A congressional investigation into the Food and Drug Administration's review process for an Alzheimer's treatment found that the agency "deviated" from its standard procedures to approve the Aduhelm drug with inconsistent data.
Aduhelm is notable for being the first drug in recent years approved to treat the underlying cause of Alzheimer's, a disease with no known cure that is characterized by progressive dementia that affects more than six million Americans, according to the Alzheimer's Association.
The joint 18-month investigation between the House's Oversight and Reform Committee and Energy and Commerce Committee, released on Thursday, criticizes the FDA for "atypical collaboration and interactions" with Biogen, the drug's manufacturer.
In statements, Biogen and the FDA both said their interactions prior to Aduhelm's green light were appropriate in the context of the approval process.
"One of my top priorities as Chair of the Committee on Oversight and Reform is ensuring that the American people have access to effective and affordable medications," Rep. Carolyn Maloney, D-N.Y., chairwoman of the House Oversight and Reform Committee, said in a statement.
The FDA "remains committed to the integrity of our drug approval process, which includes ensuring that safe and effective new treatment options are available to the millions of people with Alzheimer's disease living in the U.S.," the agency said in a statement to ABC News.
"The FDA's decision to approve Aduhelm was based on our scientific evaluation of the data contained in the application, which is described in the approval materials. … That said, the agency has already started implementing changes consistent with the Committee's recommendations," the statement said, in part.
The report also blasts Biogen for "an unjustifiably high price for Aduhelm" that it says was meant "to make history." One year of the Aduhelm treatment originally cost $56,000 for a person of average weight, the report says.
"Biogen stands by the integrity of the actions we have taken," the company said in a statement to ABC News. "As stated in the congressional report, an FDA review concluded that, 'There is no evidence that these interactions with the sponsor in advance of filing were anything but appropriate in this situation.'"
"Alzheimer's is a highly complex disease and we have learned from the development and launch of Aduhelm. That process is continuing to inform our work as Biogen introduces new innovative treatments to the market," the statement read, in part.
Aduhelm was considered for FDA approval under the agency's traditional pathway before the agency switched to consider the drug under its Accelerated Approval Program, according to the report.
The change in course -- which the congressional investigation says occurred "abruptly" -- came after the FDA internally found Aduhelm lacked "demonstrated clinical benefit necessary for traditional approval," House investigators found.
Under the accelerated program, the FDA can approve some drugs that meet both "an unmet medical need" and "treat serious conditions," according to the agency's website. Aduhelm is not the only drug to be approved under this pathway, which the FDA carved out specifically to give more options to patients with diseases for which virtually no treatments exist. Accelerated approval is typically contingent upon the pharmaceutical company completing larger, longer-term studies.
During the monthslong approval process, the FDA and Biogen collaborated closely. FDA and Biogen officials met, spoke or otherwise had substantial email exchanges at least 115 times, according to the congressional investigation.
Although it is typical for drug companies to work closely with the FDA during the approval process, such collaboration between Biogen and its federal regulators "exceeded the norm in some respects," according to the FDA's own internal review, the report says.
The cooperation came after an independent review of Aduhelm's effects on people with Alzheimer's cast doubt on its ability "to effectively slow cognitive and functional impairment" in patients.
And when the FDA initially approved the drug for all Alzheimer's patients, the congressional investigation found that the move concerned some Biogen advisers who were wary of such broad approval. The advisers did not communicate such reservations to regulators, the report says.
The FDA later walked back its broad approval of the drug, eventually recommending the drug's use in only a narrower subset of patients with early-stage disease, which more closely mirrored the group included in Aduhelm's clinical trials.
Following the FDA's accelerated approval of Aduhelm, the Centers for Medicare & Medicaid Services established that Medicare would only pay for the drug under limited circumstances in which patients are part of approved studies.
That move severely limits the availability and practical implications of Aduhelm, essentially making it available only to people who can pay out of pocket for treatment.
And as part of the stipulations associated with accelerated approval, Biogen has more than six years to complete the final trial, per the report. Aduhelm remains available in the meantime.
Thursday's report comes as the FDA evaluates two additional Alzheimer's-related drugs, with a green light from the agency possible in the coming months. Biogen helped develop one of those drugs.
"FDA must take swift action to ensure that its processes for reviewing future Alzheimer's disease treatments do not lead to the same doubts about the integrity of FDA's review," the congressional report says.