FDA approval of Alzheimer's drug aducanumab has stirred controversy, but a Houston Methodist neurologist defends the decision as long as the treatment is reserved for the right patients.

Dr. Joseph Masdeu, director of Houston Methodist's Nantz National Alzheimer's Center, says the drug should be useful in patients in the disease's pre-clinical stage, which is characterized by the buildup of a protein in the brain called amyloid-β. The buildup creates an environment that leads to Alzheimer's.

"If imaging shows patients have amyloid in the brain, I'll recommend aducanumab to them," says Dr. Masdeu, who led the Houston Methodist arm of one of the aducanumab clinical trials. "But not once patients have begun experiencing severe symptoms. By then, the disease process is too advanced for the drug to be helpful."

Dr. Masdeu says Houston Methodist already is receiving no shortage of inquiries from patients about the drug. Most are too far along to benefit from it, he says.

When and for whom did the FDA approve the Alzheimer's drug aducanumab?

The FDA's original approval, on June 7, was for all Alzheimer's patients, a recommendation Dr. Masdeu criticizes as far too broad. Following widespread criticism of the approval, the agency in July narrowed the indication to those with mild memory or thinking problems.

The approval marked a milestone for the devastating neurodegenerative disease, the first new treatment in nearly 20 years and the first ever targeting a possible cause rather than just the symptoms. Scientists are still unclear about what exactly causes Alzheimer's, but the abnormal buildup of proteins such as amyloid — and another, tau — are considered hallmarks of the disease.

Tau begins to spread after excess amyloid has been in the brain for 10 to 15 years, notes a patient advisory on Houston Methodist's Nantz National Alzheimer's Center website. The advisory cautions that removing amyloid isn't likely to help after tau has spread.

The desperation for treatments is seemingly why the FDA approved aducanumab and why Alzheimer's advocates hailed the move. Arguing that approvals of the first drug in a new category "invigorate the field, increase investments in new treatments and encourage greater innovation," Alzheimer's Association chief science officer Maria C. Carrillo said in a statement that the approval "ushers in a new era in Alzheimer's treatment and research."

Why is there controversy around the FDA's approval of aducanumab for Alzeheimer's?

But the vast majority of doctors differ. In a recent Medscape poll, nearly 90% of neurologists and primary care physicians disagreed with the FDA approval, which followed an advisory committee's 8 to 1 vote against the proposal because trial data did not show a clinical benefit to patients.

Also of concern, the drug can cause brain swelling and bleeding, and its price tag is expected to be about $56,000 annually.

Dr. Masdeu says the side effects are typically clinically insignificant and easily treated. He laments the cost but notes that insurance coverage tends to follow when a drug is approved and proven to be helpful.

Dr. Masdeu adds that he understands the criticism of aducanumab's approval, but remains hopeful about the drug because trial data showed a decline in amyloid in the brain in response to medium and high doses. He acknowledges it will take years before researchers know if that translates into fewer diagnoses of Alzheimer's.

He also acknowledges that there likely will be a lot of misuse of the drug because of the desperation for Alzheimer's treatment.

"It's not going to help to give the drug when the patient's disease is at a stage when it's not going to be effective," says Dr. Masdeu. "But as a neurologist who knows this disease, I'll be damned if I'm going to reject it because of criteria used when this trial was run. That was 2017. We've learned a lot since then."

Dr. Masdeu says he's thus far only recommended the drug to one patient, a person with amyloid buildup and mild symptoms, but anticipates he'll recommend it to many more in the future.

An estimated 6 million Americans, most of them age 65 or older, have Alzheimer's, and the numbers are only expected to increase in coming years as Baby Boomers continue to age.