Gene Technologies

Enabling Gene Technologies

Enzo Therapeutics has developed an approach for highly specific gene regulation. This technology, known as genetic antisense or antisense RNA, utilizes a gene that codes for an RNA molecule that specifically inhibits the messenger RNA product of a specific gene. The antisense gene is delivered to the target cell ex vivo (outside the body) using a virus vector in a process called transduction. For efficient gene delivery Enzo scientists have developed a gene delivery vehicle, the StealthVector® HGTV43T transducing vector, that offers the following advantages for providing broad applicability in the field of gene medicine.

A frequent major problem of gene therapy programs has been an unacceptably low rate of delivery of the antisense genes to the target cells. With the StealthVector® we have achieved transduction rates significantly higher than those reported by other researchers.

A major problem with vectors currently used to transduce or “engineer” cells is that they produce proteins that can generate undesirable immune responses. This has occurred in some recent clinical trials where serious side effects were observed. The StealthVector® is incapable of producing any proteins, and no adverse effects have been observed in clinical trials using this vector.

We have designed our vectors to recognize specific cell types. This targeting mechanism has been achieved by incorporating specific proteins into the coat, or capsid of the virus vector. The specific proteins in the virus coat steer the vector to certain cell types by binding to receptors present on the surface of these cells, thus enabling preferential transduction of the intended cell. This target designed “smart” vector has the potential to establish a gene therapy product that could be administered directly to the patient rather than by ex-vivo delivery.

Some retroviral vectors have produced serious adverse effects that result from insertion of the corrective gene sequences into regions of the cell DNA that control cell growth and multiplication. A problem may arise if the inserted gene contains promoter sequences (sequences that can activate or “turn on” genes) and inserts into regions of the cell’s DNA that regulate cell division. This insertional activation can lead to unregulated cell division resulting in the development of cancer. The StealthVector ®contains no viral promoters and is thus incapable of insertional gene activation. No evidence of insertional gene activation was observed in clinical trials where this vector was used.

Pipeline

Stealth Vector™ HGTV43™

One application of Enzo’s gene regulation platform, the company’s proprietary StealthVector®HGTV43™ transducing vector is a vehicle designed to carry and deliver anti-HIV-1 antisense RNA genes to autologous blood stem cells ex vivo (outside the body). These genes are incorporated into the DNA of the stem cells and engraft in the bone marrow where they replicate and produce progeny immune CD4 T cells containing the antisense RNA genes (engineered cells). In circulation the engineered cells have been shown to produce anti-HIV-1 antisense RNA which can prevent replication of the HIV virus.

Preclinical in vitro studies demonstrated resistance to HIV-1 in human immune cells into which the antisense genes had been inserted.

A Phase I human clinical trial of the StealthVector®HGTV43™ was carried out on HIV-1-infected individuals. Results of the trial showed that:

  • All subjects tolerated the procedure and that there were no treatment-related adverse events
  • There was no evidence of expansion of the inserted transgenes in any subjects tested, nor was any evidence of leukemia seen by standard hematology;
  • CD34+ cells from the bone marrow of all subjects were tested for the presence of anti HIV-1 antisense RNA between 8 months and 20 months after infusion and these cells contained the antisense RNA, indicating engraftment of the engineered cells;
  • Anti-HIV-1 antisense RNA-containing immune cells were detected in the circulation of subjects, the longest at 72 months post-infusion

Based on these Phase I trial results demonstrating long-term survival and functioning of antisense RNA in circulating immune cells, we initiated a PhaseI/II study, focusing on a strategy to increase the percentage of engineered immune cells in circulation. The first patient has undergone treatment and we are monitoring the progress.