SEC Form 3

FORM 3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person* ENDO PHARMACEUTICALS HOLDINGS INC (Last) (First) (Middle) 100 ENDO BOULEVARD (Street) CHADDS FORD PA 19317 (City) (State) (Zip)	2. Date of Event Requiring Statement (Month/Day/Year) 09/20/2010	3. Issuer Name and Ticker or Trading Symbol PENWEST PHARMACEUTICALS CO [ PPCO ]
		4. Relationship of Reporting Person(s) to Issuer (Check all applicable) Director X 10% Owner Officer (give title below) Other (specify below)	5. If Amendment, Date of Original Filed (Month/Day/Year)
			6. Individual or Joint/Group Filing (Check Applicable Line) Form filed by One Reporting Person X Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Beneficially Owned
1. Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)
Common Stock, par value $0.001, per share	30,810,778	I	See footnotes(1)(2)

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

1. Name and Address of Reporting Person* ENDO PHARMACEUTICALS HOLDINGS INC (Last) (First) (Middle) 100 ENDO BOULEVARD (Street) CHADDS FORD PA 19317 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* West Acquisition Corp. (Last) (First) (Middle) 100 ENDO BOULEVARD (Street) CHADDS FORD PA 19317 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

Explanation of Responses:

1. West Acquisition Corp. ("Purchaser"), a wholly-owned subsidiary of Endo Pharmaceuticals Holdings Inc. ("Endo"), Endo and Penwest Pharmaceuticals Co. ("Issuer") entered into an Agreement and Plan of Merger, dated as of August 9, 2010, pursuant to which Purchaser conducted a cash tender offer (the "Offer") to purchase all outstanding shares of common stock, par value $0.001 (including shares of common stock issuable upon the conditional exercise of options to purchase shares of common stock and warrants to acquire shares of common stock, each option and warrant having an exercise price of less than $5.00 per share, the "Shares") per Share, of the Issuer at a price of $5.00 per Share, net to the seller in cash, without interest and less any required withholding taxes, upon the terms and subject to the conditions set forth in the Offer to Purchase, dated August 20, 2010.

2. The Offer expired at 12:00 midnight, New York City time on September 17, 2010. An aggregate of 30,810,778 Shares were validly tendered and not withdrawn (including certain Shares tendered under guaranteed delivery procedures), representing approximately 82.80% of the Issuer's outstanding Shares. On September 20, 2010, Purchaser accepted for payment all validly tendered and not withdrawn Shares (excluding certain Shares tendered under guaranteed delivery procedures). Purchaser is the owner of the Shares purchased in the Offer.

Remarks:

	/s/ Caroline B. Manogue, Executive Vice President, Chief Legal Officer and Secretary	09/20/2010
	/s/ Caroline B. Manogue, Executive Vice President, Chief Legal Officer and Secretary	09/20/2010
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 5 (b)(v).
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