The company reduced the out-of-pocket costs of EpiPen for some patients on Thursday, but kept the list price at about $600, a move that U.S. lawmakers and Presidential candidate Hillary Clinton said was not enough. EpiPen cost about $100 in 2008.
Mylan said on Monday it expected to launch the generic product "in several weeks", an unusual move considering the branded bestseller is still patent protected and major rival treatments have failed to get regulatory clearances.
Democratic senator Richard Blumenthal said Mylan may appear to be moving in the right direction, but its latest move raised as many questions as solutions, including why the price is still astronomically high and whether its action is a preemptive strike against a competing generic.
"Investigations are still vitally necessary into possible antitrust lawbreaking, and I will press for Senate hearings as well as FTC subpoenas," Blumenthal said in a statement.
Democratic senator Amy Klobuchar echoed the call for an investigation.
Mylan has defended EpiPen's high price, saying it had spent hundreds of millions of dollars to improve the product since acquiring it in 2007.
It has said it recoups less than half the list price as pharmacy benefit managers, which often require discounted prices or rebates from drugmakers, are involved, along with insurers and others.
"Our decision to launch a generic alternative to EpiPen is an extraordinary commercial response," Chief Executive Heather Bresch said Monday. "We determined that bypassing the brand system in this case and offering an additional alternative was the best option."
However, consumer watchdog group Public Citizen said Mylan's latest move was another "convoluted mechanism to avoid plain talk, admit to price gouging and just cut the price of EpiPen."
"The weirdness of a generic drug company offering a generic version of its own branded but off-patent product is a signal that something is wrong," President Robert Weissman said.
Mylan's shares were little changed at $43.17 in midday trading. The stock had fallen 12 percent last week amid a wave of criticism over prices of EpiPen, which dominates the market and generates annual sales of $1 billion.
Bernstein analyst Ronny Gal said though Mylan had "infinite possibilities" to handle the outcry over EpiPen prices, the generic launch was "the big one" and would help PBMs cap their costs.
However, he expects Mylan to still come under fire for its prices and U.S. health regulators to face more pressure to approve competing treatments.
Some lawmakers last week asked the Food and Drug Administration about its approval process for rival treatments.
The FDA rejected Adamis Pharmaceuticals Corp's rival treatment in June and Teva Pharmaceutical Industries Ltd's generic version earlier this year. Sanofi SA has pulled its device from the market last year on concerns of inaccurate dosage.
Leerink Partners said that the generic launch only removed a near-term pricing lever for Mylan as they expect the launch of Teva's version in 2018 to become a pricing headwind.
Netherlands-based Mylan said on Monday it intends to continue to market and distribute branded EpiPen.
EpiPen is a preloaded injection of epinephrine, also known as adrenaline, used in case of a dangerous allergic reaction called anaphylaxis that could cause death if untreated.
Mylan is the latest company to be caught up in the growing outrage over drug price increases. Valeant Pharmaceuticals International Inc and Turing Pharmaceuticals have both been publicly excoriated for similar price increases.