16. Subsequent events

In January 2013, Series A Warrants to purchase 520,776 shares of common stock were exercised resulting in gross proceeds of approximately $599,000.

On February 6, 2013, the facility agreement dated as of March 11, 2011 with Deerfield was amended to provide that the exercise price of the Deerfield Warrants may be satisfied through a reduction in the principal amount of our outstanding indebtedness to Deerfield. In February and March 2013, Deerfield exercised an aggregate of 6,000,000 warrants resulting in a reduction of our outstanding indebtedness to Deerfield of $7.5 million and, accordingly, cancellation of our obligation to make the 2014, 2015 and 2016 installment payments under the facility.