European survey on CAR T-Cell analytical methods from apheresis to post-infusion immunomonitoring

Abstract

Background: Chimeric Antigen Receptor (CAR) T-cell therapy has emerged as a revolutionary approach to cancer treatment. Given the rapid expansion of new indications addressed by newly developed CAR T-cell products, it is essential to standardize analytical methods for the characterization/monitoring of apheresis materials, drug products, and post-infusion patient samples.

Methods: The T2Evolve Consortium, part of the European Union's Innovative Medicines Initiative (IMI), conducted an extensive anonymous online survey between February and June 2022. Comprising 36 questions, the survey targeted a wide range of stakeholders involved in engineered T-cell therapies, including researchers, manufacturers, and clinicians. Its goal was to address the current variability within the CAR T-cell field, focusing on analytical assays for quality control of apheresis materials, drug products, and post-infusion immunomonitoring. Another objective was to identify gaps and needs in the field.

Results: A total of 53 respondents from 13 european countries completed the survey, providing insights into the most commonly used assays for apheresis material and drug product characterization, alongside safety and efficacy tests required by the Pharmacopeia. Notably, a minority of respondents conducted phenotypical characterization of T-cell subsets in the drug product and assessed activation/exhaustion T cell profiles.

Conclusion: The survey underscored the necessity to standardize CAR T-cell functional potency assays and identify predictive biomarkers for response, relapse, and toxicity. Additionally, responses indicated significant variability in CAR T-cell monitoring during short-term patient follow-up across clinical centers. This European survey represents the first initiative to report current approaches in different stages of CAR T-cell therapies via a survey, from drug product quality controls to post-infusion immunomonitoring. Based on these findings, and with input from T2EVOLVE experts, the next step will be to address harmonization in the identified areas. These efforts are anticipated to significantly enhance cancer patients' access to engineered T cell therapy safely and effectively throughout Europe.

Keywords: CAR T-cells; European survey; T2Evolve; immunomonitoring; leukapheresis; lymphodepleting chemotherapy.

Figure 1

Distribution of CAR T-cell treated patients across Europe. (A) Map representing the distribution of CAR T-cell treated patients per country in Europe based on the EBMT Registry (as of March 2022, i.e. at the time of the survey distribution). Number of treated patients is reflected by the color intensity. (B) Distribution of recruiting or active clinical trials as of the end of the survey in June 2022, sourced from ClinicalTrials.gov, in the field of CAR T-cell therapy for the treatment of hematologic indications (including ALL, lymphoma, multiple myeloma, T-ALL, and AML) and solid tumor indications (such as renal carcinoma, neuroblastoma, sarcoma, and unspecified metastatic advanced solid cancers).

Figure 2

Distribution of T2Evolve survey responding centers across Europe. Map representing the number of the survey responding centers per country in Europe. Number of respondents is reflected by the color intensity.

Figure 3

CAR T-cell application expertise for the survey respondents. (A) Venn diagram representing the number of respondents and their expertise in the field of CAR T-cells for hematological malignancies, and/or in solid tumors, and/or in auto-immune diseases. (B) Bar graph representing the number of respondents divided for their expertise in the use of commercial and/or investigational CAR T-cell products. (C) Bar graph representing the number of respondents divided for their involvement in context of academic or/and industrial-driven clinical trials.

Figure 4

Survey responses regarding analytical assays performed on the apheresis product. The bar chart illustrates the number of respondents performing the specified analytical assays on the apheresis product. The lighter-colored bars represent the frequency of assays currently performed, while the darker-colored bars indicate the number of respondents who believe these assays should be performed to optimize leukapheresis characterization. The data highlight the gap between current practices and perceived needs for improving apheresis product analysis.

Figure 5

Survey responses regarding analytical assays performed to release CAR T-cell drug product. The bar chart illustrates the number of respondents performing the specified analytical assays on the drug product. The darker-colored bars represent the frequency of assays currently performed, while the lighter-colored bars indicate the number of respondents who believe these assays should be performed to optimize drug product characterization. The data highlight the gap between current practices and perceived needs for improving drug product analysis.

Figure 6

Survey responses regarding immunomonitoring schedule of patients following CAR T-cell infusion. (A) The bar chart illustrates the frequency of immunomonitoring performed by the respondents. Percentage of respondents has been calculated on the 29 total respondents for this survey section. (B) The bar chart illustrates the frequency of immunomonitoring performed by the respondents following the occurrence of CRS/ICANS/other toxicities (after infusion of CART cells). (C) The bar chart illustrates the duration of immunomonitoring performed by the respondents following the occurrence of CRS/ICANS/other toxicities. Percentage of respondents has been calculated on the 11 total respondents for this survey section.

Figure 7

Overview of the current practice and ideal “nice-to-have” scenario of assays intended for apheresis, drug product and immunomonitoring characterization.