The Company’s Amended 2013 Plan provides for the granting of stock options, restricted stock awards, restricted stock units, stock bonus awards and performance-based awards. As of June 30, 2016, the Company had 4,080,015 of authorized unissued shares reserved and available for issuance upon exercise and conversion of outstanding awards.

The stock options are exercisable at no less than the fair market value of the underlying shares on the date of grant, and restricted stock and restricted stock units are issued at a value not less than the fair market value of the common stock on the date of the grant. Generally, stock options awarded are vested in equal increments ranging from two to four years on the annual anniversary date on which such equity grants were awarded. The stock options generally have a maximum term of 10 years. The following table summarizes stock option activity for the Amended 2013 Plan during the six months ended June 30, 2016:

The following table summarizes unvested stock options as of June 30, 2016:

The Company recognized expenses of $412,557 and $557,792 relating to stock options issued to employees, consultants, officers, and directors during the three months ended June 30, 2016 and 2015, respectively. The Company recognized expenses of $817,708 and $1,723,786 relating to stock options issued to employees, consultants, officers, and directors during the six months ended June 30, 2016 and 2015, respectively. The Company recognized expenses of $258,125 and $308,900 relating to common stock issued to employees, consultants, officers, and directors during the three months ended June 30, 2016 and 2015, respectively. The Company recognized expenses of $433,125 and $898,900 relating to common stock issued to employees, consultants, officers, and directors during the six months ended June 30, 2016 and 2015, respectively. For the three months ended June 30, 2016 and 2015, stock-based compensation of $670,682 and $857,846, was expensed to selling, general and administration, respectively. For the six months ended June 30, 2016 and 2015, stock-based compensation of $1,250,833 and $2,601,173, was expensed to selling, general and administration, respectively. For the three months ended June 30, 2016 and 2015, stock-based compensation of $0 and $8,846, was expensed to research and development, respectively. For the six months ended June 30, 2016 and 2015, stock-based compensation of $0 and $21,513, was expensed to research and development, respectively. As of June 30, 2016, total unrecognized compensation cost related to non-vested stock-based compensation arrangements granted to employees, officers, and directors was $2,672,101, which is expected to be recognized over a weighted-average period of 1.96 years.