PBTH Prolor Biotech, Inc.

ITEM 1. Security and Issuer

This Amendment No. 9 to Schedule 13D (this “ Amendment ”) amends certain Items of the Schedule 13D filed with the Securities and Exchange Commission on June 21, 2007, as amended on April 7, 2008, August 22, 2008, November 12, 2008, February 10, 2009, March 6, 2009, August 3, 2009, October 29, 2010 and May 16, 2012 (the “ Schedule 13D ”), by furnishing the information set forth below. Except as set forth below, all previous Items are unchanged.

This Amendment is filed by Phillip Frost, M.D. (“ Dr. Frost ”) and Frost Gamma Investments Trust (the “ Gamma Trust ” and, together with Dr. Frost, the “ Reporting Persons ”) with respect to the common stock, par value $0.00001 per share (the “ Issuer Common Stock ”), of PROLOR Biotech, Inc, a Nevada corporation (the “ Issuer ”). The principal executive offices of the Issuer are located at 7 Golda Meir Street, Weizmann Science Park, Nes-Ziona, Israel 74140.

This Amendment is the final amendment to the Schedule 13D and constitutes an exit filing for the Reporting Persons.

ITEM 4. Purpose of Transaction.

Item 4 is hereby amended to add the following:

On August 29, 2013, the Issuer completed the previously announced merger (the “ Merger ”) of the Issuer and POM Acquisition, Inc., a Nevada corporation (“ Merger Sub ”) and wholly-owned subsidiary of OPKO Health, Inc., a Delaware corporation (“ Parent ”), in accordance with the Agreement and Plan of Merger, dated as of April 23, 2013, by and among the Issuer, Parent and Merger Sub. The Issuer continued as the surviving corporation in the Merger as a wholly-owned subsidiary of Parent. Pursuant to the terms and conditions of the Merger, at the effective time of the Merger, each share of Issuer Common Stock held by the Reporting Persons was cancelled and converted into the right to receive 0.9951 of a share (the “ Exchange Ratio ”) of common stock, par value $0.01 per share, of Parent (the “ Parent Common Stock ”). In addition, at the effective time of the Merger, each option to purchase shares of Issuer Common Stock held by the Reporting Persons prior to the Effective Time, whether or not vested, was converted into an option to purchase Parent Common Stock and was assumed by Parent in accordance with the terms of the applicable Issuer equity incentive plan and the terms of the contract evidencing such stock option. The number of shares of Parent Common Stock subject to each assumed Issuer stock option was adjusted to an amount equal to the product of (a) the number of shares of Issuer Common Stock subject to such Issuer stock option immediately before the Effective Time and (b) the Exchange Ratio, rounded down to the nearest whole share. The per share exercise price for shares of Parent Common Stock under each assumed Issuer stock option was adjusted to a price equal to the quotient of (a) the per share exercise price of such Issuer stock option and (b) the Exchange Ratio, rounded up to the nearest whole cent. In addition, pursuant to the stock option agreements governing the outstanding Issuer stock options, each Issuer stock option held by the Reporting Persons became fully vested and exercisable upon the consummation of the Merger.

As a result of the consummation of the Merger, the Reporting Persons are no longer the beneficial owners of any shares of Issuer Common Stock.

ITEM 5. Interest in Securities of the Issuer.

Paragraphs (a), (b), (c) and (e) of Item 5 are hereby amended and restated in their entirety as follows:

ITEM 7. Material to be Filed as Exhibits

SIGNATURES

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

EXHIBIT INDEX