Note 4 - Equity 

In March 2018, the Company sold an aggregate of 30,237,894 units consisting of an aggregate of 30,237,894 shares of common stock, 7,559,445 series A warrants and 22,678,393 series B warrants, with each series A warrant exercisable for one share of Common Stock at an exercise price of $0.60 per share and each series B warrant exercisable for one share of Common Stock at an exercise price of $0.70 per share, resulting in gross proceeds to Actinium of approximately $15.1 million (each unit was sold at $0.50 per unit), and net proceeds of approximately $13.8 million after deducting expenses relating to dealer-manager fees and other offering expenses. As of September 30, 2018, in the event all of the warrants from the March 2018 offering were to be exercised, estimated gross proceeds would be $20.4 million before deducting any dealer-manager fees or expenses.

Stock Options

Following is a summary of stock option activity for the nine months ended September 30, 2018:

During the nine months ended September 30, 2018, the Company granted its employees 3,565,159 options to purchase the Company’s common stock with an exercise price ranging from $0.34 to $0.7829 per share, a term of 10 years, and a vesting period of 4 years. The options have an aggregated fair value of approximately $1.7 million that was calculated using the Black-Scholes option-pricing model. Variables used in the Black-Scholes option-pricing model include: (1) discount rate range from 2.34% to 2.94% (2) expected life of 6 years, (3) expected volatility range from 79.1% to 80.4%, and (4) no expected dividends. During the nine months ended September 30, 2018, options to purchase 1.1 million shares were cancelled upon the termination of employment for several employees.

The fair values of all options issued and outstanding are being amortized over their respective vesting periods. The unrecognized compensation expense at September 30, 2018 was approximately $3.2 million, which will be recognized over the remaining 3 years. During the nine months ended September 30, 2018 and 2017, the Company recorded compensation expense related to stock options of approximately $1.3 million and $2.5 million, respectively.

Warrants

Following is a summary of warrant activity for the nine months ended September 30, 2018:

In March 2018, the Company sold an aggregate of 30,237,894 units consisting of 30,237,894 shares of common stock, 7,559,445 series A warrants and 22,678,393 series B warrants. The series A warrants are exercisable for a period of 1 year at an exercise price of $0.60 per share. Relative fair value of the series A warrants of $0.5 million on the transaction date was determined utilizing the Black-Scholes option pricing model. Variables used in the Black-Scholes option-pricing model included: (1) discount rate of 2.06%, (2) expected term of 1 year, (3) expected volatility of 72%, and (4) no expected dividends. The series B warrants are exercisable for a period of 2.5 years at an exercise price of $0.70 per share. The transaction date relative fair value of the series B warrants of $2.5 million was determined utilizing the Black-Scholes option pricing model. Variables used in the Black-Scholes option-pricing model included: (1) discount rate of 2.33%, (2) expected term of 2.5 years, (3) expected volatility of 71%, and (4) no expected dividends.

In addition, during the nine months ended September 30, 2018, the Company issued to consultants warrants to purchase 120,628 shares of common stock, having an aggregate value of approximately $27 thousand and an exercise price range from $0.36 to $0.65.