content: <PAGE>
       As filed with the Securities and Exchange Commission on August 27, 2002
  
                                                        Registration No. 333-_____
  
  ================================================================================
  
                         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                                        91-1513032
  (State or Other Jurisdiction of                         (I.R.S. Employer
   Incorporation or Organization)                         Identification No.)
  
             2981 ROUTE 22                                   12563-2335
          PATTERSON, NEW YORK                                (Zip Code)
  (Address of Principal Executive Offices)
  
               PENWEST PHARMACEUTICALS CO. 1997 EQUITY INCENTIVE PLAN
                              (Full Title of the Plan)
  
                                   TOD R. HAMACHEK
                  CHAIRMAN OF THE BOARD AND CHIEF EXECUTIVE OFFICER
                                    2981 ROUTE 22
                           PATTERSON, NEW YORK 12563-2335
                       (Name and Address of Agent For Service)
  
                                   (845) 878-3414
            (Telephone Number, Including Area Code, of Agent For Service)
  
                           CALCULATION OF REGISTRATION FEE
  <TABLE>
  <CAPTION>
  
  ================================================================================================================
                                                  Proposed Maximum      Proposed Maximum
   Title of Securities to      Amount to be        Offering Price      Aggregate Offering         Amount of
        be Registered         Registered (2)          Per Share               Price           Registration Fee
  ----------------------------------------------------------------------------------------------------------------
  <S>                         <C>                    <C>                 <C>                       <C>
  Common Stock, $0.001 par
  value per share (1)         750,000 shares         $10.40 (3)          $7,800,000 (3)            $717.60
  ================================================================================================================
  </TABLE>
  
  (1)      Includes preferred stock purchase rights attached thereto.
  
  (2)      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.
  
  (3)      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 National Market on
           August 20, 2002.
  
  <PAGE>
  
  
                       STATEMENT OF INCORPORATION BY REFERENCE
  
           This registration statement on Form S-8 is filed to register the offer
  and sale of an additional 750,000 shares of the registrant's common stock,
  $0.001 par value per share, to be issued under the Penwest Pharmaceuticals Co.
  1997 Equity Incentive Plan (the "Plan"). This registration statement
  incorporates by reference the registration statement on Form S-8, File No.
  333-66741 filed by the registrant on November 3, 1998 relating to the Plan.
  
           ITEM 5. INTERESTS OF NAMED EXPERTS AND COUNSEL.
  
           Perkins Coie LLP has opined as to the legality of the securities being
  offered by this registration statement.
  
           ITEM 8. EXHIBITS.
  
           The Exhibit Index immediately preceding the exhibits is incorporated
  herein by reference.
  
  
                                       - 1 -
  <PAGE>
  
  
                                     SIGNATURES
  
           Pursuant to the requirements of the Securities Act of 1933, 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 the Town of Patterson, State of New York, on this 26th day of
  August, 2002.
  
                                            PENWEST PHARMACEUTICALS CO.
  
  
                                            By: /s/ Jennifer L. Good
                                                ----------------------------------
                                                Jennifer L. Good
                                                Senior Vice President, Finance and
                                                Chief Financial Officer
  
  
                          POWER OF ATTORNEY AND SIGNATURES
  
           We, the undersigned officers and directors of Penwest Pharmaceuticals
  Co., hereby severally constitute and appoint Tod R. Hamachek and Jennifer L.
  Good, 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 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.
  
  <Table>
  <Caption>
               SIGNATURE                                     TITLE                               DATE
               ---------                                     -----                               ----
  <S>                                    <C>                                                <C>
  
  /s/ Tod R. Hamachek                   Chairman of the Board and Chief Executive           August 26, 2002
  --------------------------------      Officer (Principal executive officer)
  Tod R. Hamachek
  
  
  
  /s/ Jennifer L. Good                  Senior Vice President, Finance and                  August 26, 2002
  --------------------------------      Chief Financial Officer (Principal financial
  Jennifer L. Good                      and accounting officer)
  
  
  
  /s/ Paul E. Freiman                   Director                                            August 23, 2002
  --------------------------------
  Paul E. Freiman
  
  
  /s/ Rolf H. Henel                     Director                                            August 23, 2002
  --------------------------------
  Rolf H. Henel
  </TABLE>
  
  
                                       - 2 -
  <PAGE>
  <TABLE>
  <CAPTION>
  
  
  
  <S>                                    <C>                                                <C>
  /s/ N. STEWART ROGERS                 Director                                            August 23, 2002
  ------------------------------
  N. Stewart Rogers
  
  
  
  /s/ JERE E. GOYAN                     Director                                            August 23, 2002
  ------------------------------
  Jere E. Goyan
  
  
  
  /s/ ANNE M. VANLENT                   Director                                            August 23, 2002
  ------------------------------
  Anne M. VanLent
  
  
  
  /s/ ROBERT HENNESSEY                  Director                                            August 23, 2002
  ------------------------------
  Robert Hennessey
  
  
                                        Director
  ------------------------------
  John N. Staniforth
  </TABLE>
  
  
  
                                        -3-
  <PAGE>
  
                                  INDEX TO EXHIBITS
  
      Number       Description
      ------       -----------
  
       4.1(1)      Amended and Restated Articles of Incorporation, as amended
  
       4.2(1)      Amended and Restated By-Laws of the Registrant
  
       4.3(2)      Form of Rights Agreement dated as of July 27, 1998 between the
                   Registrant and the Rights Agent
  
       5.1         Opinion of Perkins Coie LLP, counsel to the Registrant
  
      23.1         Consent of Perkins Coie LLP (included in Exhibit 5.1)
  
      23.2         Consent of Ernst & Young LLP
  
      24.1         Power of attorney (included on the signature pages of this
                   registration statement)
  
  ----------------
  
      (1)     Previously filed with the Securities and Exchange Commission as an
              exhibit to the registrant's registration statement on Form S-3, as
              amended (File No. 333-65840), 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, as
              amended (File No. 000-23467), and incorporated herein by reference.
metadata_documents: [{"type": "S-8", "sequence": "1", "filename": "b44109ppsv8.txt", "description": "PENWEST PHARMACEUTICALS CO.", "secsgml_size_bytes": 9412}]
metadata_filer: {"company-data": {"conformed-name": "PENWEST PHARMACEUTICALS CO", "cik": "0001047188", "assigned-sic": "2834", "irs-number": "911513032", "state-of-incorporation": "WA", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-98801", "film-number": "02749853"}, "business-address": {"street1": "2981 ROUTE 22", "city": "PATTERSON", "state": "NY", "zip": "12563-9970", "phone": "9148783414"}, "mail-address": {"street1": "2981 ROUTE 22", "city": "PATTERSON", "state": "NY", "zip": "12563-9970"}}
text: As filed with the Securities and Exchange Commission on August 27, 2002
  
                                                        Registration No. 333-_____
  
  ================================================================================
  
                         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                                        91-1513032
  (State or Other Jurisdiction of                         (I.R.S. Employer
   Incorporation or Organization)                         Identification No.)
  
             2981 ROUTE 22                                   12563-2335
          PATTERSON, NEW YORK                                (Zip Code)
  (Address of Principal Executive Offices)
  
               PENWEST PHARMACEUTICALS CO. 1997 EQUITY INCENTIVE PLAN
                              (Full Title of the Plan)
  
                                   TOD R. HAMACHEK
                  CHAIRMAN OF THE BOARD AND CHIEF EXECUTIVE OFFICER
                                    2981 ROUTE 22
                           PATTERSON, NEW YORK 12563-2335
                       (Name and Address of Agent For Service)
  
                                   (845) 878-3414
            (Telephone Number, Including Area Code, of Agent For Service)
  
                           CALCULATION OF REGISTRATION FEE
  ================================================================================================================
                                                  Proposed Maximum      Proposed Maximum
   Title of Securities to      Amount to be        Offering Price      Aggregate Offering         Amount of
        be Registered         Registered (2)          Per Share               Price           Registration Fee
  ----------------------------------------------------------------------------------------------------------------
  Common Stock, $0.001 par
  value per share (1)         750,000 shares         $10.40 (3)          $7,800,000 (3)            $717.60
  ================================================================================================================
  (1)      Includes preferred stock purchase rights attached thereto.
  
  (2)      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.
  
  (3)      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 National Market on
           August 20, 2002.
  STATEMENT OF INCORPORATION BY REFERENCE
  
           This registration statement on Form S-8 is filed to register the offer
  and sale of an additional 750,000 shares of the registrant's common stock,
  $0.001 par value per share, to be issued under the Penwest Pharmaceuticals Co.
  1997 Equity Incentive Plan (the "Plan"). This registration statement
  incorporates by reference the registration statement on Form S-8, File No.
  333-66741 filed by the registrant on November 3, 1998 relating to the Plan.
  
           ITEM 5. INTERESTS OF NAMED EXPERTS AND COUNSEL.
  
           Perkins Coie LLP has opined as to the legality of the securities being
  offered by this registration statement.
  
           ITEM 8. EXHIBITS.
  
           The Exhibit Index immediately preceding the exhibits is incorporated
  herein by reference.
  
                                       - 1 -
  SIGNATURES
  
           Pursuant to the requirements of the Securities Act of 1933, 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 the Town of Patterson, State of New York, on this 26th day of
  August, 2002.
  
                                            PENWEST PHARMACEUTICALS CO.
  
                                            By: /s/ Jennifer L. Good
                                                ----------------------------------
                                                Jennifer L. Good
                                                Senior Vice President, Finance and
                                                Chief Financial Officer
  
                          POWER OF ATTORNEY AND SIGNATURES
  
           We, the undersigned officers and directors of Penwest Pharmaceuticals
  Co., hereby severally constitute and appoint Tod R. Hamachek and Jennifer L.
  Good, 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 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/ Tod R. Hamachek                   Chairman of the Board and Chief Executive           August 26, 2002
  --------------------------------      Officer (Principal executive officer)
  Tod R. Hamachek
  
  /s/ Jennifer L. Good                  Senior Vice President, Finance and                  August 26, 2002
  --------------------------------      Chief Financial Officer (Principal financial
  Jennifer L. Good                      and accounting officer)
  
  /s/ Paul E. Freiman                   Director                                            August 23, 2002
  --------------------------------
  Paul E. Freiman
  
  /s/ Rolf H. Henel                     Director                                            August 23, 2002
  --------------------------------
  Rolf H. Henel
  - 2 -
  /s/ N. STEWART ROGERS                 Director                                            August 23, 2002
  ------------------------------
  N. Stewart Rogers
  
  /s/ JERE E. GOYAN                     Director                                            August 23, 2002
  ------------------------------
  Jere E. Goyan
  
  /s/ ANNE M. VANLENT                   Director                                            August 23, 2002
  ------------------------------
  Anne M. VanLent
  
  /s/ ROBERT HENNESSEY                  Director                                            August 23, 2002
  ------------------------------
  Robert Hennessey
  
                                        Director
  ------------------------------
  John N. Staniforth
  -3-
  INDEX TO EXHIBITS
  
      Number       Description
      ------       -----------
  
       4.1(1)      Amended and Restated Articles of Incorporation, as amended
  
       4.2(1)      Amended and Restated By-Laws of the Registrant
  
       4.3(2)      Form of Rights Agreement dated as of July 27, 1998 between the
                   Registrant and the Rights Agent
  
       5.1         Opinion of Perkins Coie LLP, counsel to the Registrant
  
      23.1         Consent of Perkins Coie LLP (included in Exhibit 5.1)
  
      23.2         Consent of Ernst & Young LLP
  
      24.1         Power of attorney (included on the signature pages of this
                   registration statement)
  
  ----------------
  
      (1)     Previously filed with the Securities and Exchange Commission as an
              exhibit to the registrant's registration statement on Form S-3, as
              amended (File No. 333-65840), 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, as
              amended (File No. 000-23467), and incorporated herein by reference.