Pirtobrutinib for First-Line Chronic Lymphocytic Leukemia: A Non-Anchored Indirect Comparison Using Reconstructed Patient-Level Data

Background: Pirtobrutinib has recently emerged as a promising first-line treatment option for chronic lymphocytic leukemia (CLL). Unlike currently established regimens, which are generally based on doublet combinations, pirtobrutinib can be administered as monotherapy. Because no head-to-head trials comparing pirtobrutinib with contemporary first-line combinations are currently available, indirect comparative evidence may help define its potential role. Methods: A non-anchored indirect comparison based on reconstructed individual patient data (IPD) was conducted using published Kaplan-Meier curves from randomized controlled trials evaluating first-line treatments for CLL. Progression-free survival (PFS) was the endpoint of interest. Reconstructed IPD were generated using WebPlotDigitizer and the IPDfromKM algorithm. Pirtobrutinib monotherapy was compared indirectly with acalabrutinib plus obinutuzumab, venetoclax plus obinutuzumab, and venetoclax plus ibrutinib. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using univariate Cox models. Results: The analysis included four randomized trials. Compared with pirtobrutinib monotherapy, HRs for PFS were 0.5544 (95%CI, 0.2696-1.1397) versus venetoclax plus obinutuzumab, 0.4583 (95%CI, 0.2066-1.0200) versus venetoclax plus ibrutinib, and 1.4453 (95%CI, 0.6684-3.1240) versus acalabrutinib plus obinutuzumab. Confidence intervals were wide and crossed unity in all comparisons, indicating substantial statistical uncertainty. Visual inspection of reconstructed Kaplan-Meier curves did not suggest inferior PFS for pirtobrutinib relative to established doublet regimens. Conclusions: This exploratory non-anchored analysis suggests that pirtobrutinib monotherapy may provide PFS outcomes broadly comparable to current first-line combination regimens for CLL. Given the methodological limitations inherent to indirect comparisons, prospective head-to-head studies are needed to clarify the optimal positioning of pirtobrutinib in treatment-naïve CLL.