Monday, November 14, 2011

TeloVac vaccine trial for Pancreatic Cancer

It is a common knowledge that pancreatic cancer is one of the most dangerous known types. It has the worst survival rate of all common cancers, mostly because patients are usually diagnosed with the disease too late for an efficient treatment, when the cancer is inoperable. In many cases, patients often have less than six months to live, and unlike other cancers, there has been very little improvement in long-term survival in the past 40 years.

However, there are some, potentially good, news for the new vaccine which may turn out to be breakthrough in the pancreatic cancer treatment and prevention. Actually, if successful, the vaccine will open a way to treat and prevent other cancers as well, revolutionizing the mere approach to the disease.

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The TeloVac vaccine is part of a new generation of drugs that use the body’s own defenses to fight the disease, stopping tumors in their tracks. Yes, most vaccines are used to prevent infection, but therapeutic cancer vaccines mark a different approach by aiming to treat disease, stimulating the immune system to recognise and target the cancer.

The TeloVac trial involves more than 50 hospitals, is funded by Cancer Research UK and coordinated by Royal Liverpool University Hospital. It is a Phase 3 trial, which involves comparing the new treatment to standard therapy, and is essential before any new therapy is licensed.

The vaccine, also named GV1001, contains small sections of telomerase -- a protein that is over-produced by cancer cells. The injection of the vaccine, therefore, presents the immune system with telomerase, helping T-cells to recognize and target the cancer cells more effectively. Found at high levels in many cancer cells, telomerase effectively makes them immortal, allowing them to live on when healthy cells would die – easing the growth and spread of the tumor.

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Telomerase is a ribonucleoprotein enzyme which is involved in the DNA replication of the cell cycle. The enzyme is over expressed in majority of human cancers including 90% of advanced pancreatic cancer patients and therefore is a natural therapeutic target in the treatment of cancer. 

The over-expression of Telomerase enables the cancer cells to overcome mortality and therefore be a major contributing factor to progression of cancer. Telomerase is one of the body’s own proteins and therefore not recognized or attacked by the immune response.

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The scientists and doctors involved in the TeloVac trial are keen not to raise the expectations of patients. In earlier small-scale trials, some patients did have a prolonged life-expectancy of several months (three months in average). But until the results of this major trial are known it won't be clear whether this was anything to do with the vaccine.

In the largest trial of its kind in the UK, more than 1,000 men and women in the late stages of pancreatic cancer are either being given the vaccine alongside their normal drugs or treated as usual. The results from the 53 hospitals taking part will not be available until next year but, anecdotally, some patients credit their participation in the trial with giving them an extra year or two of life.

Professor John Neoptolemos from Royal Liverpool University Hospital, who is co-coordinating the large-scale British trial, said: “When you have got pancreatic cancer, it is like a time bomb in people.” Pancreatic cancer cells are normally invisible to the immune system but the vaccine ‘spots’ the telomerase spilling out from them and kick-starts the fight back. “The problem is tumors are clever and are able to turn the immune cells into traitors which help to guard the tumor,” said Professor Neoptolemos. “The vaccine takes away the masking effect of the tumor.” Healthy cells escape the attack because their levels of telomerase are too low to bother the immune system. This cuts the risk of side-effects such as nausea and hair loss normally seen with cancer drugs.

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If TeloVac passes the current trial successfully, it would be available for treating advanced forms of pancreatic cancer by the end of 2013. However, more studies would be underway to assess its effectiveness in preventing pancreatic cancer and treating patients suffering from earlier stages of the disease.

Scientists hope the method could work on other types of cancers as well and therefore have planned a trial on patients with lung tumor for later this year.

“We strongly believe this has the potential to overcome the limits of other current cancer vaccines and become part of the standard of care not only for pancreatic cancer but for various other types of cancers,” said Jay Sangjae Kim, the founder of GemVax, the Korean company developing the TeloVac vaccine.  “In other words, a truly 'universal' vaccine will be available in the near future,” he added.

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