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<FISCAL-YEAR-END>1231
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<p align="right" style="margin:0in 0in .0001pt;text-align:right;text-indent:0in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p align="right" style="margin:0in 0in .0001pt;text-align:right;text-indent:0in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Filed by Aerogen,
Inc. Pursuant to Rule 425</font></p>

<p align="right" style="margin:0in 0in .0001pt;text-align:right;text-indent:0in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Under the Securities Act
of 1933</font></p>

<p align="right" style="margin:0in 0in .0001pt;text-align:right;text-indent:0in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">And Deemed Filed Pursuant
to Rule 14a-12</font></p>

<p align="right" style="margin:0in 0in .0001pt;text-align:right;text-indent:0in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Under the Securities
Exchange Act of 1934</font></p>

<p align="right" style="margin:0in 0in .0001pt;text-align:right;text-indent:0in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Subject Company: Aerogen,
Inc.</font></p>

<p align="right" style="margin:0in 0in .0001pt;text-align:right;text-indent:0in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Commission File No. of
Subject Company: 0-31913</font></p>

<p align="right" style="margin:0in 0in .0001pt;text-align:right;text-indent:0in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">On
August 15, 2005, Nektar Therapeutics (&#147;Nektar&#148;) and Aerogen, Inc. (&#147;Aerogen&#148;)
issued a joint press release announcing that Nektar and Aerogen had entered
into a definitive merger agreement, dated as of August 12, 2005. The text of
the joint press release is as follows:</font></p>

<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<table border="0" cellspacing="0" cellpadding="0" width="100%" style="border-collapse:collapse;width:100.0%;">
 <tr>
  <td width="13%" valign="top" style="padding:0in .7pt 0in .7pt;width:13.28%;">
  <p style="margin:0in 0in .0001pt;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">Contacts:</font></b></p>
  </td>
  <td width="86%" valign="top" style="padding:0in .7pt 0in .7pt;width:86.72%;">
  <p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Nektar
  &#151; Joyce Strand (650) 631-3138</font></p>
  </td>
 </tr>
 <tr>
  <td width="13%" valign="top" style="padding:0in .7pt 0in .7pt;width:13.28%;">
  <p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:1.0pt;">&nbsp;</font></p>
  </td>
  <td width="86%" valign="top" style="padding:0in .7pt 0in .7pt;width:86.72%;">
  <p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Aerogen
  &#151; Robert Breuil (650) 864-7431</font></p>
  </td>
 </tr>
</table>

<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">NEKTAR TO ACQUIRE AEROGEN TO BROADEN PULMONARY TECHNOLOGY BASE AND
STRENGTHEN CAPABILITIES FOR TREATMENT IN THE ACUTE CARE SETTING</font></b></p>

<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p style="margin:0in 0in .0001pt;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">San
Carlos, Calif. &amp; Mountain View, Calif., August 15, 2005 </font></b><font size="2" style="font-size:10.0pt;">&#160;&#151; Nektar Therapeutics (Nasdaq:NKTR) and
Aerogen, Inc. (Pink Sheets:AEGN.PK) announced today that they have signed a
definitive merger agreement whereby Nektar will acquire Aerogen in a
transaction valued at approximately $32 million.</font></p>

<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&#147;The
acquisition of Aerogen broadens Nektar&#146;s pulmonary delivery capabilities by
adding advanced inhaleable liquid drug technology to Nektar&#146;s base of leading
inhaleable powdered drug technology,&#148; said Ajit S. Gill, Nektar president and
chief executive officer.&#160; &#147;Over the last
ten years, Aerogen has built the capabilities for treatment of acute care
pulmonary conditions, an area of interest for us for proprietary products.&#160; The addition of Aerogen&#146;s technology, people,
products, programs, and intellectual property with a patent portfolio of more
than 35 patents will extend the range of inhaleable proprietary opportunities
for Nektar.&#160; We plan to provide greater
detail on the Aerogen acquisition and how it fits with our proprietary products
program at our investor meeting on September 29, 2005.&#148;</font></p>

<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Aerogen
develops products based on its OnQ&#174; Aerosol Generator technology to improve the
treatment of respiratory disorders in the acute care setting.&#160; Nektar enables high-value, differentiated
therapeutics with its industry-leading drug delivery technologies, including
inhaleable powdered drugs for treating systemic and local lung indications.</font></p>

<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&#147;We
believe this transaction is in the best interests of our stockholders, customers
and patients,&#148; said John C. Hodgman, Aerogen president and chief executive
officer.&#160; &#147;As a leader in advanced
inhaleable powdered drug products, Nektar has an understanding of the value and
potential of Aerogen&#146;s advanced inhaleable liquid capabilities.&#160; Aerogen</font></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<div style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">

<hr size="2" width="100%" noshade color="gray" align="left">

</font></div>

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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">technology
and expertise will facilitate the development of certain product opportunities
that best lend themselves to an inhaleable liquid delivery system.&#148;</font></p>

<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p style="margin:0in 0in .0001pt;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">Terms
of the Agreement</font></b></p>

<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">The
transaction is structured as a cash and stock transaction, with Nektar
providing approximately $8 million in cash and approximately $24 million in
stock with the option of paying all in cash as described below.</font></p>

<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Under
the terms of the agreement, and upon completion of the acquisition, each share
of common stock will be exchanged for a total of approximately $0.75 per common
share, comprising either $0.1875 in cash, and approximately $0.5625 per common
share in Nektar common stock (valued based on the volume-weighted average price
of Nektar common stock during the twenty trading days ended two days prior to
the completion of the acquisition) or all cash as discussed below. &#160;Also upon completion of the acquisition, each
share of Aerogen A-1 preferred stock will be exchanged for a total of
approximately $29.0251 per A-1 Preferred share, comprising either $7.2563 in
cash, and approximately $21.7688 in Nektar common stock (valued as described
above), or all cash.</font></p>

<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">At
any time prior to September 15, 2005, Nektar may, at its sole discretion, elect
to pay the entire consideration in cash, resulting in payments to Aerogen
stockholders of approximately $0.75 in cash per common share and approximately
$29.0251 in cash per A-1 Preferred share.&#160;
It is anticipated that the merger will be treated as a taxable
transaction.&#160; The premium over the average
closing price per common share over the last 30 trading days is 50%.</font></p>

<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">The
boards of directors of Nektar and Aerogen have approved the transaction, which
is subject to Aerogen shareholders&#146; approval and other customary closing
conditions.&#160; The transaction is anticipated
to be consummated sometime in the fourth quarter of this year.&#160; The transaction does not affect Nektar&#146;s
previous guidance for year-end 2005 cash balance of greater than $270 million.</font></p>

<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p style="margin:0in 0in .0001pt;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">About
Aerogen</font></b></p>

<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Aerogen,
Inc. develops products based on its OnQ Aerosol Generator technology to improve
the treatment of respiratory disorders in the acute care setting.&#160; Aerogen has commercialized its Aeroneb&#174;
Micropump Nebulizer products for hospital, home and pre-clinical use through a
network of world-class respiratory distribution partners that includes
Puritan-Bennett, Respironics, Maquet, Cardinal Health, Evo Medical Solutions,
and Buxco.&#160; Aerogen also has development
collaborations with pharmaceutical and biotechnology companies for use of its
technology in the delivery of novel compounds that treat respiratory and other
disorders.&#160; Founded in 1990, Aerogen has
its headquarters in Mountain View, Calif. with a facility in Galway, Ireland. &#160;In 2004, Aerogen reported revenue of $6.2
million and net loss of $10.1 million. For more information, visit
www.aerogen.com.</font></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<div style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">

<hr size="2" width="100%" noshade color="gray" align="left">

</font></div>

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<div>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p style="margin:0in 0in .0001pt;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">About
Nektar</font></b></p>

<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Nektar
Therapeutics enables high-value, differentiated therapeutics with its
industry-leading drug delivery technologies, expertise and manufacturing
capabilities.&#160; The world&#146;s top
biotechnology and pharmaceutical companies are developing new and better
therapeutics using Nektar&#146;s advanced technologies and know-how.&#160; Nektar also develops its own products by
applying its drug delivery technologies and its expertise to existing medicines
to enhance performance, such as improving efficacy, safety and compliance.&#160; For more information, visit www.nektar.com.</font></p>

<p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p style="margin:0in 0in .0001pt;text-autospace:none;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">Additional Information about the
Merger and Where to Find It</font></b></p>

<p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">In connection with Nektar
Therapeutics&#146; proposed acquisition of Aerogen, Inc. (the &#147;Acquisition&#148;),
Aerogen intends to file a proxy statement and other relevant materials and
Nektar intends to file a registration statement/prospectus and other relevant
materials, with the Securities and Exchange Commission (the &#147;SEC&#148;), in the
event that Nektar does not make the election to pay all cash in the
transaction.&#160; INVESTORS AND SECURITY
HOLDERS OF AEROGEN ARE URGED TO READ THE PROXY STATEMENT/PROSPECTUS AND THE
OTHER RELEVANT MATERIALS WHEN THEY BECOME AVAILABLE BECAUSE THEY WILL CONTAIN
IMPORTANT INFORMATION ABOUT NEKTAR, AEROGEN AND THE ACQUISITION.&#160; The proxy statement/prospectus and other
relevant materials (when they become available), and any other documents filed
by Nektar or Aerogen with the SEC, may be obtained free of charge at the SEC&#146;s WEB
site at www.sec.gov.&#160; In addition,
investors and security holders may obtain free copies of the documents filed
with the SEC by Nektar by directing a written request to:&#160; Nektar Therapeutics, 150 Industrial Road, San
Carlos, CA 94070, ATTN:&#160; Investor Relations.&#160; Investors and security holders may obtain
free copies of the documents filed with the SEC by Aerogen by contacting Aerogen,
Inc., 2071 Stierlin Court, Suite 100, Mountain View, CA 94043,&#160; ATTN:&#160;
Investor Relations.&#160; Investors and
security holders are urged to read the proxy statement, prospectus and the
other relevant materials when they become available before making any voting or
investment decision with respect to the Acquisition.</font></p>

<p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Nektar, Aerogen and their
respective executive officers and directors may be deemed to be participants in
the solicitation of proxies from the stockholders of Aerogen in favor of the
Acquisition.&#160; Information about those
executive officers and directors of Nektar and their ownership of Nektar common
stock is set forth in the proxy statement for Nektar&#146;s 2005 Annual Meeting of
Stockholders, which was filed with the SEC on April 14, 2005.&#160; Information about the executive officers and
directors of Aerogen and their ownership of Aerogen common stock is set forth
in the proxy statement for Aerogen&#146;s Form 10-K, which was filed with the SEC on
April 15, 2005, as amended by Amendment No. 1 on Form 10-K/A, which was filed
with the SEC on April 19, 2005.&#160;
Investors and security holders may obtain more detailed information
regarding the direct and indirect interests of Nektar, Aerogen and their
respective executive officers and directors in the Acquisition by reading the
proxy statement/prospectus regarding the Acquisition when it becomes available.</font></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<div style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">

<hr size="2" width="100%" noshade color="gray" align="left">

</font></div>

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<div>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p style="margin:0in 0in .0001pt;text-autospace:none;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">Aerogen Safe Harbor</font></b></p>

<p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">To the extent any statements
made in this release relate to information that is not historical, these
statements are necessarily forward-looking.&#160;
As such, they are subject to the occurrence of many events outside of
Aerogen&#146;s control and other uncertainties, and are subject to various risk
factors that could cause Aerogen&#146;s actual results to differ materially from
those expressed in any forward-looking statement.&#160; The risk factors include, without limitation,
the risk that the conditions to the Acquisition are not satisfied, that the
Acquisition does not close, the need for additional funding, the inherent risks
of product development, clinical outcomes, regulatory risks and risks related
to proprietary rights, market acceptance and competition, and are described in
Aerogen&#146;s reports and other filings with the SEC, including Aerogen&#146;s Annual
Report on Form 10-K/A for the year ended December 31, 2004, filed with the SEC
on April 19, 2005, and Aerogen&#146;s Quarterly Report filed on Form 10-Q for the
quarter ended June 30, 2005, filed with the SEC on July 27, 2005.&#160; Aerogen does not undertake any obligation to
update forward-looking statements.</font></p>

<p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p style="margin:0in 0in .0001pt;text-autospace:none;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">Nektar Safe Harbor</font></b></p>

<p style="margin:0in 0in .0001pt;text-autospace:none;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">This release contains
forward-looking statements that reflect management&#146;s current views as to Nektar&#146;s
business strategy, product and technology development plans and funding,
collaborative arrangements, clinical trials, and other future events and
operations.&#160; These forward-looking
statements involve uncertainties and other risks that are detailed in Nektar&#146;s
reports and other filings with the SEC, including its Annual Report on Form
10-K, as amended, for the year ended December 2004 and its Quarterly Report on
10-Q for the quarter ended June 30, 2005.&#160;
Actual results could differ materially from these forward-looking
statements.</font></p>

<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;"># # #</font></p>

<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>

<div style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">

<hr size="2" width="100%" noshade color="gray" align="left">

</font></div>

</div>
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