People with diabetes have too much sugar in their blood, so a drug that lowers blood sugar ought to be a good treatment, right?
Maybe not. Consider the diabetes drug Avandia, or rosiglitazone, which was approved in 1999. It lowers blood sugar, and about a million people in the US have been taking it for Type 2 diabetes, the most common form of the disease. But last week, doctors reported that Avandia might increase the risk of heart attacks.
Heart disease is a major complication of diabetes, so a drug that could make the risk worse is bad news indeed.
The jury is still out on Avandia. Meanwhile, patient advocates and some politicians and researchers are already denouncing it, and the Food and Drug Administration (FDA) has issued a tepid “safety alert” telling patients to ask their doctors what to do while the agency “is carefully weighing several complex sources of data”. Avandia’s manufacturer, GlaxoSmithKline, insists it is safe. Personal injury lawyers are advertising on the Internet for clients who think they were injured by the drug.
What happened here reflects a larger question—the tricky problem of how to judge whether a drug is safe and effective. Avandia was approved because it lowered blood sugar, and seemed safe in clinical trials.
But the real test of whether a drug is any good is, how are the patients? Not their blood tests or X-rays or ECGs (electrocardiograms), but the people themselves, and not after just six months, but after years, especially if they have a chronic disease and will be taking medicine for the rest of their lives. Are those taking the drug more or less likely than people not taking it to have heart attacks, die or develop heart disease or other illnesses?
The problem is, it can take a long time and a lot of patients—and, therefore, a lot of money—to get a real picture of health and survival. That is especially true for something like heart disease, which develops slowly and is so common that it may be hard to detect a small increase in risk. Studies might have to go on for years instead of months, and include far more than the few thousand patients in whom drugs are typically tested before they get approved.
So, instead of waiting to see if people die or have heart attacks, drug companies have looked for other traits that seem to correlate with health and survival and that could stand in as a yardstick—objective measures such as blood pressure, cholesterol levels, blood sugar or tests of heart function. Researchers call these measurements “surrogate endpoints”, and FDA has encouraged companies to find surrogates that could reliably predict how patients would fare.
These kinds of tests are seen as a way to streamline the drug approval process.
But reliable surrogates are hard to find. There are plenty of endpoints that in theory should do the job, but do not. Tumour size, for instance: there are drugs that can shrink tumours without prolonging a patient’s life.
Heart rhythm can also be deceptive. Certain medicines can stabilize dangerous, abnormal heartbeats in people who have had heart attacks—and yet have been found to increase their odds of dying. Cholesterol levels do not always tell the whole story, either.
Part of the problem is that surrogate endpoints do not always reflect what’s happening to the whole patient. The disease being treated may be too complicated to gauge with just one tool, and the drug in question may have many more effects than the one being measured. Avandia, for instance, does a good job of lowering blood sugar. But it also activates a whole array of genes, and can cause weight gain, fluid retention, heart failure, anaemia and unfavourable changes in lipid levels in the blood, according to an editorial last week in The New England Journal of Medicine. It’s not clear whether the drug’s benefits will trump its risks in the long run.
Is there any way to protect the public from unsafe or ineffective drugs without creating an approval process that drags on forever? For years, researchers and government officials have been saying that the solution lies at least in part in continuing to study drugs after they are marketed—a process called postmarketing surveillance, or Phase 4 studies. But as the editorial writers pointed out, only a small proportion of the promised studies ever seem to get done.
As long as that remains the case, the consequences will be drugs such as Avandia—on the market for eight years to treat one of the leading causes of death in this country, with patients now left wondering whether it will make their health better or worse.