Exhibit 99.1

NEWS RELEASE - for immediate release

Alexza Retains Guggenheim Securities, LLC to Explore Strategic Options

Mountain View, California - September 28, 2015 - Alexza Pharmaceuticals, Inc. (Nasdaq: ALXA) announced today that it has retained Guggenheim Securities, LLC to assist in exploring strategic options to enhance stockholder value, including a possible sale or disposition of one or more corporate assets, a strategic business combination, partnership or other transactions.

“We continue to see long-term opportunities for our Staccato inhaled drug technology, especially in light of the positive responses from physicians and patients who have used our lead product, ADASUVE,” said Thomas B. King, President and CEO of Alexza. “Our Board is focused on evaluating additional options that may enhance or accelerate the value that we believe is inherent in an approved technology-platform product, which has been successfully screened for numerous drugs as a novel delivery method that enables pharmacokinetics similar to intravenous administration. Given this strength of our Staccato technology, we believe now is the appropriate time to explore strategic alternatives.”

About Alexza Pharmaceuticals, Inc.

Alexza Pharmaceuticals is focused on the research, development, and commercialization of novel, proprietary products for the acute treatment of central nervous system conditions. Alexza’s products and development pipeline are based on the Staccato^® system, a hand-held inhaler designed to deliver a pure drug aerosol to the deep lung, providing rapid systemic delivery and therapeutic onset, in a simple, non-invasive manner. Active pipeline product candidates include AZ-002 (Staccato alprazolam) for the management of epilepsy in patients with acute repetitive seizures and AZ-007 (Staccato zaleplon) for the treatment of patients with middle of the night insomnia.

ADASUVE^® is Alexza’s first commercial product and has been approved for sale by the U.S. Food and Drug Administration, the European Commission and in several Latin American countries. Teva Pharmaceuticals USA, Inc., a subsidiary of Teva Pharmaceutical Industries Ltd., is Alexza’s commercial partner for ADASUVE in the United States. Grupo Ferrer Internacional SA is Alexza’s commercial partner for ADASUVE in Europe, Latin America, the Commonwealth of Independent States countries, the Middle East and North Africa countries, Korea, Philippines and Thailand.

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ADASUVE^® and Staccato^® are registered trademarks of Alexza Pharmaceuticals, Inc. For more information about Alexza, the Staccato system technology or the Company’s development programs, please visit www.alexza.com.

This news release contains forward-looking statements that involve significant risks and uncertainties. Any statement describing the Company’s 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 exploring strategic transactions and commercializing drugs, including the ability of Alexza and its partners, Teva and Ferrer, to effectively and profitably commercialize ADASUVE, estimated product revenues and royalties associated with the sale of ADASUVE, the adequacy of the Company’s capital to support the Company’s operations, the Company’s ability to raise additional funds and the potential terms of such potential financings, and the likelihood of completing a strategic transaction. The Company does not have a defined timeline for the strategic process and is not confirming that the process will result in any specific action or transaction. 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 are described in additional detail in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014 and the Company’s other Periodic and Current Reports filed with the Securities and Exchange Commission. Forward-looking statements contained in this announcement are made as of this date, and the Company undertakes no obligation to publicly update any forward-looking statement, whether as a result of new information, future events or otherwise.

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