Viracta Investment	6 Months Ended
Jun. 30, 2020
Investments All Other Investments [Abstract]
Viracta Investment	4. Viracta Investment In March 2017, we participated in a Series B convertible preferred stock financing and invested $8.5 million in Viracta Therapeutics, Inc., or Viracta, a clinical stage drug development company. In May 2017, we executed an exclusive worldwide license with Viracta to develop and commercialize Viracta’s proprietary histone deacetylase inhibitor drug candidate for use in combination with natural killer cell therapy and possibly additional therapies. At June 30, 2020, our investment in Viracta totaled $9.3 million. Our investment in Viracta is reflected in equity investment on the condensed consolidated balance sheets. In June 2018, Viracta executed a 2018 Note and Warrant Purchase Agreement with existing and new investors, including us. The initial closing under the Purchase Agreement occurred in June 2018, at which point we purchased a convertible note for $0.4 million, which under certain circumstances was convertible into preferred stock of Viracta, and a warrant to purchase Viracta’s common shares. The convertible note accrued interest at 8% and had a one-year maturity date. In September 2018, a milestone closing under the Purchase Agreement occurred, at which point we purchased an additional convertible note for $0.4 million, which under certain circumstances was convertible into preferred stock of Viracta, and a warrant to purchase Viracta’s common shares. The convertible note accrued interest at 8% and had a one-year maturity date. We classified the convertible notes as held-to-maturity notes receivable on the consolidated balance sheets. Effective January 31, 2019, the notes, together with accrued interest then outstanding, were converted to Series B preferred stock resulting in an increase to our investment in Viracta’s Series B convertible preferred stock of $0.8 million. In May 2019, we exercised warrants to acquire 253,120 shares of Viracta common stock. At December 31, 2019, our investment in Viracta totaled $9.3 million. Based on the level of equity investment at risk, Viracta is not a VIE and therefore is not consolidated under the VIE Model. In addition, we do not hold a controlling financial interest in Viracta and therefore we do not consolidate Viracta under the voting interest model. As the preferred stock is not considered in-substance common stock, the investment is not within the scope of accounting for the investment under the equity method. As the preferred stock does not have a readily determinable fair value and does not qualify for the practical expedient to estimate fair value in accordance with ASC 820, we have elected to apply the measurement alternative under ASC 321, pursuant to which we measure our investment in Viracta at cost, less impairment, adjusted for observable price changes in an orderly market for an identical or similar investment of the same issuer. As of June 30, 2020, our qualitative impairment assessment did not indicate there were events or changes in circumstances that may have had a significant adverse effect on the fair value of the investment. We have not recorded any impairments as of June 30, 2020, or on a cumulative basis. Further, we have not identified any downward or upward adjustments due to observable price changes in the investment as of June 30, 2020, or on a cumulative basis.

Viracta Investment

6 Months Ended

Jun. 30, 2020

Investments All Other Investments [Abstract]

4. Viracta Investment

In March 2017, we participated in a Series B convertible preferred stock financing and invested $8.5 million in Viracta Therapeutics, Inc., or Viracta, a clinical stage drug development company. In May 2017, we executed an exclusive worldwide license with Viracta to develop and commercialize Viracta’s proprietary histone deacetylase inhibitor drug candidate for use in combination with natural killer cell therapy and possibly additional therapies. At June 30, 2020, our investment in Viracta totaled $9.3 million. Our investment in Viracta is reflected in equity investment on the condensed consolidated balance sheets.

In June 2018, Viracta executed a 2018 Note and Warrant Purchase Agreement with existing and new investors, including us. The initial closing under the Purchase Agreement occurred in June 2018, at which point we purchased a convertible note for $0.4 million, which under certain circumstances was convertible into preferred stock of Viracta, and a warrant to purchase Viracta’s common shares. The convertible note accrued interest at 8% and had a one-year maturity date. In September 2018, a milestone closing under the Purchase Agreement occurred, at which point we purchased an additional convertible note for $0.4 million, which under certain circumstances was convertible into preferred stock of Viracta, and a warrant to purchase Viracta’s common shares. The convertible note accrued interest at 8% and had a one-year maturity date. We classified the convertible notes as held-to-maturity notes receivable on the consolidated balance sheets. Effective January 31, 2019, the notes, together with accrued interest then outstanding, were converted to Series B preferred stock resulting in an increase to our investment in Viracta’s Series B convertible preferred stock of $0.8 million. In May 2019, we exercised warrants to acquire 253,120 shares of Viracta common stock. At December 31, 2019, our investment in Viracta totaled $9.3 million.

Based on the level of equity investment at risk, Viracta is not a VIE and therefore is not consolidated under the VIE Model. In addition, we do not hold a controlling financial interest in Viracta and therefore we do not consolidate Viracta under the voting interest model. As the preferred stock is not considered in-substance common stock, the investment is not within the scope of accounting for the investment under the equity method. As the preferred stock does not have a readily determinable fair value and does not qualify for the practical expedient to estimate fair value in accordance with ASC 820, we have elected to apply the measurement alternative under ASC 321, pursuant to which we measure our investment in Viracta at cost, less impairment, adjusted for observable price changes in an orderly market for an identical or similar investment of the same issuer.

As of June 30, 2020, our qualitative impairment assessment did not indicate there were events or changes in circumstances that may have had a significant adverse effect on the fair value of the investment. We have not recorded any impairments as of June 30, 2020, or on a cumulative basis. Further, we have not identified any downward or upward adjustments due to observable price changes in the investment as of June 30, 2020, or on a cumulative basis.