BRUIN CLL-322: a phase 3 open-label, randomized study of fixed duration pirtobrutinib plus venetoclax and rituximab versus venetoclax and rituximab in previously treated chronic lymphocytic leukemia/small lymphocytic lymphoma (trial in progress)

Background: Covalent Bruton's Tyrosine Kinase (BTK) inhibitors (BTKi) have transformed the management of chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), but these treatments are not curative and the majority of patients will require additional treatment. The MURANO study established the time-limited combination of 2 years venetoclax plus rituximab as a clinically important regimen for patients with R/R CLL/SLL. However, that trial almost exclusively enrolled patients who were never treated with a covalent BTKi, a population less relevant in the context of today's standard of care. Pirtobrutinib is a highly selective, non-covalent BTKi that inhibits both wild type (WT) and C481-mutated BTK with equal low nM potency. In a phase 1/2 BRUIN trial, pirtobrutinib achieved pharmacokinetic exposures that exceeded its BTK IC96 at trough, was well tolerated, and demonstrated promising efficacy in CLL/SLL patients regardless of prior therapy, number of prior lines of therapy, or BTK C481 mutation status (Mato et al. Lancet 2021;397,10277:892-901). Therefore, adding fixed duration pirtobrutinib to the time-limited MURANO regimen may allow for even deeper and more prolonged disease control, and generate a clinically relevant dataset in a BTK-pretreated CLL/SLL population.