WASHINGTON (Reuters) - U.S. health reviewers are concerned that clinicians may not be able to properly interpret brain scans using Eli Lilly & Co’s imaging agent for Alzheimer’s and that the tests may be of limited use in assessing the degenerative disease.
The radioactive dye is intended for use with positron emission tomography, or PET, scans that help detect the presence of beta-amyloid plaques linked to Alzheimer’s disease.
The Food and Drug Administration staff reviewers’ main concerns “relate to an apparent insufficient development of the reader training methods proposed for clinical use,” according to documents released on Tuesday ahead of a Thursday meeting in which an advisory panel will consider recommending approval.
But at least one reviewer also cited the high variability in reading the scans and the study’s small sample size. “No clear clinical utility is demonstrated” in the company’s clinical trial, the reviewer added.
Such tests are already stirring debate since there is no cure for Alzheimer’s, which affects anywhere from 2.4 million to more than 5 million Americans mostly over the age of 65, according to the National Institutes of Health.
While such tests could help rule out Alzheimer’s and point doctors to other possible causes of memory problems, they raise questions about whether their use and cost are worthwhile.
Alzheimer’s is the most common form of dementia, although damage to the brain can occur years before symptoms arise, according to the NIH.
Companies are racing to tap into the market as Americans live longer and “baby boomers” begin to boost the number of Americans over the age of 65.
Other companies, including General Electric Co and Bayer AG, are developing rival products for a potential global market that the companies have estimated at anywhere from $1 billion to $5 billion.
So far Lilly, which acquired florbetapir through its recent purchase of Avid Radiopharmaceuticals Inc, has been ahead in developing its agent.
At the meeting on Thursday, the panel of outside experts will weigh the FDA staff’s assessment along with company data before offering the agency its recommendation on whether to approve the drug. The FDA will later make the final decision, but usually follows panel recommendations.
Florbetapir aims to stick to brain plaques so they are visible on a PET scan to help doctors identify them, possibly before patients develop memory problems.
Also known by the proposed brand name Amyvid, florbetapir could also give more drugmakers a tool for clinical trials aimed at developing treatments for Alzheimer’s by using the dye, also known as 18F-AV-45, in various studies. Avid had already been making it available to researchers studying the disease.
In a separate document released on Tuesday, Avid said that using the radioactive dye with PET scans was useful because a negative finding would help doctors rule out the presence of Alzheimer’s brain plaques.
Seven studies, including some that compared brain images with autopsy findings, support the drug’ safety and efficacy, it said. Avid has proposed using a website to help train nuclear medicine and radiology physicians in using the drug with PET scans.
But FDA reviewers said just 14 subjects in one major trial had their images read using Avid’s intended methods, a sample size that was too small to draw wider conclusions.
“We have to make sure we have a way of training them. If we were just to launch this tomorrow, no one would know how to read it,” Avid Founder and CEO Dr. Daniel Skovronsky told Reuters in an interview.
He said the company will not need to do additional clinical trials to use the scans to rule out Alzheimer’s disease, but more studies will be needed to figure out exactly what a positive scan means.
Shares of Lilly were off 0.2 percent at $34.84 in afternoon trading, while the broad Standard & Poor’s 500 Index was barely higher.
Reporting by Susan Heavey; Additional reporting by Julie Steenhuysen in Chicago; Editing by Lisa Von Ahn and Tim Dobbyn