target engagement

From Tracers to Kinetic Selectivity: Highlights from the Target Engagement in Chemical Biology Symposium

Posted on by Anna Bennett

In April 2024, Promega hosted the “Target Engagement in Chemical Biology Symposium” at the Kornberg Center, a research and development hub on Promega’s campus in Madison, Wisconsin. The goal of the symposium was to gather interdisciplinary researchers interested in the field of small molecule target engagement to foster collaboration through knowledge sharing and innovation. The symposium featured a 1.5-day agenda packed with 23 speakers, 4 workshops, poster sessions and social events. Over 130 attendees gathered to participate in the multifaceted event, with participants from different geographic regions and in different research sectors from academia to government to industry.  

People gather in a large atrium with scientific posters and table displays.
Attendees gather for the poster session in Kornberg Atrium. Photo by Anna Bennett (Promega Corporation)

The symposium highlighted the collective commitment to overcoming the challenges in drug discovery by developing more targeted and efficacious treatments, driven by a shared determination to create innovative solutions that address unmet medical needs. While we cannot share all the exciting research presented at the symposium, we are thrilled to highlight a few talks that exemplify the novel work and collaborative spirit of this research community.  

Continue reading “From Tracers to Kinetic Selectivity: Highlights from the Target Engagement in Chemical Biology Symposium”

Cell-Based Target Engagement and Functional Assays for NLRP3 Inhibitor Profiling Help Identify Successes and Failures

Posted on by Kari Kenefick

Identifying Inflammasome Inhibitors: What’s Missing
The NLRP3 inflammasome is implicated in a wide range of diseases. The ability to inhibit this protein complex could provide more precise, targeted relief to inflammatory disease sufferers than current broad-spectrum anti-inflammatory compounds, potentially without side effects.

Studies of NLRP3 inflammasome inhibitors have relied on cell-free assays using purified NLRP3. But cell-free assays cannot assess physical engagement of the inhibitor and target in the cellular micro-environment. Cell-free assays cannot show if an NLRP3 inhibitor enters the cell, binds the target and how long the inhibitor binding lasts.

Cell-based assays that interrogate the physical interaction of the NLRP3 target and inhibitor inside cells are needed.

Continue reading “Cell-Based Target Engagement and Functional Assays for NLRP3 Inhibitor Profiling Help Identify Successes and Failures”

Designing Science: A Behind-the-Scenes Look at Our Recent Journal Cover Art

Posted on by Jordan Nutting
A 3D illustration showing RAF inhibitor LXH254 engages BRAF or CRAF protomers (orange), but spares ARAF (red). Unoccupied ARAF is competent to trigger downstream mitogenic signaling, which is demonstrated with lightning bolts. Red cells in the background are fluorescently labeled RAS proteins, expressed in live cells. The Cell Chemical Biology cover type superimposes the image.
Image adapted from original artwork by iSO-FORM LLC.

We made the cover! Of Cell Chemical Biology, that is.

This July, Cell Chemical Biology editors accepted a study from Promega scientists and invited the research team to submit cover art for the issue. The study in question details a BRET-based method to quantify drug-target occupancy within RAF-KRAS complexes in live cells. Promega scientists Matt Robers and Jim Vasta collaborated with one of our talented designers, Michael Stormberg, to craft an image that accurately represents the science in a dynamic and engaging way.

You can check out the paper and cover art in the November 16 issue of Cell Chemical Biology.

I spoke with Michael Stormberg to learn more about the creative process that went into creating this cover art and how he worked with the research team and other collaborators.

Continue reading “Designing Science: A Behind-the-Scenes Look at Our Recent Journal Cover Art”

RAF Inhibitors: Quantifying Drug-Target Occupancy at Active RAS-RAF Complexes in Live Cells

Posted on by Ken Doyle

Mitogen-activated protein kinases (MAPKs) are a large family of proteins that regulate diverse cellular functions in eukaryotes, including gene expression, proliferation, differentiation and apoptosis (1). MAPK signaling pathways typically include three sequentially activated kinases, and these pathways are triggered in response to extracellular stimuli, such as cytokines, mitogens, growth factors and oxidative stress (1). Ultimately, the signal is transmitted to the nucleus, with the activation of a specific transcription factor that modulates the expression of one or more genes.

Among MAPK pathways, the RAS-RAF-MEK-ERK signaling pathway has been studied extensively. Mutations in RAS family proteins and resultant dysregulation of the signaling pathway are implicated in a variety of cancers. Therefore, this pathway is a popular target for anticancer drug development.

An overview of the RAS-RAF-MEK-ERK signaling pathway.
Continue reading “RAF Inhibitors: Quantifying Drug-Target Occupancy at Active RAS-RAF Complexes in Live Cells”

From Hit to Live-Cell Target Engagement Assay: DNA-Encoded Library Screens and NanoBRET™ Dye

Posted on by Tian Yang

Monitoring and quantifying drug-target binding in a live-cell setting is important to bridging the gap between in vitro assay results and the phenotypic outcome, and therefore represents a crucial step in target validation and drug development (1). The NanoBRET™ Target Engagement (TE) assay is a biophysical technique that enables quantitative assessment of small molecule-target protein binding in live cells. This live-cell target engagement assay uses the bioluminescence resonance energy transfer (BRET) from a NanoLuc® luciferase-tagged target protein and a cell-permeable fluorescent tracer that reversibly binds the target protein of interest. In the presence of unlabeled test compound that engages the target protein, the tracer is displaced, and a loss of BRET signal is observed. Due to the tight distance constraints for BRET, the signal measured is specific to the target fused to NanoLuc® luciferase.

Live-cell target engagement assay using NanoBRET to measure small molecule binding to a target transmembrane protein.

Promega offers over 400 ready-to-use assays for multiple target classes, including kinases, E3 ligases, RAS, and many others. For targets that do not have an existing NanoBRET™ TE assay, Promega offers NanoBRET™ dyes, NanoLuc® cloning vectors, and NanoBRET™ detection reagents to develop novel NanoBRET™ TE assays.

To learn more about the NanoBRET™ TE platform, see the NanoBRET™ Target Engagement Technology Page on our website.

One critical component in the development of novel NanoBRET™ TE assay is the creation of the cell-permeable fluorescent tracers (NanoBRET™ tracers) against the target protein of interest. The tracers are bifunctional, consisting of a NanoBRET™-compatible fluorophore and a target-binding moiety connected by a linker. While the NanoBRET™ 590 dyes have demonstrated consistently robust cell permeability and optimal spectral overlap with NanoLuc® for BRET, a ligand capable of binding to the target protein of interest needs to be identified to generate a NanoBRET™ tracer.

What Are DNA-Encoded Libraries?

DNA-Encoded Libraries, (DELs), have emerged as powerful tools for discovering small molecule ligands to target proteins of interest at an unprecedented scale. . owing to the ability of a DEL  to enable the synthesis of larger libraries of compounds and to target proteins without any prior structural knowledge of the proteins or their ligands (2). Because each member of a DEL contains a DNA barcode and a small molecule separated by a linker, DEL is primed for discovering leads within therapeutic modalities that rely on bifunctional chemistry, such as proteolysis targeting chimeras (PROTACs). Since NanoBRET™ tracers are also bifunctional, ligands identified from DEL selections could serve as ideal candidates for developing novel NanoBRET™ tracers that can enable NanoBRET™ TE assays for new targets.

Continue reading “From Hit to Live-Cell Target Engagement Assay: DNA-Encoded Library Screens and NanoBRET™ Dye”

GPCRs and PROTACs: New Approaches for Designing More Effective Drug Candidates

Posted on by Ken Doyle
NanoBRET target engagement assay

G protein-coupled receptors (GPCRs) comprise a large group of cell surface receptors, characterized by the unique structural property of crossing the cell membrane seven times. They respond to a diverse group of signaling molecules, such as peptides, neurotransmitters, cytokines, hormones and other small molecules (1). Upon activation, GPCRs interact with GTP-binding (G) proteins and arrestins to regulate a wide variety of signaling pathways. This broad range of functions makes GPCRs attractive targets for drug discovery. The importance of GPCR research was highlighted in 2012, with the Nobel Prize in chemistry being awarded to Robert Lefkowitz and Brian Kobilka “for studies of G-protein–coupled receptors”.

Based on structure and function, GPCRs are categorized into six classes, A–F. The class A GPCRs, or rhodopsin-like receptors, have been studied extensively due to their association with many types of diseases (2). Within the class A GPCRs is a group that share a highly conserved structural motif (3) and respond to chemokines—small “chemotactic cytokines” that stimulate cell migration, especially that of white blood cells (4). A subfamily of class A GPCRs respond to chemokines that have two cysteine residues near the N-terminus, known as CC chemokines. GPCRs activated by CC chemokines are called CC chemokine receptors or CCRs, and these interactions have been implicated in both pro- and anti-cancer pathways (5).

Continue reading “GPCRs and PROTACs: New Approaches for Designing More Effective Drug Candidates”

The Surprising Landscape of CDK Inhibitor Selectivity in Live Cells

Posted on by Promega

Cyclin-dependent kinases (CDKs) are promising therapeutic targets in cancer and are currently among the most intensely studied enzymes in drug discovery. The FDA has recently approved three drugs for breast cancer that target members of this kinase subfamily, fueling interest in the entire family. Although broad efforts in drug discovery have produced many CDK inhibitors (CDKIs), few have been characterized in living cells. So just how potent are these compounds in a cellular environment? Are these compounds selective for their intended CDK target, or do they bind many similar kinases in cells? To address these questions, teams at the Structural Genomics Consortium and Promega used the NanoBRET™ Target Engagement technology to uncover surprising patterns of selectivity for touted CDKIs and abandoned clinical leads (1). The results offer exciting opportunities for repurposing some inhibitors as selective chemical probes for lesser-studied CDK family members.

CDKs and CDKIs

nanobret technology for kinase target engagement

Cyclin-dependent kinases (CDKs) regulate a number of key global cellular processes, including cell cycle progression and gene transcription. As the name implies, CDK activity is tightly regulated by interactions with cyclin proteins. In humans, the CDK subfamily consists of 21 members and several are validated drivers of tumorigenesis. For example, CDKs 1, 2, 4 and 6 play a role in cell cycle progression and are validated therapeutic targets in oncology. However, the majority of the remaining CDK family is less studied. For example, some members of the CDK subfamily, such as CDKs 14–18, lack functional annotation and have unclear roles in cell physiology. Others, such as the closely related CDK8/19, are members of multiprotein complexes involved broadly in gene transcription. How these kinases function as members of such large complexes in a cellular context remains unclear, but their activity has been associated with several pathologies, including colorectal cancer. Despite their enormous therapeutic potential, our knowledge of the CDK family members remains incomplete.

Continue reading “The Surprising Landscape of CDK Inhibitor Selectivity in Live Cells”

Illuminating the Function of a Dark Kinase (DCLK1) with a Selective Chemical Probe

Posted on by Promega

The understudied kinome represents a major challenge as well as an exciting opportunity in drug discovery. A team of researchers lead by Nathanael Gray at the Dana Farber Cancer Institute was able to partially elucidate the function of an understudied kinase, Doublecortin-like kinase 1 (DCLK1), in pancreatic ductal adenocarcinoma cells (PDAC). The characterization of DCLK1 in PDAC was realized by developing a highly specific chemical probe (1). Promega NanoBRET™ Target Engagement (TE) technology enabled intracellular characterization of this chemical probe.

The Dark Kinome

NanoBRET target engagement

Comprised of over 500 proteins, the human kinome is among the broadest class of enzymes in humans and is rife with targets for small molecule therapeutics. Indeed, to date, over 50 small molecule kinase inhibitors have achieved FDA approval for use in treating cancer and inflammatory diseases, with nearly 200 kinase inhibitors in various stages of clinical evaluation (2). Moreover, broad genomic screening efforts have implicated the involvement of a large fraction of kinases in human pathologies (3). Despite such advancements, our knowledge of the kinome is limited to only a fraction of its family members (3,4). For example, currently less than 20% of human kinases are being targeted with drugs in clinical trials. Moreover, only a subset of kinases historically has garnered substantial citations in academic research journals (4). As a result, a large proportion of the human kinome lacks functional annotation; as such, these understudied or “dark” kinases remain elusive to therapeutic intervention (4).

Continue reading “Illuminating the Function of a Dark Kinase (DCLK1) with a Selective Chemical Probe”

NanoLuc® Luciferase Powers More than Reporter Assays

Posted on by Sara Klink
Bright NanoLuc® Luciferase

What can you do with a small, super bright luciferase? Amazing things. We’ve highlighted many of the papers and new applications that NanoLuc® luciferase has enabled on this blog. While NanoLuc® luciferase was first introduced as a reporter enzyme to assess promoter activity, its capabilities have expanded far beyond a genetic reporter, creating bioluminescent tools used to study endogeneous protein dynamics, target engagement, protein degradation, immunodetection and more. So where did the NanoLuc luciferase come from and how does one enzyme power so many research capabilities? Read further for a primer on the various technologies and applications developed from this enzyme over the last 10 years.

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Voted Drug Discovery and Development Product for 2018: NanoBRET TE Kinase Assays

Posted on by Kari Kenefick

Choice Drug Discovery and Development Product 2019 award
Michael Curtin, Promega, accepting the Reviewers’ Choice for Drug Discovery and Development Product of the Year award from SelectScience.

As announced at SLAS in Washington, D.C. recently, we are excited to have NanoBRET Target Engagement (TE) Intracellular Kinase Assays awarded the SelectScience Reviewers’ Choice for Drug Discovery and Development Product of the Year 2018!

The NanoBRET™ Target Engagement (TE) Kinase Assay, first available in the fall of 2017, has been getting great reviews on the SelectScience site for more than a year now. Continue reading “Voted Drug Discovery and Development Product for 2018: NanoBRET TE Kinase Assays”