Gene silencing as antiviral and anticancer treatment
Gene silencing is achieved by a novel principle, which is related to but distinct from siRNA and is designated as siDNA. The effect is similar in respect to sequence specificity and efficiency and also results in gene silencing. In contrast to siRNA, siDNA can be taken up by viruses or cells without the need of carriers. This is a novel principle for gene silencing. The discovery of siRNA for gene silencing was the Nobelprice in Decmber 2006. However, that field is not protectable by patents because of too much prior art. We are applying a next generation silencing fo HIV and other viruses as well as cancer.
Most advanced are results we obtained with HIV, where antiviral treatment has been performed successfully with three systems: cell-free virus particles, early during viral infection of the cell, as well as a small animal mouse model, in which an oncogenic retrovirus was analysed instead of HIV. There is no mouse model for HIV available. The antiviral effect by siDNA has been studied extensively and is shown to function against a highly concerned region of HIV in a dose-dependent fashion. HIV can be fully inactivated. In the mouse model a therapeutic as well as a prophylactic effect can be achieved depending on the regimen of treatment. In the therapeutic model fully infected mice are treated by siDNA, which results in reduction of virus load in the blood within four hours. Furthermore, disease progression can be reduced as evidenced by reduced tumor size and increase of survival. In the prophylactic model virus is treated early during infection, which allows to fully prevent establishment of infection in the animal.
We have also applied a recombinant lentivirus to the vagina of mice and showed reduction of the virus load in a prophylactic as well as therapeutic model. About 10fold reduction was achieved in 4 hours.
Furthermore, the virus load in the blood of infected patients from Zurich and Africa was reduced after treatment of the freshly isolated samples ex vivo within a few hours. This is a study precluding the effect of the compound inside the body as soon as we have GMP material for injection into humans.
We also showed prevention of infection in 5/6 humanized SCID mice infected with HIV and treated with the compound.
We believe most strongly in a microbicide application with the siDNA approach because we can destroy the virus before infection. Thus, it would complement the approaches with inhibitors early during infection of the cell as used in the CAPRISA study by SA Karim.
We are pursuing monkey studies and plan a collaboration with Dr. Karim in south Africa.
Another approach is silencing of Influenza which we have shown in mice and virus titers after treatment, including the new pandemic strain H1N1 in in vitro studies. Furthermore, silencing of HCV against Hepatocellular Carcinoma we envisage in a collaboration with Egypt, where this is a predominant problem. Finally HSV-1 and -2 and other viruses in immune suppressed transplant recipients will be considered for antiviral therapy.
We envisage three possible applications for HIV carriers by this novel approach
- siDNA is effective against HIV and can therefore be used as microbicide. This would involve a local treatment. Virus particles and preliminary studies have indicated that it is effective against the virus in the vagina of mice. All combinations are possible. The compound is heat-stable.
- Reduction of virus transmission from mother-to-child during delivery by a single treatment of the mother within a few hours before delivery. Thus, a long pre-treatment of the mother and treatment of the newborn child can be avoided. Treatment of multi-drug resistant HIV-carriers can be achieved. We have already shown our compound to be effective against multi-drug resistant primary patient isolates. Our approach is unique and is directed against a novel target, which has not been exploited yet. It will complement all previous therapies.
- Preliminary data suggest that there is no or only a very low frequency of escape mutants. No toxicity has been observes as yet. All these therapies can be combined with all available drugs or investigational new therapies because it is based on a unique principle.
- Other viruses such as Influenza, HCV against Hepatocellular Carcinoma, HSV-1 and -2, and viruses in immune suppressed transplant recipients.
The next steps require analyses of non-human primates and toxicology studies. Also GMP production of the compound is required for a Phase I/II clinical trial, which will be initiated within the next two years. Production and synthesis of the compound is known, machines are available, the production can be scaled up.
A similar approach is under investigation against Hepatitis B Virus (HBV), Hepatitis C Virus (HCV), Herpes Simplex Virus (HSV), Respiratory Syncytia Virus (RSV), Influenza A Virus. In all these cases a direct comparison has been performed for siDNA, antisense single-stranded DNA and siRNA. The three mechanisms for gene silencing are all effective with different efficiencies, depending on dose, time course, cell-type, carrier for cellular uptake, stability, chemical modifications.
For several viruses mouse models have shown efficacies in mouse models in vivo. Influenza is one of them.
Another approach is a general treatment of cancer cells, by targeting a proliferation specific effect, which involves the deregulated growth of the tumor cell. The compound targets the chromosomal ends of tumor cells (telomere). This approach is universal for any kind of tumor. We have shown reduction of metastases in a melanoma mouse model. The mechanism is gene silencing and possibly also blockage of the telomer.
Minimal Finances for HIV: 100.000CHF for primates, 200.000CHF for limited toxicology study, 50.000 CHF for a second small animal model (SCID), 500.000CHF for compound under GMP production, 100.000 for chemical modification of compound, patenting costs, Clinical research organization, Protocol, legal affairs, one coordinator makes in totat 1 Mio €.