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  <H5 align="left" style="page-break-before:always"><A HREF="#toc">Table of Contents</A></H5><P>
  <DIV style="font-family: 'Times New Roman',Times,serif">
  
  
  <DIV align="center" style="font-size: 10pt; margin-top: 18pt">As filed with the Securities and Exchange Commission on July&nbsp;2, 2008
  </DIV>
  
  
  <DIV align="right" style="font-size: 10pt; margin-top: 6pt">Registration No.&nbsp;333-_____
  </DIV>
  
  <DIV align="right" style="font-size: 10pt; margin-top: 0pt">&nbsp;
  </DIV>
  <DIV style="width: 100%; border-bottom: 2pt solid black; font-size: 1pt">&nbsp;</DIV>
  <DIV style="width: 100%; border-bottom: 1pt solid black; font-size: 1pt">&nbsp;</DIV>
  
  
  
  
  <DIV align="center" style="font-size: 14pt; margin-top: 12pt"><B>UNITED STATES<BR>
  SECURITIES AND EXCHANGE COMMISSION</B>
  </DIV>
  
  <DIV align="center" style="font-size: 12pt"><B>Washington, D.C. 20549</B>
  </DIV>
  
  <DIV align="center" style="font-size: 18pt; margin-top: 12pt"><B>FORM S-8</B>
  </DIV>
  
  
  <DIV align="center" style="font-size: 12pt; margin-top: 12pt"><B>REGISTRATION STATEMENT<BR>
  UNDER<BR>
  THE SECURITIES ACT OF 1933</B>
  </DIV>
  
  <DIV align="center" style="font-size: 24pt; margin-top: 12pt"><B>PENWEST PHARMACEUTICALS CO.</B>
  </DIV>
  
  <DIV align="center" style="font-size: 10pt">(Exact Name of Registrant as Specified in Its Charter)</DIV>
  
  
  <DIV align="center">
  <TABLE style="font-size: 10pt" cellspacing="0" border="0" cellpadding="0" width="100%">
  <!-- Begin Table Head -->
  <TR valign="bottom">
      <TD width="47%">&nbsp;</TD>
      <TD width="5%">&nbsp;</TD>
      <TD width="47%">&nbsp;</TD>
  </TR>
  <!-- End Table Head -->
  <!-- Begin Table Body -->
  <TR valign="bottom">
      <TD align="center" valign="top"><B>Washington</B><BR>
  (State or Other Jurisdiction of Incorporation <BR>
  or Organization)
  </TD>
      <TD>&nbsp;</TD>
      <TD align="center" valign="top"><B>91-1513032</B><BR>
  (I.R.S. Employer<BR>
  Identification No.)</TD>
  </TR>
  <!-- End Table Body -->
  </TABLE>
  </DIV>
  
  <DIV align="center">
  <TABLE style="font-size: 10pt" cellspacing="0" border="0" cellpadding="0" width="100%">
  <!-- Begin Table Head -->
  <TR valign="bottom">
      <TD width="47%">&nbsp;</TD>
      <TD width="5%">&nbsp;</TD>
      <TD width="47%">&nbsp;</TD>
  </TR>
  <!-- End Table Head -->
  <!-- Begin Table Body -->
  <TR valign="bottom">
      <TD align="center" valign="top"><B>39 Old Ridgebury Road, Suite&nbsp;11<BR>
  Danbury, Connecticut</B><BR>
  (Address of Principal Executive Offices)
  </TD>
      <TD>&nbsp;</TD>
      <TD align="center" valign="top"><B>06810-5120<br><br></B>
  (Zip Code)</TD>
  </TR>
  <!-- End Table Body -->
  </TABLE>
  </DIV>
  
  
  <DIV align="center" style="font-size: 10pt; margin-top: 18pt"><B>Penwest Pharmaceuticals Co. 2005 Stock Incentive Plan</B><BR>
  (Full Title of the Plan)
  </DIV>
  
  
  <DIV align="center" style="font-size: 10pt; margin-top: 18pt"><B>Jennifer L. Good<BR>
  President and Chief Executive Officer<BR>
  39 Old Ridgebury Road, Suite&nbsp;11, Danbury, Connecticut 06810-5120</B><BR>
  (Name and Address of Agent For Service)<BR>
  <B>(877)&nbsp;736-9378</B><BR>
  (Telephone Number, Including Area Code, of Agent For Service)
  </DIV>
  
  <DIV align="left" style="font-size: 10pt; margin-top: 12pt">Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a
  non-accelerated filer, or a smaller reporting company. See the definitions of &#147;large accelerated
  filer,&#148; &#147;accelerated filer&#148; and &#147;smaller reporting company&#148; in Rule&nbsp;12b-2 of the Exchange Act.
  (Check one):
  </DIV>
  
  <DIV align="center">
  <TABLE style="font-size: 10pt" cellspacing="0" border="0" cellpadding="0" width="100%">
  <!-- Begin Table Head -->
  <TR valign="bottom">
      <TD width="23%">&nbsp;</TD>
      <TD width="0%">&nbsp;</TD>
      <TD width="25%">&nbsp;</TD>
      <TD width="0%">&nbsp;</TD>
      <TD width="25%">&nbsp;</TD>
      <TD width="0%">&nbsp;</TD>
      <TD width="27%">&nbsp;</TD>
  </TR>
  <!-- End Table Head -->
  <!-- Begin Table Body -->
  <TR valign="bottom">
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">Large Accelerated Filer <FONT style="font-family: Wingdings">&#111;</FONT>
  </DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="center" valign="top">Accelerated Filer <FONT style="font-family: Wingdings">&#254;</FONT>
  </TD>
      <TD>&nbsp;</TD>
      <TD align="center" valign="top">Non-Accelerated Filer <FONT style="font-family: Wingdings">&#111;</FONT>
  </TD>
      <TD>&nbsp;</TD>
      <TD align="right" valign="top">Smaller Reporting Company <FONT style="font-family: Wingdings">&#111;</FONT></TD>
  </TR>
  <TR valign="bottom">
      <TD valign="top">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD colspan="5" valign="top" align="center">(Do not check if a smaller reporting company)</TD>
  </TR>
  <!-- End Table Body -->
  </TABLE>
  </DIV>
  
  
  <DIV align="center" style="font-size: 10pt; margin-top: 18pt"><B>CALCULATION OF REGISTRATION FEE</B>
  </DIV>
  
  <DIV align="center">
  <TABLE style="font-size: 10pt" cellspacing="0" border="0" cellpadding="0" width="100%">
  <!-- Begin Table Head -->
  <TR valign="bottom">
      <TD width="1%">&nbsp;</TD>
      <TD width="26%">&nbsp;</TD>
      <TD width="1%">&nbsp;</TD><!-- VRule -->
      <TD width="1%">&nbsp;</TD>
      <TD width="7%">&nbsp;</TD>
      <TD width="1%">&nbsp;</TD>
      <TD width="8%">&nbsp;</TD>
      <TD width="1%">&nbsp;</TD><!-- VRule -->
      <TD width="1%">&nbsp;</TD>
      <TD width="7%">&nbsp;</TD>
      <TD width="1%">&nbsp;</TD>
      <TD width="8%">&nbsp;</TD>
      <TD width="1%">&nbsp;</TD><!-- VRule -->
      <TD width="1%">&nbsp;</TD>
      <TD width="7%">&nbsp;</TD>
      <TD width="1%">&nbsp;</TD>
      <TD width="8%">&nbsp;</TD>
      <TD width="1%">&nbsp;</TD><!-- VRule -->
      <TD width="1%">&nbsp;</TD>
      <TD width="7%">&nbsp;</TD>
      <TD width="1%">&nbsp;</TD>
      <TD width="8%">&nbsp;</TD>
  
      <TD width="1%">&nbsp;</TD>
  </TR><TR style="font-size: 1px" valign="bottom">
      <TD nowrap align="left" colspan="23" style="border-bottom: 3px double #000000">&nbsp;</TD>
  </TR>
  <TR style="font-size: 10pt" valign="bottom">    <TD width="1%">&nbsp;</TD>
  
      <TD>&nbsp;</TD>
      <TD style="border-right: 1px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD style="border-right: 1px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="3">Proposed</TD>
      <TD style="border-right: 1px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="3">Proposed</TD>
      <TD style="border-right: 1px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="3">&nbsp;</TD>
      <TD width="1%">&nbsp;</TD>
  </TR>
  <TR style="font-size: 10pt" valign="bottom">    <TD width="1%">&nbsp;</TD>
  
      <TD nowrap align="center">Title of</TD>
      <TD style="border-right: 1px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD style="border-right: 1px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="3">Maximum</TD>
      <TD style="border-right: 1px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="3">Maximum</TD>
      <TD style="border-right: 1px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="3">&nbsp;</TD>
      <TD width="1%">&nbsp;</TD>
  </TR>
  <TR style="font-size: 10pt" valign="bottom">    <TD width="1%">&nbsp;</TD>
  
      <TD nowrap align="center">Securities to be</TD>
      <TD style="border-right: 1px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="3">Amount to be</TD>
      <TD style="border-right: 1px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="3">Offering Price Per</TD>
      <TD style="border-right: 1px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="3">Aggregate</TD>
      <TD style="border-right: 1px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="3">Amount of</TD>
      <TD width="1%">&nbsp;</TD>
  </TR>
  <TR style="font-size: 10pt" valign="bottom">    <TD width="1%">&nbsp;</TD>
  
      <TD nowrap align="center">Registered</TD>
      <TD style="border-right: 1px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="3">Registered(1)</TD>
      <TD style="border-right: 1px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="3">Share</TD>
      <TD style="border-right: 1px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="3">Offering Price</TD>
      <TD style="border-right: 1px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="3">Registration Fee</TD>
      <TD width="1%">&nbsp;</TD>
  </TR>
  
  <!-- End Table Head -->
  <!-- Begin Table Body -->
  <TR valign="bottom">
      <TD width="1%" style="border-top: 1px solid #000000">&nbsp;</TD>
                      <TD valign="top" style="border-top: 1px solid #000000"><DIV style="margin-left:0px; text-indent:-0px">Common Stock,
  $0.001 par value
  per share
  (including the
  associated
  Preferred Stock
  Purchase Rights)
  </DIV></TD>
      <TD style="border-right: 1px solid #000000; border-top: 1px solid #000000">&nbsp;</TD>
      <TD style="border-top: 1px solid #000000">&nbsp;</TD>
      <TD nowrap align="right" valign="top" style="border-top: 1px solid #000000">&nbsp;</TD>
      <TD align="right" valign="top" style="border-top: 1px solid #000000">2,500,000</TD>
      <TD nowrap valign="top" style="border-top: 1px solid #000000">&nbsp;</TD>
      <TD style="border-right: 1px solid #000000; border-top: 1px solid #000000">&nbsp;</TD>
      <TD style="border-top: 1px solid #000000">&nbsp;</TD>
      <TD nowrap align="right" valign="top" style="border-top: 1px solid #000000">$</TD>
      <TD align="right" valign="top" style="border-top: 1px solid #000000">2.63</TD>
      <TD nowrap valign="top" style="border-top: 1px solid #000000">(2)</TD>
      <TD style="border-right: 1px solid #000000; border-top: 1px solid #000000">&nbsp;</TD>
      <TD style="border-top: 1px solid #000000">&nbsp;</TD>
      <TD nowrap align="right" valign="top" style="border-top: 1px solid #000000">$</TD>
      <TD align="right" valign="top" style="border-top: 1px solid #000000">6,575,000</TD>
      <TD nowrap valign="top" style="border-top: 1px solid #000000">(2)</TD>
      <TD style="border-right: 1px solid #000000; border-top: 1px solid #000000">&nbsp;</TD>
      <TD style="border-top: 1px solid #000000">&nbsp;</TD>
      <TD nowrap align="right" valign="top" style="border-top: 1px solid #000000">$</TD>
      <TD align="right" valign="top" style="border-top: 1px solid #000000">259</TD>
      <TD nowrap valign="top" style="border-top: 1px solid #000000">&nbsp;</TD>
      <TD width="1%" style="border-top: 1px solid #000000">&nbsp;</TD>
  </TR>
  <TR style="font-size: 1px" valign="bottom">
      <TD nowrap align="left" colspan="23" style="border-top: 3px double #000000">&nbsp;</TD>
  </TR>
  
  <!-- End Table Body -->
  </TABLE>
  </DIV>
  
  <DIV style="margin-top: 6pt">
  <TABLE width="100%" border="0" cellpadding="0" cellspacing="0" style="font-size: 10pt">
  
  <TR valign="top" style="font-size: 10pt; color: #000000; background: transparent">
      <TD width="1%" nowrap align="left">(1)</TD>
      <TD width="1%">&nbsp;</TD>
      <TD>In accordance with Rule&nbsp;416 under the Securities Act of 1933, as amended, this registration
  statement shall be deemed to cover any additional securities that may from time to time be
  offered or issued to prevent dilution resulting from stock splits, stock dividends or similar
  transactions.</TD>
  </TR>
  
  </TABLE>
  </DIV>
  
  <DIV style="margin-top: 6pt">
  <TABLE width="100%" border="0" cellpadding="0" cellspacing="0" style="font-size: 10pt">
  
  <TR valign="top" style="font-size: 10pt; color: #000000; background: transparent">
      <TD width="1%" nowrap align="left">(2)</TD>
      <TD width="1%">&nbsp;</TD>
      <TD>Estimated solely for the purpose of calculating the registration fee pursuant to Rules 457(c)
  and 457(h) of the Securities Act of 1933, as amended, and based upon the average of the high
  and low prices of the Registrant&#146;s Common Stock as reported on the Nasdaq Global Market on
  July&nbsp;1, 2008.</TD>
  </TR>
  
  </TABLE>
  </DIV>
  
  <DIV style="width: 100%; border-bottom: 1pt solid black; margin-top: 10pt; font-size: 1pt">&nbsp;</DIV>
  <DIV style="width: 100%; border-bottom: 2pt solid black; font-size: 1pt">&nbsp;</DIV>
  
  
  
  
  
  <P align="center" style="font-size: 10pt"><!-- Folio -->&nbsp;<!-- /Folio -->
  </DIV>
  
  <!-- PAGEBREAK -->
  <P><HR noshade><P>
  
  <DIV style="font-family: 'Times New Roman',Times,serif">
  
  
  
  
  
  
  <!-- TOC -->
  <A name="toc"><DIV align="CENTER" style="page-break-before:always"><U><B>TABLE OF CONTENTS</B></U></DIV></A>
  
  <P><CENTER>
  <TABLE border="0" width="90%" cellpadding="0" cellspacing="0">
  <TR>
  	<TD width="3%"></TD>
  	<TD width="3%"></TD>
  	<TD width="3%"></TD>
  	<TD width="3%"></TD>
  	<TD width="3%"></TD>
  	<TD width="3%"></TD>
  	<TD width="3%"></TD>
  	<TD width="3%"></TD>
  	<TD width="76%"></TD>
  </TR>
  <TR><TD colspan="9"><A HREF="#000">STATEMENT OF INCORPORATION BY REFERENCE</A></TD></TR>
  <TR><TD></TD><TD colspan="8"><A HREF="#001">Item&nbsp;8.&nbsp;&nbsp; Exhibits.</A></TD></TR>
  <TR><TD colspan="9"><A HREF="#002">SIGNATURES</A></TD></TR>
  <TR><TD colspan="9"><A HREF="#003">INDEX TO EXHIBITS</A></TD></TR>
  <TR><TD colspan="9"><A HREF="b70903ppexv4w2.htm">EX-4.2 Amended and Restated Bylaws of the Registrant, as amended</A></TD></TR>
  <TR><TD colspan="9"><A HREF="b70903ppexv5w1.htm">EX-5.1 Opinion of Perkins Coie LLP</A></TD></TR>
  <TR><TD colspan="9"><A HREF="b70903ppexv23w2.htm">EX-23.2 Consent of Ernst & Young LLP</A></TD></TR>
  </TABLE>
  </CENTER>
  <!-- /TOC -->
  <P><HR noshade><P>
  <H5 align="left" style="page-break-before:always"><A HREF="#toc">Table of Contents</A></H5><P>
  
  
  
  
  <!-- link1 "STATEMENT OF INCORPORATION BY REFERENCE" -->
  <DIV align="left"><A NAME="000"></A></DIV>
  
  <DIV align="center" style="font-size: 10pt; margin-top: 18pt"><B>STATEMENT OF INCORPORATION BY REFERENCE</B>
  </DIV>
  
  
  <DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;This Registration Statement on Form S-8 is filed to register the offer and sale of an
  additional 2,500,000 shares of the Registrant&#146;s common stock, $0.001 par value per share, to be
  issued under the Registrant&#146;s 2005 Stock Incentive Plan. This Registration Statement incorporates
  by reference the contents of the registration statement on Form S-8, File No.&nbsp;333-126897, filed by
  the Registrant on July&nbsp;26, 2005, relating to the Registrant&#146;s 2005 Stock Incentive Plan, except for
  information required by Item&nbsp;8, which is contained below.
  </DIV>
  <!-- link2 "Item&nbsp;8.&nbsp;&nbsp; Exhibits." -->
  <DIV align="left"><A NAME="001"></A></DIV>
  
  <DIV align="left" style="font-size: 10pt; margin-top: 12pt"><B>Item&nbsp;8.&nbsp;&nbsp; Exhibits.</B>
  </DIV>
  
  <DIV align="left" style="font-size: 10pt; margin-top: 6pt">The Exhibit&nbsp;Index immediately preceding the exhibits is incorporated herein by reference.
  </DIV>
  
  
  <P align="center" style="font-size: 10pt"><!-- Folio -->-1-<!-- /Folio -->
  </DIV>
  
  <!-- PAGEBREAK -->
  <P><HR noshade><P>
  <H5 align="left" style="page-break-before:always"><A HREF="#toc">Table of Contents</A></H5><P>
  
  <DIV style="font-family: 'Times New Roman',Times,serif">
  
  
  
  <!-- link1 "SIGNATURES" -->
  <DIV align="left"><A NAME="002"></A></DIV>
  
  <DIV align="center" style="font-size: 10pt; margin-top: 18pt"><B>SIGNATURES</B>
  </DIV>
  
  
  <DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Pursuant to the requirements of the Securities Act of 1933, as amended, the Registrant
  certifies that it has reasonable grounds to believe that it meets all of the requirements for
  filing on Form S-8 and has duly caused this registration statement to be signed on its behalf by
  the undersigned, thereunto duly authorized, in Danbury, Connecticut, on this 2<SUP style="font-size: 85%; vertical-align: text-top">nd</SUP> day of
  July, 2008.
  </DIV>
  
  <TABLE width="100%" border="0" cellspacing="0" cellpadding="0" style="font-size: 10pt">
  <TR>
      <TD width="48%">&nbsp;</TD>
      <TD width="1%">&nbsp;</TD>
      <TD width="1%">&nbsp;</TD>
      <TD width="35%">&nbsp;</TD>
      <TD width="15%">&nbsp;</TD>
  </TR>
  <TR>
      <TD valign="top" align="left">&nbsp;</TD>
      <TD colspan="3" align="left">PENWEST PHARMACEUTICALS CO.<BR>
  &nbsp;</TD>
      <TD>&nbsp;</TD>
  </TR><TR>
      <TD align="left">&nbsp;</TD>
      <TD valign="top">By:&nbsp;&nbsp;</TD>
      <TD colspan="2" style="border-bottom: 1px solid #000000" align="left">/s/ Jennifer L. Good
  &nbsp;</TD>
      <TD>&nbsp;</TD>
  </TR><TR>
      <TD align="left">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD colspan="2" align="left">Jennifer L. Good&nbsp;</TD>
      <TD>&nbsp;</TD>
  </TR><TR>
      <TD align="left">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD colspan="2" align="left">President and Chief Executive Officer&nbsp;</TD>
      <TD>&nbsp;</TD>
  </TR>
  <TR>
      <TD colspan="5">&nbsp;</TD>
  </TR>
  </TABLE>
  
  <DIV align="center" style="font-size: 10pt; margin-top: 18pt"><B>POWER OF ATTORNEY AND SIGNATURES</B>
  </DIV>
  
  
  
  <DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;We, the undersigned officers and directors of Penwest Pharmaceuticals Co., hereby severally
  constitute and appoint Jennifer L. Good and Benjamin L. Palleiko, and each of them singly, our true
  and lawful attorneys with full power to them, and each of them singly, to sign for us and in our
  names in the capacities indicated below, the registration statement on Form S-8 filed herewith and
  any and all subsequent amendments to said registration statement, and generally to do all such
  things in our names and on our behalf in our capacities as officers and directors to enable Penwest
  Pharmaceuticals Co. to comply with the provisions of the Securities Act of 1933, as amended, and
  all requirements of the Securities and Exchange Commission, hereby ratifying and confirming our
  signatures as they may be signed by our said attorneys, or any of them, to said registration
  statement and any and all amendments thereto.
  </DIV>
  
  <DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Pursuant to the requirements of the Securities Act of 1933, this registration statement has
  been signed by the following persons in the capacities and on the dates indicated.
  </DIV>
  <DIV align="center">
  <TABLE style="font-size: 10pt" cellspacing="0" border="0" cellpadding="0" width="100%">
  <!-- Begin Table Head -->
  <TR valign="bottom">
      <TD width="40%">&nbsp;</TD>
      <TD width="5%">&nbsp;</TD>
      <TD width="30%">&nbsp;</TD>
      <TD width="10%">&nbsp;</TD>
      <TD width="15%">&nbsp;</TD>
  </TR>
  <TR style="font-size: 10pt" valign="bottom">
      <TD nowrap align="center"><u><B>Signature</B></u></TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center"><u><B>Title</B></u></TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center"><u><B>Date</B></u></TD>
  </TR>
  
  <!-- End Table Head -->
  <!-- Begin Table Body -->
  <TR valign="bottom" style="padding-top: 1em">
      <TD align="left" nowrap valign="top">/s/ Jennifer L. Good
  <DIV style="font-size: 1pt; border-bottom: 1px solid #000000">&nbsp;</DIV>
  Jennifer L. Good</TD>
      <TD>&nbsp;</TD>
      <TD align="left" nowrap valign="top">
  President and Chief
  Executive Officer,
  Director <br>(Principal
  Executive Officer)
  </TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">July 2, 2008</TD>
  </TR>
  <TR valign="bottom" style="padding-top: 1em">
      <TD align="left" nowrap valign="top">/s/ Benjamin L. Palleiko
  <DIV style="font-size: 1pt; border-bottom: 1px solid #000000">&nbsp;</DIV>
  Benjamin L. Palleiko</TD>
      <TD>&nbsp;</TD>
      <TD align="left" nowrap valign="top">
  Senior Vice
  President, Corporate
  Development <br>and
  Chief Financial
  Officer <br>(Principal
  Financial Officer)
  </TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">July 2, 2008</TD>
  </TR>
  <TR valign="bottom" style="padding-top: 1em">
      <TD align="left" nowrap valign="top">/s/ Frank P. Muscolo
  <DIV style="font-size: 1pt; border-bottom: 1px solid #000000">&nbsp;</DIV>
  Frank P. Muscolo</TD>
      <TD>&nbsp;</TD>
      <TD align="left" nowrap valign="top">
  Controller and Chief
  Accounting Officer
  <br>(Principal
  Accounting Officer)
  </TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">July 2, 2008</TD>
  </TR>
  <TR valign="bottom" style="padding-top: 1em">
      <TD align="left" nowrap valign="top">/s/ Paul E. Freiman
  <DIV style="font-size: 1pt; border-bottom: 1px solid #000000">&nbsp;</DIV>
  Paul E. Freiman</TD>
      <TD>&nbsp;</TD>
      <TD align="left" nowrap valign="top">
  Chairman of the Board
  </TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">July 2, 2008</TD>
  </TR>
  <!-- End Table Body -->
  </TABLE>
  </DIV>
  
  
  <P align="center" style="font-size: 10pt"><!-- Folio -->-2-<!-- /Folio -->
  </DIV>
  
  <!-- PAGEBREAK -->
  <P><HR noshade><P>
  <H5 align="left" style="page-break-before:always"><A HREF="#toc">Table of Contents</A></H5><P>
  
  <DIV style="font-family: 'Times New Roman',Times,serif">
  
  <DIV align="center">
  <TABLE style="font-size: 10pt" cellspacing="0" border="0" cellpadding="0" width="100%">
  <!-- Begin Table Head -->
  <TR valign="bottom">
      <TD width="40%">&nbsp;</TD>
      <TD width="5%">&nbsp;</TD>
      <TD width="30%">&nbsp;</TD>
      <TD width="10%">&nbsp;</TD>
      <TD width="15%">&nbsp;</TD>
  </TR>
  <!-- End Table Head -->
  <!-- Begin Table Body -->
  <TR valign="bottom" style="padding-top: 1em">
      <TD align="left" nowrap valign="top">/s/ Christophe Bianchi&nbsp;<BR>
  <DIV style="font-size: 1pt; border-bottom: 1px solid #000000">&nbsp;</DIV>
  Christophe Bianchi, M.D.</TD>
      <TD>&nbsp;</TD>
      <TD align="left" nowrap valign="top">
  Director</TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">July 1, 2008</TD>
  </TR>
  <TR valign="bottom" style="padding-top: 1em">
      <TD align="left" nowrap valign="top">/s/ Peter F. Drake
  <DIV style="font-size: 1pt; border-bottom: 1px solid #000000">&nbsp;</DIV>
  Peter F. Drake, Ph.D.</TD>
      <TD>&nbsp;</TD>
      <TD align="left" nowrap valign="top">
  Director
  </TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">July 2, 2008</TD>
  </TR>
  <TR valign="bottom" style="padding-top: 1em">
      <TD align="left" nowrap valign="top">/s/ Robert J. Hennessey
  <DIV style="font-size: 1pt; border-bottom: 1px solid #000000">&nbsp;</DIV>
  Robert J. Hennessey</TD>
      <TD>&nbsp;</TD>
      <TD align="left" nowrap valign="top">
  Director
  </TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">July 2, 2008</TD>
  </TR>
  <TR valign="bottom" style="padding-top: 1em">
      <TD align="left" nowrap valign="top">/s/ David P. Meeker
  <DIV style="font-size: 1pt; border-bottom: 1px solid #000000">&nbsp;</DIV>
  David P. Meeker, M.D.</TD>
      <TD>&nbsp;</TD>
      <TD align="left" nowrap valign="top">
  Director
  </TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">June 27, 2008</TD>
  </TR>
  <TR valign="bottom" style="padding-top: 1em">
      <TD align="left" nowrap valign="top">/s/ William J. O&#146;Shea
  <DIV style="font-size: 1pt; border-bottom: 1px solid #000000">&nbsp;</DIV>
  William J. O&#146;Shea</TD>
      <TD>&nbsp;</TD>
      <TD align="left" nowrap valign="top">
  Director
  </TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">July 2, 2008</TD>
  </TR>
  <TR valign="bottom" style="padding-top: 1em">
      <TD align="left" nowrap valign="top">&nbsp;<BR>
  <DIV style="font-size: 1pt; border-bottom: 1px solid #000000">&nbsp;</DIV>
  John N. Staniforth, Ph.D.</TD>
      <TD>&nbsp;</TD>
      <TD align="left" nowrap valign="top">
  Director</TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">&nbsp;</TD>
  </TR>
  <TR valign="bottom" style="padding-top: 1em">
      <TD align="left" nowrap valign="top">/s/ Anne M. VanLent
  <DIV style="font-size: 1pt; border-bottom: 1px solid #000000">&nbsp;</DIV>
  Anne M. VanLent</TD>
      <TD>&nbsp;</TD>
      <TD align="left" nowrap valign="top">
  Director
  </TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">July 2, 2008</TD>
  </TR>
  <!-- End Table Body -->
  </TABLE>
  </DIV>
  
  
  
  <P align="center" style="font-size: 10pt"><!-- Folio -->-3-<!-- /Folio -->
  </DIV>
  
  <!-- PAGEBREAK -->
  <P><HR noshade><P>
  <H5 align="left" style="page-break-before:always"><A HREF="#toc">Table of Contents</A></H5><P>
  
  <DIV style="font-family: 'Times New Roman',Times,serif">
  
  
  
  <!-- link1 "INDEX TO EXHIBITS" -->
  <DIV align="left"><A NAME="003"></A></DIV>
  
  <DIV align="center" style="font-size: 10pt; margin-top: 18pt"><B>INDEX TO EXHIBITS</B>
  </DIV>
  
  <DIV align="center">
  <TABLE style="font-size: 10pt" cellspacing="0" border="0" cellpadding="0" width="100%">
  <!-- Begin Table Head -->
  <TR valign="bottom">
      <TD width="10%">&nbsp;</TD>
      <TD width="5%">&nbsp;</TD>
      <TD width="90%">&nbsp;</TD>
  </TR>
  <TR style="font-size: 8pt" valign="bottom">
      <TD nowrap align="left"><u>Number</u></TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="left"><u>Description</u></TD>
  </TR>
  
  <!-- End Table Head -->
  <!-- Begin Table Body -->
  <TR valign="bottom"><!-- Blank Space -->
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">&nbsp;</TD>
  </TR>
  <TR valign="bottom">
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">4.1 (1)
  </DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">Amended and Restated Articles of Incorporation of the Registrant, as
  amended</TD>
  </TR>
  <TR valign="bottom"><!-- Blank Space -->
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">&nbsp;</TD>
  </TR>
  <TR valign="bottom">
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">4.2
  </DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">Amended and Restated Bylaws of the Registrant, as amended</TD>
  </TR>
  <TR valign="bottom"><!-- Blank Space -->
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">&nbsp;</TD>
  </TR>
  <TR valign="bottom">
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">4.3 (2)
  </DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">Form of Rights Agreement dated as of July&nbsp;27, 1998 between the
  Registrant and the Rights Agent</TD>
  </TR>
  <TR valign="bottom"><!-- Blank Space -->
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">&nbsp;</TD>
  </TR>
  <TR valign="bottom">
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">4.4 (3)
  </DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">Amendment to Rights Agreement dated as of March&nbsp;5, 2008 between the
  Registrant and Mellon Investor Services LLC</TD>
  </TR>
  <TR valign="bottom"><!-- Blank Space -->
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">&nbsp;</TD>
  </TR>
  <TR valign="bottom">
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">4.5 (4)
  </DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">Amendment No.&nbsp;2 to Rights Agreement dated as of March&nbsp;20, 2008
  between the Registrant and Mellon Investor Services LLC</TD>
  </TR>
  <TR valign="bottom"><!-- Blank Space -->
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">&nbsp;</TD>
  </TR>
  <TR valign="bottom">
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">4.6 (5)
  </DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">Amendment No.&nbsp;3 to Rights Agreement dated as of April&nbsp;18, 2008
  between the Registrant and Mellon Investor Services LLC</TD>
  </TR>
  <TR valign="bottom"><!-- Blank Space -->
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">&nbsp;</TD>
  </TR>
  <TR valign="bottom">
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">5.1
  </DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">Opinion of Perkins Coie LLP</TD>
  </TR>
  <TR valign="bottom"><!-- Blank Space -->
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">&nbsp;</TD>
  </TR>
  <TR valign="bottom">
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">23.1
  </DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">Consent of Perkins Coie LLP (included in opinion filed as Exhibit&nbsp;5.1)</TD>
  </TR>
  <TR valign="bottom"><!-- Blank Space -->
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">&nbsp;</TD>
  </TR>
  <TR valign="bottom">
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">23.2
  </DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">Consent of Ernst &#038; Young LLP</TD>
  </TR>
  <TR valign="bottom"><!-- Blank Space -->
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">&nbsp;</TD>
  </TR>
  <TR valign="bottom">
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">24
  </DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">Power of attorney (included on the signature pages of this
  registration statement)</TD>
  </TR>
  <TR valign="bottom"><!-- Blank Space -->
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">&nbsp;</TD>
  </TR>
  <TR valign="bottom">
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">99.1 (6)
  </DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">Penwest Pharmaceuticals Co. 2005 Stock Incentive Plan</TD>
  </TR>
  <!-- End Table Body -->
  </TABLE>
  </DIV>
  
  
  <DIV style="margin-top: 12pt">
  <TABLE width="100%" border="0" cellpadding="0" cellspacing="0" style="font-size: 10pt">
  
  <TR valign="top" style="font-size: 10pt; color: #000000; background: transparent">
      <TD width="1%" nowrap align="left">(1)</TD>
      <TD width="1%">&nbsp;</TD>
      <TD>Previously filed with the Securities and Exchange Commission as an Exhibit to the
  Registrant&#146;s Quarterly Report on Form 10-Q for the quarterly period ended June&nbsp;30, 2004 filed
  on August&nbsp;3, 2004 (File No.&nbsp;000-23467) and incorporated herein by reference.</TD>
  </TR>
  
  </TABLE>
  </DIV>
  
  <DIV style="margin-top: 6pt">
  <TABLE width="100%" border="0" cellpadding="0" cellspacing="0" style="font-size: 10pt">
  
  <TR valign="top" style="font-size: 10pt; color: #000000; background: transparent">
      <TD width="1%" nowrap align="left">(2)</TD>
      <TD width="1%">&nbsp;</TD>
      <TD>Previously filed with the Securities and Exchange Commission as an Exhibit to the
  Registrant&#146;s Registration Statement on Form&nbsp;10/A filed on July&nbsp;17, 1998 (File No.&nbsp;000-23467)
  and incorporated herein by reference.</TD>
  </TR>
  
  </TABLE>
  </DIV>
  
  <DIV style="margin-top: 6pt">
  <TABLE width="100%" border="0" cellpadding="0" cellspacing="0" style="font-size: 10pt">
  
  <TR valign="top" style="font-size: 10pt; color: #000000; background: transparent">
      <TD width="1%" nowrap align="left">(3)</TD>
      <TD width="1%">&nbsp;</TD>
      <TD>Previously filed with the Securities and Exchange Commission as an Exhibit to the
  Registrant&#146;s Current Report on Form 8-K filed on March&nbsp;6, 2008 (File No.&nbsp;000-23467) and
  incorporated herein by reference.</TD>
  </TR>
  
  </TABLE>
  </DIV>
  
  <DIV style="margin-top: 6pt">
  <TABLE width="100%" border="0" cellpadding="0" cellspacing="0" style="font-size: 10pt">
  
  <TR valign="top" style="font-size: 10pt; color: #000000; background: transparent">
      <TD width="1%" nowrap align="left">(4)</TD>
      <TD width="1%">&nbsp;</TD>
      <TD>Previously filed with the Securities and Exchange Commission as an Exhibit to the
  Registrant&#146;s Current Report on Form 8-K filed on March&nbsp;20, 2008 (File No.&nbsp;000-23467) and
  incorporated herein by reference.</TD>
  </TR>
  
  </TABLE>
  </DIV>
  <P align="center" style="font-size: 10pt"><!-- Folio -->&nbsp;<!-- /Folio -->
  </DIV>
  
  <!-- PAGEBREAK -->
  <P><HR noshade><P>
  <H5 align="left" style="page-break-before:always"><A HREF="#toc">Table of Contents</A></H5><P>
  
  <DIV style="font-family: 'Times New Roman',Times,serif">
  
  
  <DIV style="margin-top: 6pt"><TABLE width="100%" border="0" cellpadding="0" cellspacing="0" style="font-size: 10pt">
  
  
  
  </TABLE>
  </DIV>
  
  <DIV style="margin-top: 6pt">
  <TABLE width="100%" border="0" cellpadding="0" cellspacing="0" style="font-size: 10pt">
  
  <TR valign="top" style="font-size: 10pt; color: #000000; background: transparent">
      <TD width="1%" nowrap align="left">(5)</TD>
      <TD width="1%">&nbsp;</TD>
      <TD>Previously filed with the Securities and Exchange Commission as an Exhibit to the
  Registrant&#146;s Current Report on Form 8-K filed on April&nbsp;22, 2008 (File No.&nbsp;000-23467) and
  incorporated herein by reference.</TD>
  </TR>
  
  </TABLE>
  </DIV>
  
  <DIV style="margin-top: 6pt">
  <TABLE width="100%" border="0" cellpadding="0" cellspacing="0" style="font-size: 10pt">
  
  <TR valign="top" style="font-size: 10pt; color: #000000; background: transparent">
      <TD width="1%" nowrap align="left">(6)</TD>
      <TD width="1%">&nbsp;</TD>
      <TD>Previously filed with the Securities and Exchange Commission as an Exhibit to the
  Registrant&#146;s definitive proxy statement on Schedule&nbsp;14A filed on April&nbsp;28, 2008 and
  incorporated herein by reference.</TD>
  </TR>
  
  </TABLE>
  </DIV>
  
  
  <P align="center" style="font-size: 10pt"><!-- Folio -->&nbsp;<!-- /Folio -->
  </DIV>
  
  
  
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text: sv8
  Table of Contents
  As filed with the Securities and Exchange Commission on July 2, 2008
  Registration No. 333-_____
  UNITED STATES
  SECURITIES AND EXCHANGE COMMISSION
  Washington, D.C. 20549
  FORM S-8
  REGISTRATION STATEMENT
  UNDER
  THE SECURITIES ACT OF 1933
  PENWEST PHARMACEUTICALS CO.
  (Exact Name of Registrant as Specified in Its Charter)
  Washington
  (State or Other Jurisdiction of Incorporation
  or Organization)
  91-1513032
  (I.R.S. Employer
  Identification No.)
  39 Old Ridgebury Road, Suite 11
  Danbury, Connecticut
  (Address of Principal Executive Offices)
  06810-5120
  (Zip Code)
  Penwest Pharmaceuticals Co. 2005 Stock Incentive Plan
  (Full Title of the Plan)
  Jennifer L. Good
  President and Chief Executive Officer
  39 Old Ridgebury Road, Suite 11, Danbury, Connecticut 06810-5120
  (Name and Address of Agent For Service)
  (877) 736-9378
  (Telephone Number, Including Area Code, of Agent For Service)
  Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a
  non-accelerated filer, or a smaller reporting company. See the definitions of "large accelerated
  filer," "accelerated filer" and "smaller reporting company" in Rule 12b-2 of the Exchange Act.
  (Check one):
  Large Accelerated Filer
  o
  Accelerated Filer
  þ
  Non-Accelerated Filer
  o
  Smaller Reporting Company
  o
  (Do not check if a smaller reporting company)
  CALCULATION OF REGISTRATION FEE
  Proposed
  Proposed
  Title of
  Maximum
  Maximum
  Securities to be
  Amount to be
  Offering Price Per
  Aggregate
  Amount of
  Registered
  Registered(1)
  Share
  Offering Price
  Registration Fee
  Common Stock,
  $0.001 par value
  per share
  (including the
  associated
  Preferred Stock
  Purchase Rights)
  2,500,000
  $
  2.63
  (2)
  $
  6,575,000
  (2)
  $
  259
  (1)
  In accordance with Rule 416 under the Securities Act of 1933, as amended, this registration
  statement shall be deemed to cover any additional securities that may from time to time be
  offered or issued to prevent dilution resulting from stock splits, stock dividends or similar
  transactions.
  (2)
  Estimated solely for the purpose of calculating the registration fee pursuant to Rules 457(c)
  and 457(h) of the Securities Act of 1933, as amended, and based upon the average of the high
  and low prices of the Registrant's Common Stock as reported on the Nasdaq Global Market on
  July 1, 2008.
  TABLE OF CONTENTS
  STATEMENT OF INCORPORATION BY REFERENCE
  Item 8.   Exhibits.
  SIGNATURES
  INDEX TO EXHIBITS
  EX-4.2 Amended and Restated Bylaws of the Registrant, as amended
  EX-5.1 Opinion of Perkins Coie LLP
  EX-23.2 Consent of Ernst & Young LLP
  Table of Contents
  STATEMENT OF INCORPORATION BY REFERENCE
  This Registration Statement on Form S-8 is filed to register the offer and sale of an
  additional 2,500,000 shares of the Registrant's common stock, $0.001 par value per share, to be
  issued under the Registrant's 2005 Stock Incentive Plan. This Registration Statement incorporates
  by reference the contents of the registration statement on Form S-8, File No. 333-126897, filed by
  the Registrant on July 26, 2005, relating to the Registrant's 2005 Stock Incentive Plan, except for
  information required by Item 8, which is contained below.
  Item 8.   Exhibits.
  The Exhibit Index immediately preceding the exhibits is incorporated herein by reference.
  -1-
  Table of Contents
  SIGNATURES
  Pursuant to the requirements of the Securities Act of 1933, as amended, the Registrant
  certifies that it has reasonable grounds to believe that it meets all of the requirements for
  filing on Form S-8 and has duly caused this registration statement to be signed on its behalf by
  the undersigned, thereunto duly authorized, in Danbury, Connecticut, on this 2
  nd
  day of
  July, 2008.
  PENWEST PHARMACEUTICALS CO.
  By:
  /s/ Jennifer L. Good
  Jennifer L. Good
  President and Chief Executive Officer
  POWER OF ATTORNEY AND SIGNATURES
  We, the undersigned officers and directors of Penwest Pharmaceuticals Co., hereby severally
  constitute and appoint Jennifer L. Good and Benjamin L. Palleiko, and each of them singly, our true
  and lawful attorneys with full power to them, and each of them singly, to sign for us and in our
  names in the capacities indicated below, the registration statement on Form S-8 filed herewith and
  any and all subsequent amendments to said registration statement, and generally to do all such
  things in our names and on our behalf in our capacities as officers and directors to enable Penwest
  Pharmaceuticals Co. to comply with the provisions of the Securities Act of 1933, as amended, and
  all requirements of the Securities and Exchange Commission, hereby ratifying and confirming our
  signatures as they may be signed by our said attorneys, or any of them, to said registration
  statement and any and all amendments thereto.
  Pursuant to the requirements of the Securities Act of 1933, this registration statement has
  been signed by the following persons in the capacities and on the dates indicated.
  Signature
  Title
  Date
  /s/ Jennifer L. Good
  Jennifer L. Good
  President and Chief
  Executive Officer,
  Director
  (Principal
  Executive Officer)
  July 2, 2008
  /s/ Benjamin L. Palleiko
  Benjamin L. Palleiko
  Senior Vice
  President, Corporate
  Development
  and
  Chief Financial
  Officer
  (Principal
  Financial Officer)
  July 2, 2008
  /s/ Frank P. Muscolo
  Frank P. Muscolo
  Controller and Chief
  Accounting Officer
  (Principal
  Accounting Officer)
  July 2, 2008
  /s/ Paul E. Freiman
  Paul E. Freiman
  Chairman of the Board
  July 2, 2008
  -2-
  Table of Contents
  /s/ Christophe Bianchi
  Christophe Bianchi, M.D.
  Director
  July 1, 2008
  /s/ Peter F. Drake
  Peter F. Drake, Ph.D.
  Director
  July 2, 2008
  /s/ Robert J. Hennessey
  Robert J. Hennessey
  Director
  July 2, 2008
  /s/ David P. Meeker
  David P. Meeker, M.D.
  Director
  June 27, 2008
  /s/ William J. O'Shea
  William J. O'Shea
  Director
  July 2, 2008
  John N. Staniforth, Ph.D.
  Director
  /s/ Anne M. VanLent
  Anne M. VanLent
  Director
  July 2, 2008
  -3-
  Table of Contents
  INDEX TO EXHIBITS
  Number
  Description
  4.1 (1)
  Amended and Restated Articles of Incorporation of the Registrant, as
  amended
  4.2
  Amended and Restated Bylaws of the Registrant, as amended
  4.3 (2)
  Form of Rights Agreement dated as of July 27, 1998 between the
  Registrant and the Rights Agent
  4.4 (3)
  Amendment to Rights Agreement dated as of March 5, 2008 between the
  Registrant and Mellon Investor Services LLC
  4.5 (4)
  Amendment No. 2 to Rights Agreement dated as of March 20, 2008
  between the Registrant and Mellon Investor Services LLC
  4.6 (5)
  Amendment No. 3 to Rights Agreement dated as of April 18, 2008
  between the Registrant and Mellon Investor Services LLC
  5.1
  Opinion of Perkins Coie LLP
  23.1
  Consent of Perkins Coie LLP (included in opinion filed as Exhibit 5.1)
  23.2
  Consent of Ernst & Young LLP
  24
  Power of attorney (included on the signature pages of this
  registration statement)
  99.1 (6)
  Penwest Pharmaceuticals Co. 2005 Stock Incentive Plan
  (1)
  Previously filed with the Securities and Exchange Commission as an Exhibit to the
  Registrant's Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2004 filed
  on August 3, 2004 (File No. 000-23467) and incorporated herein by reference.
  (2)
  Previously filed with the Securities and Exchange Commission as an Exhibit to the
  Registrant's Registration Statement on Form 10/A filed on July 17, 1998 (File No. 000-23467)
  and incorporated herein by reference.
  (3)
  Previously filed with the Securities and Exchange Commission as an Exhibit to the
  Registrant's Current Report on Form 8-K filed on March 6, 2008 (File No. 000-23467) and
  incorporated herein by reference.
  (4)
  Previously filed with the Securities and Exchange Commission as an Exhibit to the
  Registrant's Current Report on Form 8-K filed on March 20, 2008 (File No. 000-23467) and
  incorporated herein by reference.
  Table of Contents
  (5)
  Previously filed with the Securities and Exchange Commission as an Exhibit to the
  Registrant's Current Report on Form 8-K filed on April 22, 2008 (File No. 000-23467) and
  incorporated herein by reference.
  (6)
  Previously filed with the Securities and Exchange Commission as an Exhibit to the
  Registrant's definitive proxy statement on Schedule 14A filed on April 28, 2008 and
  incorporated herein by reference.