Pirtobrutinib versus venetoclax in covalent Bruton tyrosine kinase inhibitor-pretreated chronic lymphocytic leukemia: a matching-adjusted indirect comparison

Venetoclax is a standard treatment for patients with chronic lymphocytic leukemia (CLL) following covalent Bruton tyrosine kinase inhibitor (cBTKi) therapy, despite relatively limited prospective data in this setting. Pirtobrutinib is a highly selective, non-covalent (reversible) BTKi that was designed to overcome the pharmacologic limitations of cBTKi and re-establish BTK inhibition. An unanchored matching-adjusted indirect comparison (MAIC) was conducted to estimate the treatment effect of pirtobrutinib versus venetoclax monotherapy in patients with cBTKi-pretreated CLL. Data from patients with CLL who were venetoclax-naïve and pretreated with cBTKi received pirtobrutinib (N=146) in the phase I/II BRUIN study were compared with the only identified trial of patients with CLL receiving venetoclax after a cBTKi (N=91), as administered as monotherapy until progression. Outcomes included progression-free survival (PFS), overall survival (OS), objective response rate (ORR), and treatment-emergent adverse events. Both unweighted and weighted analyses were conducted. PFS and OS of pirtobrutinib and venetoclax were comparable in both unweighted and weighted analyses (weighted hazard ratios for PFS: 1.01, 95% confidence interval [CI]: 0.58-1.73, P=0.98 and OS: 0.64, 95% CI: 0.25-1.67, P=0.34). ORR was significantly higher for pirtobrutinib (80.2% vs. 64.8%, P=0.01). Grade ≥3 treatment-emergent adverse events were lower in weighted analyses for pirtobrutinib versus venetoclax (all P<0.01), except for pneumonia, which was similar. These results suggest that pirtobrutinib may also be considered as an effective and well-tolerated treatment for patients with relapsed CLL following cBTKi.