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, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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(Print or Type Responses)

1. Name and Address of Reporting Person *   MPM BioVentures IV LLC 2. Date of Event Requiring Statement (Month/Day/Year) 05/17/2011 3. Issuer Name and Ticker or Trading Symbol Radius Health, Inc. [NONE] (Last) (First) (Middle) C/O MPM ASSET MANAGEMENT, 200 CLARENDON ST., 54TH FLOOR 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 Original Filed(Month/Day/Year) (Street) BOSTON, MA 02116 6. Individual or Joint/Group Filing(Check Applicable Line) ___ Form filed by One Reporting Person _X_ Form filed by More than One Reporting Person (City) (State) (Zip) 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)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.			SEC 1473 (7-02)
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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 of Derivative Security: 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 A-1 Convertible Preferred Stock	  (1)	  (1)	Common Stock	540,010	$ (1)	I	See footnote (2)
Series A-2 Convertible Preferred Stock	  (1)	  (1)	Common Stock	1,842,420	$ (1)	I	See footnote (2)

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
MPM BioVentures IV LLC C/O MPM ASSET MANAGEMENT 200 CLARENDON ST., 54TH FLOOR BOSTON, MA 02116	Â	  X	Â	Â
MPM BioVentures IV GP LLC C/O MPM ASSET MANAGEMENT 200 CLARENDON ST., 54TH FLOOR BOSTON, MA 02116	Â	  X	Â	Â
MPM Bio IV NVS Strategic Fund LP C/O MPM ASSET MANAGEMENT 200 CLARENDON ST., 54TH FLOOR BOSTON, MA 02116	Â	  X	Â	Â
DOMBKOWSKI ASHLEY L C/O MPM ASSET MANAGEMENT 601 GATEWAY BLVD., SUITE 350 SOUTH SAN FRANCISCO, CA 94080	Â	  X	Â	Â
Greene William C/O MPM ASSET MANAGEMENT 601 GATEWAY BLVD., SUITE 350 SOUTH SAN FRANCISCO, CA 94080	Â	  X	Â	Â
KAILIAN VAUGHN M C/O MPM ASSET MANAGEMENT 200 CLARENDON ST., 54TH FLOOR BOSTON, MA 02116	Â	  X	Â	Â
Scopa James Paul C/O MPM ASSET MANAGEMENT 601 GATEWAY BLVD., SUITE 350 SOUTH SAN FRANCISCO, CA 94080	Â	  X	Â	Â
St Peter Steven C/O MPM ASSET MANAGEMENT 200 CLARENDON ST., 54TH FLOOR BOSTON, MA 02116	Â	  X	Â	Â
Vander Vort John C/O MPM ASSET MANAGEMENT 200 CLARENDON ST., 54TH FLOOR BOSTON, MA 02116	Â	  X	Â	Â

Signatures

/s/ Luke Evnin, Member of MPM BioVentures IV LLC		05/19/2011
**Signature of Reporting Person		Date
/s/ Luke Evnin, Member of MPM BioVentures IV LLC, the general partner of MPM BioVentures IV GP LLC		05/19/2011
**Signature of Reporting Person		Date
/s/ Luke Evnin, Member of MPM BioVentures IV LLC, the general partner of MPM BioVentures IV GP LLC, the general partner of MPM Bio IV NVS Strategic Fund. L.P.		05/19/2011
**Signature of Reporting Person		Date
/s/ Ashley L. Dombkowski		05/19/2011
**Signature of Reporting Person		Date
/s/ William Greene		05/19/2011
**Signature of Reporting Person		Date
/s/ Vaughn M. Kailian		05/19/2011
**Signature of Reporting Person		Date
/s/ James Paul Scopa		05/19/2011
**Signature of Reporting Person		Date
/s/ Steven St. Peter		05/19/2011
**Signature of Reporting Person		Date
/s/ John Vander Vort		05/19/2011
**Signature of Reporting Person		Date

Explanation of Responses:

*	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).
(1)	Each share of Series A-1 Convertible Preferred Stock and Series A-2 Convertible Preferred Stock (collectively, the "Preferred Stock") has no expiration date and is convertible at any time, in whole or in part, at the election of the holder at a conversion ratio of 10 shares of Common Stock for every 1 share of Preferred Stock.
(2)	The shares are held by MPM Bio IV NVS Strategic Fund, L.P. ("MPM NVS"). MPM BioVentures IV GP LLC ("BV IV GP LLC") and MPM BioVentures IV LLC ("BV IV LLC") are the direct and indirect general partners of MPM NVS. Luke Evnin, Ansbert Gadicke, Ashley L. Dombkowski, Willliam Greene, Vaughn M. Kailian, James Paul Scopa, Steven St. Peter and John Vander Vort are the members of MPM NVS. Each reporting person disclaims beneficial ownership of the securities reported herein except to the extent of his, her or its respective pecuniary interest therein.

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