Subsequent Event	12 Months Ended
Dec. 31, 2018
Subsequent Event
Subsequent Event	13. Subsequent Event Genentech Agreement In February 2019, the Company entered into a collaboration and license agreement (the Genentech Agreement) with Genentech, Inc. and F. Hoffmann La-Roche Ltd. (collectively, Genentech) for the development and commercialization of novel IL-15 Collaboration Products, including XmAb24306, an IL-15/IL15Rα cytokine complex engineered with the Company’s bispecific Fc and Xtend technologies. The Company’s IL-15 bispecific cytokine platform provides a more druggable version of IL-15 with potentially superior tolerability, slower receptor-mediated clearance and a prolonged half-life, and is intended for development with a wide-range of combination agents due to its proposed mechanism of activating tumor-killing immune cells. Under the terms of the Genentech Agreement, Genentech received an exclusive worldwide license to XmAb24306 and other Collaboration Products, including any new IL-15 programs identified during the joint research collaboration. The Company will receive a non-refundable upfront payment of $120 million after the Genentech Agreement becomes effective and is eligible to receive up to an aggregate of $160 million in clinical milestone payments for each Collaboration Product that advances to Phase 3 clinical trials. The Company is eligible to receive a 45% share of net profits for sales of XmAb24306 and other Collaboration Products, while also sharing in the net losses at the same percentage rate. The parties will also jointly share development and commercialization costs at the same percentage rate, while Genentech will bear launch costs entirely. The profit/cost share is subject to ratchet at the Company’s discretion and convertible to a royalty under certain circumstances. The Company and Genentech will also conduct joint research activities for a two-year period to discover additional IL-15 candidates developed from the Company’s cytokine and bispecific Fc technologies. The Company will receive a $20 million development milestone for each new Collaboration Product that is identified from the research efforts and advances into a Phase 1 clinical trial. The Genentech Agreement is subject to customary closing conditions, including clearance under the Hart-Scott-Rodino Antitrust Improvements Act, and closing is expected to occur in the first quarter of 2019.

13. Subsequent Event

Genentech Agreement

In February 2019, the Company entered into a collaboration and license agreement (the Genentech Agreement) with Genentech, Inc. and F. Hoffmann La-Roche Ltd. (collectively, Genentech) for the development and commercialization of novel IL-15 Collaboration Products, including XmAb24306, an IL-15/IL15Rα cytokine complex engineered with the Company’s bispecific Fc and Xtend technologies. The Company’s IL-15 bispecific cytokine platform provides a more druggable version of IL-15 with potentially superior tolerability, slower receptor-mediated clearance and a prolonged half-life, and is intended for development with a wide-range of combination agents due to its proposed mechanism of activating tumor-killing immune cells.

Under the terms of the Genentech Agreement, Genentech received an exclusive worldwide license to XmAb24306 and other Collaboration Products, including any new IL-15 programs identified during the joint research collaboration. The Company will receive a non-refundable upfront payment of $120 million after the Genentech Agreement becomes effective and is eligible to receive up to an aggregate of $160 million in clinical milestone payments for each Collaboration Product that advances to Phase 3 clinical trials. The Company is eligible to receive a 45% share of net profits for sales of XmAb24306 and other Collaboration Products, while also sharing in the net losses at the same percentage rate. The parties will also jointly share development and commercialization costs at the same percentage rate, while Genentech will bear launch costs entirely. The profit/cost share is subject to ratchet at the Company’s discretion and convertible to a royalty under certain circumstances. The Company and Genentech will also conduct joint research activities for a two-year period to discover additional IL-15 candidates developed from the Company’s cytokine and bispecific Fc technologies. The Company will receive a $20 million development milestone for each new Collaboration Product that is identified from the research efforts and advances into a Phase 1 clinical trial.

The Genentech Agreement is subject to customary closing conditions, including clearance under the Hart-Scott-Rodino Antitrust Improvements Act, and closing is expected to occur in the first quarter of 2019.