Traditionally, clinically relevant cell types such as hematopoietic stem cells (HSCs) and T cells have a low transduction efficiency, regardless of the method used to introduce the exogenous DNA. Although there has been demonstrated success in clinical trials using engineered T cells to treat certain types of cancer, favorable outcomes can be limited by the number of cells that acquire and express the exogenous DNA. In one cancer and immune gene therapy technique, adoptive cell therapy (ACT), T cells engineered to express chimeric antigen receptors (CAR) can recognize cancer cells—like those in bone marrow tumors in patients with acute lymphocytic leukemia who are refractory to chemotherapy—and they will eradicate those malignant cells. Although CAR T-cell therapy gives hope to these patients, the typical low transduction efficiency and T-cell expansion rates can compromise the procedure and get in the way of recovery.

To address these bottlenecks, RetroNectin GMP grade reagent improves retroviral- and lentiviral-mediated gene transfer by colocalizing retrovirus particles and target cells. Colocalization is thought to be accomplished by direct binding of viral particles to sequences in the heparin-binding domain and interaction of cellular integrins VLA-4 and/or VLA-5 with the RetroNectin molecule (Hosoi et al. 2014).

The RetroNectin method is being widely used during ex vivo gene therapy to allow efficient transduction of genes into difficult-to-transduce human cell types. In ex vivo gene therapy, cells are taken from a patient, the disease-fighting gene(s) are introduced, and the modified cells are transplanted back into the patient.

The following section is a curated selection of publications on the use of RetroNectin reagents in clinical settings.

Adoptive cell therapy

T-cell receptor (TCR) gene therapy is an ACT against cancer. In this therapy, a TCR/CAR that recognizes a specific cancer antigen is introduced into lymphocytes from a patient. The modified lymphocytes are cultured in large scale and then infused back into the patient. These cells specifically attack tumor cells expressing the cancer antigen. Here, it is important to have high transduction efficiency for introducing the CAR genes into the lymphocytes.

RetroNectin GMP grade reagent is used to enhance transduction and T-cell expansion for therapies. Dr. Steven Rosenberg at the National Institutes of Health (US), one of the pioneers of ACT, is conducting clinical trials of TCR/CAR gene therapy (Kochenderfer et al. 2012). His group uses RetroNectin GMP grade reagent to transduce patient-derived lymphocytes with TCR/CAR genes that recognize cancer antigens (e.g., MART-1, gp100, or NY-ESO-1) for therapy (Robbins et al. 2011).

T-cell immunotherapy for acute lymphoblastic leukemia

The prognosis for adults with relapsed acute lymphoblastic leukemia is extremely poor, as few therapeutic options are available. Scientists at Memorial Sloan-Kettering Cancer Center reported an immunotherapy strategy for the treatment of five adult patients with acute lymphoblastic leukemia (Brentjens et al. 2013). Each patient's T cells were isolated, altered by the introduction of DNA that would cause the cells to target CD19 and thus attack bone marrow tumor cells, and infused back into the patient's bloodstream. According to the researchers, all patients achieved tumor eradication and complete remission. RetroNectin GMP grade reagent was used during T-cell transduction.

Transduction of CD34+ hematopoietic stem cells

Standardized methodology for transduction of human CD34+ HSCs is critical for the success of gene therapy for a variety of hematopoietic diseases. In 2009, Millington et al. systematically investigated factors involved in ex vivo transduction of Granulocyte-Colony Stimulating Factor (G-CSF)-mobilized peripheral blood CD34+ cells. Their team used a self-inactivating lentiviral vector carrying eGFP to investigate the effect of serum, cytokine combinations, prestimulation time, multiplicity of infection (MOI), transduction duration, and the use of spinoculation and/or RetroNectin reagent on transduction efficiency. The researchers found that transduction using RetroNectin reagent alone resulted in a statistically significant increase in transduction rate (~10% in untreated controls compared to 24.6 ± 1.3% with RetroNectin reagent). RetroNectin reagent in combination with spinoculation resulted in the highest transduction rate (34.1 ± 0.5%), but spinoculation alone had no effect.

With the RetroNectin method, increasing the efficiency of the virus-cell interaction leads to a higher transduction rate and increases the likelihood of a successful outcome. The RetroNectin method has been utilized in gene therapy clinical trials and over 68 protocols at 44 institutions worldwide. RetroNectin GMP grade reagent for use in ex vivo clinical applications is now available for direct purchase by researchers, without the need for a Material Transfer Agreement (MTA). RetroNectin GMP grade is manufactured as a quality-assured product according to guidelines for Good Manufacturing Practice (GMP) for Investigational Products. Takara Bio owns exclusive worldwide rights to the use of RetroNectin technology.

Brentjens, R. J. et al. CD19-targeted T cells rapidly induce molecular remissions in adults with chemotherapy-refractory acute lymphoblastic leukemia. Sci. Transl. Med. 5, 177ra38 (2013).      

Hosoi, H. et al. Stimulation through very late antigen-4 and -5 improves the multifunctionality and memory formation of CD8⁺ T cells. Eur. J. Immunol. 44, 1747–58 (2014).               

Kochenderfer, J. N. et al. B-cell depletion and remissions of malignancy along with cytokine-associated toxicity in a clinical trial of anti-CD19 chimeric-antigen-receptor-transduced T cells. Blood 119, 2709–20 (2012).        

Robbins, P. F. et al. Tumor regression in patients with metastatic synovial cell sarcoma and melanoma using genetically engineered lymphocytes reactive with NY-ESO-1. J. Clin. Oncol. 29, 917–24 (2011).