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

OMB APPROVAL OMB Number: 3235-0104 Estimated average burden hours per response: 0.5

1. Name and Address of Reporting Person* INTERWEST PARTNERS X LP (Last) (First) (Middle) 2710 SAND HILL ROAD, SUITE 200 (Street) MENLO PARK CA 94025 (City) (State) (Zip)	2. Date of Event Requiring Statement (Month/Day/Year) 06/27/2012	3. Issuer Name and Ticker or Trading Symbol TESARO, Inc. [ TSRO ]
		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
Series B Preferred Stock	(1)	(1)	Common Stock	2,627,257	(1)	D(2)

1. Name and Address of Reporting Person* INTERWEST PARTNERS X LP (Last) (First) (Middle) 2710 SAND HILL ROAD, SUITE 200 (Street) MENLO PARK CA 94025 (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* CASH HARVEY B (Last) (First) (Middle) 2710 SAND HILL ROAD, SUITE 200 (Street) MENLO PARK CA 94025 (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* CLEVELAND BRUCE A (Last) (First) (Middle) 2710 SAND HILL ROAD, SUITE 200 (Street) MENLO PARK CA 94025 (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* Ehrlich Christopher B (Last) (First) (Middle) 2710 SAND HILL ROAD, SUITE 200 (Street) MENLO PARK CA 94025 (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* GIANOS PHILIP T (Last) (First) (Middle) 2710 SAND HILL ROAD, SUITE 200 (Street) MENLO PARK CA 94025 (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* Kjellson Nina S (Last) (First) (Middle) 2710 SAND HILL ROAD, SUITE 200 (Street) MENLO PARK CA 94025 (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* Kliman Gilbert H (Last) (First) (Middle) 2710 SAND HILL ROAD, SUITE 200 (Street) MENLO PARK CA 94025 (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* Pepper Douglas A (Last) (First) (Middle) 2710 SAND HILL ROAD, SUITE 200 (Street) MENLO PARK CA 94025 (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* Holmes W Stephen (Last) (First) (Middle) 2710 SAND HILL ROAD, SUITE 200 (Street) MENLO PARK CA 94025 (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 reported securities are convertible at any time, in whole or in part, at the option of the holder, have no expiration date, and will convert into shares of common stock immediately prior to the closing of the Issuer's initial public offering.

2. The shares are owned by InterWest Partners X, LP ("IW10"). InterWest Management Partners X, LLC ("IMP10") is the general partner of IW10. Harvey B. Cash, Bruce A. Cleveland, Christopher B. Ehrlich, Philip T. Gianos, W. Stephen Holmes, Nina S. Kjellson, Gilbert H. Kliman, Arnold L. Oronsky, Douglas A. Pepper and Thomas L. Rosch are managing directors of IMP10. Keval Desai and Khaled A. Nasr are venture members of IMP10. Each managing director and venture member of IMP10 disclaims beneficial ownership of such shares, except to the extent of their pecuniary interest therein.

Remarks:

Due to limitations of the EDGAR software, this Form 3 is filed on behalf of InterWest Partners X, LP and certain other Reporting Persons, and is being filed on two Forms 3 (Part I and Part II) (collectively, the ''InterWest Form 3''). This filing represents Part I of the InterWest Form 3 and should be read together with Part II. Part I and Part II of the InterWest Form 3 shall constitute one filing. Exhibit List Exhibit 24.1- Power of Attorney of Harvey B. Cash Exhibit 24.2- Power of Attorney of Bruce A. Cleveland Exhibit 24.3- Power of Attorney of Christopher B. Ehrlich Exhibit 24.4- Power of Attorney of Philip T. Gianos Exhibit 24.5- Power of Attorney of Nina Kjellson Exhibit 24.6- Power of Attorney of Gilbert H. Kliman Exhibit 24.7- Power of Attorney of Douglas A. Pepper Exhibit 99 - Form 3 Joint Filer Information

	/s/ W. Stephen Holmes, Managing Director	06/27/2012
	/s/ Harvey B. Cash by Karen A. Wilson Power of Attorney	06/27/2012
	/s/ Bruce A. Cleveland by Karen A. Wilson Power of Attorney	06/27/2012
	/s/ Christopher B. Ehrlich by Karen A. Wilson Power of Attorney	06/27/2012
	/s/ Philip T. Gianos by Karen A. Wilson Power of Attorney	06/27/2012
	/s/ W. Stephen Holmes	06/27/2012
	/s/ Nina Kjellson by Karen A. Wilson Power of Attorney	06/27/2012
	/s/ Gilbert H. Kliman by Karen A. Wilson Power of Attorney	06/27/2012
	/s/ Douglas A. Pepper by Karen A. Wilson Power of Attorney	06/27/2012
	** 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).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.