AKAO 2017 Annual Report

129 as to future awards. As of December 31, 2017, a total of 829,586 shares of common stock are subject to options outstanding under the 2003 plan, which shares will become available under the 2014 Plan to the extent the options are forfeited or lapse unexercised. Total stock-based compensation recognized in the Company’s consolidated statements of operations for the years ended December 31, 2017, 2016 and 2015, was classified as follows (in thousands): Year Ended December 31, 2017 2016 2015 Research and development........................................................... $ 6,340 $ 2,165 $ 1,404 General and administrative........................................................... 7,312 1,682 1,579 Total ............................................................................................. $ 13,652 $ 3,847 $ 2,983 Stock-based compensation expense for the year ended December 31, 2017 includes $0.7 million of expense that relates to the stock options and restricted stock units held by the former Chief Medical Officer, which were modified upon his resignation in March 2017. A summary of stock option activity is as follows: Outstanding Options Shares Available for grant Number of Shares Weighted- Average Exercise Price Weighted- Average Remaining Contractual Life (in years) Aggregate Intrinsic Value (in thousands) Balance, January 1, 2015 ....................................... 1,111,470 1,885,372 $ 7.95 Additional shares reserved ............................... 716,285 — Options granted ................................................ (929,100) 929,100 $ 7.95 Options exercised ............................................. — (190,128) $ 5.54 $ 923 Options forfeited............................................... 237,007 (237,007) $ 10.22 RSUs granted.................................................... (291,525) — RSUs cancelled................................................. 49,325 — Balance, December 31, 2015 ................................. 893,462 2,387,337 $ 7.92 $ 293 Additional shares reserved ............................... 1,235,808 — Options granted ................................................ (1,477,600) 1,477,600 $ 4.10 Options exercised ............................................. — (14,190) $ 4.59 $ 89 Options forfeited............................................... 310,454 (310,454) $ 8.19 RSUs granted.................................................... (380,500) — RSUs cancelled................................................. 57,750 — Balance, December 31, 2016 ................................. 639,374 3,540,293 $ 6.31 7.98 $ 23,837 Additional shares reserved ............................... 2,325,522 — Options granted ................................................ (1,806,157) 1,806,157 $ 21.12 Options exercised ............................................. — (227,444) $ 7.23 — Options forfeited............................................... 280,408 (280,408) $ 9.14 RSUs granted.................................................... (544,185) — RSUs cancelled................................................. 72,116 — Balance, December 31, 2017 ................................. 967,078 4,838,598 $ 11.63 7.69 $ 14,174 At December 31, 2017 Vested and exercisable ..................................... 2,074,120 $ 8.25 6.41 $ 7,705 Vested and expected to vest ............................. 4,704,835 $ 11.50 7.70 $ 14,005