EXPLANATORY NOTE

This Post-Effective Amendment No. 1 to Form S-1 (this “Post-Effective Amendment) is being filed pursuant to Section 10(a)(3) of the Securities Act of 1933, as amended (the “Securities Act”), to update the Registration Statement on Form S-1 (No. 333-205519), which was previously declared effective by the Securities and Exchange Commission (the “Commission”) on July 20, 2015. The Post-Effective Amendment includes (i) the Registrant’s audited financial statements and the notes thereto included in the Registrant’s Annual Report on Form 10-K for the fiscal year ended December 31, 2015, as filed with the Commission on March 30, 2016 and (ii) an updated prospectus relating to the offering and sale of the securities described therein.

Pursuant to Rule 429(b) under the Securities Act, this Post-Effective Amendment to Registration Statement No. 333-205519 shall also act, upon effectiveness, as a post-effective amendment to the Registrant’s Registration Statement on Form S-1 (No. 333-200033). The prospectus originally included in Registration Statement No. 333-205519, and the prospectus included in this Post-Effective Amendment, is a single combined prospectus relating to (i) the issuance of certain securities of the Registrant upon exercise of Unit Purchase Options and common stock purchase warrants originally registered pursuant to Registration Statement No. 333-200033, which was initially declared effective by the Commission on December 18, 2014, and (ii) a secondary offering of the Registrant’s common stock initially registered on Registration Statement No. 333-205519.

All applicable registration fees were paid at the time of the original filing of the Registration Statements No. 333-200033 and No. 333-205519 on November 10, 2014, and July 6, 2015, respectively.