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

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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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