2 (MKLP2/KIF20A) is a key mitotic regulator frequently overexpressed in human malignancies and its abundance is positively correlated with poor outcomes of the disease. Despite extensive research on MKLP2 as a potential target for oncology, the development of small-molecule inhibitors specific to MKLP2 remains limited. We have previously identified a benzoazipinone compound, HJ81 as a potent disruptor of Aurora kinase B (AURKB) localization during late mitosis. This study reveals that such disruption results from a failure of AURKB relocation at the onset of anaphase and this phenomenon can be specifically attributed to the disablement of MKLP2, a recognized facilitator of the relocation process. Further optimization of HJ81 leads to identifying compounds such as 12a as promising lead inhibitors of MKLP2-mediated processes, with improved pharmacokinetic properties. 12a inhibits the microtubule-stimulated ATPase activity of the recombinant MKLP2 in vitro. Significant suppression of tumor growth was observed in mice bearing the Calu-6 lung cancer cell line when treated with 12a at a well-tolerated dose. Overall, our findings suggest that benzoazipinone derivatives represent a novel chemical scaffold with the potential to be developed to mimic MKLP2 inhibition for cancer treatment.

Activity-based drug screens have successfully led to the development of various inhibitors of the catalytic activity of aurora kinases (AURKs), major regulatory kinases of cell division. Disrupting the localization of AURKB, rather than its catalytic activity, represents a largely unexplored alternative approach to disabling AURKB-dependent processes. Localization disruptors could be just as specific as direct inhibitors of AURKB activity, may bypass their off-target and select on-target toxicities, and are likely less susceptible to drug resistance resulting from mutations of the AURKB catalytic site. In this study, we demonstrate that the pan-AURK inhibitor AMG900 works at a low concentration not by inhibiting the phosphorylation of H3 at Ser10, an AURKB substrate, but by disrupting the mitotic localization of AURKB. Structural deletion studies pinpoint this undescribed activity to the 2-phenoxy-3,4'-bipyridine moiety of AMG900. Guided by a mechanism-informed phenotypic screening (MIPS) assay, the drug fragment is optimized into a novel class of inhibitors that, at low nanomolar concentrations, can disable AURKB through disruption of its mitotic localization and have desirable oral PK properties. Hierarchical clustering of cell fitness profiles reveals that these compounds cluster with each other, rather than with known AURK inhibitors such as AMG900 and VX-680. Validation studies in mice demonstrate that compound 15a elicits mitotic arrest and apoptosis in NCI-H23 human lung adenocarcinoma xenografts, resulting in a pronounced suppression of tumor growth. The discovery and optimization of compounds that disrupt AURKB localization are successfully facilitated by MIPS. Our findings suggest that 2-phenoxy-3, 4'-bipyridine derivatives have the potential to be further developed as effective therapeutics for the treatment of malignancy by delocalizing AURKB.

AbstractSelpercatinib (LOXO292) and pralsetinib (BLU667) are RET protein tyrosine kinase inhibitors (TKIs) recently approved for treating RET-altered cancers. However, RET mutations that confer selpercatinib/pralsetinib resistance have been identified, necessitating development of next-generation RET TKIs. While acquired RET G810C/R/S/V mutations were reported in selpercatinib-treated patients, it was unclear whether all of these and other potential G810 mutants are resistant to selpercatinib and pralsetinib. Here, we profiled selpercatinib and pralsetinib on all six possible G810 mutants derived from single nucleotide substitution and developed novel alkynyl nicotinamide-based RET TKIs to inhibit selpercatinib/pralsetinib-resistant RET G810 mutants. Surprisingly, the G810V mutant found in a clinical study was not resistant to selpercatinib or pralsetinib. Besides G810C/R/S, G810D also conferred selpercatinib/pralsetinib resistance. Alkynyl nicotinamide compounds such as HSN608, HSL476, and HSL468 have better drug-like properties than alkynyl benzamides. Six of these compounds inhibited all six G810 solvent-front mutants and the V804M gatekeeper mutant with IC50 < 50 nmol/L in cell culture. Oral administration of HSN608 at a well-tolerated dose (30 mg/kg) gave plasma level > 30x the IC50s of inhibiting all G810 mutants in cell culture. In cell-derived xenograft tumors driven by KIF5B-RET (G810C) that contains the most frequently observed solvent-front mutant in selpercatinib-treated patients, HSN608, HSL476, and HSL468 significantly suppressed and caused regression of the selpercatinib-resistant tumors. This study clarifies the sensitivities of different RET solvent-front mutants to selpercatinib and pralsetinib and identifies novel alkylnyl nicotinamide-based RET TKIs for inhibiting selpercatinib/pralsetinib-resistant G810 mutants.

We investigated a novel 4-phenoxy-quinoline-based scaffold that mislocalizes the essential mitotic kinase, Aurora kinase B (AURKB). Here, we evaluated the impact of halogen substitutions (F, Cl, Br, and I) on this scaffold with respect to various drug parameters. Br-substituted LXY18 was found to be a potent and orally bioavailable disruptor of cell division, at sub-nanomolar concentrations. LXY18 prevents cytokinesis by blocking AURKB relocalization in mitosis and exhibits broad-spectrum antimitotic activity in vitro. With a favorable pharmacokinetic profile, it shows widespread tissue distribution including the blood-brain barrier penetrance and effective accumulation in tumor tissues. More importantly, it markedly suppresses tumor growth. The novel mode of action of LXY18 may eliminate some drawbacks of direct catalytic inhibition of Aurora kinases. Successful development of LXY18 as a clinical candidate for cancer treatment could enable a new, less toxic means of antimitotic attack that avoids drug resistance mechanisms.

We combined a mechanism-informed phenotypic screening (MIPS) assay with a structural simplification strategy to guide the discovery of compounds that disrupt the localization of the mitotic regulator, Aurora kinase B (AURKB), rather than inhibiting its catalytic activity. An initial hit 4-(4-methylthiophen-2-yl)-N-(4-(quinolin-4-yloxy)phenyl)phthalazin-1-amine was identified after screening an in-house library of small molecules and phenocopied the loss of function mutations in AURKB without inhibiting its catalytic activity. We isolated this hit compound activity to its 4-phenoxy-quinoline moiety. The fragment was further optimized into a class of new chemical entities that potently disrupt the mitotic localization of AURKB at low nanomolar concentrations and consequently elicit severe growth inhibition in diverse human cancer cell lines. A lead compound, N-(3-methoxy-5-(6-methoxyquinolin-4-yl)oxy)phenyl)acetamide possessed desirable pharmacokinetic properties such as AUC0-infinity: 227.15 [ng center dot h/mL/(mg/kg)]; Cmax: 3378.52 ng/mL T1/2: 3.52 h; and F%: 42 % and produced the AURKB-inhibitory phenotypes in a mouse xenograft model. A lead compound is a powerful tool for interrogating the regulation of AURKB and has the potential to be further developed as a first-in-class oncology therapeutic.

Selpercatinib (LOXO-292, LY3527723) and pralsetinib (BLU-667) are first-in-class RET-targeted cancer therapy drugs. However, secondary RET mutations that confer selpercatinib/pralsetinib resistance have been identified, necessitating development of next-generation RET Tyrosine kinase inhibitors (TKIs). While the G810C/R/S/V mutations located at the RET kinase solvent-front site were detected in selpercatinib-treated patients, it was unclear whether all of these and other potential G810 mutants are resistant to selpercatinib and pralsetinib. We profiled selpercatinib and pralsetinib on all six possible G810 mutants derived from single nucleotide substitution. Surprisingly, the G810V mutant found in a clinical study was not resistant to selpercatinib or pralsetinib. Besides G810C/R/S, G810D also conferred selpercatinib/pralsetinib resistance. We found that alkynyl nicotinamide compounds such as HSN608 have better drug-like properties than alkynyl benzamides. HSN608 inhibited RET and RET V804M gatekeeper mutant, and all six G810 mutants with low nanomolar IC50s in the BaF3/KIF5B-RET mutant cell model. In cell derived xenograft (CDX) tumors driven by KIF5B-RET(G810C), HSN608 caused regression of the selpercatinib-resistant tumors. This study clarifies the sensitivities of different RET solvent-front mutants to selpercatinib and pralsetinib, and identifies an alkylnyl nicotinamide-based RET TKI for inhibiting selpercatinib/pralsetinib-resistant G810 mutants. Citation Format: Ujjwol Khatri, Neetu Dayal, Xueqing Hu, Elizabeth Larocque, Nimishetti Naganna, Tao Shen, Xuan Liu, Frederick W. Holtsberg, M. Javad Aman, Herman O. Sintim, Jie Wu. Targeting RET solvent-front mutants with an alkynyl nicotinamide-based inhibitor. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3851.

This study investigated the metabolism of LXY18, a quinolone-based compound that suppresses tumorigenesis by blocking AURKB localization. Metabolite profiling of LXY18 in liver microsomes from six species and human S9 fractions revealed that LXY18 undergoes various conserved metabolic reactions, such as N-hydroxylation, N-oxygenation, O-dealkylation, and hydrolysis, resulting in ten metabolites. These metabolites were produced through a combination of CYP450 enzymes, and non-CYP450 enzymes including CES1, and AO. Two metabolites, M1 and M2 were authenticated by chemically synthesized standards. M1 was the hydrolyzed product catalyzed by CES1 whereas M2 was a mono-N-oxidative derivative catalyzed by a CYP450 enzyme. AO was identified as the enzyme responsible for the formation of M3 with the help of AO-specific inhibitors and LXY18 analogs, 5b and 5c. M1 was the intermediate of LXY18 to produce M7, M8, M9, and M10. LXY18 potently inhibited 2C19 with an IC50 of 290 nM but had a negligible impact on the other CYP450s, indicating a low risk of drug-drug interaction. Altogether, the study provides valuable insights into the metabolic process of LXY18 and its suitability as a drug candidate. The data generated serves as a significant reference point for conducting further safety assessments and optimizing drug development.

A new class of alkynyl isoquinoline antibacterial compounds, synthesized via Sonogashira coupling, with strong bactericidal activity against a plethora of Gram-positive bacteria including methicillin- and vancomycin-resistant Staphylococcus aureus (S. aureus) strains is presented. HSN584 and HSN739, representative compounds in this class, reduce methicillin-resistant S. aureus (MRSA) load in macrophages, whilst vancomycin, a drug of choice for MRSA infections, was unable to clear intracellular MRSA. Additionally, both HSN584 and HSN739 exhibited a low propensity to develop resistance. We utilized comparative global proteomics and macromolecule biosynthesis assays to gain insight into the alkynyl isoquinoline mechanism of action. Our preliminary data show that HSN584 perturb S. aureus cell wall and nucleic acid biosynthesis. The alkynyl isoquinoline moiety is a new scaffold for the development of potent antibacterial agents against fatal multidrug-resistant Gram-positive bacteria.

We used mechanism-informed phenotypic screening to identify and optimize compounds that phenocopy the genetic depletion of the mitotic aurora kinase B (AURKB) kinase. After assaying nine aryl fused seven-membered lactam compounds, we identified a hit compound 6a that was subsequently optimized to five lead compounds with low nanomolar activity, represented by the lead compound 6v (19 nM). With excellent drug-like properties, these compounds reproduced the loss of function in phenotypes of AURKB and exhibited potent cytotoxic activities in various cancer cell lines. Collectively, these data support that seven-membered lactam-based analogs might be valuable for further development as a new type of antimitotic agents for the treatment of cancer.

Two out of five patients with non‐small cell lung cancer (NSCLC) develop brain metastases with 3‐8 month overall survival time. One of the greatest challenges for developing chemotherapeutics for brain metastases of NSCLC is the blood‐brain barrier (BBB). The BBB is composed of endothelial cells with distinct tight junctions, pericytes, a unique basement membrane and astrocyte endfeet. This unique vasculature structure opposes the movement of deleterious molecules, toxins, and drugs from the bloodstream into the central nervous system. We have previously characterized a shift from the impermeable BBB to a heterogeneously permeable blood‐tumor barrier (BTB) during the formation of brain metastases of non‐small cell lung cancer. These changes in permeability and composition may make brain tumors more accessible to therapeutics delivered through the bloodstream. One potential therapeutic is aminoisoquinolines. In vitrodata has demonstrated the efficacy of aminoisoquinolines in growth inhibition of lung cancers. They do so through inhibition of AuroraB and p70S6K kinases, two kinases critical to proliferation of lung cancer cells. Herein, we investigate the ability of aminoisoquinolines to inhibit metastasis of NSCLC to the brain through the BTB. We hypothesize that treatment of mice harboring brain‐seeking NSCLC cells with aminoisoquinolines will prevent formation of brain metastases. Nineteen athymic nude mice were injected with brain‐seeking NSCLC tumor cells, adenocarcinoma subtype (A549), via ultrasound‐guided intracardiac injection. The mice were then treated with one of two aminoisoquinolines or a vehicle control. After 10 days of treatment, brains were procured from the animals and evaluated microscopically for presence or absence of brain metastases. We identified an average of 4.25 (n=4) metastases in animals treated with the aminoisoquinoline HSN 789, with an average diameter of 15.66 micrometers. Animals treated with the aminoisoquinoline HSN 804 had an average of 18.5 metastases (n=2), with an average diameter of 23.00 micrometers. Animals treated with the vehicle control failed to form brain metastases; we are investigating cell viability in this experimental group. A complete evaluation of cell viability in all treatment groups will reveal the in vivo therapeutic efficacy of aminoisoquinolines for treatment of brain metastases of NSCLC. Preliminary data suggest that treatment with aminoisoquinolines may be sufficient to inhibit growth of brain metastases from NSCLC.

To identify novel bioactive compounds, an image-based, cell culture screening of natural product extracts was conducted. Specifically, our screen was designed to identify phytochemicals that might phenocopy inhibition of the chromosomal passenger protein complex in eliciting mitotic and cytokinetic defects. A known alkaloid, scoulerine, was identified from the rhizomes of the plant Corydalis decumbens as being able to elicit a transient mitotic arrest followed by either apoptosis induction or polyploidy. In examining the mitotic abnormality further, we observed that scoulerine could elicit supernumerary centrosomes during mitosis, but not earlier in the cell cycle. The localization of NUMA1 at spindle poles was also inhibited, suggesting diminished potential for microtubule recruitment and spindle-pole focusing. Polyploid cells emerged subsequent to cytokinetic failure. The concentration required for scoulerine to elicit all its cell division phenotypes was similar, and an examination of related compounds highlighted the requirement for proper positioning of a hydroxyl and a methoxy group about an aromatic ring for activity. Mechanistically, scoulerine inhibited AURKB activity at concentrations that elicited supernumerary centrosomes and polyploidy. AURKA was only inhibited at higher concentrations, so AURKB inhibition is the likely mechanism by which scoulerine elicited division defects. AURKB inhibition was never complete, so scoulerine may be a suboptimal AURK inhibitor or work upstream of the chromosomal passenger protein complex to reduce AURKB activity. Scoulerine inhibited the viability of a variety of human cancer cell lines. Collectively, these findings uncover a previously unknown activity of scoulerine that could facilitate targeting human cancers. Scoulerine, or a next-generation analogue, may be useful as a nontoxic component of combination therapies where inhibiting the chromosomal passenger protein complex is desired.

Natural sources are a valuable reserve of chemical diversity for drug development. However, creative screening assays are required to unlock this potential. A high-content screen was developed to isolate anti-mitotic and polyploidy-inducing activity in mammalian cancer cells from plant extracts. The assay was utilized in an analysis of more than 2000 medicinal plants and activity was identified in a rhizome extract from Corydalis longicalcarata. Two bioactive benzophenanthridine alkaloids, corynoline and its close analog acetylcorynoline, were purified. These compounds display pleiotropic effects on cell division, including prevention of chromosome congression, compromise of the spindle checkpoint response, and blockade of cytokinesis. Corynoline and acetylcorynoline are known entities but the potential for development as anti-mitotic drugs has never been ascribed to these two phytochemicals. This study highlights the requirement and ability of novel bioassays to unlock novel function for known phytochemicals.