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* Warburg Pincus Partners LLC (Last) (First) (Middle) 466 LEXINGTON AVENUE (Street) NEW YORK NY 10017 (City) (State) (Zip)	2. Date of Event Requiring Statement (Month/Day/Year) 01/25/2006	3. Issuer Name and Ticker or Trading Symbol Altus Pharmaceuticals Inc. [ ALTU ]
		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)

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
Warrants	05/21/2004	05/21/2011	Series C Convertible Preferred Stock(1)(2)	1,630,914	$4.31	D(3)
Series C Convertible Preferred Stock	05/21/2004	01/31/2006(4)	Common Stock(2)	3,263,251	$0.00(2)	D(3)

1. Name and Address of Reporting Person* Warburg Pincus Partners LLC (Last) (First) (Middle) 466 LEXINGTON AVENUE (Street) NEW YORK NY 10017 (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* WARBURG PINCUS LLC (Last) (First) (Middle) 466 LEXINGTON AVENUE (Street) NEW YORK NY 10017 (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* WARBURG PINCUS & CO (Last) (First) (Middle) 466 LEXINGTON AVENUE (Street) NEW YORK NY 10017 (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. The Series C Convertible Preferred Stock is convertible into Common Stock.

2. Series C Convertible Preferred Stock converts to common stock on a 1-for-0.44077 basis.

3. The stockholder is Warburg Pincus Private Equity VIII, L.P. ("WP VIII"). Warburg Pincus Partners, LLC ("WPP LLC"), a subsidiary of Warburg Pincus & Co. ("WP"), is the sole general partner of WP VIII. WP VIII is managed by Warburg Pincus LLC ("WP LLC"). The address of the Warburg Pincus entities is 466 Lexington Avenue, New York, New York 10017. Jonathan S. Leff and Stewart J. Hen, directors of the Company, are general partners of WP and managing directors and members of WP LLC. Messrs. Leff and Hen disclaim beneficial ownership of all shares held by the Warburg Pincus entities. Charles R. Kaye and Joseph P. Landy are Managing General Partners of WP and Managing Members of WP LLC and may be deemed to control the Warburg Pincus entities. Messrs. Kaye and Landy disclaim beneficial ownership of all shares held by the Warburg Pincus entities.

4. This is the anticipated date of the closing of the Issuer's initial public offering, which will trigger the mandatory conversion of the Series C Convertible Preferred Stock into common stock.

Remarks:

	/s/ Scott Arenare	02/02/2006
	Scott Arenare	02/02/2006
	Scott Arenare	02/02/2006
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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