Real-World Outcomes with Chimeric Antigen Receptor T Cell Therapies in Large B Cell Lymphoma: A Systematic Review and Meta-Analysis

Chimeric antigen receptor T cell (CAR-T) therapies, including axicabtagene ciloleucel (axi-cel) and tisagenlecleucel (tisa-cel), are innovative treatments for patients with relapsed or refractory (r/r) large B cell lymphoma (LBCL). Following initial regulatory approvals, real-world evidence (RWE) of clinical outcomes with these therapies has been accumulating rapidly. Notably, several large registry studies have been published recently. Here we comprehensively describe clinical outcomes with approved CAR-T therapies in patients with r/r LBCL using available RWE. We systematically searched Embase, MEDLINE, and 15 conference proceedings to identify studies published between 2017 and July 2022 that included ≥10 patients with r/r LBCL treated with commercially available CAR-T therapies. Eligible study designs were retrospective or prospective observational studies. Key outcomes of interest were objective response rate (ORR), complete response (CR) rate, overall survival (OS), progression-free survival (PFS), cytokine release syndrome (CRS), and immune effector cell-associated neurotoxicity syndrome (ICANS). Random-effects meta-analyses were used to compare real-world outcomes with those of pivotal clinical trials and to compare clinical outcomes associated with axi-cel and tisa-cel. Study cohort mapping was conducted to avoid including patients more than once. Of 76 cohorts we identified, 46 reported patients treated specifically with either axi-cel or tisa-cel, with 39 cohorts (n = 2754 patients) including axi-cel and 20 (n = 1649) including tisa-cel. No studies of liso-cel that met the inclusion criteria were identified during the search period. One-half of the tisa-cel cohorts were European, compared with 33% of the axi-cel cohorts. Among studies with available data, axi-cel had a significantly shorter median time from apheresis to CAR-T infusion than tisa-cel. Despite including broader patient populations, real-world effectiveness and safety of both axi-cel and tisa-cel were consistent with data from the pivotal clinical trials. Comparative meta-analysis of axi-cel versus tisa-cel demonstrated adjusted hazard ratios for OS and PFS of .60 (95% confidence interval [CI], .47 to .77) and .67 (95% CI, .57 to .78), respectively, both in favor of axi-cel. Odds ratios (ORs) for ORR and CR rate, both favoring axi-cel over tisa-cel, were 2.05 (95% CI, 1.76 to 2.40) and 1.70 (95% CI, 1.46 to 1.96), respectively. The probability of grade ≥3 CRS was comparable with axi-cel and tisa-cel, whereas axi-cel was associated with a higher incidence of grade ≥3 ICANS (OR, 3.95; 95% CI, 3.05 to 5.11). Our meta-analysis indicates that CAR-T therapies have manageable safety profiles and are effective in a wide range of patients with r/r LBCL, and that axi-cel is associated with improved OS and PFS and increased risk of grade ≥3 ICANS compared with tisa-cel. Limitations of this study include nonrandomized treatments, potential unknown prognostic factors, and the lack of available real-world data for liso-cel.

Point-of-care CAR T-cell therapy as salvage strategy for out-of-specification tisagenlecleucel

Tisagenlecleucel (tisa-cel) is an anti-CD19 chimeric antigen receptor (CAR) T-cell therapy approved for patients with relapsed/refractory large B-cell lymphoma. Outcomes of patients with out-of-commercial specification (OOS) CAR T products are not well characterized. We therefore assessed 37 adult patients who underwent leukapheresis for tisa-cel therapy in a single center. In nine (24%) patients, manufactured tisa-cel was considered OOS. Three of them (33%) received tisa-cel after institutional review board approval; 2/9 (22%) did not receive tisa-cel due to disease progression; and 4/9 (44%) received academic point-of-care (POC) CAR T-cell as salvage therapy, at a median of 35 days following OOS notification. Three of those four patients achieved a complete response. In univariate analysis, risk factors for OOS were ≥ 4 prior therapies or previous bendamustine exposure. In conclusion, we report high OOS incidence of 24% in real-life setting. Forty-four percent of those patients received POC CAR T-cell as salvage therapy.

Droplet digital PCR allows vector copy number assessment and monitoring of experimental CAR T cells in murine xenograft models or approved CD19 CAR T cell-treated patients

BACKGROUND

Genetically engineered chimeric antigen receptor (CAR) T lymphocytes are promising therapeutic tools for cancer. Four CAR T cell drugs, including tisagenlecleucel (tisa-cel) and axicabtagene-ciloleucel (axi-cel), all targeting CD19, are currently approved for treating B cell malignancies. Flow cytometry (FC) remains the standard for monitoring CAR T cells using a recombinant biotinylated target protein. Nevertheless, there is a need for additional tools, and the challenge is to develop an easy, relevant, highly sensitive, reproducible, and inexpensive detection method. Molecular tools can meet this need to specifically monitor long-term persistent CAR T cells.

METHODS

Based on 2 experimental CAR T cell constructs, IL-1RAP and CS1, we designed 2 quantitative digital droplet (ddPCR) PCR assays. By targeting the 4.1BB/CD3z (28BBz) or 28/CD3z (28z) junction area, we demonstrated that PCR assays can be applied to approved CD19 CAR T drugs. Both 28z and 28BBz ddPCR assays allow determination of the average vector copy number (VCN) per cell. We confirmed that the VCN is dependent on the multiplicity of infection and verified that the VCN of our experimental or GMP-like IL-1RAP CAR T cells met the requirement (< 5 VCN/cell) for delivery to the clinical department, similar to approved axi-cel or tisa-cel drugs.

RESULTS

28BBz and 28z ddPCR assays applied to 2 tumoral (acute myeloid leukemia (AML) or multiple myeloma (MM) xenograft humanized NSG mouse models allowed us to quantify the early expansion (up to day 30) of CAR T cells after injection. Interestingly, following initial expansion, when circulating CAR T cells were challenged with the tumor, we noted a second expansion phase. Investigation of the bone marrow, spleen and lung showed that CAR T cells disseminated more within these tissues in mice previously injected with leukemic cell lines. Finally, circulating CAR T cell ddPCR monitoring of R/R acute lymphoid leukemia or diffuse large B cell lymphoma (n = 10 for tisa-cel and n = 7 for axi-cel) patients treated with both approved CAR T cells allowed detection of early expansion, which was highly correlated with FC, as well as long-term persistence (up to 450 days), while FC failed to detect these events.

CONCLUSION

Overall, we designed and validated 2 ddPCR assays allowing routine or preclinical monitoring of early- and long-term circulating approved or experimental CAR T cells, including our own IL-1RAP CAR T cells, which will be evaluated in an upcoming phase I clinical trial.