Related Party Transactions	6 Months Ended
Jun. 30, 2017
Related Party Transactions [Abstract]
Related Party Transactions	7. Related Party Transactions *Collaborations with Intrexon* On January 6, 2011, the Company entered into the Channel Agreement with Intrexon (Note 6). A director of the Company, Randal J. Kirk, is the CEO, a director, and the largest stockholder of Intrexon. On February 3, 2015, Intrexon purchased 1,440,000 shares of common stock in the Company’s public offering upon the same terms as others that participated in the offering. On March 27, 2015, the Company and Intrexon entered into a Second Amendment to the Exclusive Channel Partner Agreement amending the Channel Agreement, which is referred to as the ECP Amendment. The ECP Amendment modified the scope of the parties’ collaboration under the Channel Agreement in connection with the worldwide License and Collaboration Agreement, or the Ares Trading Agreement, which the Company and Intrexon entered into with Ares Trading S.A., or Ares Trading, on March 27, 2015. The ECP Amendment provided that Intrexon will pay to the Company 50% of all payments that Intrexon receives for upfronts, milestones and royalties under the Ares Trading Agreement (Note 6). The Amendment also reduces Intrexon’s aggregate commitment under a Stock Purchase Agreement that the parties executed in connection with the initial Channel Agreement to purchase the Company’s common stock from $50.0 million to $43.5 million, which has been satisfied. On June 29, 2015, the Company re-purchased 3,711 shares of common stock from Intrexon, at a discount of 5% to the closing price of the Company’s common stock on the date of purchase, which represented fractional shares that resulted from Intrexon’s special stock dividend of the Company’s shares to Intrexon’s shareholders, for $34 thousand. On January 8, 2016, the Company re-purchased an additional 168 shares of common stock from Intrexon for $2 thousand at the same terms as the previous share purchase. On September 28, 2015, the Company entered into the GvHD Agreement with Intrexon, whereby the Company will use Intrexon’s technology directed towards in vivo expression of biologics to research, develop and commercialize products for use in the treatment or prevention of graft-versus-host disease, or GvHD (Note 6). The Company paid Intrexon a technology access fee of $10.0 million in cash in October 2015 and will reimburse Intrexon for all research and development costs. Subject to certain expense allocations and other offsets provided in the ECC Agreement, the ECC Agreement also provides for equal sharing of the profits derived from the sale of the Products. On June 29, 2016, the Company entered into a Third Amendment to Exclusive Channel Partner Agreement, or the 2016 ECP Amendment, with Intrexon, amending the Channel Agreement, and an Amendment to Exclusive Channel Collaboration Agreement, or the 2016 GvHD Amendment, amending their existing Exclusive Channel Collaboration Agreement, effective September 28, 2015, which the Company refers to as the GvHD Agreement. The 2016 ECP Amendment reduced the royalty percentage that the Company will pay to Intrexon under the Channel Agreement on a quarterly basis from 50% to 20% of net profits derived in that quarter from the sale of ZIOPHARM Products (as defined in the Channel Agreement), calculated on a ZIOPHARM Product-by-ZIOPHARM Product basis, subject to certain expense allocations and other offsets provided in the Channel Agreement. The 2016 GvHD Amendment reduced the royalty percentage that the Company will pay to Intrexon under the GvHD Agreement on a quarterly basis from 50% to 20% of net profits derived in that quarter from the sale of Products (as defined in the GvHD Agreement), subject to certain expense allocations and other offsets provided in the GvHD Agreement. The reductions in the royalty percentages provided by the 2016 ECP Amendment and the 2016 GvHD Amendment do not apply to sublicensing revenue or royalties under the Channel Agreement and GvHD Agreement, nor do they apply to any royalties or other payments made with respect to sublicensing revenue from the Company’s existing collaboration with Merck Serono, the biopharmaceutical business of Merck KGaA. In consideration for the execution and delivery of the 2016 ECP Amendment and the 2016 GvHD Amendment, the Company issued Intrexon 100,000 shares of its Series 1 preferred stock. Each share of the Company’s Series 1 preferred stock has a stated value of $1,200, subject to appropriate adjustment in the event of any stock dividend, stock split, combination or other recapitalization, and certain other rights, preferences, privileges and obligations (Note 9). The holders of the shares of Series 1 preferred stock are entitled to receive a monthly dividend, payable in additional shares of Series 1 preferred stock, equal to $12.00 per preferred share held by such holder per month divided by the stated value of the preferred shares, rounded down to the nearest whole share. During the three months ended June 30, 2017, the Company issued an aggregate of 3,313 shares of Series 1 preferred stock to Intrexon, the holder of all of the outstanding shares of the Company’s Series 1 preferred stock, as monthly dividend payments. The Company recorded such shares of Series 1 preferred stock at a fair value of $4.9 million, which is a component of temporary equity and recorded a gain on the change of the derivative liabilities in the amount of $66 thousand. See Notes 4 and 9 for additional discussion regarding the accounting for and valuation of these derivative financial instruments. During the six months ended June 30, 2017 and 2016, the Company expensed $11.2 million and $12.1 million, respectively, for services performed by Intrexon. As of June 30, 2017 and December 31, 2016 the Company recorded $3.7 million and $3.4 million, respectively, in current liabilities on its balance sheet for amounts due to Intrexon. *Collaboration with Intrexon and MD Anderson* On January 13, 2015, the Company, together with Intrexon, entered into a license agreement with MD Anderson, which is referred to as the MD Anderson License. Pursuant to the MD Anderson License, the Company and Intrexon hold an exclusive, worldwide license to certain technologies owned and licensed by MD Anderson, including technologies relating to novel CAR⁺ T cell therapies arising from the laboratory of Laurence Cooper, M.D., Ph.D., who is now the Company’s Chief Executive Officer and was formerly a professor of pediatrics at MD Anderson and now currently a visiting scientist under that institution’s policies, as well as either co-exclusive or non-exclusive licenses under certain related technologies. In partial consideration for entering into the MD Anderson License, the Company issued MD Anderson an aggregate of 11,722,163 shares of common stock for which the Company incurred a $67.3 million charge recorded in 2015. The Company has determined that the rights acquired in the MD Anderson License represent in-process research and development with no alternative future use. During the six months ending June 30, 2017, the Company made two quarterly payments totaling $6.2 million, bringing the total aggregate payments to $32.5 million under this arrangement.

7. Related Party Transactions

Collaborations with Intrexon

On January 6, 2011, the Company entered into the Channel Agreement with Intrexon (Note 6). A director of the Company, Randal J. Kirk, is the CEO, a director, and the largest stockholder of Intrexon.

On February 3, 2015, Intrexon purchased 1,440,000 shares of common stock in the Company’s public offering upon the same terms as others that participated in the offering.

On March 27, 2015, the Company and Intrexon entered into a Second Amendment to the Exclusive Channel Partner Agreement amending the Channel Agreement, which is referred to as the ECP Amendment. The ECP Amendment modified the scope of the parties’ collaboration under the Channel Agreement in connection with the worldwide License and Collaboration Agreement, or the Ares Trading Agreement, which the Company and Intrexon entered into with Ares Trading S.A., or Ares Trading, on March 27, 2015. The ECP Amendment provided that Intrexon will pay to the Company 50% of all payments that Intrexon receives for upfronts, milestones and royalties under the Ares Trading Agreement (Note 6). The Amendment also reduces Intrexon’s aggregate commitment under a Stock Purchase Agreement that the parties executed in connection with the initial Channel Agreement to purchase the Company’s common stock from $50.0 million to $43.5 million, which has been satisfied.

On June 29, 2015, the Company re-purchased 3,711 shares of common stock from Intrexon, at a discount of 5% to the closing price of the Company’s common stock on the date of purchase, which represented fractional shares that resulted from Intrexon’s special stock dividend of the Company’s shares to Intrexon’s shareholders, for $34 thousand. On January 8, 2016, the Company re-purchased an additional 168 shares of common stock from Intrexon for $2 thousand at the same terms as the previous share purchase.

On September 28, 2015, the Company entered into the GvHD Agreement with Intrexon, whereby the Company will use Intrexon’s technology directed towards in vivo expression of biologics to research, develop and commercialize products for use in the treatment or prevention of graft-versus-host disease, or GvHD (Note 6). The Company paid Intrexon a technology access fee of $10.0 million in cash in October 2015 and will reimburse Intrexon for all research and development costs. Subject to certain expense allocations and other offsets provided in the ECC Agreement, the ECC Agreement also provides for equal sharing of the profits derived from the sale of the Products.

On June 29, 2016, the Company entered into a Third Amendment to Exclusive Channel Partner Agreement, or the 2016 ECP Amendment, with Intrexon, amending the Channel Agreement, and an Amendment to Exclusive Channel Collaboration Agreement, or the 2016 GvHD Amendment, amending their existing Exclusive Channel Collaboration Agreement, effective September 28, 2015, which the Company refers to as the GvHD Agreement. The 2016 ECP Amendment reduced the royalty percentage that the Company will pay to Intrexon under the Channel Agreement on a quarterly basis from 50% to 20% of net profits derived in that quarter from the sale of ZIOPHARM Products (as defined in the Channel Agreement), calculated on a ZIOPHARM Product-by-ZIOPHARM Product basis, subject to certain expense allocations and other offsets provided in the Channel Agreement. The 2016 GvHD Amendment reduced the royalty percentage that the Company will pay to Intrexon under the GvHD Agreement on a quarterly basis from 50% to 20% of net profits derived in that quarter from the sale of Products (as defined in the GvHD Agreement), subject to certain expense allocations and other offsets provided in the GvHD Agreement. The reductions in the royalty percentages provided by the 2016 ECP Amendment and the 2016 GvHD Amendment do not apply to sublicensing revenue or royalties under the Channel Agreement and GvHD Agreement, nor do they apply to any royalties or other payments made with respect to sublicensing revenue from the Company’s existing collaboration with Merck Serono, the biopharmaceutical business of Merck KGaA.

In consideration for the execution and delivery of the 2016 ECP Amendment and the 2016 GvHD Amendment, the Company issued Intrexon 100,000 shares of its Series 1 preferred stock. Each share of the Company’s Series 1 preferred stock has a stated value of $1,200, subject to appropriate adjustment in the event of any stock dividend, stock split, combination or other recapitalization, and certain other rights, preferences, privileges and obligations (Note 9). The holders of the shares of Series 1 preferred stock are entitled to receive a monthly dividend, payable in additional shares of Series 1 preferred stock, equal to $12.00 per preferred share held by such holder per month divided by the stated value of the preferred shares, rounded down to the nearest whole share.

During the three months ended June 30, 2017, the Company issued an aggregate of 3,313 shares of Series 1 preferred stock to Intrexon, the holder of all of the outstanding shares of the Company’s Series 1 preferred stock, as monthly dividend payments. The Company recorded such shares of Series 1 preferred stock at a fair value of $4.9 million, which is a component of temporary equity and recorded a gain on the change of the derivative liabilities in the amount of $66 thousand. See Notes 4 and 9 for additional discussion regarding the accounting for and valuation of these derivative financial instruments.

During the six months ended June 30, 2017 and 2016, the Company expensed $11.2 million and $12.1 million, respectively, for services performed by Intrexon. As of June 30, 2017 and December 31, 2016 the Company recorded $3.7 million and $3.4 million, respectively, in current liabilities on its balance sheet for amounts due to Intrexon.

Collaboration with Intrexon and MD Anderson

On January 13, 2015, the Company, together with Intrexon, entered into a license agreement with MD Anderson, which is referred to as the MD Anderson License. Pursuant to the MD Anderson License, the Company and Intrexon hold an exclusive, worldwide license to certain technologies owned and licensed by MD Anderson, including technologies relating to novel CAR⁺ T cell therapies arising from the laboratory of Laurence Cooper, M.D., Ph.D., who is now the Company’s Chief Executive Officer and was formerly a professor of pediatrics at MD Anderson and now currently a visiting scientist under that institution’s policies, as well as either co-exclusive or non-exclusive licenses under certain related technologies. In partial consideration for entering into the MD Anderson License, the Company issued MD Anderson an aggregate of 11,722,163 shares of common stock for which the Company incurred a $67.3 million charge recorded in 2015. The Company has determined that the rights acquired in the MD Anderson License represent in-process research and development with no alternative future use. During the six months ending June 30, 2017, the Company made two quarterly payments totaling $6.2 million, bringing the total aggregate payments to $32.5 million under this arrangement.