Sec Form 3 Filing - MPM BioVentures IV LLC @ Radius Health, Inc. - 2011-05-17

FORM 3 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP 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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1. Name and Address of Reporting Person MPM BioVentures IV LLC 2. Issuer Name and Ticker or Trading Symbol Radius Health, Inc. [ NONE] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O MPM ASSET MANAGEMENT, 200 CLARENDON ST., 54TH FLOOR 3. Date of Earliest Transaction (MM/DD/YY) 05/17/2011 (Street) BOSTON, MA02116 4. If Amendment, Date Original Filed (MM/DD/YY) 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 Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Series A-1 Convertible Preferred Stock ( 1 ) ( 1 ) ( 1 ) Common Stock 540,010 I See footnote ( 2 ) Series A-2 Convertible Preferred Stock ( 1 ) ( 1 ) ( 1 ) Common Stock 1,842,420 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, MA02116 X MPM BioVentures IV GP LLC C/O MPM ASSET MANAGEMENT 200 CLARENDON ST., 54TH FLOOR BOSTON, MA02116 X MPM Bio IV NVS Strategic Fund LP C/O MPM ASSET MANAGEMENT 200 CLARENDON ST., 54TH FLOOR BOSTON, MA02116 X DOMBKOWSKI ASHLEY L C/O MPM ASSET MANAGEMENT 601 GATEWAY BLVD., SUITE 350 SOUTH SAN FRANCISCO, CA94080 X Greene William C/O MPM ASSET MANAGEMENT 601 GATEWAY BLVD., SUITE 350 SOUTH SAN FRANCISCO, CA94080 X KAILIAN VAUGHN M C/O MPM ASSET MANAGEMENT 200 CLARENDON ST., 54TH FLOOR BOSTON, MA02116 X Scopa James Paul C/O MPM ASSET MANAGEMENT 601 GATEWAY BLVD., SUITE 350 SOUTH SAN FRANCISCO, CA94080 X St Peter Steven C/O MPM ASSET MANAGEMENT 200 CLARENDON ST., 54TH FLOOR BOSTON, MA02116 X Vander Vort John C/O MPM ASSET MANAGEMENT 200 CLARENDON ST., 54TH FLOOR BOSTON, MA02116 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:

( 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.

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 4(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).

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