Biochemical characterization of tirabrutinib and other irreversible inhibitors of Bruton's tyrosine kinase reveals differences in on - and off - target inhibition.

Abstract

BACKGROUND:

Bruton's tyrosine kinase (BTK) is a key component of the B-cell receptor (BCR) pathway and a clinically validated target for small molecule inhibitors such as ibrutinib in the treatment of B-cell malignancies. Tirabrutinib (GS-4059/ONO-4059) is a selective, once daily, oral BTK inhibitor with clinical activity against many relapsed/refractory B-cell malignancies.

METHODS:

Covalent binding of tirabrutinib to BTK Cys-481 was assessed by LC-MSMS analysis of BTK using compound as a variable modification search parameter. Inhibition potency of tirabrutinib, ibrutinib, acalabrutinib, and spebrutinib against BTK and related kinases was studied in a dose-dependent manner either after a fixed incubation time (as used in conventional IC50 studies) or following a time course where inactivation kinetics were measured.

RESULTS:

Tirabrutinib irreversibly and covalently binds to BTK Cys-481. The inactivation efficiency kinact/Ki was measured and used to calculate selectivity among different kinases for each of the four inhibitors studied. Tirabrutinib showed a kinact/Ki value of 2.4 ± 0.6 × 104 M-1 s-1 for BTK with selectivity against important off-targets.

CONCLUSIONS:

For the BTK inhibitors tested in this study, analysis of the inactivation kinetics yielded a more accurate measurement of potency and selectivity than conventional single-time point inhibition measurements. Subtle but clear differences were identified between clinically tested BTK inhibitors which may translate into differentiated clinical efficacy and safety.

GENERAL SIGNIFICANCE:

This is the first study that offers a detailed side-by-side comparison of four clinically-relevant BTK inhibitors with respect to their inactivation of BTK and related kinases.

• Authors: Albert Liclican, Loredana Serafini, Weimei Xing, Gregg Czerwieniec, Bart Steiner, Ting Wang, Katherine M Brendza, Justin D Lutz, Kathleen S Keegan, Adrian S Ray, Brian E Schultz, Roman Sakowicz, Joy Y Feng
• Journal: Biochimica et biophysica acta. General subjects (Biochim Biophys Acta Gen Subj) Vol. 1864 Issue 4 Pg. 129531 (04 2020) ISSN: 1872-8006 [Electronic] Netherlands
• PMID: 31953125 (Publication Type: Journal Article)
• Copyright: Copyright © 2020 The Authors. Published by Elsevier B.V. All rights reserved.

Chemical References

• Imidazoles
• Protein Kinase Inhibitors
• Pyrimidines
• Agammaglobulinaemia Tyrosine Kinase
• BTK protein, human
• tirabrutinib

Topics

• Agammaglobulinaemia Tyrosine Kinase (antagonists & inhibitors, metabolism)
• Dose-Response Relationship, Drug
• Humans
• Imidazoles (chemistry, pharmacology)
• Kinetics
• Mass Spectrometry
• Molecular Structure
• Protein Kinase Inhibitors (chemistry, pharmacology)
• Pyrimidines (chemistry, pharmacology)
• Structure-Activity Relationship