Glofitamab use may significantly reduce the efficacy of CAR-T therapy in R/R DLBCL patients

Abstract Background Glofitamab (a CD20×CD3 bispecific antibody) has been approved for the treatment of relapsed/refractory diffuse large B-cell lymphoma (R/R DLBCL). In clinical practice, we observed that some patients received glofitamab before leukapheresis. Theoretically, glofitamab exerts its effects by activating T cells, which may lead to excessive T-cell activation and exhaustion. Therefore, we hypothesized whether glofitamab treatment before leukapheresis could result in CAR-T manufacturing failure or impair in vivo CAR-T expansion, thereby affecting its efficacy. This study aimed to investigate the impact of glofitamab on CAR-T manufacturing and therapeutic outcomes, as well as its potential mechanisms. MethodsFrom October 2024 to June 2025, 16 R/R DLBCL patients at our center received CAR-T therapy (NCT07093086, registered on ClinicalTrials.gov). Based on whether they had received glofitamab before leukapheresis, they were divided into two groups: the exposed group (n=6) and the unexposed group (n=10). Through baseline characteristics, immunophenotyping of apheresis products, CAR-T manufacturing parameters, post-infusion safety, post-infusion efficacy and post-infusion cellular kinetics analysis, we thoroughly examined the potential impact of glofitamab on CAR-T therapy in R/R DLBCL patients.Results Patient Characteristics: In the exposed group, the median interval between the last glofitamab dose and leukapheresis was 20 days (range: 8-108 days), with a median treatment duration of 4 cycles (range: 2-12 cycles). The baseline characteristics of the two groups were similar, with no significant differences in age, gender, pathological subtype, ECOG score, IPI score, or prior lines of therapy. None of the exposed group patients had undergone ASCT or CAR-T therapy previously, whereas in the unexposed group, 2 (20%) had received ASCT and 3 (30%) had prior CD19 CAR-T therapy. Immunophenotyping of Apheresis Products: No significant differences were observed in the proportions of Tscm, Tcm, Teff, or Tem in the leukapheresis samples between the two groups. However, the unexposed group showed a trend toward lower Treg proportion (p=0.0778) and PD-1 expression (p=0.3406) compared to the exposed group. CAR-T Manufacturing Parameters: CAR-T cells were successfully manufactured in all patients (100%). No significant differences were observed in CAR-T culture duration, transduction efficiency, CD8+ T-cell proportion, or final product viability. However, the exposed group exhibited slightly lower in vitro expansion fold (p=0.0726), suggesting that glofitamab might impair T-cell proliferation capacity. CAR-T product subsets (Tscm, Tcm, Teff, Tem) showed no significant differences, but the unexposed group had marginally lower Tregproportion and PD-1 expression in the CAR-T products. Post-Infusion Safety: In the exposed group, 5 (83%) patients experienced CRS, with 50% (3/6) being grade 1-2 and 33% (2/6) grade 3. In the unexposed group, 5 (50%) patients developed CRS, all grade 1-2 (50%, 5/10), with no grade 3 CRS. No ICANS of any grade was observed in either group. Both groups demonstrated favorable safety profiles. Post-Infusion Efficacy: The overall ORR was 63% (CR 56%). However, the exposed group had significantly lower ORR than the unexposed group (33% vs. 80%, p=0.026) and a higher progression rate (50% vs. 10%). Logistic regression identified glofitamab exposure as an independent risk factor for reduced ORR (OR=0.08, 95% CI 0.01–0.74). Post-Infusion Cellular Kinetics: No significant differences were observed in in vivo expansion parameters (Tmax, Cmax, AUC0-28d) between the two groups. Conclusion Glofitamab exposure is an independent risk factor for reduced ORR. Pre-leukapheresis glofitamab use may impair T-cell function by increasing Treg and PD-1+ T-cell proportions, leading to diminished CAR-T efficacy (50% lower ORR). We recommend extending the glofitamab washout period and conducting multicenter clinical studies to further clarify the impact of glofitamab on T-cell function and CAR-T efficacy.