Enrichment of BTK Leu528Trp mutations in patients with CLL on zanubrutinib: potential for pirtobrutinib cross-resistance

• Published in: Blood advances 2022-10, Vol.6 (20), p.5589-5592
• Main Authors: Blombery, Piers, Thompson, Ella R., Lew, Thomas E., Tiong, Ing Soo, Bennett, Rory, Cheah, Chan Y., Lewis, Katharine Louise, Handunnetti, Sasanka M., Tang, Chloe Pek Sang, Roberts, Andrew, Seymour, John F., Tam, Constantine S.
• Format: Article
• Language: English
• Subjects: Stimulus Report
• ISSN: 2473-9529; 2473-9537
• DOI: 10.1182/bloodadvances.2022008325

•Patients with CLL progressing on zanubrutinib have an enrichment of the BTK Leu528Trp compared with those who progress on ibrutinib.•Cross-resistance may be observed in patients who progress while on zanubrutinib with BTK Leu528Trp mutations and subsequent pirtobrutinib. The covalent Bruton’s tyrosine kinase inhibitors (BTKis) are highly effective for the treatment of chronic lymphocytic leukemia (CLL). The dominant resistance mechanism observed with the BTKi ibrutinib is the development of BTK Cys481 codon mutations. Whether a similar resistance mutation profile exists for the newer-generation, more selective BTKi zanubrutinib is unknown. In samples referred for diagnostic next-generation sequencing in patients with progressive CLL, we observed an enrichment in the kinase-dead BTK Leu528Trp mutation in patients treated with zanubrutinib compared with ibrutinib (54%; 7 of 13 vs 4%; 1 of 24, P = .001). We describe 2 patients with BTK Leu528Trp mutations who showed clinical cross-resistance and progressive enrichment of the BTK Leu528Trp mutation over time when treated with the noncovalent BTKi pirtobrutinib. Both patients subsequently responded to venetoclax-based treatment. In summary, we have identified an enrichment of the BTK Leu528Trp mutation arising in patients treated with zanubrutinib that may impart cross-resistance to the noncovalent inhibitor pirtobrutinib and therefore may have implications for sequencing of these treatments in CLL.