When the nascent medical field of molecular imaging finally emerges as a clinical reality, it will permit doctors to diagnose us before we even know that we're sick, and to treat us individually based on our personal molecular makeup.
Although its use in humans is years away, medical imaging equipment manufacturers and drug giants are spending billions on research to ensure leadership positions in this arena. It was the promise of molecular imaging that drove General Electric's $9.5 billion acquisition of Amersham in October 2003. The company currently makes medical imaging agents and is developing the imaging probes used in molecular imaging.
In theory, the concept of molecular imaging is simple enough. Scientists are designing molecules that are programmed to find and bind to cells with characteristics that indicate diseases like cancer, heart disease or Alzheimer's. These molecules, also called probes, then attach themselves to the biomarkers and "light up" under a standard imaging device, usually PET scanners (short for positron emission tomography). Those images are processed on computers using algorithms that can identify quantitative changes in the data.
Detecting disease before symptoms develop
The technology, which is now being developed using animals, will eventually give doctors the ability to detect disease on the molecular level before symptoms appear, as well as quickly determine how well a particular treatment is working by visualizing just how diseased cells are responding.
Molecular imaging is not to be confused with the well-established field of genomics, which can now analyze human genes and in some cases detect genes that may be involved in disease.
"Genomic profiling may tell me the I have the likelihood of having cancer, but it can't tell you where it is or how it will respond to treatments," says Dr. Ralph Weissleder, M.D., Ph.D., who is the Director of the Center for Molecular Imaging Research, run jointly buy Massachusetts General Hospital and Harvard Medical School. "That's where molecular imaging comes in."
PET scanners are already used in medical imaging -- just not yet at the molecular level, but their sales are an indicator for the molecular imaging market. Frost and Sullivan estimates that $600 million worth of these scanners were sold in 2003 in the United States, and projects $826 million in sales for 2004. Sales of radiopharmaceuticals, which are the imaging agents that already help light up medical scans and include the probes used in molecular imaging, are also on the rise, expected to hit $1.4 billion in 2004 in the United States, up from $1.2 billion in 2003.
Molecular imaging likely to become widespread
As another way of looking at the potential, consider that 20 million X-rays, CAT scans and MRI's are administered annually for oncology diagnostics alone, according to Piper Jaffray analyst Steve Hamill.
To the extent that molecular imaging can be a more effective alternative to traditional anatomical imaging, such figures indicate a big market opportunity, says Hamill, who follows CTI Molecular Imaging. That company has a partnership with Siemens Medical making PET scanners and also makes the imaging probes.
"I can envision a day when there are three to five million PET scans done a year," says Hamill, "where you could easily see a $1 billion market just for the [probes]."
Molecular imaging will transform how disease is treated. Traditional medicine, for instance, can't diagnose Alzheimer's until a person begins exhibiting dementia or loss of memory, but scientists can now use molecular imaging to detect the betamyloids that cause the disease in animals.
"Deterioration in people's brains usually begins five or ten years before they exhibit symptoms," says GE Global Research Biotechnology Program manager Nadeem Ishaque, "so this means that we could start treating the Alzheimer's well before then."
Better drug testing
After the illness is identified, scientists can also see exactly how well a drug works in animals by continuing to track the production or inhibition of betamyloids as the drug is administered, instead of waiting months to evaluate subjectively whether behavior has changed. If a drug doesn't have the desired effect, treatment can be adjusted. "You can't take the human brain and mash it up to measure these chemicals to see if someone needs a different drug," Ishaque says. "That's why molecular imaging is so important."
Molecular imaging will also be able to detect cancer better than biopsies, because these small samples often don't capture all of the different kinds of proteins that make up a single tumor. Different proteins respond differently to drugs and radiation, so having a better understanding of the tumor helps doctors provide the most effective treatments.
For instance, the Genentech drug Herceptin is designed to target breast cancers with the Her-2 protein, but Ishaque says that only about half of women who test positive for Her-2 in a biopsy respond to the drug. "That may be because Her-2 may only be expressed in the biopsy area and not elsewhere in the tumor," says Ishaque. "By measuring Her-2 with molecular imaging, we'd have a better idea of how much Her-2 is present in a tumor and how well patients will respond to Herceptin."
Unfortunately, we won't see molecular imaging used in clinical practice in humans for years, says the Center for Molecular Imaging's Dr. Weissleder. But when it does arrive, doctors will be able to diagnose and treat abnormal cells instead of mere symptoms.