During 2015, 2014 and 2013, we paid interest aggregating $4.6 million, $2.9 million and $1.9 million, respectively.  During 2013, we issued 100,000 shares of our common stock valued at $166,000 as partial payment of a milestone fee.  During 2015, 2014, and 2013, we issued 68,157, 36,455 and 22,126 shares of our common stock, respectively, as matching contributions to our 401(k) Plan which were valued at $117,000, $100,000 and $67,000, respectively.  During 2015, 2014 and 2013, we recorded $1.0 million, $2.4 million and $1.0 million, respectively, of end-of-term fees associated with our notes payable to CRG, Oxford and GECC/MidCap.

During 2013, the Company and Platinum entered into an Exercise Agreement, pursuant to which Platinum exercised its Series X Warrant and Series AA Warrant for 2,364.9 shares of the Company’s Series B Preferred Stock.  These warrants were exercised on a cashless basis by canceling a portion of the indebtedness outstanding under the Platinum Loan Agreement equal to $4.8 million, the aggregate exercise price of the warrants.  Also during 2013, in conjunction with the GECC/MidCap Loan Agreement and the Crede Securities Purchase Agreement, we issued warrants with estimated fair values of $631,000 and $7.7 million, respectively.

During 2014, in connection with the Oxford Loan Agreement, we issued warrants with an estimated relative fair value of $465,000.  Also during 2014, in connection with entering into the R-NAV joint enterprise, Navidea executed a promissory note in the principal amount of $666,666, payable in two equal installments on July 15, 2015 and July 15, 2016, the first and second anniversaries of the R-NAV transaction.  See Note 10.

In connection with their initial investment in March 2015, the investors in MT were issued warrants that have been determined to be derivative liabilities with an estimated fair value of $63,000.  A $46,000 deemed dividend related to the beneficial conversion feature within the MT Preferred Stock was also recorded at the time of the initial investment in MT.