June 25 (Reuters) - U.S. lawmakers on Friday announced an investigation into the approval and pricing of Biogen Inc"s (BIIB.O) Alzheimer"s drug, Aduhelm, amid concerns over its steep price and doubts if the clinical evidence proves the drug works. The drug, which has a list price of $56,000 per year, was approved by the U.S. regulators as the first treatment to attack a likely cause of Alzheimer"s on June 7. "We have serious concerns about the steep price of Biogen"s new Alzheimer"s drug Aduhelm and the process that led to its approval despite questions about the drug"s clinical benefit," House Committee on Oversight and Reform said in a statement. The investigation has been announced by Rep. Carolyn Maloney, chairwoman of the Committee on Oversight and Reform, and Rep. Frank Pallone, Jr., Chairman of the Committee on Energy and Commerce. Biogen said it will "of course cooperate with any inquiry we may receive from these committees," in response to a Reuters request for comment. At $56,000 a year, the Kaiser Family Foundation estimates that Medicare could spend $57 billion or more per year on Aduhelm, which is more than Medicare Part B spends on all other drugs combined, the House Committee said. Health insurers and the Medicare program will bear most of the cost of the drug, whose price will vary based on dosage and discounts. The Food and Drug Administration (FDA) approved the drug - despite strong objection from its own expert advisory panel - for all patients with Alzheimer"s, although it has only been tested for patients in the early stages of the disease. Three of the 11 members of FDA"s independent advisory panel have resigned in protest over the agency"s decision. read more Shares of the drugmaker were down nearly 1% in after-market trading. Reporting by Dania Nadeem in Bengaluru; Editing by Arun Koyyur Our Standards: The Thomson Reuters Trust Principles.