Conference Call Scheduled for Tomorrow Morning Tuesday, June 16, 2009 at 9:00 a.m. Eastern Time

MOUNTAIN VIEW, Calif., June 15 /PRNewswire-FirstCall/ -- Alexza Pharmaceuticals, Inc. (Nasdaq: ALXA) announced today that it has exercised its option to purchase all of the equity of Symphony Allegro. The purchase of Symphony Allegro, which is subject to Alexza stockholder approval, is projected to close in Q3 2009.

Alexza and Symphony Capital Partners, LP have negotiated new terms to satisfy the exercise price for Alexza's option exercise to acquire Symphony Allegro. Under the terms of the Amended and Restated Purchase Option Agreement, Alexza will:

• issue Symphony Capital 10 million shares of Alexza Common Stock
• issue Symphony Capital a five-year warrant for 5 million shares of Alexza Common Stock at an exercise price of $2.26 per share, a 25% premium to the preceding 30-trading day average closing price, and cancel Symphony's currently outstanding 2 million shares warrant for Alexza Common Stock
• pay Symphony certain percentages of cash payments that may be generated from future partnering transactions for AZ-004, AZ-104 and/or AZ-002, the product candidates that were licensed to Symphony Allegro

Upon closing of the transaction, Symphony Capital will own approximately 23% of the total Alexza Common Stock outstanding. Symphony Capital will have the right to nominate one director to the Alexza Board of Directors, as long as its ownership exceeds more than 10% of the total outstanding Common Stock.

Symphony Allegro was capitalized with $50 million in December 2006 by Symphony Capital Partners, LP and its co-investors, with the primary purpose of funding the development of three of Alexza's product candidates. As part of that transaction, Alexza licensed to Symphony Allegro its Staccato loxapine program and its Staccato alprazolam program. Since that time, Alexza has been conducting the clinical development of AZ-004 for the acute treatment of agitation, AZ-104 for the acute treatment of migraine headache, and AZ-002 for the treatment of acute panic attacks, with the funds provided by Symphony Allegro.

'In the past 30 months, we have conducted 14 clinical trials with the three product candidates that were licensed into Symphony Allegro. This is a remarkable development achievement, by almost any standard. Moreover, we plan to submit Alexza's first NDA for AZ-004, Staccato loxapine, in the first quarter of 2010. Symphony Capital and RRD International have been a very important part of these accomplishments,' said Thomas B. King, Alexza President and CEO. 'With the closing of the purchase of Symphony Allegro, we will re-acquire full ownership of AZ-004, AZ-104 and AZ-002. In our partnership with Symphony Allegro, the intended development of these product candidates has been achieved and, assuming our stockholders approve the transaction, Symphony Capital and its investors will be able to share in the future benefits of the advancement of these product candidates.'

Mark Kessel, Managing Director of Symphony Capital, added, 'We are pleased to have been a part of this collaboration which provided capital and development assistance to enable Alexza to advance these product candidates to the point they are today.