Collaboration and Licensing Agreements	9 Months Ended
Sep. 30, 2018
Licensing Agreements [Abstract]
Collaboration and Licensing Agreements	9. Collaboration and Licensing Agreements Incyte Collaboration and License Agreement On January 27, 2017, the Company entered into a collaboration and license agreement with Incyte (the “Incyte Collaboration Agreement”). Under the terms of the Incyte Collaboration Agreement, the Company granted Incyte an exclusive, worldwide license to develop and commercialize its small molecule arginase inhibitors for hematology and oncology indications. The parties are collaborating on and co-funding the development of the licensed products, with Incyte bearing 70% and the Company bearing 30% of global development costs. The parties will share profits and losses in the United States, with 60% to Incyte and 40% to the Company. The Company will have the right to co-detail the licensed products in the United States, and Incyte will pay the Company tiered royalties ranging from the low to mid-double digits on net sales of licensed products outside the United States. The Company may opt out of its co-funding obligation, in which case the United States profit sharing will no longer be in effect, and Incyte will pay the Company tiered royalties ranging from the low to mid-double digits on net sales of licensed products both in the United States and outside the United States, and additional royalties to reimburse the Company for previously incurred development costs. Under the Incyte Collaboration Agreement, the Company received an upfront payment of $45.0 million in February 2017. In March 2017, the Company achieved a development milestone of $12.0 million, for which the Company received payment in May of 2017. The Company is also eligible to receive up to an additional $418.0 million in potential development, regulatory and sales milestones. Incyte and the Company will share in any future United States net profits and losses, with the Company bearing 40% and Incyte bearing 60%, respectively, and outside the United States the Company will be eligible to receive from Incyte tiered royalties, with rates in the low to mid-teens of sales. The Incyte Collaboration Agreement also provides that the Company may choose to opt out of its co-funding obligations at any time. In this scenario, the potential development, regulatory and commercialization milestones from Incyte will be up to an additional $738.0 million. The Company would no longer be eligible to receive future United States profits and losses but would be eligible to receive tiered royalty payments on future global sales, including United States sales. In addition, if the Company opts out, the Company will receive an incremental 3% royalty on annual net sales in the United States of such licensed product until such incremental royalty equals 120% of previous development expenditures incurred by the Company. The Incyte Collaboration Agreement is considered to be under the scope of FASB Topic 808, Collaborative Arrangements. The Company has concluded that the research and development co-funding activities were not representative of a customer relationship and this unit of account is accounted for as an increase to or reduction of research and development expenses, rather than as revenue. The performance obligations under the Incyte Collaboration Agreement consist of intellectual property licenses and the performance of certain manufacturing and manufacturing technology transfer services. The Company has determined that the license is not distinct from the associated manufacturing and technology transfer services to be performed under the agreement. Specifically, the Company believes the license is not capable of being distinct, as Incyte did not have the know-how to manufacture the collaboration product without Calithera’s assistance until completion of the manufacturing technology transfer process, and no other third parties could perform such assistance due to the early stage nature of the licensed intellectual property as well as Calithera’s propriety knowledge with respect to the licensed intellectual property. Prior to the adoption of ASC 606, the Company concluded that the delivered licenses did not have stand-alone value, and the rights conveyed to Incyte did not permit Incyte to perform all efforts necessary to use the Company’s technology to bring the compound through development and, upon regulatory approval, commercialization of the compound, without the associated manufacturing and technology transfer services. Accordingly, the Company combined these deliverables and allocated the upfront consideration of $45.0 million to the combined unit of accounting. The Company recognized the $45.0 million upfront payment on a straight-line basis over the estimated period of performance under the Incyte Collaboration Agreement, and recognized the $12.0 million developmental milestone payment from Incyte on a straight-line basis over the remaining period of performance for the combined unit of accounting. For the three and nine months ended September 30, 2017, the Company recognized revenue from its collaboration with Incyte totaling $7.3 million and $18.7 million, respectively, related to amortization of the $45.0 million upfront fee and the $12.0 million milestone. Upon the adoption of ASC 606 on January 1, 2018 under the modified retrospective approach, the transaction price was determined to be $57.0 million, representing the $45.0 million upfront payment and the $12.0 million developmental milestone payment from Incyte that was earned in March 2017. The $57.0 million transaction price was recognized over the performance period, based on the measure of progress toward completion for the combined performance obligation, rather than on a straight-line basis. The measure of progress towards completion was based on the effort of certain employees within the Company who dedicated time to complete the manufacturing services and technology transfer to Incyte. As of June 30, 2018, the manufacturing services and technology transfer to Incyte were determined to be substantially complete. For the three and nine months ended September 30, 2018, the Company recognized revenue from its collaboration with Incyte totaling $0 and $22.3 million, respectively, related to the completion of the combined performance obligation. Net costs associated with co-development activities performed under the agreement are included in research and development expenses in the accompanying unaudited condensed consolidated statements of operations, with any reimbursement of costs by Incyte reflected as a reduction of such expenses. For the three and nine months ended September 30, 2018, net costs reimbursable and/or reimbursed by Incyte were $0.6 million and $3.2 million, respectively. For the three and nine months ended September 30, 2017, net costs reimbursed by Incyte were $2.0 million and $5.7 million, respectively. As of September 30, 2018, the receivable due from Incyte was $1.7 million. Symbioscience License Agreement In December 2014, the Company entered into an exclusive license agreement with Mars, Inc., by and through its Mars Symbioscience division (“Symbioscience”), under which the Company has been granted the exclusive, worldwide license to develop and commercialize Symbioscience’s portfolio of arginase inhibitors for use in human healthcare (“Symbioscience License Agreement”). There were no expenses related to its licensing arrangement with Mars Symbioscience recorded in the three and nine months ended September 30, 2018. The Company may make future payments of up to $23.6 million contingent upon attainment of various development and regulatory milestones and $95.0 million contingent upon attainment of various sales milestones. Additionally, the Company will pay royalties on sales of the licensed product, if such product sales are ever achieved. If the Company develops additional licensed products, after achieving regulatory approval of the first licensed product, the Company would owe additional regulatory milestone payments and additional royalty payments based on sales of such additional licensed products.

9. Collaboration and Licensing Agreements

Incyte Collaboration and License Agreement

On January 27, 2017, the Company entered into a collaboration and license agreement with Incyte (the “Incyte Collaboration Agreement”). Under the terms of the Incyte Collaboration Agreement, the Company granted Incyte an exclusive, worldwide license to develop and commercialize its small molecule arginase inhibitors for hematology and oncology indications. The parties are collaborating on and co-funding the development of the licensed products, with Incyte bearing 70% and the Company bearing 30% of global development costs. The parties will share profits and losses in the United States, with 60% to Incyte and 40% to the Company. The Company will have the right to co-detail the licensed products in the United States, and Incyte will pay the Company tiered royalties ranging from the low to mid-double digits on net sales of licensed products outside the United States. The Company may opt out of its co-funding obligation, in which case the United States profit sharing will no longer be in effect, and Incyte will pay the Company tiered royalties ranging from the low to mid-double digits on net sales of licensed products both in the United States and outside the United States, and additional royalties to reimburse the Company for previously incurred development costs.

Under the Incyte Collaboration Agreement, the Company received an upfront payment of $45.0 million in February 2017. In March 2017, the Company achieved a development milestone of $12.0 million, for which the Company received payment in May of 2017. The Company is also eligible to receive up to an additional $418.0 million in potential development, regulatory and sales milestones. Incyte and the Company will share in any future United States net profits and losses, with the Company bearing 40% and Incyte bearing 60%, respectively, and outside the United States the Company will be eligible to receive from Incyte tiered royalties, with rates in the low to mid-teens of sales.

The Incyte Collaboration Agreement also provides that the Company may choose to opt out of its co-funding obligations at any time. In this scenario, the potential development, regulatory and commercialization milestones from Incyte will be up to an additional $738.0 million. The Company would no longer be eligible to receive future United States profits and losses but would be eligible to receive tiered royalty payments on future global sales, including United States sales. In addition, if the Company opts out, the Company will receive an incremental 3% royalty on annual net sales in the United States of such licensed product until such incremental royalty equals 120% of previous development expenditures incurred by the Company.

The Incyte Collaboration Agreement is considered to be under the scope of FASB Topic 808, Collaborative Arrangements. The Company has concluded that the research and development co-funding activities were not representative of a customer relationship and this unit of account is accounted for as an increase to or reduction of research and development expenses, rather than as revenue. The performance obligations under the Incyte Collaboration Agreement consist of intellectual property licenses and the performance of certain manufacturing and manufacturing technology transfer services. The Company has determined that the license is not distinct from the associated manufacturing and technology transfer services to be performed under the agreement. Specifically, the Company believes the license is not capable of being distinct, as Incyte did not have the know-how to manufacture the collaboration product without Calithera’s assistance until completion of the manufacturing technology transfer process, and no other third parties could perform such assistance due to the early stage nature of the licensed intellectual property as well as Calithera’s propriety knowledge with respect to the licensed intellectual property. Prior to the adoption of ASC 606, the Company concluded that the delivered licenses did not have stand-alone value, and the rights conveyed to Incyte did not permit Incyte to perform all efforts necessary to use the Company’s technology to bring the compound through development and, upon regulatory approval, commercialization of the compound, without the associated manufacturing and technology transfer services. Accordingly, the Company combined these deliverables and allocated the upfront consideration of $45.0 million to the combined unit of accounting. The Company recognized the $45.0 million upfront payment on a straight-line basis over the estimated period of performance under the Incyte Collaboration Agreement, and recognized the $12.0 million developmental milestone payment from Incyte on a straight-line basis over the remaining period of performance for the combined unit of accounting. For the three and nine months ended September 30, 2017, the Company recognized revenue from its collaboration with Incyte totaling $7.3 million and $18.7 million, respectively, related to amortization of the $45.0 million upfront fee and the $12.0 million milestone.

Upon the adoption of ASC 606 on January 1, 2018 under the modified retrospective approach, the transaction price was determined to be $57.0 million, representing the $45.0 million upfront payment and the $12.0 million developmental milestone payment from Incyte that was earned in March 2017. The $57.0 million transaction price was recognized over the performance period, based on the measure of progress toward completion for the combined performance obligation, rather than on a straight-line basis. The measure of progress towards completion was based on the effort of certain employees within the Company who dedicated time to complete the manufacturing services and technology transfer to Incyte. As of June 30, 2018, the manufacturing services and technology transfer to Incyte were determined to be substantially complete. For the three and nine months ended September 30, 2018, the Company recognized revenue from its collaboration with Incyte totaling $0 and $22.3 million, respectively, related to the completion of the combined performance obligation.

Net costs associated with co-development activities performed under the agreement are included in research and development expenses in the accompanying unaudited condensed consolidated statements of operations, with any reimbursement of costs by Incyte reflected as a reduction of such expenses. For the three and nine months ended September 30, 2018, net costs reimbursable and/or reimbursed by Incyte were $0.6 million and $3.2 million, respectively. For the three and nine months ended September 30, 2017, net costs reimbursed by Incyte were $2.0 million and $5.7 million, respectively. As of September 30, 2018, the receivable due from Incyte was $1.7 million.

Symbioscience License Agreement

In December 2014, the Company entered into an exclusive license agreement with Mars, Inc., by and through its Mars Symbioscience division (“Symbioscience”), under which the Company has been granted the exclusive, worldwide license to develop and commercialize Symbioscience’s portfolio of arginase inhibitors for use in human healthcare (“Symbioscience License Agreement”). There were no expenses related to its licensing arrangement with Mars Symbioscience recorded in the three and nine months ended September 30, 2018.

The Company may make future payments of up to $23.6 million contingent upon attainment of various development and regulatory milestones and $95.0 million contingent upon attainment of various sales milestones. Additionally, the Company will pay royalties on sales of the licensed product, if such product sales are ever achieved. If the Company develops additional licensed products, after achieving regulatory approval of the first licensed product, the Company would owe additional regulatory milestone payments and additional royalty payments based on sales of such additional licensed products.