Manufacture of GMP-compliant functional adenovirus-specific T-cell therapy for treatment of post-transplant infectious complications

SOHO State of the Art Updates and Next Questions | CTLs for Infections Following Stem Cell Transplantation

Allogeneic hematopoietic stem cell transplantation (AHSCT) is an important modality in the treatment of acute leukemia and other hematologic disorders. The post-transplant period is associated with prolonged periods of impaired immune function. Delayed T-cell immune reconstitution is correlated with increased risk of viral, bacterial, and fungal infections. This risk increases with high intensity inductions regimens often required for alternative donor sources. Current therapies for prophylaxis and treatment of these infections are limited by poor efficacy and significant toxicity. Adoptive cell therapy with cytotoxic T lymphocytes (CTL) has proven to be both efficacious and safe in the management of post-transplant viral infections. Recent advances have led to faster production of CTLs and broadened applications for their use. In particular, the generation of third party CTLs has helped ameliorate the problems related to donor availability and product generation time. In this review we aim to describe both the history of CTL use and current advances in the field.

Applications of Virus specific T cell Therapies Post BMT

Hematopoietic stem cell transplantation (HSCT) has been used as a curative standard of care for moderate to severe primary immunodeficiency disorders as well as relapsed hematologic malignancies for over 50 years [1,2]. However, chronic and refractory viral infections remain a leading cause of morbidity and mortality in the immune deficient period following HSCT, where use of available antiviral pharmacotherapies is limited by toxicity and emerging resistance [3]. Adoptive immunotherapy using virus-specific T cells (VSTs) has been explored for over 2 decades [4,5] in patients post-HSCT and has been shown prior phase I-II studies to be safe and effective for treatment or preventions of viral infections including cytomegalovirus, Epstein-Barr virus, BK virus, and adenovirus with minimal toxicity and low risk of graft vs host disease [6-9]. This review summarizes methodologies to generate VSTs the clinical results utilizing VST therapeutics and the challenges and future directions for the field.

Virus-specific T cells for adenovirus infection after stem cell transplantation are highly effective and class II HLA restricted

Infection with adenoviruses is a common and significant complication in pediatric patients after allogeneic hematopoietic stem cell transplantation. Treatment options with traditional antivirals are limited by poor efficacy and significant toxicities. T-cell reconstitution is critical for the management of adenoviral infections, but it generally takes place months after transplantation. Ex vivo-generated virus-specific T cells (VSTs) are an alternative approach for viral control and can be rapidly generated from either a stem cell donor or a healthy third-party donor. In the context of a single-center phase 1/2 clinical trial, we treated 30 patients with a total of 43 infusions of VSTs for adenoviremia and/or adenoviral disease. Seven patients received donor-derived VSTs, 21 patients received third-party VSTs, and 2 received VSTs from both donor sources. Clinical responses were observed in 81% of patients, with a complete response in 58%. Epitope prediction and potential epitope identification for common HLA molecules helped elucidate HLA restriction in a subset of patients receiving third-party products. Intracellular interferon-γ expression in T cells in response to single peptides and response to cell lines stably transfected with a single HLA molecule demonstrated HLA-restricted CD4+ T-cell response, and these results correlated with clinical outcomes. Taken together, these data suggest that VSTs are a highly safe and effective therapy for the management of adenoviral infection in immunocompromised hosts. The trials were registered at www.clinicaltrials.gov as #NCT02048332 and #NCT02532452.

Third-Party BK Virus-Specific Cytotoxic T Lymphocyte Therapy for Hemorrhagic Cystitis Following Allotransplantation

PURPOSE

BK virus-associated hemorrhagic cystitis (BKV-HC) is a common complication of allogenic hematopoietic stem cell transplantation (AHSCT), particularly in recipients of alternative donor transplants, which are being performed in increasing numbers. BKV-HC typically results in painful hematuria, urinary obstruction, and renal dysfunction, without a definitive therapeutic option.

METHODS

We performed a clinical trial (ClinicalTrials.gov identifier: NCT02479698) to assess the feasibility, safety, and efficacy of administering most closely HLA-matched third-party BKV-specific cytotoxic T lymphocytes (CTLs), generated from 26 healthy donors and banked for off-the-shelf use. The cells were infused into 59 patients who developed BKV-HC following AHSCT. Comprehensive clinical assessments and correlative studies were performed.

RESULTS

Response to BKV-CTL infusion was rapid; the day 14 overall response rate was 67.7% (40 of 59 evaluable patients), which increased to 81.6% among evaluable patients at day 45 (40 of 49 evaluable patients). No patient lost a previously achieved response. There were no cases of de novo grade 3 or 4 graft-versus-host disease, graft failure, or infusion-related toxicities. BKV-CTLs were identified in patient blood samples up to 3 months postinfusion and their in vivo expansion predicted for clinical response. A matched-pair analysis revealed that, compared with standard of care, after accounting for prognostic covariate effects, treatment with BKV-CTLs resulted in higher probabilities of response at all follow-up timepoints as well as significantly lower transfusion requirement.

CONCLUSION

Off-the-shelf BKV-CTLs are a safe and effective therapy for the management of patients with BKV-HC after AHSCT.

Cytometric analysis of T cell phenotype using cytokine profiling for improved manufacturing of an EBV-specific T cell therapy

Adoptive immunotherapy using Epstein–Barr Virus (EBV)‐specific T cells is a potentially curative treatment for patients with EBV‐related malignancies where other clinical options have proved ineffective. We describe improved good manufacturing practice (GMP)‐compliant culture and analysis processes for conventional lymphoblastoid cell line (LCL)‐driven EBV‐specific T cell manufacture, and describe an improved phenotyping approach for analysing T cell products. We optimized the current LCL‐mediated clinical manufacture of EBV‐specific T cells to establish an improved process using xenoprotein‐free GMP‐compliant reagents throughout, and compared resulting products with our previous banked T cell clinical therapy. We assessed effects of changes to LCL:T cell ratio in T cell expansion, and developed a robust flow cytometric marker panel covering T cell memory, activation, differentiation and intracellular cytokine release to characterize T cells more effectively. These data were analysed using a t‐stochastic neighbour embedding (t‐SNE) algorithm. The optimized GMP‐compliant process resulted in reduced cell processing time and improved retention and expansion of central memory T cells. Multi‐parameter flow cytometry determined the optimal protocol for LCL stimulation and expansion of T cells and demonstrated that cytokine profiling using interleukin (IL)‐2, tumour necrosis factor (TNF)‐α and interferon (IFN)‐γ was able to determine the differentiation status of T cells throughout culture and in the final product. We show that fully GMP‐compliant closed‐process culture of LCL‐mediated EBV‐specific T cells is feasible, and profiling of T cells through cytokine expression gives improved characterization of start material, in‐process culture conditions and final product. Visualization of the complex multi‐parameter flow cytometric data can be simplified using t‐SNE analysis.

Lymphocyte expansion in bioreactors: upgrading adoptive cell therapy

Bioreactors are essential tools for the development of efficient and high-quality cell therapy products. However, their application is far from full potential, holding several challenges when reconciling the complex biology of the cells to be expanded with the need for a manufacturing process that is able to control cell growth and functionality towards therapy affordability and opportunity. In this review, we discuss and compare current bioreactor technologies by performing a systematic analysis of the published data on automated lymphocyte expansion for adoptive cell therapy. We propose a set of requirements for bioreactor design and identify trends on the applicability of these technologies, highlighting the specific challenges and major advancements for each one of the current approaches of expansion along with the opportunities that lie in process intensification. We conclude on the necessity to develop targeted solutions specially tailored for the specific stimulation, supplementation and micro-environmental needs of lymphocytes’ cultures, and the benefit of applying knowledge-based tools for process control and predictability.

Evolution of the role of haploidentical stem cell transplantation: past, present, and future

INTRODUCTION

The accessibility to haplo-donors has led to an increase in the number of haplo-HSCT worldwide. A systematic search of the PubMed database between 2000 to present was performed.

AREAS COVERED

In this review, the authors discussed the most used approaches to perform haplo-HSCT and its results: T-cell depletion (TCD, including Perugia platform and its modifications) and T-cell repleted haplo (TCR, including the high-dose post-transplant cyclophosphamide strategy (Baltimore protocol) and the Beijing protocol). The improvements and modifications made to the different strategies have increased the indications of haplo-HSCT, including both malignant and nonmalignant disorders. Focusing on the Baltimore protocol, the authors review the results of the retrospective studies that have compared it to other donor transplants. The limitations of this strategy in terms of toxicity, graft complications, and GVHD are also discussed in detail. Finally, possible approaches to improve the outcomes of TCR haplo-HSCT are presented.

EXPERT OPINION

The recent advances in the field of haplo-HSCT have allowed a large number of patients with incurable diseases to benefit from this procedure despite not having a matched donor. With all available strategies, virtually no patient who needs an allogeneic transplant should be excluded by the absence of a donor.

Streamlined production of genetically modified T cells with activation, transduction and expansion in closed-system G-Rex bioreactors

BACKGROUND

Gas Permeable Rapid Expansion (G-Rex) bioreactors have been shown to efficiently expand immune cells intended for therapeutic use, but do not address the complexity of the viral transduction step required for many engineered T-cell products. Here we demonstrate a novel method for transduction of activated T cells with Vectofusin-1 reagent. Transduction is accomplished in suspension, in G-Rex bioreactors. The simplified transduction step is integrated into a streamlined process that uses a single bioreactor with limited operator intervention.

METHODS

Peripheral blood mononuclear cells (PBMCs) from healthy donors were thawed, washed and activated with soluble anti-CD3 and anti-CD28 antibodies either in cell culture bags or in G-Rex bioreactors. Cells were cultured in TexMACS GMP medium with interleukin (IL)-7 and IL-15 and transduced with RetroNectin in bags or Vectorfusin-1 in the G-Rex. Total viable cell number, fold expansion, viability, transduction efficiency, phenotype and function were compared between the two processes.

RESULTS

The simplified process uses a single vessel from activation through harvest and achieves 56% transduction with 29-fold expansion in 11 days. The cells generated in the simplified process do not differ from cells produced in the conventional bag-based process functionally or phenotypically.

DISCUSSION

This study demonstrates that T cells can be transduced in suspension. Further, the conventional method of generating engineered T cells in bags for clinical use can be streamlined to a much simpler, less-expensive process without compromising the quality or function of the cell product.

Adenovirus in solid organ transplant recipients: Guidelines from the American Society of Transplantation Infectious Diseases Community of Practice

These updated guidelines from the Infectious Diseases Community of Practice of the American Society of Transplantation review the diagnosis, prevention, and management of adenovirus infections after solid organ transplantation. Adenovirus is an important cause of infectious complications in both stem cell transplant and SOT patients, causing a range of clinical syndromes including pneumonitis, colitis, and disseminated disease. The current update of the guidelines highlights that adenovirus surveillance testing should not be performed in asymptomatic recipients. Serial quantitative PCR might play a role in the decision to initiate or assess response to therapy in a symptomatic patient. The initial and most important components of therapy remain supportive care and decrease in immunosuppression. The use of antiviral therapy is not supported by prospective randomized clinical trials. However, intravenous cidofovir is considered the standard practice for treatment of severe, progressive, or disseminated adenovirus disease in most transplant centers. Intravenous immunoglobulin may be beneficial, primarily in a select group of patients with hypogammaglobulinemia. Future approaches to treatment of adenovirus disease may include administration of adenovirus-specific T-cell therapy.

Role of Epstein-Barr Virus in the Pathogenesis of Head and Neck Cancers and Its Potential as an Immunotherapeutic Target

The role of Epstein-Barr virus (EBV) infection in the development and progression of tumor cells has been described in various cancers. Etiologically, EBV is a causative agent in certain variants of head and neck cancers such as nasopharyngeal cancer. Proteins expressed by the EVB genome are involved in invoking and perpetuating the oncogenic properties of the virus. However, these protein products were also identified as important targets for therapeutic research in the past decades, particularly within the context of immunotherapy. The adoptive transfer of EBV-targeted T-cells as well as the development of EBV vaccines has opened newer lines of research to conceptualize novel therapeutic approaches toward the disease. This review addresses the most important aspects of the association of EBV with head and neck cancers from an immunological perspective. It also aims to highlight the current and future prospects of enhanced EBV-targeted immunotherapies.

Multicenter phase 1/2 application of adenovirus-specific T cells in high-risk pediatric patients after allogeneic stem cell transplantation

BACKGROUND

Adenovirus (ADV) reactivation can cause significant morbidity and mortality in children after allogeneic stem cell transplantation. Antiviral drugs can control viremia, but viral clearance requires recovery of cell-mediated immunity.

METHOD

This study was an open-label phase 1/2 study to investigate the feasibility of generating donor-derived ADV-specific T cells (Cytovir ADV, Cell Medica) and to assess the safety of pre-emptive administration of ADV-specific T cells in high-risk pediatric patients after allogeneic hematopoietic stem cell transplantation (HSCT) to treat adenoviremia. Primary safety endpoints included graft-versus-host disease (GvHD), and secondary endpoints determined antiviral responses and use of antiviral drugs.

RESULTS

Between January 2013 and May 2016, 92 donors were enrolled for the production of ADV T cells at three centers in the United Kingdom (UK), and 83 products were generated from 72 mobilized peripheral blood harvests and 20 steady-state whole blood donations. Eight children received Cytovir ADV T cells after standard therapy and all resolved ADV viremia between 15 and 127 days later. ADV-specific T cells were detectable using enzyme-linked immunospot assay (ELISpot) in the peripheral blood of all patients analyzed. Serious adverse events included Grade II GvHD, Astrovirus encephalitis and pancreatitis.

CONCLUSION

The study demonstrates the safety and feasibility of pre-emptively manufacturing peptide pulsed ADV-specific cells for high-risk pediatric patients after transplantation and provides early evidence of clinical efficacy.