Two powerful congressional committees investigating the controversial federal approval of Biogen's Alzheimer's drug, Aduhelm, demanded extensive information and documents from the Food and Drug Administration in a letter released Thursday, making it clear that the committees' leaders are troubled by unusual actions the agency took in the course of evaluating and approving the drug.

"We are concerned by apparent anomalies in FDA's processes surrounding its review of Aduhelm," the committee chairs said in a letter asking for a raft of documentation and answers to questions.

"We are also concerned by reports of unusual coordination between FDA and Biogen throughout the drug's approval process," the committee added.

The letter — addressed to the FDA's acting commissioner, Dr. Janet Woodcock, and signed by Rep. Carolyn Maloney, chair of the House Committee on Oversight and Reform, and Rep. Frank Pallone, chair of the House Energy and Commerce Committee — asks for information about virtually every step of the FDA's handling of Aduhelm, the brand name for aducanumab.

Citing details first reported in a New York Times investigation in July, the letter notes that two months before the drug was greenlighted in June, a council of senior FDA officials " 'concluded that another clinical trial was necessary before approving the drug,' with one member noting that approval could 'result in millions of patients taking aducanumab without any indication of actually receiving any benefit, or worse, cause harm.' "

The approval of Aduhelm — a treatment requiring monthly intravenous infusions that Biogen has priced at $56,000 a year — has been met with a firestorm of criticism from many Alzheimer's experts and other scientists.

While some Alzheimer's experts did support the approval, given that there are so few therapies available for the devastating condition, many are concerned that the evidence does not convincingly show the drug can provide any benefit. There is also concern because the medication can cause brain swelling or brain bleeding.

The congressional letter also cites objections to the drug's approval from a former Biogen senior medical director, Dr. Vissia Viglietta, who helped design the late-stage clinical trials of Aduhelm. She told the Times in July that the approval "defeats everything I believe in scientifically, and it lowers the rigor of regulatory bodies."

Since the approval, some major medical centers have decided not to offer Aduhelm to patients.

And the Department of Veterans Affairs has decided not to include the drug in its formulary, a development first reported by Endpoints News, which quoted a spokesperson for the VA saying the decision was made "due to the risk of significant adverse drug events and to the lack of evidence of a positive impact on cognition."

The letter from the committees says that on July 23, several days after the Times' investigation was published, Woodcock and leaders of the agency's Center for Drug Evaluation and Research provided a briefing to the congressional staff and materials including the minutes of the council meeting cited in the Times article.

In a statement in response to the letter, the FDA said it would work with Congress to respond to the requests for documents and information. It also noted that in July, Woodcock called for the Department of Health and Human Services' Office of Inspector General to conduct an investigation of interactions between Biogen and agency officials.