Host: Mignon Fogarty
Transcript: This episode originally aired November 11, 2005
LISTEN TO THE PODCAST
BIRD FLU: CLEARING UP MISINFORMATION
By now, you've almost certainly heard of the bird flu that's washing over Asia and seems to be rapidly spreading to birds in other regions, including parts of Europe. There's even a new report today that the virus has officially reached the middle east, with a confirmed case in Kuwait.
This flu is called H5N1 after the two major surface proteins. So H5 refers to the 5 subtype of hemagglutanin, which is the surface antigen that allows the virus to bind to the cell that it is infecting, and N1 refers to the 1 subtype of the neuraminadase, which is the other surface antigen that helps the virus get out of cells after it is done with them. H5 in, N1 out.
And the reason people are so afraid of the H5N1 is that humans don't have any natural immunity to a flu virus with these specific surface antigens.
So now that we've covered the bare basics let's get to the misinformation floating around out there.
First, it is perfectly safe to continue eating chicken and eggs. Just make sure they are well cooked. The heat from cooking would kill the virus even if it were there. Just wash you hands like you normally would after handling raw chicken or eggs, and it is perfectly fine. The people who are getting sick right now are those people who live with their chickens, sleep with their chickens, and they eat very sick chickens that are raw or are not well cooked. These are not the people who get their chicken at the grocery store and grill it on the BBQ.
Second, an occasional reporting error that I am seeing that makes the situation look more frightening than it is, is that I'm hearing reporters say that they can't make a vaccine to the H5N1 virus because they can't grow it in eggs, and vaccines are made from eggs. It is true that vaccines are made using eggs, but it is simply not true that the H5N1 virus kills the eggs used to make vaccines. Experimental vaccines are already being made in eggs right now. So cross that off your worry list.
Now the third, and final, bit of misinformation I find particularly annoying because it comes from people who should know better, the U.S. Department of Health and Human Services. Last week they put out a report that described the worst-case scenario for flu that 1.9 million U.S. Citizens could die as a result of a bird flu pandemic. This was widely, widely reported as THE worst case scenario. But their predictions were based on what we know about the flu pandemic that occurred in 1918. In that flu pandemic, that virus had a death rate of about 2%. Now so far, the H5N1 virus has killed 50% of the humans reported to have contracted the disease. Big difference 2% and 50%. So even though there are a lot of reasons why the death rate of an H5N1 virus might not reach 50% when it becomes a pandemic, I feel pretty safe saying that 1.9 million deaths isn't anything even remotely close to the worst case scenario, and the irritating part is that the people who put together the report just have to know that.
So, now you're up to speed: it's fine to eat chickens and eggs, there's no reason we can't make H5N1 vaccine in eggs, and the worst case scenario is a lot worse than the government is representing.
PROVENGE: A PROSTATE CANCER VACCINE MOVES FORWARD
Prostate cancer is one of the most common cancers in the developed world, in the U.S. About two hundred and twenty thousand men are diagnosed each year. And when men progress past the point where hormones are useful against the disease, treatment becomes much more difficult.
Now there is a prostate cancer vaccine called Provenge from a company called Dendreon that is designed to treat those men that have advanced to the hormone-refractory stage, and Provenge has just recently completed some pivotal phase III trials. This is the final stage before the company can submit the drug for approval to the U.S. FDA.
Now, there are a couple of interesting things about Provenge that made it rise to the top of potential stories we could cover this week. First, Provenge represents a relatively new concept in treating cancer, because it is a cancer vaccine, and second, the story of how Provenge has been developed really highlights just how long and arduous the path can be to develop a cancer drug, especially one that is so unique.
First, let's go over how vaccines for cancer are different from vaccines for infectious diseases like the flu. With a flu vaccine, you get the treatment before you are exposed to the flu, as a way of revving up your immune system to fight it off. Flu vaccines are preventative, as are pneumonia vaccines, and probably most other vaccines you can think of or might have received.
Cancer vaccines, on the other hand, are meant as treatment for the disease after you know that you have it. It's very confusing, and I wish they would have chosen a different name for these kinds of drugs, but they didn't. So, remember, cancer vaccines don't prevent cancer; they treat it. Or at least they try to treat it, and they work by showing your immune system proteins called antigens that are only found on cancer cells. Or at least that is what they hope, sometimes they are just much more common on cancer cells than healthy cells. But either way, the goal of cancer vaccines is to get your immune system to do a better job of attacking the cancer.
So, now you know what cancer vaccines do...they treat cancer by trying to coax your immune system to go on a cancer-specific attack.
Disappointing, but by the time they reach a phase III trial, if a company can keep going, they aren't going to just give up when they have such tantalizing results.
So then the company did what a lot of companies do at this point; they started subgroup analysis. Which means basically they went hunting through their data for a group of patients who might have benefited more than others...where the result might have reached statistical significance. And they found a group; men with something called a Gleason score of 7 or less. Basically, this means that when they excluded men who were really sick from the analysis, then their drug showed statistically significant activity. But subgroup analysis like this is dangerous because the trial wasn't designed to look at just those men. So in the summer of 2003, the FDA asked the company to conduct another, redesigned phase III trial, to see if the results held up.
At that point they were hoping to have Provenge on the market in 2005 if the results were good from this new, redesigned trial.
So now we jump ahead to January 2005, and more bad news. Provenge flunked the first part of the new phase III trial. Even with the healthier men, there was a trend to slower disease progression, but it still wasn't statistically significant. The company's stock price plummeted, but they toiled on, running the numbers on the second part of the trial that was set up to look at survival instead of the rate of disease progression. And now, just last week Dendreon finally had some good news to announce, Provenge had shown that it could improve survival by 22% and the results were finally statistically significant. Finally, they have something to take to the FDA to seek approval.
If the drug gets approved, Provenge will be the first cancer vaccine to ever make it to market; a pretty amazing feat. The company sounds optimistic, especially because their drug has very mild side effects. But the drug isn't approved, and the story isn't over yet. We'll have to wait and see what the FDA thinks of all the data in the end.
I should note that nobody associated with Absolute Science has any kind of financial stake in Dendreon. We just thought that this story provided a great example of the ups and downs of biotech drug development; and it would be great if this cancer vaccine makes it to market. There are a number of other companies developing these kinds of drugs too, and if one makes it, it could give a boost to all those other companies too.
