Pirtobrutinib

Pirtobrutinib is a small molecule and a highly selective non-covalent inhibitor of Bruton’s tyrosine kinase (BTK). Its high selectivity has been associated with lower discontinuation rates due to adverse events and a lower incidence of atrial fibrillation. Unlike BTK covalent inhibitors, such as ibrutinib, that bind to the cysteine 481 (Cys481) amino acid within the active site of BTK, the inhibitory activity of pirtobrutinib is maintained even in the presence of Cys481 mutations. Although the mechanisms of resistance to covalent BTK inhibitors have not been fully elucidated, it appears that the presence of Cys481 mutations is the most common reason for resistance to covalent BTK inhibitors. However, other mutations may confer resistance to non-covalent BTK inhibitors such as pirtobrutinib.

In January 2023, the use of pirtobrutinib for the treatment of relapsed or refractory mantle cell lymphoma (MCL) after at least two lines of systemic therapy was approved under the FDA's Accelerated Approval pathway.

Pirtobrutinib is indicated for the treatment of adult patients with relapsed or refractory mantle cell lymphoma (MCL) after at least two lines of systemic therapy, including a BTK inhibitor.