Clinical bottom line
Relapsed or refractory diffuse large B-cell lymphoma (R/R DLBCL) remains a significant clinical challenge due to frequent development of resistance to standard immunochemotherapy. Emerging novel agents targeting specific resistance mechanisms—including bispecific antibodies, epigenetic modulators, and small molecule inhibitors—offer promising therapeutic avenues. While early-phase trials demonstrate encouraging response rates, durability and long-term safety require further validation. These novel therapies represent a paradigm shift toward precision targeting of molecular and immune escape pathways in R/R DLBCL, potentially improving outcomes for patients who have exhausted conventional options.
What the evidence shows
Resistance in R/R DLBCL arises from complex molecular and microenvironmental mechanisms that impair efficacy of standard treatments such as rituximab-based chemoimmunotherapy. Kusowska et al. (2022) comprehensively review molecular alterations contributing to immunotherapy resistance, including antigen loss, immune checkpoint upregulation, and epigenetic dysregulation. These insights have catalyzed development of agents designed to circumvent or reverse resistance pathways.
Bispecific antibodies that simultaneously engage CD3 on T cells and CD20 or other B-cell antigens have demonstrated notable activity in heavily pretreated R/R DLBCL. Lewis et al. (2024) highlight bispecifics’ ability to redirect cytotoxic T cells against lymphoma cells independent of prior resistance mechanisms, with early trials reporting overall response rates (ORRs) around 40-60%. These agents may overcome antigen escape and T-cell exhaustion that limit CAR T-cell therapy efficacy.
Epigenetic therapies targeting DNA methylation and histone modification abnormalities are another promising approach. Dual epigenetic agents combined with salvage chemotherapy and rituximab have shown preliminary efficacy in patients refractory to multiple lines of therapy (reviewed in Hematological Oncology 2022). Such combinations may re-sensitize resistant lymphoma cells by restoring apoptotic pathways and enhancing immune recognition.
Small molecule inhibitors targeting signaling pathways implicated in resistance, such as BCL2, BTK, and PI3K, are also under active investigation. Varma et al. (2023) summarize recent advances in these agents, noting their potential to disrupt survival signals in resistant clones. However, single-agent activity is often modest, supporting combination strategies.
Maxwell et al. (2013) provide foundational context on molecular strategies to overcome drug resistance in B-cell lymphomas, underscoring the importance of integrating molecular profiling to guide therapy selection. Harris Leonard et al. (2020) further emphasize the need for novel agents in R/R DLBCL given poor outcomes with salvage chemotherapy alone.
Caveats and uncertainty
Most data derive from early-phase or single-arm studies with limited sample sizes and short follow-up, restricting definitive conclusions on long-term benefit and safety. The heterogeneity of resistance mechanisms across patients complicates identification of predictive biomarkers for response. Additionally, the optimal sequencing and combination of novel agents with existing therapies remain unclear.
Toxicity profiles, particularly immune-related adverse events with bispecific antibodies and epigenetic modifiers, require careful monitoring in clinical practice. The impact of these therapies on quality of life and cost-effectiveness has yet to be established.
Moreover, resistance may evolve dynamically under selective pressure from novel agents themselves, necessitating ongoing research into mechanisms of secondary resistance and strategies to prevent or overcome it.
How this may change practice
Clinicians managing R/R DLBCL should remain abreast of emerging targeted agents that address specific resistance pathways, as these may soon expand therapeutic options beyond conventional salvage chemotherapy and CAR T-cell therapy. Incorporation of molecular and immunophenotypic profiling into routine practice could facilitate personalized treatment selection.
Bispecific antibodies represent a promising off-the-shelf immunotherapy alternative, potentially accessible to patients ineligible for or relapsed after CAR T-cell therapy. Epigenetic therapies combined with chemoimmunotherapy may offer salvage options for refractory cases, pending further validation.
Ultimately, these advancements underscore a shift toward precision medicine in lymphoma, emphasizing the need for multidisciplinary collaboration and enrollment in clinical trials to optimize outcomes in this challenging population.