Diffuse large B-cell lymphoma (DLBCL) is the most diagnosed non-Hodgkin lymphoma (NHL), accounting for up to one-third of cases. For many decades, R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone) has been the standard first-line treatment approach for eligible patients in the first-line setting, resulting in long-term remissions in about two-thirds of patients. However, as our understanding of the biologic heterogeneity of this disease has advanced with the ability to perform more sophisticated molecular testing at diagnosis, researchers have been able to identify high-risk patient subtypes with suboptimal outcomes. While survival outcomes among low-risk patient subgroups are favorable with first-line immunochemotherapy, the majority of high-risk patients will experience relapse and often succumb to their disease.
Given the poor outcomes among patients with relapsed or refractory (R/R) DLBCL, there has been a massive research effort over the last decade to improve survival in this setting. Many experts agree that the approval of chimeric antigen receptor (CAR) T-cell therapy was the first major victory in this uphill battle. First approved in October of 2017, axicabtagene ciloleucel was the first of the 3 currently available commercial CAR T-cell therapy constructs to be approved in the third-line setting for DLBCL. Compared to historical controls, CAR T-cell therapy is associated with significant improvement in patient survival with complete response (CR) rates of 40%-50% compared to <20% with standard salvage immunochemotherapy.
Following approval in the third-line setting, these agents were quickly expedited to second-line therapy with pivotal trials demonstrating superiority with CAR T-cell therapy in the second line compared to salvage immunochemotherapy followed by autologous stem cell transplant. In 2022 the ZUMA-7 study reported a 24-month event-free survival (EFS) of 41% with axicabtagene ciloleucel compared to 16% with standard of care, and the TRANSFORM study documented a median EFS not yet reached with lisocabtagene ciloleucel compared to 2.3 months with standard of care. Despite these drastic improvements in patient outcomes, more than half of patients will still fail CAR T-cell therapy and require further systemic therapy.
Thankfully, this year has seen even more advancement in the treatment landscape of R/R DLBCL with two new commercially approved agents in yet another novel therapeutic category: bispecific antibodies. The following is a description of the newest data leading to the latest approvals by the US Food and Drug Administration.
Bispecific antibodies (BsAbs) are an off-the-shelf product that activate endogenous immune cells by cotargeting both tumor antigens as well as host T cells or natural killer cells. Several different experimental agents with varying constructs are under active observation in a wide variety of both hematologic and solid malignancies. Specifically within the realm of B-cell NHL, however, this class of agents is extremely promising and possibly represents the next significant milestone in the treatment of lymphoma.
The toxicity profile of these agents has been reliably predictable in most early phase clinical studies and is related predominantly to T-cell overactivation. The most commonly reported adverse events consist of cytokine release syndrome (CRS) as well as neutropenia, anemia, and hypophosphatemia. While neurologic toxicity has been reported, the incidence is low, and the mechanism is thought to be different than that reported with CAR T-cell therapy given that BsAbs are not likely to cross the blood–brain barrier.