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EXPLANATORY NOTE

Deregistration of Securities

We originally registered 20,166,666 shares of our common stock pursuant to a Registration Statement on Form S-1 (File No. 333-150650) filed with the Securities and Exchange Commission (the “SEC”) on May 5, 2008, as most recently amended January 7, 2009, and subsequently declared effective by the SEC on January 9, 2009 (the “Registration Statement”). The Registration Statement related to the sale of shares of our common stock by Platinum-Montaur Life Sciences, LLC, named therein as the “selling stockholder,” upon the purchase of shares of our common stock through the conversion of promissory notes and shares of preferred stock, or the exercise of warrants.

We have filed this Post-effective Amendment No. 2 to the Registration Statement solely for the purpose of fulfilling the Company’s obligation under Item 512(a)(3) of Regulation S-K promulgated under the Securities Act of 1933, as amended, which requires that the Company remove from registration by means of a post-effective amendment any of the securities originally registered by the Registration Statement that remained unsold at the termination of the offering. The offering related to the Registration Statement terminated upon the selling stockholder’s surrender to us of the promissory notes and warrants pursuant to a Securities Amendment and Exchange Agreement. Pursuant to this Post-effective Amendment No. 2 to the Registration Statement, we are seeking to deregister 20,097,216 shares of our common stock that were registered pursuant to the Registration Statement and not sold prior to the termination of the offering. Therefore, in accordance with our undertaking contained in Part II of the Registration Statement, we hereby respectfully request that the Securities and Exchange Commission remove from registration those shares of common stock that were registered pursuant to the Registration Statement and remain unsold thereunder. The Registration Statement is hereby amended, as appropriate, to reflect the deregistration of such shares.

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