UPDATED: GMO virus approved for cancer trial – Expert reaction

The Environmental Protection Authority (EPA) has approved the use of a genetically modified virus (Pexa-Vec) for a liver cancer treatment trial.

Vials and SyringeThe Pexa-Vec virus is the first genetically modified organism for a human therapeutic purpose that is capable of reproducing itself, to be approved by the EPA for release under the HSNO Act.

In a separate media release Environment Minister Dr Nick Smith, welcomed the approval.

“We should embrace new technologies like GM where there are clear benefits and where any risks to the environment can be effectively managed,” he said.

The SMC collected the following expert commentary.

NEW: Dr James Ussher, Clinical Academic, Department of Microbiology and Immunology, University of Otago, comments:

“Pexa-Vec is an genetically modified version of the vaccinla poxvirus, a live viral vaccine that has previously been extensively used in humans to eliminate smallpox. Pexa-Vec has been further attenuated (weakened) from the parental vaccinia strain by deletion of a viral gene. It is, however, still able to replicate in cancer cells and kill them. It has also had a gene inserted to stimulate an anti-tumour immune response. Pena-Vac is directly injected into primary liver cancers, killing the cancer cells and stimulating an immune response. It has been shown to be well tolerated in phase I clinical trials. A phase 2 trial is planned in patients with advanced primary liver cancer.

“I am very pleased to see that the EPA has approved the importation of Pexa-Vac for use in a phase II clinical trial. It is exciting that New Zealand patients who may have no other treatment options will get an opportunity to participate in this trial. It is important that these sorts of cutting edge therapies are evaluated and, if demonstrated to be efficacious, made available in New Zealand.

“These treatments are being used in patients who have failed other therapies. Genetic modification has been used to attenuate (weaken) the virus, making it safer. It has also been modified to enhance the ability of the virus to stimulate an anti-tumour immune response. This is important as anti-tumour immune responses are often suppressed by the tumour, yet have the potential to kill tumour cells throughout the body (including those that may have spread from the primary site of the tumour). This therapy seeks to overcome that suppression.

“There are many investigational treatments and vaccines in the developmental pipeline that utilise genetic modification. Many of these are showing promising results in pre-clinical and early clinical trials. These will undoubtedly become more common in the future.”

Assoc Prof Peter Dearden, Director of Genetics Otago, comments:

“In my opinion this is an interesting development. Liver carcinoma is a very serious condition and there are few treatment options. The treatment considered here is a targeted virus that should target and kill just the cancer cells. The virus is based on vaccinia, a virus commonly used in vaccinations. By targeting the virus to just cancer cells may be an effective and safe treatment for this condition.

“The genetic modification in this case is to target the virus, a way of dealing with the big problem of cancer treatment; how do you kill cancer cells but not normal ones? Such uses of genetic modification are very likely to become more common to deal with this problem.”

Prof Graham Le Gros, Research Director of the Malaghan Institute of Medical Research, notes that there are a wide range of avenues immunologists are investigating which include viruses. He  comments: 

“The BCG vaccine is already in use for those with early bladder cancer as a way to stimulate the immune system against the cancer.

“Today there is news of another immunotherapy approach against melanoma – using a genetically modified Herpes virus. In that article it says, “A 2013 review in the journal Molecular Cancer concluded that cancer-fighting viruses armed with genes that stimulate the immune system “are potent therapeutic cancer vaccines”.