Alexza Announces Submission of AZ-004 (Staccato(R) Loxapine) NDA

Filing of the First Staccato-Based NDA Completed Ahead of Schedule

MOUNTAIN VIEW, California, December 14 - Alexza Pharmaceuticals, Inc. (Nasdaq: ALXA) today announced that it has
submitted its New Drug Application (NDA) for Staccato(R) loxapine (AZ-004) to
the US Food and Drug Administration (FDA). AZ-004 is an inhalation product
candidate being developed for the rapid treatment of agitation in patients
with schizophrenia or bipolar disorder. The IND for Staccato loxapine was
filed with the FDA in August 2005.

"AZ-004 has delivered a predictable and consistent safety and efficacy
profile in treating patients with agitation," said James V. Cassella, PhD,
Senior Vice President, Research and Development at Alexza. "We believe that
AZ-004, if approved, has the potential to change the treatment practices for
acute agitation, as the only product able to meet both the patients' desire
for quickly and comfortably gaining control, and the clinicians' goal of
rapidly and reliably calming an agitated patient."

"The data we have seen from the Staccato loxapine trials are compelling,"
said Michael Lesem, MD, Executive Medical Director, Claghorn-Lesem Research
Clinic, Houston, TX. "The product exhibits a rapid and predictable reduction
in agitation, and appears to have a favorable safety profile in these patient
populations."

"We once again exceeded our corporate goal timeline with the AZ-004 NDA
submission," said Thomas B. King, President and CEO of Alexza. "The continued
concentrated effort of the entire Alexza team throughout 2009 has been
nothing short of remarkable and allowed us to complete this landmark
milestone for the company. We eagerly look forward to 2010, as we work toward
the approval of this product candidate."

"When Alexza was founded, I had the vision that its proprietary
technology had the potential to improve the therapeutic value of drugs," said
Alejandro C. Zaffaroni, PhD, Chairman Emeritus and Co-Founder of Alexza. "It
is splendid that Alexza has reached its first NDA so quickly and is on the
doorstep of its first Staccato-based product, Staccato loxapine."

AZ-004 Clinical Results Summary

The AZ-004 NDA contains efficacy and safety data from
more than 1600 patients and subjects who have been studied in thirteen
different clinical trials. In 2008, the Company successfully initiated and
completed two pivotal Phase 3 clinical trials. In these studies, both doses
of AZ-004 (5 and 10 mg) met the primary and key secondary endpoints of the
studies, with highly statistically significant reductions in agitation, as
compared to placebo. Additionally, the 10 mg dose of AZ-004 exhibited a rapid
onset of effect, with statistically significant reductions in agitation at 10
minutes post-dose, the first time point measured. The reduction of agitation
was sustained through the 24-hour study period. In both studies, the
administration of AZ-004 was generally safe and well tolerated.

In 2009, Alexza initiated and completed five
non-pivotal safety and NDA-supporting studies for AZ-004. Alexza believes
these data, along with data from the other efficacy and safety trials
conducted with AZ-004, adequately demonstrate the efficacy and safety of
AZ-004 for the proposed indication.

Agitation Market Opportunity

Episodes of agitation afflict many people suffering
from major psychiatric disorders, including schizophrenia, which affects
approximately 2.4 million adults in the United States, and bipolar disorder,
which affects approximately 5.7 million adults in the United States. More
than 90% of these patients will experience agitation in their lifetime.

Agitation generally escalates over time with patients
initially feeling uncomfortable, tense and restless. As the agitation
intensifies, their behavior appears more noticeable to others as they become
threatening and potentially violent, especially if the agitation is not
treated. While patients seek treatment at different points along this
agitation continuum, those with the most severe symptoms generally require
treatment with injectable drugs in emergency medical settings, and currently
are thought of to represent the agitation market. Alexza, however, believes
the therapeutic market for agitation is broader than only this limited
perspective of patients in severe crisis - many more are in need of treatment
for an agitation episode.

Alexza's primary market research indicates that
approximately 50% of treated acute agitation episodes are treated in
emergency settings. Another approximately 35% of the treated agitation
episodes suffered by schizophrenic and bipolar patients are treated in an
inpatient setting (hospital and long-term residential settings), and
approximately 15% are treated in a physician's office.

Alexza's market research studies with schizophrenia patient caregivers
and bipolar patients indicate these patients currently experience an average
of 11 to 12 episodes of acute agitation each year.

Agitation episodes are currently treated about 55% of the time with oral
antipsychotics and about 45% of the time with intra-muscular, or IM,
injections. Oral medications work relatively slowly, but are easy to
administer, painless and are less threatening to patients. IM injections
have a faster onset of action and a higher predictability of drug effect, but
because they are invasive and can be frightening to patients, IM injections
are usually the treatment option of last-resort. Currently, no non-invasive
therapies are available that work faster than 30 minutes to help agitated
patients in need of treatment.

About AZ-004 (Staccato loxapine)

AZ-004 is an anti-agitation therapeutic that combines Alexza's
proprietary Staccato system with loxapine, a drug belonging to the class of
compounds known generally as antipsychotics. Loxapine is currently available
in an oral formulation in the United States for the management of the
manifestations of schizophrenia. The Staccato system is a hand-held,
chemically-heated, single-dose inhaler that delivers a pure drug aerosol to
the highly vascularized tissues of the deep lung.

As an easy-to-use, patient-controlled, and highly reliable therapeutic
that provides rapid reduction in agitation, the Company believes that
AZ-004 meets the three key attributes for the treatment of acute agitation
as specified in the American Association of Emergency Psychiatrists' Expert
Consensus Guidelines for the Treatment of Behavioral Emergencies: speed of
onset, reliability of medication delivery and patient preference.

Conference Call Information

Alexza will host a conference call tomorrow morning, December 15, 2009,
at 8:30 a.m. Eastern Time. A replay of the call will be available for two
weeks following the event. The conference call and replay are open to all
interested parties.

To access the conference call via the Internet, go to www.alexza.com,
under the "Investor Relations" link. Please join the call at least 15 minutes
prior to the start of the call to ensure time for any software downloads that
may be required. Interested parties may also pre-register to avoid pre-call
delays at
https://www.theconferencingservice.com/prereg/key.process?key=P3WV9ALJV.

To access the live conference call via phone, dial +1-888-680-0860.
International callers may access the live call by dialing +1-617-213-4852.
The reference number to enter the call is 29185934.

The replay of the conference call may be accessed via the Internet, at
www.alexza.com, or via phone at +1-888-286-8010 for domestic callers or
+1-617-801-6888 for international callers. The reference number for the
replay of the call is 86237542.

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.

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 submission in December 2009.

Alexza has completed an end-of-Phase 2 meeting with the FDA for AZ-001
(Staccato prochlorperazine) and has completed two Phase 2 studies with AZ-104
(Staccato loxapine, low-dose). Both product candidates are being developed
for the acute treatment of migraine headache.

AZ-002 (Staccato alprazolam) has completed Phase 1 testing and one Phase
2a proof-of-concept clinical trial. Product candidates that have completed
Phase 1 testing are AZ-003 (Staccato fentanyl) for the treatment of
breakthrough pain, and AZ-007 (Staccato zaleplon) for the treatment of
insomnia. More information, including this and past press releases from
Alexza, is available online at www.alexza.com.

Safe Harbor Statement

This press release includes forward-looking statements regarding the
development, therapeutic potential and safety of AZ-004. Any statement
describing a product candidate or Alexza's goals, 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. Alexza'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 Alexza's
Annual Report on Form 10-K for the year ended December 31, 2008, and Alexza's
other Periodic and Current Reports filed with the Securities and Exchange
Commission, including the risks under the headings: "We will need substantial
additional capital in the future. If additional capital is not available, we
will have to delay, reduce or cease operations.", "Regulatory authorities may
not approve our product candidates even if they meet safety and efficacy
endpoints in clinical trials." and "If we do not establish strategic
partnerships, we will have to undertake development and commercialization
efforts on our own, which would be costly and delay our ability to
commercialize any future products". Forward-looking statements contained in
this announcement are made as of this date, and we undertake no obligation to
publicly update any forward-looking statement, whether as a result of new
information, future events or otherwise.

Thomas B. King, President & CEO, +1-650-944-7634, tking at alexza.com, or August J. Moretti, Senior Vice President and CFO, +1-650-944-7788, amoretti at alexza.com, both of Alexza Pharmaceuticals, Inc.