Pirtobrutinib is a highly selective, non-covalent BTK inhibitor that has demonstrated activity across multiple treatment settings in CLL, including patients previously exposed to covalent BTK inhibitors. BRUIN CLL-322 evaluated whether adding pirtobrutinib to the established venetoclax-rituximab backbone could deepen responses and improve long-term disease control. 

The study enrolled 639 patients with relapsed/refractory CLL/SLL, including a heavily BTKi-pretreated population. Nearly 80% had prior covalent BTK inhibitor exposure, and most of these patients discontinued therapy due to disease progression.

Safety Outcomes-

• Rates of any Grade AEs (PVR vs. VR: 99.7% vs. 98.1%) and Grade ≥ 3 AEs (78.8% vs. 73.0%) were similar between arms, including low rates of any Grade atrial fibrillation/flutter (3.5% vs. 2.6%), hypertension (12.0% vs. 7.4%), and hemorrhage (14.2% vs. 10.6%). 

• Grade ≥ 3 clinical AEs of interest included neutropenia (50.3% vs. 43.7% [febrile neutropenia 2.2% vs. 3.5%]) and tumor lysis syndrome (0.9% vs. 3.9%). 

• Discontinuation rates due to treatment-related AEs were similar for PVR vs. VR (5.4% vs. 5.1%). 

KOL Insights-

“The durability of responses observed with PVR is particularly encouraging. These data provide confidence that a fixed-duration approach can deliver prolonged remissions and extended treatment-free intervals, even among patients with high-risk CLL. The consistently favorable outcomes across clinically relevant subgroups suggest that PVR has the potential to redefine expectations for long-term disease control in the relapsed/refractory setting.”– Expert Opinion

“Fixed-duration combination treatments with covalent BTK inhibitors and venetoclax have achieved deep remissions and long-term disease control in patients with CLL/SLL; however, the real-world utility of these regimens has been limited. Moreover, in the modern era, many patients receive covalent BTK inhibitors as frontline continuous therapy, making their use in combination regimens significantly less relevant in the relapsed setting.”– Expert Opinion

Conclusion-

CLL is the most common adult leukemia in Western countries, accounting for approximately 25–30% of all leukemias. The treatment landscape has been transformed by BTK and BCL2 inhibitors; however, optimal management after covalent BTK inhibitor exposure remains a significant unmet need.

The Phase III BRUIN CLL-322 trial demonstrated that fixed-duration pirtobrutinib plus venetoclax-rituximab significantly improves PFS, delays the need for subsequent therapy, and achieves deeper MRD responses compared with venetoclax-rituximab alone. Importantly, these efficacy gains were achieved with a manageable safety profile and similar treatment discontinuation rates. As the first randomized Phase III study to establish a BTK inhibitor-based fixed-duration regimen in relapsed/refractory CLL, BRUIN CLL-322 has the potential to redefine the standard of care, particularly for patients previously treated with covalent BTK inhibitors.