Ownership Submission
FORM 4
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 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. Issuer Name and Ticker or Trading Symbol
Radius Health, Inc. [RDUS]
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 STREET, 54TH FLOOR
3. Date of Earliest Transaction (Month/Day/Year)
04/23/2013
(Street)

BOSTON, MA 02116
4. If Amendment, Date 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
(City)
(State)
(Zip)
Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1.Title of Security
(Instr. 3)
2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 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

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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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 (Month/Day/Year) 3A. Deemed Execution Date, if any (Month/Day/Year) 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
(Month/Day/Year)
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 B Convertible Preferred Stock (1) 04/23/2013   P   71,638 (2)     (1)   (1) Common Stock 716,380 $ 61.42 71,638 I See footnote (2)
Common Stock Warrant $ 6.142 04/23/2013   P   179,095 (2)   04/23/2013 04/23/2018 Common Stock 179,095 $ 6.142 179,095 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 STREET, 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    
Vander Vort John
C/O MPM ASSET MANAGEMENT
200 CLARENDON STREET, 54TH FLOOR
BOSTON, MA 02116
    X    
MPM BioVentures IV GP LLC
C/O MPM ASSET MANAGEMENT
200 CLARENDON STREET, 54TH FLOOR
BOSTON, MA 02116
    X    
MPM Bio IV NVS Strategic Fund LP
C/O MPM ASSET MANAGEMENT
200 CLARENDON STREET, 54TH FLOOR
BOSTON, MA 02116
    X    
Foley Todd
C/O MPM ASSET MANAGEMENT
200 CLAREDON STREET, 54TH FLOOR
BOSTON, MA 02116
    X    
KAILIAN VAUGHN M
C/O MPM ASSET MANAGEMENT
200 CLARENDON STREET, 54TH FLOOR
BOSTON, MA 02116
    X    

Signatures

 /s/ Luke Evnin, Member of MPM BioVentures IV LLC   04/30/2013
**Signature of Reporting Person Date

 /s/ James Paul Scopa   04/30/2013
**Signature of Reporting Person Date

 /s/ John Vander Vort   04/30/2013
**Signature of Reporting Person Date

 /s/ Luke Evnin, Member of MPM BioVentures IV LLC, the Managing Member of MPM BioVentures IV GP LLC   04/30/2013
**Signature of Reporting Person Date

 /s/ Luke Evnin, Member of MPM BioVentures IV LLC, the Managing Member of MPM BioVentures IV GP LLC, the general partner of MPM Bio IV NVS Strategic Fund. L.P.   04/30/2013
**Signature of Reporting Person Date

 /s/ Todd Foley   04/30/2013
**Signature of Reporting Person Date

 Vaughn M. Kailian   04/30/2013
**Signature of Reporting Person Date

Explanation of Responses:

* 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).
(1) Each share of Series B Convertible Preferred Stock has no expiration date and is convertible, in whole or in part, at the election of the holder at a conversion rate of 10 shares of Common Stock for every 1 share of Series B Convertible Stock.
(2) The shares and warrants 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, Todd Foley, Vaughn M. Kailian, James Paul Scopa and John Vander Vort are the members of BV IV LLC. Each reporting person disclaims beneficial ownership of the securities reported herein except to the extent of his or its respective pecuniary interest therein.

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