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July 25, 2018

5.4M Americans have Alzheimer's. So why are clinical trials hurting for participants?

Daily Briefing

    Scientists are having trouble finding patients to enroll in clinical trials for treatments for Alzheimer's disease—a problem with "enormous implications" for the treatment of the disease, the New York Times reports.

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    Alzheimer's disease is a type of dementia traditionally defined as a clinical syndrome involving the progressive decline of cognitive abilities—particularly memory loss—that ultimately results in the loss of independence. About 5.4 million U.S. residents have Alzheimer's. There is no proven treatment.

    Pharmaceutical companies over more than a decade have spent billions of dollars on research to find a treatment for Alzheimer's, according to the Times.

    Researchers have largely focused on the beta amyloid protein, which accumulates in the brains of Alzheimer's patients years before they experience memory loss. Researchers have repeatedly tested anti-amyloid drugs in hopes of slowing or stopping Alzheimer's, but have failed to find a treatment that diminishes the disease's clinical symptoms.

    After several failed clinical trials, Pfizer in January announced it was stopping its research on discovering new drugs to treat Alzheimer's and Parkinson's diseases. However, other drugmakers, such as Eli Lilly, are continuing to search for Alzheimer's treatments—and they are facing challenges with recruiting patients for their research.

    Recruitment challenges

    Recruiting patients for research on Alzheimer's is an "onerous process" that "is becoming an insurmountable obstacle" on the path to developing a treatment, the Times reports.

    The Global Alzheimer's Platform Foundation estimates it would have to reach out to between 15,000 to 18,000 people who fall into the appropriate age group in order to secure 375 patients with early Alzheimer's for a clinical trial testing a two-drug combination treatment. Of the thousands of people the foundation would contact, about 2,000 would have to pass an initial screening to be selected to proceed to further testing.

    According to the Times, about 20% of those who pass that first screening would then pass the next screening to enroll in Lilly's latest clinical trial, which requires that patients:

    • Be between ages 60 to 89;
    • Have experienced at least for six months mild to progressive memory loss; and
    • Have two different types of brain scans indicating Alzheimer's is developing.

    John Dwyer, president of the Global Alzheimer's Platform Foundation, said finding patients who meet criteria to enroll in an Alzheimer's trial is only one problem. He explained that the cost per diagnosis—with the use of brain scans, lab tests, and memory tests—can be as much as $100,000 per enrollee.

    Another problem, Dwyer explains, is that the number of Alzheimer's trials has grown over the years. He said there are currently more than 100 Alzheimer's studies searching for 25,000 participants. To enroll all those patients, 37.5 million Alzheimer's patients in the appropriate age group would have to be informed about the trial.

    According to the Times, "The numbers make it clear: There's no way scientists are going to find 25,000 participants for all of the Alzheimer's trials that have been approved."

    In addition, the Times reports, many Alzheimer's patients do not consider enrolling in a clinical trial because:

    • There are no successful drugs to draw interest;
    • They are elderly and cannot easily access trial sites;
    • They are unaware that any possible treatments have been found; and
    • They tend to see private physicians who are unaware of Alzheimer's research or do not suggest trials.

    Experts also note that some patients with Alzheimer's might not seek to be diagnosed because of the stigma surrounding the disease. Ira Goodman, neuroscience medical director of Bioclinica Research, a site for the Lilly trial, said, "It can take a long time to get a diagnosis. Even the primary care doctors say, 'Oh, don't worry about it, you're just getting older.'" On top of that, according to the Times, Alzheimer's diagnoses are incorrect more frequently than most people realize.

    Regarding the recruitment challenges, Dwyer said, "The irony is that the science has never been more promising. How many promising drugs will be abandoned or their evaluation seriously delayed? Some good science is going to be left on cutting-room floor."

    Researchers present evidence female sex hormone level relate to Alzheimer's risk

    In related news, researchers have found new evidence that levels of female sex hormones—such as estrogen and progesterone—can affect a woman's risk of Alzheimer's and other forms of dementia, researchers said on Monday at the Alzheimer's Association International Conference in Chicago.

    Women comprise about 60% of dementia patients and are twice as likely as men to develop dementia, according to the Los Angeles Times.

    For their study, researchers examined the reproductive history of 14,595 women who were Kaiser Permanente members between 1964 and 2017. The women who participated in the study were 40 to 55 between 1964 and 1973 and remained Kaiser Permanente members between 1996 and 2017.

    The researchers found an association between women's Alzheimer's risk and the number of children, miscarriages, total months of pregnancy, and years between their first menstrual period and menopause. For example, the researchers found the risk of dementia was 12% lower for women who had three or more children as compared with women who had only one child, according to Paola Gilsanz, of Kaiser Permanente Northern California Division of Research and Rachel Whitmer of the University of California, Davis.

    The researchers also found women who started to menstruate earlier and began menopause later were less likely develop dementia. Specifically, women who started to menstruate between ages 10 and 13 were 22% less likely than women who started menstruating at age 16 or later to develop dementia. Women who stopped menstruating at age 45 or before had a 28% higher risk of developing dementia than women who stopped menstruating later, according to the study.

    "One hypothesized reason is that it is cumulative exposure to estrogen across the life course, [that protects against dementia risk]" Gilsaz said.

    According to Gilsanz, the new research offers "a window into sex-specific modes of action" underlying dementia (Kolata, New York Times, 7/23; Hamilton, "Shots," NPR, 7/23; Bahrampour, Washington Post, 7/23; Healy, Los Angeles Times, 7/23).

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