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

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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