More than an attachment module: covalent inhibitor warheads influence BTK dynamics and function.
Raji E Joseph1, Robert G Britton2, David Yin-Wei Lin1
1Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011, USA.
Biorxiv : the Preprint Server for Biology
|May 18, 2026
Summary
The warhead chemical structure of Bruton's Tyrosine Kinase (BTK) inhibitors influences their target protein dynamics and signaling interactions. This finding may explain how resistance to these important cancer drugs develops.
Area of Science:
- Biochemistry
- Pharmacology
- Oncology
Background:
- Covalent inhibitors targeting Bruton's Tyrosine Kinase (BTK) are standard treatments for B-cell cancers.
- These inhibitors utilize reactive warheads, typically acrylamide or 2-butynamide, to irreversibly bind BTK.
- The functional inertness of these warheads has been presumed, with focus on their modification efficiency and selectivity.
Purpose of the Study:
- To investigate how chemical differences in BTK inhibitor warheads affect protein dynamics and signaling interactions.
- To explore the potential link between warhead-specific effects and the emergence of drug resistance mechanisms.
- To compare the impact of 2-butynamide and acrylamide warheads on BTK conformation and substrate binding.
Main Methods:
- Utilized a panel of BTK covalent inhibitors: Tirabrutinib, Acalabrutinib (2-butynamide warhead), Ibrutinib, and Zanubrutinib (acrylamide warhead).
- Analyzed BTK conformational states and dynamics upon inhibitor binding using biophysical techniques.
- Assessed the binding affinity to the substrate PLCγ and the efficacy of PLCγ signaling inhibition.
Main Results:
- The 2-butynamide warhead (Tirabrutinib, Acalabrutinib) induced conformational heterogeneity in BTK, unlike the acrylamide warhead (Ibrutinib, Zanubrutinib).
- BTK bound by 2-butynamide inhibitors adopted multiple dynamic states, increased PLCγ binding, and showed reduced PLCγ signaling inhibition compared to Ibrutinib.
- Warhead swapping experiments confirmed that the warhead dictates BTK dynamics and inhibitor efficacy, revealing unanticipated allosteric effects.
Conclusions:
- Warhead structure is a critical determinant of BTK inhibitor's allosteric effects, influencing protein dynamics and substrate interactions.
- These warhead-specific allosteric effects offer novel insights into potential mechanisms of inhibitor-specific resistance.
- Understanding these drug-specific structural features is crucial for developing next-generation BTK inhibitors that overcome or circumvent resistance.
Keywords:
AcalabrutinibBTKBTK inhibitorsBruton’s Tyrosine KinaseIbrutinibTirabrutinibZanubrutinibconformational heterogeneitycovalent warheadkinase allosterykinase dynamicskinase inhibitorMore Related Videos
06:17Covalent Fragment Screening Using the Quantitative Irreversible Tethering Assay
Published on: February 28, 2025
10:33Development of Inhibitors of Protein-protein Interactions through REPLACE: Application to the Design and Development Non-ATP Competitive CDK Inhibitors
Published on: October 26, 2015
Related Concept Videos
01:17Intracellular Signaling Affects Focal Adhesions
Integrins act both as extracellular input receivers and as intracellular processing activators. As their name suggests, integrins are entirely integrated into the membrane structure. Their hydrophobic membrane-spanning regions interact with the phospholipid bilayer's hydrophobic region. These membrane receptors provide extracellular attachment sites for effectors like hormones and growth factors. They activate intracellular response cascades when their effectors are bound and active.
Some...
Some...
01:25Drug-Receptor Bonds
Drug-receptor bonds are formed through various chemical forces when drugs interact with target cells. Covalent bonds, strong and irreversible, are exemplified by DNA-alkylating anticancer agents that inhibit cell division. However, such irreversible drug binding lacks selectivity and can modify the DNA of the surrounding healthy cells. Covalent binding often contributes to tissue toxicity, as seen with chloroform and paracetamol metabolites binding to the liver, causing hepatotoxicity.
In...
In...
01:28Inhibitors of Bacterial DNA Synthesis
Bacterial pathogens depend on precise and efficient DNA replication to sustain infection. Two type II topoisomerases—DNA gyrase and topoisomerase IV—are critical to this process, as they resolve DNA supercoiling and unlink chromosomes during replication. Fluoroquinolones, synthetic derivatives of quinolones, exploit this mechanism by stabilizing the transient DNA–enzyme cleavage complex, preventing strand religation, and causing lethal double-strand breaks. These antibiotics are selectively...
02:04Covalently Linked Protein Regulators
Proteins can undergo many types of post-translational modifications, often in response to changes in their environment. These modifications play an important role in the function and stability of these proteins. Covalently linked molecules include functional groups, such as methyl, acetyl, and phosphate groups, and also small proteins, such as ubiquitin. There are around 200 different types of covalent regulators that have been identified.
These groups modify specific amino acids in a protein.
These groups modify specific amino acids in a protein.
02:04Covalently Linked Protein Regulators
Proteins can undergo many types of post-translational modifications, often in response to changes in their environment. These modifications play an important role in the function and stability of these proteins. Covalently linked molecules include functional groups, such as methyl, acetyl, and phosphate groups, and also small proteins, such as ubiquitin. There are around 200 different types of covalent regulators that have been identified.
These groups modify specific amino acids in a protein.
These groups modify specific amino acids in a protein.
01:25Inhibitors of Bacterial Protein Synthesis
Aminoglycosides constitute a highly potent class of bactericidal antibiotics that exert their antimicrobial effects by targeting the bacterial ribosome, specifically disrupting protein synthesis. These polycationic molecules consist of amino-modified sugars linked via glycosidic bonds to an aminocyclitol core such as 2-deoxystreptamine or streptamine. Their strong positive charges facilitate tight binding to the negatively charged phosphate backbone of ribosomal RNA (rRNA), primarily at the 16S...