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Stock-Based Compensation (Tables)
9 Months Ended
Sep. 30, 2016
Summary of Stock-based Compensation Expense Recognized

During the three and nine months ended September 30, 2016 and 2015, the Company recognized the following stock-based compensation expense:

 

 

 

Three Months Ended September 30,

 

Nine Months Ended September 30,

 

 

 

2016

 

 

2015

 

 

 

 

2016

 

 

2015

 

Stock-based compensation expense by type of award:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Stock options

 

$

154,228

 

 

$

373,881

 

 

 

 

$

762,067

 

 

$

725,572

 

Restricted stock and restricted stock units

 

 

158,931

 

 

 

227,712

 

 

 

 

 

644,979

 

 

 

1,348,432

 

Employee stock purchase plan

 

 

7,794

 

 

 

 

 

 

 

 

28,706

 

 

 

 

Total stock-based compensation expense included

   in expenses

 

$

320,953

 

 

$

601,593

 

 

 

 

$

1,435,752

 

 

$

2,074,004

 

Stock-based compensation expense by line item:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Research and development expenses

 

$

60,202

 

 

$

164,125

 

 

 

 

$

1,006,781

 

 

$

665,226

 

General and administrative expenses

 

 

260,751

 

 

 

437,468

 

 

 

 

 

428,971

 

 

 

1,408,778

 

Total stock-based compensation expense included

   in expenses

 

$

320,953

 

 

$

601,593

 

 

 

 

$

1,435,752

 

 

$

2,074,004

 

 

 

 

Schedule of Unrecognized Stock-based Compensation Expense, Net of Estimated Forfeitures, by Type of Award and Weighted-average Recognition Period

The following table sets forth the Company’s unrecognized stock-based compensation expense, net of estimated forfeitures, by type of award and the weighted-average period over which that expense is expected to be recognized:

 

 

 

As of September 30, 2016

 

 

 

Unrecognized

Expense,

Net of

Estimated

Forfeitures

 

 

Weighted-

average

Recognition

Period

(in years)

 

 

 

 

 

 

 

 

 

 

Type of award:

 

 

 

 

 

 

 

 

Stock options

 

$

1,272,626

 

 

 

2.55

 

Restricted stock and restricted stock units

 

$

1,354,388

 

 

 

1.93

 

 

Summary of Stock Option Activity

The following table summarizes stock option activity during the nine months ended September 30, 2016:

 

 

 

Shares Subject to Stock Options

 

 

Weighted-

Average

Exercise

Price

 

 

Weighted-

Average

Remaining

Contractual

Term (in years)

 

Options outstanding at December 31, 2015

 

 

365,394

 

 

$

8.48

 

 

 

 

 

Granted

 

 

520,818

 

 

$

2.17

 

 

 

 

 

Exercised

 

 

 

 

$

 

 

 

 

 

Cancelled

 

 

(50,250

)

 

$

4.34

 

 

 

 

 

Options outstanding at September 30, 2016

 

 

835,962

 

 

$

4.80

 

 

 

8.95

 

Options exercisable at September 30, 2016

 

 

291,824

 

 

$

6.30

 

 

 

8.46

 

 

Schedule of Weighted Average Assumptions using Black-Scholes Option Pricing Model

The fair value of each employee option grant during the nine months ended September 30, 2016 was estimated on the date of grant using the Black-Scholes option pricing model with the following weighted average assumptions:

 

 

 

Nine months ended September 30, 2016

 

Expected volatility

 

 

81.77

%

Expected term (in years)

 

 

5.92

 

Risk-free interest rate

 

 

1.51

%

Expected dividend yield

 

 

0

%

 

Restricted stock [Member]  
Summary of Stock Activity

The following table is a summary of restricted stock activity during the nine months ended September 30, 2016:

 

 

 

Shares of Restricted Stock

 

 

Weighted-

Average

Grant Date

Fair Value

 

Unvested at December 31, 2015

 

 

667,963

 

 

$

3.73

 

Granted

 

 

 

 

$

 

Vested

 

 

(108,218

)

 

$

7.48

 

Forfeited

 

 

(69,554

)

 

$

6.37

 

Repurchased

 

 

 

 

$

 

Unvested at September 30, 2016

 

 

490,191

 

 

$

2.53

 

 

 

 

Restricted stock units [Member]  
Summary of Stock Activity

The following table summarizes restricted stock unit activity during the nine months ended September 30, 2016:

 

 

 

Shares Subject to Restricted Stock Units

 

 

Weighted-

Average

Grant Date

Value

 

Unvested at December 31, 2015

 

 

75,750

 

 

$

8.27

 

Granted

 

 

 

 

$

 

Vested

 

 

(18,937

)

 

$

8.27

 

Forfeited

 

 

 

 

$

 

Repurchased

 

 

 

 

$

 

Unvested September 30, 2016

 

 

56,813

 

 

$

8.27