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As filed with the Securities and Exchange Commission on November 7, 2012

Registration No. 333-179397

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549

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AMENDMENT NO. 3
to
FORM S-1
REGISTRATION STATEMENT
UNDER
THE SECURITIES ACT OF 1933

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Radius Health, Inc.
(Exact name of registrant as specified in its charter)

201 Broadway, 6th Floor
Cambridge, Massachusetts 02139
(617) 551-4700
(Address, including zip code, and telephone number, including
area code, of registrant's principal executive offices)

Michael S. Wyzga
Chief Executive Officer
Radius Health, Inc.
201 Broadway, 6th Floor
Cambridge, Massachusetts 02139
(617) 551-4700
(Name, address, including zip code, and telephone number, including area code, of agent for service)

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Copies To:

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Approximate date of commencement of proposed sale to the public:
As soon as practicable after this Registration Statement becomes effective.

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         If any of the securities being registered on this form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, check the following box. o

         If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. o

         If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. o

         If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. o

         Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See definitions of "large accelerated filer," "accelerated filer," and "smaller reporting company" in Rule 12b-2 of the Exchange Act. (Check one):

         The Registrant hereby amends this Registration Statement on such date or dates as may be necessary to delay its effective date until the Registrant shall file a further amendment which specifically states that this Registration Statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933 or until the Registration Statement shall become effective on such date as the Commission, acting pursuant to said Section 8(a), may determine.

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EXPLANATORY NOTE

        This Amendment No. 3 to the Registration Statement on Form S-1 (File No. 333-179397) of Radius Health, Inc., or the Registration Statement, is being filed solely for the purpose of filing an exhibit and updating information regarding expenses of the offering, as indicated in Part II of this Amendment No. 3. This Amendment No. 3 does not modify any provision of the prospectus that forms a part of the Registration Statement. Accordingly, a prospectus has been omitted.

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PART II
INFORMATION NOT REQUIRED IN PROSPECTUS

Item 13.    Other Expenses of Issuance and Distribution

        The following table sets forth the costs and expenses, other than underwriting discounts and commissions, payable in connection with the sale and distribution of the securities being registered. All amounts are estimated except the SEC registration fee, the FINRA filing fee and the NASDAQ Global Market listing fee.

Item 14.   Indemnification of Directors and Officers

        Section 145 of the Delaware General Corporation Law provides that a corporation may indemnify its directors and officers from certain expenses in connection with legal proceedings and permits a corporation to include in its charter documents, and in agreements between the corporation and its directors and officers, provisions expanding the scope of indemnification beyond that specifically provided by this section.

        The registrant's amended and restated bylaws provide for the indemnification of officers and directors if such persons act in good faith and in a manner reasonably believed to be in and not opposed to the registrant's best interest, and, with respect to any criminal action or proceeding, such indemnified party had no reason to believe his or her conduct was unlawful.

        In addition, the registrant has entered into separate indemnification agreements with the registrant's directors and executive officers which would require the registrant, among other things, to indemnify them against certain liabilities which may arise by reason of their status or service (other than liabilities arising from willful misconduct of a culpable nature). The indemnification provisions in the registrant's amended and restated bylaws and the indemnification agreements entered into between the registrant and the registrant's directors and executive officers may be sufficiently broad to permit indemnification of the registrant's directors and executive officers for liabilities (including reimbursement of expenses incurred) arising under the Securities Act. The registrant also intends to maintain director and officer liability insurance, if available on reasonable terms, to insure the registrant's directors and officers against the cost of defense, settlement or payment of a judgment under certain circumstances.

        The underwriting agreement will provide for indemnification by the underwriters of the registrant and the registrant's executive officers and directors, and indemnification of the underwriters by the registrant, for certain liabilities, including liabilities arising under the Securities Act of 1933, as amended, in connection with certain matters.

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Item 15.    Recent Sales of Unregistered Securities

        The following summarizes all sales of unregistered securities by the registrant since January 1, 2009:

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On May 17, 2011, the registrant issued 413,254 shares of A-1 convertible preferred stock, 983,208 shares of series A-2 convertible preferred stock, 142,227 shares of series A-3 convertible preferred stock, 3,998 shares of series A-4 convertible preferred stock, 6,443 shares of series A-5 convertible preferred stock and 555,594 shares of common stock, and a warrant to purchase 818 shares of series A-1 convertible preferred stock, in the Merger to the former stockholders of the Former Operating Company in exchange for shares held in the Former Operating Company pursuant to Section 4(2) of the Securities Act and Rule 506 to 34 accredited investors and 17 investors who were not accredited and who the registrant believed immediately prior to making any sale that each such purchaser had such knowledge and experience in financial and business matters as to be capable of evaluating the merits and risks of the prospective investment.



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On May 23, 2011, the registrant issued warrants to purchase an aggregate of 3,070 shares of series A-1 convertible preferred stock to two lenders, both of whom were accredited investors, in connection with a debt financing, pursuant to Section 4(2) of the Securities Act and Rule 506. No separate amount of consideration was paid for the issuance of the warrant under the loan agreement.



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On November 18, 2011, the registrant issued a warrant to purchase 818 shares of series A-1 preferred stock to Leerink Swann LLC as consideration for services rendered in connection with the series A-1 preferred stock financing pursuant to Section 4(2) of the Securities Act. No separate amount of consideration was paid for the issuance of the warrant under the agreement.



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On November 18, 2011, the registrant issued an aggregate of 263,178 shares of series A-1 preferred stock to accredited investors that were the former stockholders of the Former Operating Company pursuant to Section 4(2) of the Securities Act and Rule 506.



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On November 21, 2011, the registrant issued warrants for the purchase of up to an aggregate of 3,070 shares of series A-1 preferred stock to two lenders, pursuant to Section 4(2) of the Securities Act and Rule 506. No separate amount of consideration was paid for the issuance of the warrant under the loan agreement.



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On December 14, 2011, the registrant issued an aggregate of 263,180 shares of series A-1 preferred stock to accredited investors that were the former stockholders of the Former Operating Company pursuant to Section 4(2) of the Securities Act and Rule 506.



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On December 14, 2011, the registrant issued a warrant to purchase 818 shares of series A-1 preferred stock to Leerink Swann LLC as consideration for services rendered in connection with the series A-1 preferred stock financing pursuant to Section 4(2) of the Securities Act. No separate amount of consideration was paid for the issuance of the warrant under the agreement.



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On May 29, 2012, the registrant issued warrants for the purchase of up to an aggregate of 6,140 shares of series A-1 preferred stock to two lenders, pursuant to Section 4(2) of the Securities Act and Rule 506. No separate amount of consideration was paid for the issuance of the warrant under the loan agreement.

        The offers, sales, and issuances of the securities described above were deemed to be exempt from registration under the Securities Act in reliance on Section 4(2) of the Securities Act or Rule 506 of Regulation D promulgated thereunder as transactions by an issuer not involving a public offering. The recipients of securities in each of these transactions acquired the securities for investment only and not with a view to or for sale in connection with any distribution thereof and appropriate legends were affixed to the securities issued in these transactions. Each of the recipients of securities in these

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transactions had adequate access, through employment, business, stockholder, other relationships or the delivery of an information statement, to information about the registrant.

Item 16.    Exhibits and Financial Statements

(a)   Exhibits

        See the Exhibit Index beginning on page E-1, which follows the signature pages hereof and is incorporated herein by reference.

(b)   Financial Statement Schedules

        None.

Item 17.    Undertakings

        Insofar as indemnification for liabilities arising under the Securities Act may be permitted to directors, officers and controlling persons of the registrant pursuant to the provisions described in Item 14, or otherwise, the registrant has been advised that in the opinion of the SEC such indemnification is against public policy as expressed in the Securities Act and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the registrant of expenses incurred or paid by a director, officer or controlling person of the registrant in the successful defense of any action, suit or proceeding) is asserted by such director, officer or controlling person in connection with the securities being registered, the registrant will, unless in the opinion of the registrant's counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Securities Act and will be governed by the final adjudication of such issue.

        The undersigned registrant hereby undertakes that:

        (1)   For purposes of determining any liability under the Securities Act, the information omitted from the form of prospectus as filed as part of this registration statement in reliance upon Rule 430A and contained in a form of prospectus filed by the registrant pursuant to Rule 424(b)(1) or (4) or 497(h) under the Securities Act shall be deemed to be part of this registration statement as of the time it was declared effective.

        (2)   For the purpose of determining any liability under the Securities Act, each post-effective amendment that contains a form of prospectus shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

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SIGNATURES

        Pursuant to the requirements of the Securities Act of 1933, as amended, the registrant has duly caused this Amendment No. 3 to the Registration Statement on Form S-1 to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Cambridge, The Commonwealth of Massachusetts, on the 7th day of November, 2012.

        Pursuant to the requirements of the Securities Act of 1933, this statement has been signed by the following persons in the capacities indicated on the dates indicated.

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II-5

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EXHIBIT INDEX

E-1

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E-2

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E-3

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E-4

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E-5

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E-6

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E-7

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E-8

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EXPLANATORY NOTE
SIGNATURES
EXHIBIT INDEX