Mantle cell lymphoma (MCL) is a rare and often heterogenous subtype of non-Hodgkin lymphoma (NHL). Though patients can experience prolonged remissions after frontline therapy, most patients ultimately relapse. Treatment of relapsed/refractory disease can be challenging, but there have recently been a growing number of therapeutic options in this setting. Covalent Bruton tyrosine kinase (BTK) inhibitors, for example, have demonstrated activity in patients with MCL and are approved by the US Food and Drug Administration (FDA) for relapsed/refractory disease. Chimeric antigen receptor (CAR) T-cell therapy is also an effective option for relapsed/refractory disease, though this is typically available only at select centers and is associated with toxicities, such as cytokine release syndrome and neurologic toxicity.
Recently, a novel BTK inhibitor, pirtobrutinib, has also been studied across NHL, including MCL ( Wang et al ) Pirtobrutinib is a selective, noncovalent BTK inhibitor with the ability to bind both the C481S-mutant and wild-type BTK. The multicenter, phase 1/2 BRUIN study included 90 patients with MCL who were previously treated with a covalent BTK inhibitor. Patients in the phase 1 portion of the study were treated with oral pirtobrutinib at a dose of 25-300 mg once daily, and patients in the phase 2 study were treated at the recommended dose of 200 mg once daily. The overall response rate was 57.8% (95% CI 46.9%-68.1%), with the complete response rate being 20.0%. At a median follow-up of 12 months, the median duration of response was 21.6 (95% CI 7.5 to not reached) months. Treatment-related adverse events that were grade 3 or higher were not frequent, with neutropenia (8.5%) being the most common. Of note, grade 3 or higher hemorrhage and atrial fibrillation, which can be seen with BTK inhibitors, were rare, occurring in 3.7% and 1.2% of patients, respectively. Based on the results of this study, pirtobrutinib has been approved by the FDA for patients with relapsed/refractory MCL after at least two prior lines of therapy, including a BTK inhibitor. This is an appealing oral option for patients with relapsed disease.
Options for patients with relapsed/refractory large B-cell lymphoma (LBCL) have also significantly increased in recent years. One of the most important advances in this disease has been the use of anti-CD19 CAR T-cell therapy. There are currently three FDA-approved options for patients with relapsed/refractory LBCL who have received at least two prior lines of therapy. 1-3 More recently, axicabtagene ciloleucel ( axi-cel) and lisocabtagene maraleucel ( liso-cel) have also been approved for the second line based on the results of the ZUMA-7 and TRANSFORM studies, respectively. 4,5
Longer follow-up of the ZUMA-7 trial continues to confirm the advantage of axi-cel over standard-care therapy for patients with primary refractory or early relapse of disease, now with evidence of an overall survival advantage ( Westin et al ). The ZUMA-7 trial included 359 adults with LBCL (refractory to or relapsed within 12 months of first-line treatment) who were randomly assigned to receive axi-cel (n = 180) or standard care (n = 179). At a median follow-up of 47.2 mo, patients receiving axi-cel vs standard care had a significantly longer median overall survival (not reached vs 31.1 mo; hazard ratio [HR] 0.73; P = .03) and an absolute improvement in overall survival (8.6 percentage points at 4 years). No new treatment-related deaths were reported since the primary event-free survival analysis. These data confirm that early use of axi-cel is preferred over standard-care therapy with high-dose chemotherapy and autologous stem cell transplantation.