Exhibit 99.1

NEWS RELEASE — for immediate release

Alexza Prices $16.1 Million Registered Direct Offering

Mountain View, California — May 3, 2011 - Alexza Pharmaceuticals, Inc. (Nasdaq: ALXA), or the Company, today announced that it has entered into a definitive agreement with three institutional investors, including RA Capital Management and Tavistock Life Sciences, to raise approximately $16.1 million in gross proceeds in a registered direct offering through the sale of common stock and warrants. The Company agreed to sell a total of 11,927,034 units, each unit consisting of (i) one share of common stock and (ii) one warrant to purchase 0.35 of a share of common stock, at a purchase price of $1.35 per unit. The warrants will be exercisable six months after issuance at $1.755 per share and will expire five years from the date of issuance. The shares of common stock and warrants are immediately separable and will be issued separately.

Alexza estimates that net proceeds from the offering will be approximately $15.8 million, after deducting estimated offering expenses. The Company intends to use the net proceeds from the sale of the securities primarily for general corporate purposes, including regulatory activity, clinical trial, research and development, general and administrative and manufacturing expenses.

The securities described above are being offered pursuant to a registration statement on Form S-3 previously declared effective by the Securities and Exchange Commission on May 20, 2010. The transaction is expected to close on or about May 6, 2011, subject to customary closing conditions.

A copy of the prospectus supplement relating to the offering and the accompanying base prospectus may be obtained by contacting Alexza Pharmaceuticals, Inc., Attention: Corporate Secretary, 2091 Stierlin Court, Mountain View, California 94043, or by calling (650) 944-7000. A copy of the prospectus supplement relating to the offering and the accompanying base prospectus may also be accessed on the SEC website, http://www.sec.gov.

This press release does not constitute an offer to sell or the solicitation of an offer to buy any securities of Alexza nor shall there be any sale of such securities in any state in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of such state.

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About Alexza Pharmaceuticals, Inc.

Alexza Pharmaceuticals is a pharmaceutical company focused on the research, development and commercialization of novel, proprietary products for the acute treatment of central nervous system conditions. Alexza’s technology, the Staccato^® system, vaporizes unformulated drug to form a condensation aerosol that, when inhaled, allows for rapid systemic drug delivery through deep lung inhalation. The drug is quickly absorbed through the lungs into the bloodstream, providing speed of therapeutic onset that is comparable to intravenous administration, but with greater ease, patient comfort and convenience. (Click here to see an animation of how the Staccato system works.)

AZ-004 (Staccato loxapine) is Alexza’s lead program, which is being developed for the rapid treatment of agitation in schizophrenic or bipolar disorder patients. Alexza has completed and announced positive results from both of its AZ-004 Phase 3 clinical trials, and submitted a New Drug Application, or NDA, for AZ-004 in December 2009. In October 2010, the Company received a Complete Response Letter, or CRL, from the U.S. Food and Drug Administration, or FDA, regarding its NDA for AZ-004. A CRL is issued by the FDA’s Center for Drug Evaluation and Research indicating that the NDA review cycle is complete and that the application is not ready for approval in its present form. The Company completed an end-of-review meeting with the FDA in late December 2010. In January 2011, Alexza received the official FDA minutes of the meeting, and the Company anticipates resubmitting the AZ-004 NDA in July 2011. Alexza is seeking commercial partners for the worldwide development and commercialization of AZ-004.

For more information about Alexza, the Staccato technology or Alexza’s development programs, please visit www.alexza.com.

Safe Harbor Statement

This news release contains forward-looking statements that involve significant risks and uncertainties. Any statement describing the Company’s intent, expectations or beliefs is a forward-looking statement, as defined in the Private Securities Litigation Reform Act of 1995, and should be considered an at-risk statement. Such statements are subject to certain risks and uncertainties, particularly those inherent in the process of developing and commercializing drugs, and the risk that the financing may be delayed or may not occur due to market or other conditions and the satisfaction of customary closing conditions related to the proposed public offering. The Company’s forward-looking statements also involve assumptions that, if they prove incorrect, would cause its results to differ materially from those expressed or implied by such forward-looking statements. These and other risks concerning Alexza’s business and this offering are described in additional detail in the Company’s Annual Report on Form 10-K for the year ended December 31, 2010, the Company’s other Periodic and Current Reports filed with the Securities and Exchange Commission and the prospectus supplement related to this offering. Forward-looking statements contained in this

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CONTACTS:		Thomas B. King				August J. Moretti
		President and CEO				Senior Vice President and CFO
		650.944.7634				650.944.7788
		tking@alexza.com				amoretti@alexza.com

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