SC 13G

SECURITIES AND EXCHANGE COMMISSION

Washington, DC  20549

SCHEDULE 13G

(Rule 13d-102)

INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO RULES 13d-1(b), (c), AND

(d) AND AMENDMENTS THERETO FILED PURSUANT TO RULE 13D-2

(Amendment No.  )*

Penwest Pharmaceuticals Co.

(Name of Issuer)

Common Stock, par value $0.001 per share

(Title of Class of Securities)

709754105

(CUSIP Number)

November 6, 2008

(Date of Event Which Requires Filing of This Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

o           Rule 13d-1(b)

ý           Rule 13d-1(c)

o           Rule 13d-1(d)

*The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

Page 1 of 8 pages

CUSIP No.  709754105				13G	Page 2 of 8 Pages
1	NAMES OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) TANG CAPITAL PARTNERS, LP
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*					(a)  ¨  (b)  ý
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION DELAWARE
NUMBER OF		5	SOLE VOTING POWER 0
SHARES BENEFICIALLY OWNED BY		6	SHARED VOTING POWER 1,626,196
EACH REPORTING PERSON WITH		7	SOLE DISPOSITIVE POWER 0
		8	SHARED DISPOSITIVE POWER 1,626,196
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 1,626,196
10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES ¨
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 5.1%
12	TYPE OF REPORTING PERSON PN

Page 2 of 8 pages

CUSIP No.  709754105				13G	Page 3 of 8 Pages
1	NAMES OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) TANG CAPITAL MANAGEMENT, LLC
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*					(a)  ¨  (b)  ý
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION DELAWARE
NUMBER OF		5	SOLE VOTING POWER 0
SHARES BENEFICIALLY OWNED BY		6	SHARED VOTING POWER 1,626,196
EACH REPORTING PERSON WITH		7	SOLE DISPOSITIVE POWER 0
		8	SHARED DISPOSITIVE POWER 1,626,196
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 1,626,196
10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES ¨
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 5.1%
12	TYPE OF REPORTING PERSON OO

Page 3 of 8 pages

CUSIP No.  709754105				13G	Page 4 of 8 Pages
1	NAMES OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) KEVIN C. TANG
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*					(a)  ¨  (b)  ý
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION UNITED STATES
NUMBER OF		5	SOLE VOTING POWER 0
SHARES BENEFICIALLY OWNED BY		6	SHARED VOTING POWER 1,626,196
EACH REPORTING PERSON WITH		7	SOLE DISPOSITIVE POWER 0
		8	SHARED DISPOSITIVE POWER 1,626,196
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 1,626,196
10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES ¨
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 5.1%
12	TYPE OF REPORTING PERSON IN

Page 4 of 8 pages

Item 1(a).	Name of Issuer:
	Penwest Pharmaceuticals Co., a Washington corporation (the “Issuer”)
Item 1(b).	Address of Issuer’s Principal Executive Offices:
	39 Old Ridgebury Road, Suite 11, Danbury, CT 06810
Item 2(a).	Name of Person Filing:
	This Statement on Schedule 13G (this “Statement”) is filed by Tang Capital Partners, LP (“Tang Capital Partners”); Tang Capital Management, LLC, the general partner of Tang Capital Partners (“Tang Capital Management”); and Kevin C. Tang, the manager of Tang Capital Management.
Item 2(b).	Address of Principal Business Office or, if none, Residence:
	4401 Eastgate Mall, San Diego, CA 92121
Item 2(c).	Citizenship:
	Tang Capital Partners is a Delaware limited partnership. Tang Capital Management is a Delaware limited liability company. Mr. Tang is a United States citizen.
Item 2(d).	Title of Class of Securities:
	Common Stock, par value $0.001 per share (the “Common Stock”)
Item 2(e).	CUSIP Number:  709754105

Item 3.	Not applicable.
Item 4.	Ownership.
	(a)	Amount Beneficially Owned:
		Tang Capital Partners.  Tang Capital Partners is the record and beneficial owner of 1,626,196 shares of Common Stock. Tang Capital Partners shares voting and dispositive power over such shares with Tang Capital Management and Kevin C. Tang.
		Tang Capital Management. Tang Capital Management, as the general partner of Tang Capital Partners, may be deemed to beneficially own the 1,626,196 shares held of record by Tang Capital Partners. Tang Capital Management shares voting and dispositive power over such shares with Tang Capital Partners and Kevin C. Tang.
		Kevin C. Tang.  Kevin C. Tang, as manager of Tang Capital Management, may be deemed to beneficially own the 1,626,196 shares held of record by Tang Capital Partners.  Mr. Tang shares voting and dispositive power over such shares with Tang Capital Partners and Tang Capital Management.
		Mr. Tang disclaims beneficial ownership of all shares reported herein except to the extent of his pecuniary interest therein.

Page 5 of 8 pages

	(b)	Percent of Class:
		Tang Capital Partners		5.1%
		Tang Capital Management		5.1%
		Kevin C. Tang		5.1%
	(c)	Number of shares as to which such person has:
		(i)	sole power to vote or to direct the vote:
			Tang Capital Partners	0 shares
			Tang Capital Management	0 shares
			Kevin C. Tang	0 shares
		(ii)	shared power to vote or to direct the vote:
			Tang Capital Partners	1,626,196 shares
			Tang Capital Management	1,626,196 shares
			Kevin C. Tang	1,626,196 shares
		(iii)	sole power to dispose or to direct the disposition of:
			Tang Capital Partners	0 shares
			Tang Capital Management	0 shares
			Kevin C. Tang	0 shares
		(iv)	shared power to dispose or to direct the disposition of:
			Tang Capital Partners	1,626,196 shares
			Tang Capital Management	1,626,196 shares
			Kevin C. Tang	1,626,196 shares
Item 5.	Ownership of Five Percent or Less of a Class.
	If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than five percent of the class of securities, check the following:   ¨
Item 6.	Ownership of More than Five Percent on Behalf of Another Person.
	Not applicable
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company.
	Not applicable.
Item 8.	Identification and Classification of Members of the Group.
	Not applicable.
Item 9.	Notice of Dissolution of Group.
	Not applicable.

Page 6 of 8 pages

Item 10.	Certification.
	By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect.

Page 7 of 8 pages

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Date:	November 17, 2008
TANG CAPITAL PARTNERS, LP
By:  Tang Capital Management, LLC, its General Partner
By:	/s/ Kevin C. Tang
	Kevin C. Tang, Manager
TANG CAPITAL MANAGEMENT, LLC
By:	/s/ Kevin C. Tang
	Kevin C. Tang, Manager
/s/ Kevin C. Tang
Kevin C. Tang

Page 8 of 8 pages

EX-99.1

Exhibit 99.1

JOINT FILING AGREEMENT

     In accordance with Rule 13d-1(k)(1) promulgated under the Securities Exchange Act of 1934, the undersigned agree to the joint filing of a Statement on Schedule 13G (including any and all amendments thereto) with respect to the Common Stock, $0.001 par value, of Penwest Pharmaceuticals Co. and further agree to the filing of this agreement as an exhibit thereto.  In addition, each party to this Agreement expressly authorizes each other party to this Agreement to file on its behalf any and all amendments to such Statement on Schedule 13G.

Date: November 17, 2008	TANG CAPITAL PARTNERS, LP
	By:	Tang Capital Management, LLC
	Its:	General Partner
	By:	/s/ Kevin C. Tang
		Name:	Kevin C. Tang
		Title:	Manager
	TANG CAPITAL MANAGEMENT, LLC
	By:	/s/ Kevin C. Tang
		Name:	Kevin C. Tang
		Title:	Manager
	/s/ Kevin C. Tang
	Name:	Kevin C. Tang