Replication competent retrovirus testing (RCR) in the National Gene Vector Biorepository: No evidence of RCR in 1,595 post-treatment peripheral blood samples obtained from 60 clinical trials

CAR-NK cell therapy: promise and challenges in solid tumors

Over the past few years, cellular immunotherapy has emerged as a promising treatment for certain hematologic cancers, with various CAR-T therapies now widely used in clinical settings. However, challenges related to the production of autologous cell products and the management of CAR-T cell toxicity highlight the need for new cell therapy options that are universal, safe, and effective. Natural killer (NK) cells, which are part of the innate immune system, offer unique advantages, including the potential for off-the-shelf therapy. A recent first-in-human trial of CD19-CAR-NK infusion in patients with relapsed/refractory lymphoid malignancies demonstrated safety and promising clinical activity. Building on these positive clinical outcomes, current research focuses on enhancing CAR-NK cell potency by increasing their in vivo persistence and addressing functional exhaustion. There is also growing interest in applying the successes seen in hematologic malignancies to solid tumors. This review discusses current trends and emerging concepts in the engineering of next-generation CAR- NK therapies. It will cover the process of constructing CAR-NK cells, potential targets for their manufacturing, and their role in various solid tumors. Additionally, it will examine the mechanisms of action and the research status of CAR-NK therapies in the treatment of solid tumors, along with their advantages, limitations, and future challenges. The insights provided may guide future investigations aimed at optimizing CAR-NK therapy for a broader range of malignancies.

The design of retroviral vectors used in the CAR-T products, risk management, and future perspective

Chimeric antigen receptor T-cell (CAR-T) therapy is a revolutionary approach in cancer treatment. More than 10 CAR-T products have already approved on market worldly wide, and they use either gamma retroviral vectors or lentiviral vectors to deliver the CAR gene. Both vectors have the ability to effectively and persistently integrate the CAR gene into T cells. Despite the advancements in CAR-T therapy, the potential risks associated with the vectors, particularly the risks of the secondary malignancies, still remain as a concern. This article compares the characteristics of gamma retroviral and lentiviral vectors, discusses the development of vector packaging systems, and examines the design of self-inactivating (SIN) vectors. It also addresses the risks of secondary malignancies that might possibly be associated with the retroviral vectors, and the strategies to decrease the risks and increase the safer clinical use of the vectors. This article also discusses the current regulatory landscape and management approaches aiming to mitigate these risks through stringent safety measures and ongoing monitoring. Future perspectives focus on improving the safety profiles of the vectors and broadening their scope of use. The article provides a thorough overview of the most recent research discoveries and regulatory updates in the field of CAR-T therapy, highlighting the significance of a balanced strategy that strikes a balance between innovation and patient safety in the development and implementation of CAR-T therapy.

Accurate vector copy number determination in gammaretroviral vector producer cell clones using triplex digital droplet PCR

Gammaretroviral vectors are widely used in cellular and gene therapy products because of the availability of stable vector producer cells. Accurately assessing vector copy number (VCN) is critical for selecting appropriate clones to avoid the risks of homologous recombination and complications in mutation detection. Traditional methods such as quantitative polymerase chain reaction (PCR) and Southern blotting have limitations in accuracy and throughput. This study presents a triplex droplet digital PCR (ddPCR) method for analyzing the VCN in gammaretroviral vector producer cells. We designed a universal primer- probe set targeting the packaging signal sequence common to murine leukemia virus- and murine stem cell virus- based gammaretroviral vectors. Two reference genes were selected after karyotyping the PG13 gammaretroviral vector packaging cell line to identify stable chromosomes. The triplex ddPCR assay was optimized and verified using PG13 cells transduced with constructs of different transgene and vector backbones. The assay showed high concordance with Southern blot. Using multiple reference genes ensures accurate and robust VCN assessment, especially in cell lines with chromosomal instability. This method improves the clone selection process for gammaretroviral vector producer cells, accelerates the development of novel cellular and gene therapy products, and ensures their rapid delivery to patients.

Update on Managing the Risks of Exposure to Lentiviral and Retroviral Vectors

OBJECTIVE

This paper aims to review the risks associated with using lentiviral and retroviral vectors in research and clinical settings and to propose an update to an effective treatment plan.

METHODS

Risks of exposure were evaluated based on vector design, safety features, viral tropism, transgene, and means and modes of transmission. These risks were weighed against the potential risks and benefits of current HIV medications.

RESULTS

We recommend the following postexposure prophylactic treatment for significant lentiviral vector exposures: 1) dolutegravir 50 mg taken once a day for 7 days and 2) tenofovir disoproxil fumarate 300 mg taken once a day for 7 days (28 days of both medications for replication-competent vectors).

CONCLUSIONS

Because of the highly efficient delivery of transgenes by modern lentiviral and retroviral vectors, postexposure prophylaxis is indicated to prevent vector integration and oncogenic risks.

Current understanding and management of CAR T cell-associated toxicities

Chimeric antigen receptor (CAR) T cell therapy has revolutionized the treatment of several haematological malignancies and is being investigated in patients with various solid tumours. Characteristic CAR T cell-associated toxicities such as cytokine-release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) are now well-recognized, and improved supportive care and management with immunosuppressive agents has made CAR T cell therapy safer and more feasible than it was when the first regulatory approvals of such treatments were granted in 2017. The increasing clinical experience with these therapies has also improved recognition of previously less well-defined toxicities, including movement disorders, immune effector cell-associated haematotoxicity (ICAHT) and immune effector cell-associated haemophagocytic lymphohistiocytosis-like syndrome (IEC-HS), as well as the substantial risk of infection in patients with persistent CAR T cell-induced B cell aplasia and hypogammaglobulinaemia. A more diverse selection of immunosuppressive and supportive-care pharmacotherapies is now being utilized for toxicity management, yet no universal algorithm for their application exists. As CAR T cell products targeting new antigens are developed, additional toxicities involving damage to non-malignant tissues expressing the target antigen are a potential hurdle. Continued prospective evaluation of toxicity management strategies and the design of less-toxic CAR T cell products are both crucial for ongoing success in this field. In this Review, we discuss the evolving understanding and clinical management of CAR T cell-associated toxicities.

Unanswered questions following reports of secondary malignancies after CAR-T cell therapy

Reports of T cell malignancies after CAR-T cell therapy should be investigated, but existing data from follow-up studies suggest a low risk compared with other cancer treatments.

Long-term follow-up of CD19-CAR T-cell therapy in children and young adults with B-ALL

The tremendous successes of CD19-directed CAR T cells in children and young adults with B-cell acute lymphoblastic leukemia (B-ALL) has led to the more widespread use of this important treatment modality. With an ability to induce remission and potentially lead to long-term survival in patients with multiply relapsed/chemotherapy refractory disease, more children are now receiving this therapy with the hope of inducing a long-term durable remission (with or without consolidative hematopoietic cell transplantation). While overcoming the acute toxicities was critical to its broad implementation, the emerging utilization requires close evaluation of subacute and delayed toxicities alongside a consideration of late effects and issues related to survivorship following CAR T cells. In this underexplored area of toxicity monitoring, this article reviews the current state of the art in relationship to delayed toxicities while highlighting areas of future research in the study of late effects in children and young adults receiving CAR T cells.