Simplified protocol for clinical-grade tumor-infiltrating lymphocyte manufacturing with use of the Wave bioreactor

Background aimsThe high level of complexity of current Good Manufacturing Practice–compliant methods of manufacturing hampers rapid and broad application of treatment with tumor-infiltrating lymphocytes (TILs).MethodsTo ensure higher applicability of TIL production to laboratory routine, a practical and simple protocol of TIL manufacturing with the use of a closed-system bioreactor was developed and implemented at our institution.ResultsThis protocol enabled significant work load reduction during the most labor-intense step of TIL expansion, and allowed generation of high-quality TIL products, which mediated clinical regression in patients with metastatic melanoma.ConclusionsImplementation of simplified methods of TIL expansion will speed up dissemination of TIL methods worldwide and will increase patient access to this highly effective treatment.     

Ex vivo enrichment of circulating anti-tumor T cells from both cutaneous and ocular melanoma patients: clinical implications for adoptive cell transfer therapy

Tumor-infiltrating lymphocytes (TILs) have been successfully used for adoptive cell transfer (ACT) immunotherapy; however, due to their scarce availability, this therapy is possible for a limited fraction of cutaneous melanoma patients. We assessed whether an effective protocol for ex vivo T-cell expansion from peripheral blood mononuclear cells (PBMCs), suitable for ACT of both cutaneous and ocular melanoma patients, could be identified. PBMCs from both cutaneous and ocular melanoma patients were stimulated in vitro with autologous, irradiated melanoma cells (mixed lymphocyte tumor cell culture; MLTCs) in the presence of IL-2 and IL-15 followed by the rapid expansion protocol (REP). The functional activity of these T lymphocytes was characterized and compared with that of TILs. In addition, the immune infiltration in vivo of ocular melanoma lesions was analyzed. An efficient in vitro MLTC expansion of melanoma reactive T cells was achieved from all PBMC's samples obtained in 7 cutaneous and ocular metastatic melanoma patients. Large numbers of melanoma-specific T cells could be obtained when the REP protocol was applied to these MLTCs. Most MLTCs were enriched in non-terminally differentiated T(EM) cells homogeneously expressing co-stimulatory molecules (e.g., NKG2D, CD28, CD134, CD137). A similar pattern of anti-tumor activity, in association with a more variable expression of co-stimulatory molecules, was detected on short-term in vitro cultured TILs isolated from the same patients. In these ocular melanoma patients, we observed an immune infiltrate with suppressive characteristics and a low rate of ex vivo growing TILs (28.5% of our cases). Our MLTC protocol overcomes this limitation, allowing the isolation of T lymphocytes with effector functions even in these patients. Thus, anti-tumor circulating PBMC-derived T cells could be efficiently isolated from melanoma patients by our novel ex vivo enrichment protocol. This protocol appears suitable for ACT studies of cutaneous and ocular melanoma patients.     

Optimization of manufacturing conditions for chimeric antigen receptor T cells to favor cells with a central memory phenotype

BackgroundChimeric antigen receptor (CAR)-T cells are genetically engineered to recognize tumor-associated antigens and have potent cytolytic activity against tumors. Adoptive therapy with CAR-T cells has been highly successful in B-cell leukemia and lymphoma. However, in solid tumor settings, CAR-T cells face a particularly hostile tumor microenvironment where multiple immune suppressive factors serve to thwart the anti-cancer immune response. Clinical trials of solid tumor antigen-targeted CAR-T cells have shown limited efficacy, and issues for current CAR-T cell therapies include failures of expansion and persistence, tumor entry, deletion and functional exhaustion.MethodsWe compared our standard protocol for CAR-T cell manufacturing, currently used to generate CAR-T cells for a phase 1 clinical trial, with two alternative approaches for T-cell activation and expansion. The resulting cultures were analyzed using multicolor flow cytometry, cytokine bead array and xCELLigence cytotoxicity assays.ResultsWe have found that by changing the method of activation we can promote generation of CAR-T cells with enhanced CD62L and CCR7 expression, increased interleukin (IL)-2 production and retention of cytolytic activity, albeit with slower kinetics.DiscussionWe propose that these phenotypic characteristics are consistent with a central memory phenotype that will better enable CAR-T cell survival and persistence after activation in vivo, and we aim to test this in a continuation of our current phase 1 clinical trial of CAR-T cells in patients with advanced melanoma.     

Generation of colon cancer–derived tumor-infiltrating T cells (TILs) for adoptive cell therapy

Adoptive cell therapy (ACT) using specific immune cells and stem cells has emerged as a promising treatment option that could complement traditional cancer therapies in the future. In particular, tumor-infiltrating lymphocytes (TILs) have been shown to be effective against solid tumors in various clinical trials. Despite the enormous disease burden and large number of premature deaths caused by colorectal cancer (CRC), studies on TILs isolated from tumor tissue of patients with CRC are still rare. To date, studies on ACT often lack controlled and comparable expansion processes as well as selected ACT-relevant T-cell populations. We describe a procedure for generating patient-specific TILs, which are prerequisites for clinical trials of ACT in CRC. The manufacturing and characteristics of these TILs differ in important modalities from TILs commonly used for this therapeutic approach. Tumor tissue samples were obtained from 12 patients undergoing surgery for primary CRC, predominantly with low microsatellite instability (pMMR-MSI-L). Tumors in the resected specimens were examined pathologically, and an approved volume of tumor tissue was transferred to a disposable perfusion bioreactor. Tissue samples were subjected to an automatically controlled and highly reproducible cultivation process in a GMP-conform, closed perfusion bioreactor system using starting medium containing interleukin-2 and interleukin-12. Outgrowth of TIL from tissue samples was initiated by short-term supplementation with a specific activation cocktail. During subsequent expansion, TILs were grown in interleukin-2–enriched medium. Expansion of TILs in a low-scaled, two-phase process in the Zellwerk ZRP bioreactor under hyperoxic conditions resulted in a number of approximately 2 × 10⁹ cells. The expanded TILs consisted mainly (73%) of the ACT-relevant CD3⁺/CD8⁺ effector memory phenotype (CD45RO⁺/CCR7⁻). TILs harvested under these conditions exhibited high functional potential, which was confirmed upon nonspecific stimulation (interferon-γ, tumor necrosis factor-α cytokine assay)     

Clinical-grade,large-scale,feeder-free expansion of highly active human natural killer cells for adoptive immunotherapy using an automated bioreactor

Background aimsNatural killer (NK) cell-based adoptive immunotherapy is a promising approach for the treatment of cancer. Ex vivo expansion and activation of NK cells under good manufacturing practice (GMP) conditions are crucial for facilitating large clinical trials. The goal of this study was to optimize a large-scale, feeder-free, closed system for efficient NK cell expansion.MethodsPeripheral blood mononuclear cells (PBMCs) from healthy donors and myeloma patients were cultured for 21 days using flasks, cell culture bags and bioreactors. Final products from different expansions were evaluated comparatively for phenotype and functionality.ResultsSignificant NK cell expansions were obtained in all systems. The bioreactor yielded a final product rich in NK cells (mean 38%) ensuring that a clinically relevant cell dose was reached (mean 9.8 × 10⁹ NK cells). Moreover, we observed that NK cells expanded in the bioreactor displayed significantly higher cytotoxic capacity. It was possible to attribute this partially to a higher expression level of NKp44 compared with NK cells expanded in flasks.ConclusionsThese results demonstrate that large amounts of highly active NK cells for adoptive immunotherapy can be produced in a closed, automated, large-scale bioreactor under feeder-free current GMP conditions, facilitating clinical trials for the use of these cells.     

Marrow-Derived Autologous Stromal Cells for the Restoration of Salivary Hypofunction (MARSH): Study protocol for a phase 1 dose-escalation trial of patients with xerostomia after radiation therapy for head and neck cancer: MARSH: Marrow-Derived Autologous Stromal Cells for the Restoration of Salivary Hypofunction

BackgroundXerostomia, or dry mouth, is a common side effect of head and neck radiation. Current treatment options for radiation-induced xerostomia are generally supportive in nature. Adult stem cells are the ultimate source for replenishment of salivary gland tissue. Bone marrow–derived mesenchymal stromal cells (BM-MSCs) are a viable cell-based therapy for xerostomia. We have undertaken studies enabling U.S. Food and Drug Administration Investigational New Drug status, demonstrating the normal phenotype, intact functionality, and pro-growth secretome of interferon-γ (IFNγ)-stimulated BM-MSCs taken from patients with head and neck cancer who have undergone radiation ± chemotherapy. Here we present the protocol of MARSH, a first-in-human clinical trial of bone marrow–derived, IFNγ-activated BM-MSCs for the treatment of radiation-induced xerostomia.MethodsThis single-center phase 1 dose-escalation with expansion cohort, non–placebo-controlled study will assess the safety and tolerability of BM-MSCs for the treatment of radiation-induced xerostomia in patients who had head and neck cancer. The phase 1 dose-escalation study will be a 3 + 3 design with staggered enrollment. A total of 21 to 30 subjects (9 to 18 in phase 1 study, 12 in expansion cohort) will be enrolled. The primary endpoint is determining the recommended phase 2 dose (RP2D) of IFNγ-stimulated BM-MSCs to enable further studies on the efficacy of BM-MSCs. Patients’ bone marrow will be aspirated, and BM-MSCs will be expanded, stimulated with IFNγ, and injected into the submandibular gland. The RP2D will be determined by dose-limiting toxicities occurring within 1 month of BM-MSC injection. Secondary outcomes of saliva amounts and composition, ultrasound of salivary glands, and quality of life surveys will be taken at 3-, 6-, 12-, and 24-month visits.DiscussionAutotransplantation of IFNγ-stimulated BM-MSCs in salivary glands after radiation therapy or chemoradiation therapy may provide an innovative remedy to treat xerostomia and restore quality of life. This is the first therapy for radiation-induced xerostomia that may be curative.Trial registrationWorld Health Organization International Clinical Trials Registry Platform: NCT04489732     

An Efficient Large-Scale Retroviral Transduction Method Involving Preloading the Vector into a RetroNectin-Coated Bag with Low-Temperature Shaking

In retroviral vector-mediated gene transfer, transduction efficiency can be hampered by inhibitory molecules derived from the culture fluid of virus producer cell lines. To remove these inhibitory molecules to enable better gene transduction, we had previously developed a transduction method using a fibronectin fragment-coated vessel (i.e., the RetroNectin-bound virus transduction method). In the present study, we developed a method that combined RetroNectin-bound virus transduction with low-temperature shaking and applied this method in manufacturing autologous retroviral-engineered T cells for adoptive transfer gene therapy in a large-scale closed system. Retroviral vector was preloaded into a RetroNectin-coated bag and incubated at 4°C for 16 h on a reciprocating shaker at 50 rounds per minute. After the supernatant was removed, activated T cells were added to the bag. The bag transduction method has the advantage of increasing transduction efficiency, as simply flipping over the bag during gene transduction facilitates more efficient utilization of the retroviral vector adsorbed on the top and bottom surfaces of the bag. Finally, we performed validation runs of endoribonuclease MazF-modified CD4⁺ T cell manufacturing for HIV-1 gene therapy and T cell receptor-modified T cell manufacturing for MAGE-A4 antigen-expressing cancer gene therapy and achieved over 200-fold (≥10¹⁰) and 100-fold (≥5×10⁹) expansion, respectively. In conclusion, we demonstrated that the large-scale closed transduction system is highly efficient for retroviral vector-based T cell manufacturing for adoptive transfer gene therapy, and this technology is expected to be amenable to automation and improve current clinical gene therapy protocols.     

Coupling programmed cell death 1-positive tumor-infiltrating T cells with anti-programmed cell death 1 antibody improves the efficacy of adoptive T-cell therapy

Background aimsAdoptive cell therapy (ACT) with tumor-infiltrating lymphocytes (TILs) has shown great success in clinical trials. Programmed cell death 1 (PD-1)-expressing TILs show high specificity to autologous tumor cells. However, limited therapeutic efficiency is observed as a result of the tumor immune microenvironment (TIME).MethodsCoupling PD-1⁺ ex vivo-derived TILs with a monoclonal antibody against anti-PD-1 (aPD-1) reinvigorated the anti-tumor response of TILs against solid tumor without altering their high tumor targeting ability.ResultsUsing a melanoma-bearing mouse model, PD-1⁺ TILs blocked with aPD-1 (PD-1⁺ TILs-aPD-1) exhibited a high capability for tumor targeting as well as improved anti-tumor response in TIME. Tumor growth was substantially delayed in the mice treated with PD-1⁺ TILs-aPD-1.ConclusionsThe strategy utilizing TIL therapy coupled with immune checkpoint antibodies may extend to other therapeutic targets of ACT.     

Assessment of the LOVO device for final harvest of novel cell therapies: a Production Assistance for Cellular Therapies multi-center study

Background aimsThe final harvest or wash of a cell therapy product is an important step in manufacturing, as viable cell recovery is critical to the overall success of a cell therapy. Most harvest/wash approaches in the clinical lab involve centrifugation, which can lead to loss of cells and decreased viability of the final product. Here the authors report on a multi-center assessment of the LOVO Cell Processing System (Fresenius Kabi, Bad Homburg, Germany), a cell processing device that uses a spinning filtration membrane instead of centrifugation.MethodsFour National Institutes of Health Production Assistance for Cellular Therapies cell processing facilities (CPFs) assessed the LOVO Cell Processing System for final harvest and/or wash of the following three different cell products: activated T cells (ATCs), tumor-infiltrating lymphocytes (TILs) and bone marrow-derived mesenchymal stromal cells (MSCs). Each site compared their current in-house, routinely used method of final cell harvest and/or wash with that of the LOVO device.ResultsFinal harvest and/or wash of ATCs, TILs and MSCs using the LOVO system resulted in satisfactory cell viability and recovery with some substantial improvement over the in-house methods of CPFs. Processing time was variable among cell types/facilities.ConclusionsThe LOVO Cell Processing System provides an alternative to centrifuge-based technologies. The system employs a spinning membrane filter, exposing cells to minimal g-forces compared with centrifugation, and is automated and closed. This small multi-center study demonstrated the ability of the LOVO device to yield satisfactory cell viability and recovery of T cells and MSCs.     

胃癌的过继性免疫治疗研究进展

胃癌是目前世界上发病率及致死率较高的恶性肿瘤之一,在东亚地区尤其显著。针对胃癌的治疗手段仍是传统的手术联合化疗、放疗为主,尽管靶向药物治疗提供了新的选择,但其对晚期胃癌的疗效仍然有限。胃癌的免疫治疗作为独特的治疗手段,在近十多年发展较为活跃,特别是过继性免疫治疗手段不断有创新。过继性免疫治疗主要依赖回输具有抗肿瘤活性的细胞,目前回输的细胞由具有非特异性抗肿瘤作用向具有特异性抗肿瘤作用演变,特别是嵌合性抗原T细胞治疗的出现,为进展期胃癌患者提供了有一种潜在的选择。本文对胃癌过继性免疫治疗中采用的不同免疫活性细胞的作用机制、临床应用等进行总结,并针对其不足提出利用基因工程技术增强治疗靶向性、降低免疫逃逸的研究方向。     

Standardized xeno- and serum-free culture platform enables large-scale expansion of high-quality mesenchymal stem/stromal cells from perinatal and adult tissue sources

Background aimsMesenchymal stem/stromal cells (MSCs) are of interest for the treatment of graft-versus-host disease, autoimmune diseases, osteoarthritis and neurological and cardiovascular diseases. Increasing numbers of clinical trials emphasize the need for standardized manufacturing of these cells. However, many challenges related to diverse isolation and expansion protocols and differences in cell tissue sources exist. As a result, the cell products used in numerous trials vary greatly in characteristics and potency.MethodsThe authors have established a standardized culture platform using xeno- and serum-free commercial media for expansion of MSCs derived from umbilical cord (UC), bone marrow and adipose-derived (AD) and examined their functional characteristics.ResultsMSCs from the tested sources stably expanded in vitro and retained their biomarker expression and normal karyotype at early and later passages and after cryopreservation. MSCs were capable of colony formation and successfully differentiated into osteogenic, adipogenic and chondrogenic lineages. Pilot expansion of UC-MSCs and AD-MSCs to clinical scale revealed that the cells met the required quality standard for therapeutic applications.ConclusionsThe authors’ data suggest that xeno- and serum-free culture conditions are suitable for large-scale expansion and enable comparative study of MSCs of different origins. This is of importance for therapeutic purposes, especially because of the numerous variations in pre-clinical and clinical protocols for MSC-based products.     

Translation of a standardized manufacturing protocol for mesenchymal stromal cells: A systematic comparison of validation and manufacturing data

BackgroundMany data are available on expansion protocols for mesenchymal stromal cells (MSCs) for both experimental settings and manufacturing for clinical trials. However, there is a lack of information on translation of established protocols for Good Manufacturing Practice (GMP) from validation to manufacturing for clinical application. We present the validation and translation of a standardized pre-clinical protocol for isolation and expansion of MSCs for a clinical trial for reconstitution of alveolar bone.MethodsKey parameters of 22 large-scale expansions of MSCs from bone marrow (BM) for validation were compared with 11 expansions manufactured for the clinical trial “Jaw bone reconstruction using a combination of autologous mesenchymal stromal cells and biomaterial prior to dental implant placement (MAXILLO1)” aimed at reconstruction of alveolar bone.ResultsDespite variations of the starting material, the robust protocol led to stable performance characteristics of expanded MSCs. Manufacturing of the autologous advanced therapy medicinal product MAXILLO-1-MSC was possible, requiring 21 days for each product. Transport of BM aspirates and MSCs within 24 h was guaranteed. MSCs fulfilled quality criteria requested by the national competent authority. In one case, the delivered MSCs developed a mosaic in chromosomal finding, showing no abnormality in differentiation capacity, growth behavior or surface marker expression during long-term culture. The proportion of cells with the mosaic decreased in long-term culture and cells stopped growth after 38.4 population doublings.ConclusionsClinical use of freshly prepared MSCs, manufactured according to a standardized and validated protocol, is feasible for bone regeneration, even if there was a long local distance between manufacturing center and clinical site. Several parameters, such as colony forming units fibroblasts (CFU-F), percentage of CD34+ cells, cell count of mononuclear cells (MNCs) and white blood cells (WBCs), of the BM may serve as a predictive tool for the yield of MSCs and may help to avoid unnecessary costs for MSC manufacturing due to insufficient cell expansion rates.     

Improving cell viability using counterflow centrifugal elutriation

BackgroundCell viability is an important release criterion in the manufacturing of cell therapy products. Low cell viability can have significant impact on product quality and manufacturing efficiency. Counterflow centrifugation technology has been applied to the manufacturing of cell therapy products, to enable cell separation based on size and density. This study evaluated the utility of counterflow centrifugation technology for dead cell removal to improve cell viability of the final product.MethodsJurkat cell cultures with low and high dead cell burden were subjected to counterflow centrifugal elutriation to determine the correlation between process parameters (e.g., flow rate, centrifugal force) and processing outcomes (i.e., cell recovery and viability). Subsequently, the optimized parameters were applied to dead cell elutriation using expanded T cells and freshly isolated human amniotic epithelial cells (hAECs). The efficiency of dead cell removal, cell function and post-thaw viability were compared.ResultsElutriation using a low flow rate allowed better control of viable cell recovery from both low and high dead cell burden cultures of Jurkat cells. The viability of T cells and hAECs was improved by counterflow centrifugal processing, from 80.67% ± 2.33 to 94.73% ± 1.19 and 79.19% ± 5.35 to 90.34% ± 3.59, respectively. Processing increased the proliferation rate of T cells, while the metabolic activity of hAECs was unchanged.ConclusionCounterflow centrifugal elutriation can be added as an integrated step to the automated wash-and-concentrate protocol for cell manufacturing to remove dead cells and improve cell viability of the final product.     

Alteration in interactions between tumor-infiltrating lymphocytes and tumor cells in human melanomas after chemotherapy or immunotherapy

Summary Alteration in interactions between tumor-infiltrating lymphocytes (TILs) and tumor cells after chemotherapy or immunotherapy was studied in metastatic melanoma patients. Tumors were harvested from surgical specimens 17 days after the end of chemotherapy with cisplatin, vinblastine, and dacarbazine (CVD). Tumors of nonlymph-node metastases from two responders yielded neither TILs nor tumor cells, whereas those from all four nonresponders had both TILs [(1.1–13.8) × 10⁶ cells/g tumor] and tumor cells [(2.8–30.8) × 10⁶ cells/g tumor). Tumors of lymph node metastases from nine patients yielded substantial numbers both of TILs and tumor cells, regardless of different clinical responses, except with one complete responder, whose tumor did not contain tumor cells. The mean increase of TILs from these tumors (n = 14) 3–4 weeks after incubation with 200 U/ml recombinant interleukin-2 (rIL-2) was 2.5-fold, whereas there was a 56-fold increase in TILs from untreated tumors (n = 3). CD3⁺ T cells predominated in TILs before and after expansion with IL-2. IL-2-activated TILs from five of six tumors tested displayed higher cytotoxicity against autologous tumor cells than against cells from any of three allogeneic tumors. Mean tumor cell numbers (10⁶ cells/trial) obtained by serial needle biopsies for the same tumor in five patients decreased from 1.2 before therapy to 0.25 at day 4 of therapy (interferon alone), and to 0.02 at day 8 (interferon and IL-2). This decrease did not correlate with clinical responses. Yields (× 10⁶ cells/g tumor) of TILs and tumor cells in subcutaneous melanomas obtained by excisional biopsies in one nonresponder under IL-2 therapy were respectively 0.2 and 1.1 before therapy (day 0), 0.1 and <0.01 during (day 7), 0.2 and <0.01 at the end of therapy (day 21), and 0.5 and 0.5 at the time of tumor progression (day 66). Yields of TILs and tumor cells in the other nonresponder were respectively 3 and 26 before (day 0), 16 and 3 during (day 7), and 0.4 and <0.01 at the end of IL-2 therapy (day 17), and 2.5 and 6 at the time of progression (day 62). TILs in these two patients before therapy proliferated well in culture with IL-2 (570-and 720-fold, respectively), and showed higher cytotoxicity against autologous tumor cells, whereas none of those from the five tumors biopsied during or at the end of IL-2 therapy proliferated. TILs at the time of progression showed modest proliferation (54- and 76-fold, respectively) and showed major-histocompatibility-complexnonrestricted cytotoxicity. In summary, a decrease in the number of live tumor cells did not always correlate with clinical response in either therapy. CVD chemotherapy may simply impair IL-2-induced proliferation of TILs. IL-2 therapy may induce transient unresponsiveness of TILs to IL-2.This work was supported in part by grant CA 47 891 from the National Institutes of Health and a grant from the University Cancer Foundation, and Mr Richard Hunton Melanoma Found.     

The prognostic value of CD3+ tumor-infiltrating lymphocytes for stage II colon cancer according to use of adjuvant chemotherapy: A large single-institution cohort study

BackgroundHigh tumor infiltrating lymphocytes (TILs) density was previously shown to be associated with favorable prognosis for patients with colon cancer (CC). However, the impact of TILs on overall survival (OS) of stage II CC patients who received adjuvant chemotherapy (ADJ) or not (no-ADJ) is unknown. We assessed the prognostic value of CD3+ TILs in stage II CC patients according to whether they had ADJ or not.MethodsPatients treated with curative surgery for stage II CC (2002–2013) were selected from the Santa Maria alle Scotte Hospital registry. TILs at the invasive front, center of tumor, and stroma were determined by immunohistochemistry and manually quantified as the rate of TILs/total tissue areas. High TILs (H-TILs) was defined as >20%. Patients were categorized as high or low TILs (L-TILs) and ADJ or no-ADJ.ResultsOf the 678 patients included, 137 (20%) received ADJ and 541 (80%) did not. The distribution of the 4 groups were: 16% (L-TIL/ADJ), 64% (L-TIL/no-ADJ), 5% (H-TIL/ADJ), 15% (H-TIL/no-ADJ). Compared to H-TILs/no-ADJ, ADJ patients showed a significantly increased OS (P<.01) regardless of the TILs rate whereas L-TILs/no-ADJ had significantly decreased OS and higher risk of death (HR=1.41; 95% CI, 1.06–1.88; P<.0001). On multivariable analysis, the unfavorable prognostic value of L-TILs (vs. H-TILs) for no-ADJ patients was confirmed (HR=1.36; 95% CI 1.02, 1.82; P=.0373).ConclusionLow CD3+ TILs rate was associated with shorter OS in those with stage II colon cancer who did not receive adjuvant therapy. Low CD3+ TILs could be considered an additional risk factor for still ADJ-untreated stage II CC patients, which could facilitate clinical decision making.     

Telomere length of transferred lymphocytes correlates with in vivo persistence and tumor regression in melanoma patients receiving cell transfer therapy

Recent studies have indicated that adoptive immunotherapy with autologous antitumor tumor-infiltrating lymphocytes (TILs) following nonmyeloablative chemotherapy mediates tumor regression in approximately 50% of treated patients with metastatic melanoma, and that tumor regression is correlated with the degree of persistence of adoptively transferred T cells in peripheral blood. These findings, which suggested that the proliferative potential of transferred T cells may play a role in clinical responses, led to the current studies in which telomere length as well as phenotypic markers expressed on the administered TILs were examined. TILs that were associated with objective clinical responses following adoptive transfer possessed a mean telomere length of 6.3 kb, whereas TILs that were not associated with significant clinical responses were significantly shorter, averaging 4.9 kb (p < 0.01). Furthermore, individual TIL-derived T cell clonotypes that persisted in vivo following adoptive cell transfer possessed telomeres that were longer than telomeres of T cell clonotypes that failed to persist (6.2 vs 4.5 kb, respectively; p < 0.001). Expression of the costimulatory molecule CD28 also appeared to be associated with long telomeres and T cell persistence. These results, indicating that the telomere length of transferred lymphocytes correlated with in vivo T cell persistence following adoptive transfer, and coupled with the previous observation that T cell persistence was associated with clinical responses in this adoptive immunotherapy trial, suggest that telomere length and the proliferative potential of the transferred T cells may play a significant role in mediating response to adoptive immunotherapy.     

Expansion and characterization of human melanoma tumor-infiltrating lymphocytes (TILs)

Background

Various immunotherapeutic strategies for cancer are aimed at augmenting the T cell response against tumor cells. Adoptive cell therapy (ACT), where T cells are manipulated ex vivo and subsequently re-infused in an autologous manner, has been performed using T cells from various sources. Some of the highest clinical response rates for metastatic melanoma have been reported in trials using tumor-infiltrating lymphocytes (TILs). These protocols still have room for improvement and furthermore are currently only performed at a limited number of institutions. The goal of this work was to develop TILs as a therapeutic product at our institution.

Principal Findings

TILs from 40 melanoma tissue specimens were expanded and characterized. Under optimized culture conditions, 72% of specimens yielded rapidly proliferating TILs as defined as at least one culture reaching ≥3×10⁷ TILs within 4 weeks. Flow cytometric analyses showed that cultures were predominantly CD3+ T cells, with highly variable CD4+:CD8+ T cell ratios. In total, 148 independent bulk TIL cultures were assayed for tumor reactivity. Thirty-four percent (50/148) exhibited tumor reactivity based on IFN-γ production and/or cytotoxic activity. Thirteen percent (19/148) showed specific cytotoxic activity but not IFN-γ production and only 1% (2/148) showed specific IFN-γ production but not cytotoxic activity. Further expansion of TILs using a 14-day “rapid expansion protocol” (REP) is required to induce a 500- to 2000-fold expansion of TILs in order to generate sufficient numbers of cells for current ACT protocols. Thirty-eight consecutive test REPs were performed with an average 1865-fold expansion (+/− 1034-fold) after 14 days.

Conclusions

TILs generally expanded efficiently and tumor reactivity could be detected in vitro. These preclinical data from melanoma TILs lay the groundwork for clinical trials of ACT.     

Consequences of adjusting cell density and feed frequency on serum-free expansion of thymic regulatory T cells

BackgroundGiven the promising results from phase 1/2 clinical trials of therapy involving regulatory T cells (Tregs), it is critical to develop Treg manufacturing methods that use well-defined reagents.MethodsSeeking to maximize expansion of human thymic Tregs activated with anti-CD3/CD28 antibody-coated beads and cultured in serum-free medium, the authors investigated the effect of adjusting process parameters including cell density and cell concentration, and feeding strategy on Treg yield and quality.ResultsThe authors found that levels of expansion and viability varied with cell density on the day of restimulation. Tregs restimulated at low cell densities (1 × 10⁵ cells/cm²) initially had high growth rates, viability and FOXP3 expression, but these parameters decreased with time and were less stable than those observed in cultures of Tregs restimulated at high cell densities (5 × 10⁵ cells/cm²), which had slower growth rates. High-density expansion was associated with expression of inhibitory molecules and lower intracellular oxygen and extracellular nutrient concentrations as well as extracellular lactate accumulation. Experiments to test the effect of low oxygen revealed that transient exposure to low oxygen levels had little impact on expansion, viability or phenotype. Similarly, blockade of inhibitory molecules had little effect. By contrast, replenishing nutrients by increasing the feeding frequency between 2 days and 4 days after restimulation increased FOXP3, viability and expansion in high-density cultures.ConclusionThese data show the previously undescribed consequences of adjusting cell density on Treg expansion and establish a Good Manufacturing Practice-relevant protocol using non-cell-based activation reagents and serum-free media that supports sustained expansion without loss of viability or phenotype.     

Comparison between centralized and decentralized supply chains of autologous chimeric antigen receptor T-cell therapies: a UK case study based on discrete event simulation

Background aimsDecentralized, or distributed, manufacturing that takes place close to the point of care has been a manufacturing paradigm of heightened interest within the cell therapy domain because of the product's being living cell material as well as the need for a highly monitored and temperature-controlled supply chain that has the potential to benefit from close proximity between manufacturing and application.MethodsTo compare the operational feasibility and cost implications of manufacturing autologous chimeric antigen receptor T (CAR T)-cell products between centralized and decentralized schemes, a discrete event simulation model was built using ExtendSIM 9 for simulating the patient-to-patient supply chain, from the collection of patient cells to the final administration of CAR T therapy in hospitals. Simulations were carried out for hypothetical systems in the UK using three demand levels—low (100 patients per annum), anticipated (200 patients per annum) and high (500 patients per annum)—to assess resource allocation, cost per treatment and system resilience to demand changes and to quantify the risks of mix-ups within the supply chain for the delivery of CAR T treatments.ResultsThe simulation results show that although centralized manufacturing offers better economies of scale, individual facilities in a decentralized system can spread facility costs across a greater number of treatments and better utilize resources at high demand levels (annual demand of 500 patients), allowing for an overall more comparable cost per treatment. In general, raw material and consumable costs have been shown to be one of the greatest cost drivers, and genetic modification-associated costs have been shown to account for over one third of raw material and consumable costs. Turnaround time per treatment for the decentralized scheme is shown to be consistently lower than its centralized counterpart, as there is no need for product freeze-thaw, packaging and transportation, although the time savings is shown to be insignificant in the UK case study because of its rather compact geographical setting with well-established transportation networks. In both schemes, sterility testing lies on the critical path for treatment delivery and is shown to be critical for treatment turnaround time reduction.ConclusionsConsidering both cost and treatment turnaround time, point-of-care manufacturing within the UK does not show great advantages over centralized manufacturing. However, further simulations using this model can be used to understand the feasibility of decentralized manufacturing in a larger geographical setting.     

Rapid single-cell identification of Epstein–Barr virus-specific T-cell receptors for cellular therapy

Background and aimsEpstein–Barr virus (EBV) is associated with solid and hematopoietic malignancies. After allogeneic stem cell transplantation, EBV infection or reactivation represents a potentially life-threatening condition with no specific treatment available in clinical routine. In vitro expansion of naturally occurring EBV-specific T cells for adoptive transfer is time-consuming and influenced by the donor's T-cell receptor (TCR) repertoire and requires a specific memory compartment that is non-existent in seronegative individuals.The authors present highly efficient identification of EBV-specific TCRs that can be expressed on human T cells and recognize EBV-infected cells.Methods and ResultsMononuclear cells from six stem cell grafts were expanded in vitro with three HLA-B*35:01- or four HLA-A*02:01-presented peptides derived from six EBV proteins expressed during latent and lytic infection. Epitope-specific T cells expanded on average 42-fold and were single-cell-sorted and TCRαβ-sequenced. To confirm specificity, 11 HLA-B*35:01- and six HLA-A*02:01-restricted dominant TCRs were expressed on reporter cell lines, and 16 of 17 TCRs recognized their presumed target peptides. To confirm recognition of virus-infected cells and assess their value for adoptive therapy, three selected HLA-B*35:01- and four HLA-A*02:01-restricted TCRs were expressed on human peripheral blood lymphocytes. All TCR-transduced cells recognized EBV-infected lymphoblastoid cell lines.ConclusionsThe authors’ approach provides sets of EBV epitope-specific TCRs in two different HLA contexts. Resulting cellular products do not require EBV-seropositive donors, can be adjusted to cell subsets of choice with exactly defined proportions of target-specific T cells, can be tracked in vivo and will help to overcome unmet clinical needs in the treatment and prophylaxis of EBV reactivation and associated malignancies.