Development of optimized cytotoxicity assays for assessing the antitumor potential of CAR-T cells

CAR-T cells are T cells expressing a chimeric antigen receptor (CAR) rendering them capable of killing tumor cells after recognition of a target antigen. CD19 CAR-T cells have revolutionized the treatment of hematological malignancies. Their function is typically assessed by cytotoxicity assays using human allogeneic cell lines expressing the target antigen CD19 such as Nalm-6. However, an alloreactive reaction is observed with these cells, leading to a CD19-independent killing. To address this issue, we developed a fluorescence microscopy-based potency assay using murine target cells to provide an optimized cytotoxicity assay with enhanced specificity towards CD19. Murine NIH/3T3 (3T3) fibroblast-derived cell line and EL4 T-cell lymphoma-derived cell line were used as targets (no xenoreactivity was observed after coculture with human T cells). 3T3 and EL4 cells were engineered to express eGFP (enhanced Green Fluorescent Protein) and CD19 or CD22 using retroviral vectors. CD19 CAR-T cells and non-transduced (NT) control T cells were produced from several donors. After 4 h or 24 h, alloreactive cytotoxicity against CD19+ Nalm-6-GFP cells and CD19- Jurkat-GFP cells was observed with NT or CAR-T cells. In the same conditions, CAR-T but not NT cells specifically killed CD19+ but not CD19- 3T3-GFP or EL4-GFP cells. Both microscope- and flow cytometry-based assays revealed as sensitive as impedance-based assay. Using flow cytometry, we could further determine that CAR-T cells had mostly a stem cell-like memory phenotype after contact with EL4 target cells. Therefore, CD19+ 3T3-GFP or EL4-GFP cells and fluorescence microscopy- or flow cytometry-based assays provide convenient, sensitive and specific tools to evaluate CAR-T cell function with no alloreactivity.

Adipose tissue-derived stromal vascular fraction for treating hands of patients with systemic sclerosis: a multicentre randomized trial

OBJECTIVE

To assess the superiority of adipose tissue-derived stromal vascular fraction (AD-SVF) injection into the fingers vs placebo in reducing hand disability in systemic sclerosis (SSc) patients.

METHODS

We performed a double-blind, multicentre, phase II trial from October 2015 to January 2018 in France. SSc patients with a Cochin Hand Function Scale (CHFS) ≥20/90 were randomized 1:1 to receive injection of AD-SVF or placebo. AD-SVF was obtained using the automated processing Celution®800/CRS system. The placebo was lactated Ringer's solution. The primary efficacy end point was the change of the CHFS score from baseline to 3 months. Secondary efficacy endpoints included the CHFS score at 6 months, hands function, vasculopathy, hands pain, skin fibrosis, sensitivity of the finger' pulps, Scleroderma Health Assessment Questionnaire, patients and physician satisfaction and the safety.

RESULTS

40 patients were randomized. The AD-SVF and placebo groups were comparable for age, sex ratio, disease duration, skin fibrosis of the hands and main cause of hand disability. After 3 month-follow-up, hand function significantly improved in both groups with no between-group difference of CHFS (mean change of -9.2 ± 12.2 in the AD-SVF group vs -7.6 ± 13.2 in the placebo group). At 6 months, hand function improved in both groups.

CONCLUSION

This study showed an improvement of hand function in both groups other time, with no superiority of the AD-SVF. Considering the limits of this trial, studies on a larger population of patients with homogeneous phenotype and hand handicap, should be encouraged to accurately assess the benefit of AD-SVF therapy.

TRIAL REGISTRATION

ClinicalTrials.gov, https://clinicaltrials.gov, NCT02558543. Registered on September 24, 2015.

Inter-center comparison of good manufacturing practices-compliant stromal vascular fraction and proposal for release acceptance criteria: a review of 364 productions

Background

Even though the manufacturing processes of the stromal vascular fraction for clinical use are performed in compliance with the good manufacturing practices applying to advanced therapy medicinal products, specifications related to stromal vascular fraction quality remain poorly defined. We analyzed stromal vascular fraction clinical batches from two independent good manufacturing practices-compliant manufacturing facilities, the Swiss Stem Cell Foundation (SSCF) and Marseille University Hospitals (AP-HM), with the goal of defining appropriate and harmonized release acceptance criteria.

Methods

This retrospective analysis reviewed the biological characteristics of 364 batches of clinical-grade stromal vascular fraction. Collected data included cell viability, recovery yield, cell subset distribution of stromal vascular fraction, and microbiological quality.

Results

Stromal vascular fraction from SSCF cohort demonstrated a higher viability (89.33% ± 4.30%) and recovery yield (2.54 × 10⁵ ± 1.22 × 10⁵ viable nucleated cells (VNCs) per mL of adipose tissue) than stromal vascular fraction from AP-HM (84.20% ± 5.96% and 2.25 × 10⁵ ± 1.11 × 10⁵ VNCs per mL). AP-HM batches were significantly less contaminated (95.71% of sterile batches versus 74.15% for SSCF batches). The cell subset distribution was significantly different (higher proportion of endothelial cells and lower proportion of leukocytes and pericytes in SSCF cohort).

Conclusions

Both centers agreed that a good manufacturing practices-compliant stromal vascular fraction batch should exert a viability equal or superior to 80%, a minimum recovery yield of 1.50 × 10⁵ VNCs per mL of adipose tissue, a proportion of adipose-derived stromal cells at least equal to 20%, and a proportion of leukocytes under 50%. In addition, a multiparameter gating strategy for stromal vascular fraction analysis is proposed.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02445-z.

[Requirements for academic production of CAR-T cells in accordance with Good Pharmaceutical Practice (GMP). Guidelines from the Francophone Society of Bone Marrow Transplantation and Cellular Therapy (SFGM-TC)]

The extraordinary and unexpected success of cellular immunotherapy using genetically engineered T-cells to express a chimeric antigen receptor (CAR) targeting CD19, in the treatment of refractory or relapsing B-hematological malignancies, has provided a real therapeutic hope. Indeed, remission rates reach more than 80 % in patients at a stage, without any other possibilities of treatment, notably in the child's acute lymphoblastic leukemia. These results, initially resulting from academic research, led to Food and Drug accreditation for market access of two innovative autologous therapy drugs, Kimryah® and Yescarta®. Based on the impressive clinical results, mainly so far in hematological malignancies (LAL, MM, LBDGC, etc.), the development of several types of cells expressing a CAR receptor suggests a wide range of future applications, particularly in the field of solid tumors. However, while the development of CAR-T cells now appears to be in the hands of private pharmaceuticals companies, the logistical constraints, the cryopreservation and the very high cost of these personalized medicines may ultimately limit their use. The development of academic productions by CAR-T cells could bypass some of these disadvantages. The strong innovation capacity of healthcare institutions associated with research units allows them to identify the ideal tumor target and efficient performing cells. Thus, authorized production platforms could allow for shorter administration times and reasonable production costs for national health systems. The aim of this workshop is to identify the requirements for the academic production of CAR-T cells, while respecting the research standards useful to establish proof of concept, but also at the preclinical development stage, leading in fine to the manufacture, through an authorized pharmaceutical establishment, of the innovative therapy drug, and in accordance with Good Manufacturing Practice (GMP). The ultimate goal is to make these innovative and high-performance medicines available to as many patients as possible.

Chromosomal Instability but Lack of Transformation in Human Myoblast Preparations

Genetic alterations have recently been described as emerging during the culture of embryonic stem cells or induced pluripotent stem cells, raising concerns about their safety in future clinical use. Myoblasts are adult stem cells with important therapeutic potential that have been used in clinical trials for almost 20 years, but their genome integrity has not yet been established. Here we produced 10 human myoblast preparations and investigated their genomic stability. At the third passage, half of the preparations had a normal karyotype and half showed one to four alterations/30 metaphases. Chromosome 2 trisomy was found in 1–2/30 meta-phases and/or 2/100 nuclei by FISH in 3/10 samples, and there was no other recurrent anomaly. When prolonging cultures, these erratic abnormalities were never associated with a growth advantage. Cellular senescence was manifested in all samples by growth arrest before passage 15. Expression of TERT was always negative. Molecular analysis of individual p53 transcripts did not reveal tumorigenic mutations. CGH array (10 samples) and exome sequencing (one sample) failed to detect copy number variations or accumulation of mutations, respectively. Myoblasts did not grow either in soft agar or in vivo after injection in immunodeficient mice. Hence, occasional genomic abnormalities may occur during myoblast culture but are not associated with risk of transformation.

Massive expansion of regulatory T-cells following interleukin 2 treatment during a phase I-II dendritic cell-based immunotherapy of metastatic renal cancer

Cytotoxic chemotherapy is ineffective in metastatic renal cancer. However, systemic administration of interleukin 2 (IL-2) or infusion of dendritic cells (DCs) loaded with tumor extracts can lead to some response rates with concomitant survival improvements. We report the results of a phase I-II pilot study combining DCs and IL-2 where six patients were included. DCs were derived from bone marrow CD34+ cells and loaded with autologous tumor extracts. CD34-DC vaccines were infused subcutaneously at day 45, 52, 59, 90 and 120 following surgery in combination with IL-2, that was subsequently administrated after the 3rd and 4th DC vaccinations. Preparation of tumor extracts and CD34-DCs were satisfactory in all patients but one. Due to rapid tumor progression, one patient was excluded before vaccination. In the 4 remaining patients, two received 3 vaccinations, while the 2 others received 5 vaccinations and the full IL-2 treatment. No adverse effect due to the vaccinations was observed. A specific immune response against autologous tumor cells was observed in the 2 patients who completed the treatment. Interestingly, these 2 patients had a more prolonged survival than the patients receiving 3 vaccinations. Importantly, a transient and massive increase of circulating natural regulatory T-cells (nTregs) was evidenced in 3 patients following IL-2 administration. Overall, the use of CD34-DC vaccines is feasible, safe and non-toxic. A specific anti-tumor immune response can be detected. However, our data highlights that IL-2 is a potent inducer of nTregs in vivo and as such may have a negative impact on cancer immunotherapy.