The investment provides Innoviva the ability to have significant influence, but not control over Armata’s operations. Based on our evaluation, we determined that Armata is a VIE, but Innoviva is not the primary beneficiary of the VIE. We elected the fair value option to account for both Armata’s common stock and warrants. The fair value of Armata’s common stock is measured based on its closing market price. The warrants have an exercise price of $2.87 per share, are exercisable immediately within five years from the issuance date of the warrants, and include a cashless exercise option. We use the Black-Scholes-Merton pricing model to estimate the fair value of these warrants with the following input assumptions: Armata’s closing market price on the valuation date, the risk-free interest rate computed based on the U.S. Treasury yield, the remaining contractual term as the expected term, and the expected stock price volatility calculated based on the historical volatility of the common stock of Armata and its peer companies.
As of September 30, 2020, the fair values of Armata’s common stock and warrants were estimated at $27.8 million and $20.2 million, respectively. The total fair value of both financial instruments in the amount of $48.0 million was recorded as equity investments on the consolidated balance sheets as of September 30, 2020. We recorded $12.4 million in unrealized loss and $23.0 million in unrealized gain from fair value changes in Armata’s investments as changes in fair values of equity investments, net on the consolidated statements of income for the three and nine months ended September 30, 2020, respectively.
Equity Investment in Entasis
On April 12, 2020, we entered into a securities purchase agreement with Entasis (“April 2020 Entasis Agreement”) to purchase 14,000,000 shares of Entasis common stock as well as warrants to purchase 14,000,000 additional shares of its common stock for approximately $35.0 million in cash. Entasis is a clinical-stage biotechnology company focused on the discovery and development of novel antibacterial products. The investment is to support Entasis's ongoing advancement of its pathogen-targeted antibacterial product candidates, which include their global Phase 3 registration trial evaluating a fixed-dose combination of sulbactam and durlobactam (SUL-DUR) against Acinetobacter baumanii infections.
The investment was closed in two tranches on April 22, 2020 and June 11, 2020. Innoviva has a right to designate two members to Entasis's board. After the second closing, we owned approximately 51.3% of Entasis's common stock.
On August 27, 2020, we entered into another securities purchase agreement with Entasis ("August 2020 Entasis Agreement") to purchase 4,672,897 shares of Entasis common stock as well as warrants to purchase 4,672,897 additional shares of its common stock for approximately $12.5 million in cash. On September 1, 2020, we completed the purchase and increased our ownership in Entasis's common stock to 52.6%.
The investment provides Innoviva the ability to have significant influence, but not control, over Entasis's operations. Based on our evaluation, we determined that Entasis is a VIE, but Innoviva is not the primary beneficiary of the VIE. We elected the fair value option to account for both Entasis's common stock and warrants at fair value. The fair value of Entasis's common stock is measured based on its closing market price at each balance sheet date. The warrants have an exercise price of $2.50 per share under the April 2020 Entasis Agreement and an exercise price of $2.675 under the August 2020 Entasis Agreement. The warrants are exercisable immediately within five years from the issuance date of the warrants and include a cashless exercise option. We use the Black-Scholes-Merton pricing model to estimate the fair value of these warrants with the following input assumptions: Entasis's closing market price on the valuation date, the risk-free interest rate computed based on the U.S. Treasury yield, the remaining contractual term as the expected term, and the expected stock price volatility calculated based on the historical volatility of the common stock of Entasis and its peer companies.
As of September 30, 2020, the fair values of Entasis's common stock and warrants were estimated at $38.1 million and $25.7 million, respectively. The total fair value of both financial instruments in the amount of $63.8 million was recorded as equity investments on the consolidated balance sheets. We recorded $17.0 million in unrealized loss and $16.3 million in unrealized gain from fair value changes in Entasis's investments as changes in fair values of equity investments, net on the consolidated statements of income for the three and nine months ended September 30, 2020, respectively.