Oncolytic Viruses - New Cure for Cancer? Facts about Oncolytic Viruses - how they target cancer cells without killing healthy tissue - health innovation and biotech Keynote Speaker

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Video and article explaining about oncolytic viruses for a non-technical audience.

We could be about to see the most dramatic advance in cancer treatment for 30 years. 

A new form of treatment that is relatively easy to make, has virtually no side effects, with potential to treat a wide variety of cancers, when used in combination with more traditional treatments.

That is the implication of early studies in laboratories and in humans using oncolytics, if all goes well in the next stages.

Viruses are a common cause of cancer.  So what about creating a new virus to cure cancer?  Many natural viruses are known to be “oncolytic”. They destroy cancer cells but they damage normal, healthy tissue as well.

How oncolytic viruses work to attack cancer

Scientists have taken a variety of human viruses which normally cause illness, and altered their genes so that they are able to enter human cells, but cannot activate – except in cancer cells.  

You can inject a healthy person with these altered viruses, and nothing happens. The virus particles do enter cells normally, but are unable to do anything at all, and are broken down inside the cell, completely destroyed.

However, if the same defective viruses enter cancer cells, they become fully active.  The cancer cells provide a vital piece of missing machinery, which enables the oncolytic virus to take over control of the cell.

The oncolytic virus genes give the cell instructions to make hundeds or thousands more identical virus particles.  Each cell gradually turns into a bloated virus factory, until the cell bursts, releasing large numbers of oncolytic virus particles, each of which has the ability to infect another cancer cell.  And so the cycle continues.

Several different kinds of cancer tumours have shrunk following injection of live oncolytic virus directly into the mass, while others have been treated by injecting oncolytic virus into veins.  Some results in animals have been spectacular with very high cure rates with aggressive cancers.

Oncolytic viruses to target cancer chemotherapy or radiotherapy

But this is only the beginning.  Oncolytic viruses can also be used to deliver a variety of completely new genes into cancer cells, each commanding the cell to do something different.  Results can be dramatic, when the viruses are combined with other treatments.

One such combination is with radioactive iodine, which has been used for many years to treat thyroid cancer because the thyroid gland takes up iodine from the blood.  Radioactive iodine loses its power within hours, so is safe to inject.  It is rapidly concentrated into the thyroid to produce local radiation damage for a short period.

Cancer cells from other tissues can be taught the same trick by an oncolytic virus, so that they also absorb radioactive iodine which has been linked to a protein. The virus teaches cancer cells to absorb the protein and if enough iodine is taken up by the tumour as a result, the radiation dose can destroy uninfected cancer cells as well.

Another combination is with cancer chemotherapy.  The problem with normal chemo is that every dividing cell in the body is exposed to it.  That can mean side effects with hair falling out, gut problems and damage to bone marrow.

Oncolytic viruses have been used to teach cancer cells how to split a harmless pro-drug into two pieces, one of which is a highly toxic substance.  The cancer cell soon dies, releasing a tiny dose of chemo to nearby cells so they die too.  The rest of the body is unaffected.

Multiple ways for oncolytic viruses to cure cancer

So now we have three mechanisms by which an oncolytic virus can destroy cancer cells:

1) Bursting the cell as it releases new viruses
2) Destroying the cell with radioactive iodine
3) Poisoning the cell with toxic chemotherapy

There is more. The body often recognizes that infected cells are not normal and declares war on them.  The good news is that uninfected cancer cells can get caught in the cross-fire, and killed too.

Oncolytic virus research is still at a relatively early stage.  Amgen is one of the companies furthest ahead, with Phase III clinical trials due to report results in 2013.  They paid around $1bn to buy into oncolytic virus technology in 2011 (down payment of 50%), convinced by very promising results in melanoma patients.  They are using a variant of Herpes Simplex Virus (HSV).

Another company using an altered version of HSV is Virttu Biologics.  Over 60 research papers have been published on a variant called SEPREHVIR, with 5 clinical studies completed in cancer patients.

In December 2012, the virus Rheolysin was shown to improve response to chemotherapy by over 25% in Phase III trials. 

For more on oncolytic virus research: 

http://en.wikipedia.org/wiki/Oncolytic_virus

http://www.virttu.com

List of published research papers on oncolytic virus HSV-1716 (Seprehvir)

Declaration of interest: after writing this article, the author became Chairman of Virttu Biologics Ltd.  The company was subsequently bought by Sorrento Therapeutics Inc in 2017.

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