Pirtobrutinib Plus Venetoclax-Rituximab Cuts CLL Progression 45%

Adding the noncovalent Bruton tyrosine kinase (BTK) inhibitor pirtobrutinib to the standard fixed-duration regimen of venetoclax-rituximab (VR) for relapsed chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL) cut the risk of disease progression or death nearly in half for patients with previously untreated disease, compared with the regimen alone, according to primary results from the phase 3 BRUIN CLL-322 trial (NCT04965493).¹

The findings, published in The Lancet, mark the first randomized phase 3 evidence comparing a novel combination against fixed-duration VR, long considered the standard second-line option in this setting, and could reshape how payers and health systems think about sequencing therapy for a disease where most patients now cycle through only 2 targeted regimens over a lifetime.

What Did the Phase 3 BRUIN CLL-322 Trial Find?

The open-label, 152-site trial randomized 639 patients with previously treated CLL or SLL 1:1 to receive either pirtobrutinib plus VR (PVR; n = 321) or VR alone (n = 318), and most were male patients (69%). Eighty percent of participants had already been treated with a covalent BTK inhibitor, with median (IQR) lines being 2 (1-3); most had discontinued that prior drug due to disease progression. This is a population largely absent from the pivotal MURANO trial (NCT02005471) that established VR as the standard.

At a median follow-up of 27.3 months, independent review committee–assessed progression-free survival (PFS) significantly favored the PVR arm (HR, 0.547; 95% CI, 0.400-0.748; P = .0001), representing a 45.3% reduction in risk of progression or death. Median PFS was not yet reached in the PVR group vs 39.7 months with VR alone, and the 24-month PFS rate was 87% with PVR compared with 72% with VR. Earlier data from this trial presented at the 2026 European Hematology Association meeting showed investigators first flagged the magnitude of the PFS advantage along with deeper measurable residual disease (MRD) clearance in the combination arm.²

How Did the Regimen Perform in BTK Inhibitor–Pretreated Patients?

The benefit held up across prespecified subgroups, including the roughly 80% of patients previously exposed to a covalent BTK inhibitor (HR, 0.509; 95% CI, 0.351-0.738; P = .0003), and was most pronounced among those with high-risk genomic features such as TP53 aberrations.¹ Rates of undetectable MRD at the end of treatment were also higher with PVR (86%) than with VR alone (61%) among patients with evaluable samples, reinforcing the depth of response.

The study authors noted this also represents the first robust, prospective phase 3 data describing how VR performs specifically in patients who progressed after a covalent BTK inhibitor, an increasingly common clinical scenario as covalent BTK inhibitors are used earlier in the treatment course. That gap has been a persistent concern for clinicians.³

What Did the Safety Data Show?

Overall, the safety profile of PVR was broadly consistent with VR alone. Grade 3 or higher treatment-emergent adverse events occurred in 79% of the PVR group vs 73% of the VR group, while treatment discontinuation due to related adverse events was similar between arms (5% each). Grade 3 or higher tumor lysis syndrome (TLS) was less frequent with PVR (1%) than VR (4%), which investigators attributed to the cytoreductive effect of a 3-cycle pirtobrutinib-rituximab lead-in before venetoclax initiation. Rates of atrial fibrillation or flutter were low and similar between groups (3% each). Five treatment-related deaths occurred overall; 1 in the PVR arm and 4 in the VR arm.

The reduced TLS risk carries practical significance beyond the trial itself: less intensive monitoring and fewer venetoclax ramp-up-related hospitalizations could ease the resource burden on health systems managing this already resource-intensive debulking phase.

What Are the Implications for Future Treatment?

Overall survival data remain immature (HR, 0.891; 95% CI, 0.568-1.398), and the authors caution that longer follow-up is needed before drawing conclusions on that end point. Still, the authors have framed the results as support for a potential new standard of care in the relapsed/refractory setting, particularly for the large subset of patients who have already cycled through a covalent BTK inhibitor.

“The results of BRUIN CLL-322 are particularly relevant in the broader landscape of fixed-duration venetoclax-based combinations in the first-line setting,” the authors wrote, “as venetoclax can currently be combined with obinutuzumab, ibrutinib, or acalabrutinib as doublet therapy or with obinutuzumab and acalabrutinib as a triplet therapy.”

For payers and health system decision makers, the data add to a broader case for early use of the most effective available regimens rather than reserving newer combinations for later lines that many patients may never reach.

References

1. Davids MS, Eyre TA, Woyach JA, et al. Fixed-duration pirtobrutinib plus venetoclax–rituximab versus venetoclax–rituximab for patients with previously treated chronic lymphocytic leukaemia or small lymphocytic lymphoma (BRUIN CLL-322): an open-label, multicentre, randomised, controlled, phase 3 trial. Lancet. 2026;S0140-6736(26)01204-3. doi:10.1016/S0140-6736(26)01204-3
2. Mattina C. EHA 2026 late breakers deliver practice-shifting phase 3 data and novel CAR T approaches across hematology. AJMC^®. June 14, 2026. Accessed July 24, 2026. https://www.ajmc.com/view/eha-2026-late-breakers-deliver-practice-shifting-phase-3-data-and-novel-car-t-approaches-across-hematology
3. Jacobson-Sive K. Study finds pirtobrutinib associated with improved outcomes vs venetoclax in relapsed CLL. AJMC. July 13, 2024. Accessed July 24, 2026. https://www.ajmc.com/view/study-finds-pirtobrutinib-associated-with-improved-outcomes-vs-venetoclax-in-relapsed-cll