The letter means the FDA has additional questions about Afrezza's new drug application. As a result, the agency has requested two additional clinical trials -- one for patients with type 1 diabetes and one for patients with type 2 diabetes -- be conducted using the latest version of the company's MedTone inhaler. While we are disappointed with the complete response letter, we are encouraged that the FDA is asking for clinical studies only to confirm the bridging and handling of the next-generation device in order to compare it to the device used in our extensive clinical program," said Alfred Mann, the company's chairman and CEO, in a statement. "We remain committed to working with the FDA to make AFREZZA available to people with diabetes." The stock was last quoted at $5.16, down 43.4%, on volume of 2.6 million, according to Nasdaq.com. The shares had already fallen more than 7% to $9.11 in the regular session with volume running more than twice its trailing three-month daily average of 3 million. The stock sank as low as $4 in extended trades, well below its 52-week low of $4.76 from late May 2010.