Collaborations	9 Months Ended
Sep. 30, 2017
Disclosure Text Block
Collaborations	6. Collaborations Roche In March 2016, the Company entered into a collaboration and license agreement (as amended, Roche agreement) with Roche for the discovery, development and commercialization of up to five small molecule therapeutics targeting kinases believed to be important in cancer immunotherapy, as single products or possibly in combination with other therapeutics. The parties initiated activities for three of the collaboration programs in 2016, and the parties have agreed to work together to use the Company’s novel target discovery engine and proprietary compound library to select targets for up to two additional collaboration programs. Under the Roche agreement, Roche is granted up to five option rights to obtain an exclusive license to exploit products derived from the collaboration programs in the field of cancer immunotherapy. Such option rights are triggered upon the achievement of Phase 1 proof-of-concept. For up to three of the five collaboration programs, if Roche exercises its option, Roche will receive worldwide, exclusive commercialization rights for the licensed products. For up to two of the five collaboration programs, if Roche exercises its option, the Company will retain commercialization rights in the United States for the licensed products, and Roche will receive commercialization rights outside of the United States for the licensed products. The Company will also retain worldwide rights to any products for which Roche elects not to exercise its applicable option. Prior to Roche’s exercise of an option, the Company will have the lead responsibility for drug discovery and pre-clinical development of all collaboration programs. In addition, the Company will have the lead responsibility for the conduct of all Phase 1 clinical trials other than those Phase 1 clinical trials for any product in combination with Roche’s portfolio of therapeutics, for which Roche will have the right to lead the conduct of such Phase 1 clinical trials. Pursuant to the Roche agreement, the parties will share the costs of Phase 1 development for each collaboration program. In addition, Roche will be responsible for post-Phase 1 development costs for each licensed product for which it retains global commercialization rights, and the Company and Roche will share post-Phase 1 development costs for each licensed product for which the Company retains commercialization rights in the United States. Subject to the terms of the Roche agreement, the Company received an upfront cash payment of $45.0 million and will be eligible to receive up to approximately $965.0 million in contingent option fees and milestone payments related to specified research, pre-clinical, clinical, regulatory and sales-based milestones. Of the total contingent payments, up to approximately $215.0 million are for option fees and milestone payments for research, pre-clinical and clinical development events prior to licensing across all five potential collaboration programs, including contingent milestone payments for initiation of each of the collaboration programs for which the parties will work together to select targets (pre-option exercise milestones). In addition, for any licensed product for which Roche retains worldwide commercialization rights, the Company will be eligible to receive tiered royalties ranging from low double-digits to high-teens on future net sales of the licensed product. For any licensed product for which the Company retains commercialization rights in the United States, the Company and Roche will be eligible to receive tiered royalties ranging from mid-single-digits to low double-digits on future net sales in the other party’s respective territories in which it commercializes the licensed product. The upfront cash payment and any payments for milestones, option fees and royalties are non-refundable, non-creditable and not subject to set-off. The Roche agreement will continue until the date when no royalty or other payment obligations are or will become due, unless earlier terminated in accordance with the terms of the Roche agreement. Prior to its exercise of its first option, Roche may terminate the Roche agreement at will, in whole or on a collaboration target-by-collaboration target basis, upon 120 days’ prior written notice to the Company. Following its exercise of an option, Roche may terminate the Roche agreement at will, in whole, on a collaboration target-by-collaboration target basis, on a collaboration program-by-collaboration program basis or, if a licensed product has been commercially sold, on a country-by-country basis, (i) upon 120 days’ prior written notice if a licensed product has not been commercially sold or (ii) upon 180 days’ prior written notice if a licensed product has been commercially sold. Either party may terminate the Roche agreement for the other party’s uncured material breach or insolvency and in certain other circumstances agreed to by the parties. In certain termination circumstances, the Company is entitled to retain specified licenses to be able to continue to exploit the licensed products. The Company determined that there were five deliverables under the Roche agreement: (i) a non-transferable, sub-licensable and non-exclusive license to use the Company’s intellectual property and collaboration compounds to conduct research activities;(ii) conducting research and development activities through Phase 1 clinical trials under the research plan; (iii) providing pre-clinical and clinical supply of collaboration compounds; (iv) participation on a joint research committee (JRC) and joint development committee (JDC); and (v) regulatory responsibilities under Phase 1 clinical trials. The Company determined that the license did not have value to Roche on a stand-alone basis due to the specialized nature of the research activities to be provided by the Company that are not available in the marketplace and the fact that the license is to perform research and development only. Therefore, the license has limited value without the performance of the research and development activities and is not separable. The pre-clinical and clinical supply activities are integral to the performance of the research and development activities and can only be used for the performance of such activities, and the regulatory responsibilities are dependent on the research and development activities. The Company determined that the best estimate for the selling price of the JRC and JDC participation was inconsequential. Accordingly, the Company combined the license, pre-clinical and clinical supply, JRC and JDC participation and regulatory responsibilities deliverables with the research and development activities, the last item to be delivered in the arrangement, as one unit of accounting. The Company is recognizing the total allocable arrangement consideration consisting of the upfront payment of $45.0 million as revenue on a straight-line basis over the Company’s best estimate of the period it expects to perform research and development activities. The Company expects the services to be delivered ratably. The Company evaluated whether the option fees that may be received in connection with the Roche agreement are substantive. The Company concluded that the option fees were substantive due to the uncertainty around whether the goals of the collaboration will be achieved, and therefore the options are not a deliverable in the current arrangement. If Roche elects to exercise the options, the exercises and related contingent deliverables would be accounted for as a separate arrangement. The Company evaluated whether the milestones that may be received in connection with the Roche agreement are substantive milestones. Pre-option exercise milestones, of up to $215.0 million, that are expected to be achieved as a result of the Company’s efforts during the performance of the research and development activities are considered substantive and are recognized as revenue upon the achievement of the milestone, assuming all other revenue recognition criteria are met. The development event milestones are not considered substantive because the Company does not contribute effort to the achievement of such milestones as they are expected to be achieved after the performance of the research and development activities. Consideration received with respect to these milestones will be added to the total arrangement consideration that has been allocated to the identified units of accounting. As a result, that amount is recognized as revenue ratably over the period starting from the effective date of the agreement to the date that the Company will complete all of its obligations, with a cumulative catch-up from the effective date through the date of achievement of the milestone. If the consideration is received after the completion of all of the Company’s obligations, the amount will be recognized as revenue immediately. During both the three months ended September 30, 2017 and 2016, the Company recognized revenue under the Roche agreement of $1.4 million, which represents a portion of the $45.0 million upfront payment. During the nine months ended September 30, 2017 and 2016, the Company recognized revenue under the Roche agreement of $4.2 million and $3.0 million, respectively, which represents a portion of the $45.0 million upfront payment. Alexion In March 2015, the Company entered into a research, development and commercialization agreement (Alexion agreement) with Alexion to research, develop and commercialize one or more drug candidates targeting the ALK2 kinase for the treatment of fibrodysplasia ossificans progressiva (FOP). On July 26, 2017, the Company received written notice from Alexion of its election to terminate the Alexion agreement for convenience, and the termination became effective on October 24, 2017. Under the terms of the Alexion agreement, the Company and Alexion agreed to collaborate to research, develop and commercialize one or more drug candidates targeting the ALK2 kinase for the treatment of FOP, which is a rare genetic disease caused by mutations in the ALK2 gene, ACVR1. Effective upon the termination, the Company’s exclusivity obligations under the Alexion agreement terminated, including without limitation, the Company’s exclusivity obligations with respect to (i) the treatment of FOP, heterotopic ossification or diffuse intrinsic pontine glioma, (ii) ALK2, including both wild type and mutated forms, and (iii) certain molecules related to the foregoing. In addition, the research term and all licenses granted to Alexion terminated, and certain licenses granted by Alexion to the Company survived and became perpetual, irrevocable and non-terminable. The Company plans to evaluate opportunities to continue advancing this research program and is currently conducting research and pre-clinical development activities directed toward identifying a development candidate. Pursuant to the Alexion agreement, the Company was responsible for research and pre-clinical development activities related to any drug candidates, and Alexion was responsible for all clinical development, manufacturing and commercialization activities related to any drug candidates. In addition, Alexion was responsible for funding 100% of the Company’s research and development costs incurred under the research plan, including pass-through costs and a negotiated yearly rate per full-time equivalent for the Company’s employees’ time and their associated overhead expenses. As a result of the termination of the Alexion agreement, the Company will not be entitled to receive payment from Alexion for any research and development expenses incurred after the effective date of termination. Prior to termination, the Company had received an aggregate amount of $18.8 million in upfront and milestone payments. The Company received a $15.0 million non‑refundable upfront payment in March 2015 upon execution of the Alexion agreement and was eligible to receive over $250.0 million in payments upon the successful achievement of pre‑specified pre‑clinical, clinical, regulatory and commercial milestones as follows: (i) up to $6.0 million in pre‑clinical milestone payments for the first licensed product, (ii) up to $83.0 million and $61.5 million in development milestone payments for the first and second licensed products, respectively, and (iii) up to $51.0 million in commercial milestone payments for each of the first and second licensed products. Prior to termination, the Company had received an aggregate amount of $3.8 million in pre-clinical milestone payments. As a result of the termination of the Alexion agreement, the Company will not be entitled to receive payment from Alexion for any additional milestones. Prior to termination, Alexion was required to pay the Company tiered royalties, ranging from mid‑single to low‑double digit percentages, on a country‑by‑country and licensed-product‑by‑licensed product basis, on worldwide net product sales of licensed products. Prior to termination, the royalty term for each licensed product in each country was the period commencing with first commercial sale of such licensed product in such country and ending on the later of (i) the expiration of the last‑to‑expire valid claim of specified patents covering such licensed product, (ii) the expiration of the applicable regulatory exclusivity period, and (iii) 10 or 15 years from specified commercial sales. There are no refund provisions in the Alexion agreement. The Company determined that there were three deliverables under the Alexion agreement: (i) an exclusive license to research, develop, manufacture and commercialize the licensed products and the compounds in the field in the territory, (ii) conducting research and development activities under the research plan and (iii) participation on a joint steering committee (JSC) and joint project team (JPT). The Company determined that the license did not have value to Alexion on a stand-alone basis due to the specialized nature of the research services to be provided by the Company that are not available in the marketplace. Therefore, the deliverables are not separable and, accordingly, the license, undelivered research and development activities and JSC and JPT participation are a single unit of accounting. When multiple deliverables are accounted for as a single unit of accounting, the Company bases its revenue recognition model on the final deliverable. Under the Alexion agreement, the last deliverable that was anticipated to be completed was the Company’s research and development activities and participation on the JSC and JPT, which were expected to be delivered over the same performance period. The Company is recognizing the remaining deferred revenue balance related to the upfront payment and non-substantive milestone payment previously received under the Alexion collaboration utilizing the proportional performance model over the remaining period of performance, which ended October 24, 2017. The Company evaluated whether the milestones that it was eligible to receive in connection with the Alexion agreement were substantive or non-substantive milestones. The Company concluded that the first pre-clinical milestone payment received from Alexion was non-substantive due to the certainty at the date the Alexion agreement was entered into that the milestone event would be achieved. In the second quarter of 2015, the Company achieved the first pre-clinical milestone under the Alexion agreement and received a $1.8 million payment from Alexion. The Company is recognizing revenues from the related milestone payment over the remaining period of performance. The remaining non-refundable pre-clinical milestones that the Company was eligible to achieve as a result of the Company’s efforts prior to termination were considered substantive and would have been recognized as revenue upon the achievement of the milestone, assuming all other revenue recognition criteria were met. The Company has recognized and received an aggregate of $2.0 million in substantive milestones through September 30, 2017. Milestones that were expected to be achieved after the period of substantial involvement were not considered substantive because the Company would not contribute effort to the achievement of such milestones. These milestones would have been recognized as revenue upon achievement of the milestone, assuming all other revenue recognition criteria were met, as there would have been no undelivered elements remaining and no continuing performance obligations. During the three and nine months ended September 30, 2017, the Company recognized revenue under the Alexion agreement of $6.7 million and $15.6 million, respectively, which represents $3.4 million and $9.3 million, respectively, of reimbursable research and development costs, a portion of the $15.0 million upfront payment and the $1.75 million non-substantive milestone payment previously received under the collaboration. During the three and nine months ended September 30, 2016, the Company recognized revenue under the Alexion agreement of $4.8 million and $17.0 million, respectively, which represents $3.5 million and $11.0 million, respectively, of reimbursable research and development costs, the $1.75 million milestone payment recognized in the nine months ended September 30, 2016, which was recognized upon achievement, as well as a portion of the $15.0 million upfront payment and the $1.75 million non-substantive milestone payment previously received. During the nine months ended September 30, 2017, the Company received $9.5 million related to reimbursable research and development costs under the Alexion agreement. As of September 30, 2017, the Company has recorded unbilled accounts receivable of $3.4 million related to reimbursable research and development costs for activities performed during the three months ended September 30, 2017.

6. Collaborations

Roche

In March 2016, the Company entered into a collaboration and license agreement (as amended, Roche agreement) with Roche for the discovery, development and commercialization of up to five small molecule therapeutics targeting kinases believed to be important in cancer immunotherapy, as single products or possibly in combination with other therapeutics. The parties initiated activities for three of the collaboration programs in 2016, and the parties have agreed to work together to use the Company’s novel target discovery engine and proprietary compound library to select targets for up to two additional collaboration programs.

Under the Roche agreement, Roche is granted up to five option rights to obtain an exclusive license to exploit products derived from the collaboration programs in the field of cancer immunotherapy. Such option rights are triggered upon the achievement of Phase 1 proof-of-concept. For up to three of the five collaboration programs, if Roche exercises its option, Roche will receive worldwide, exclusive commercialization rights for the licensed products. For up to two of the five collaboration programs, if Roche exercises its option, the Company will retain commercialization rights in the United States for the licensed products, and Roche will receive commercialization rights outside of the United States for the licensed products. The Company will also retain worldwide rights to any products for which Roche elects not to exercise its applicable option.

Prior to Roche’s exercise of an option, the Company will have the lead responsibility for drug discovery and pre-clinical development of all collaboration programs. In addition, the Company will have the lead responsibility for the conduct of all Phase 1 clinical trials other than those Phase 1 clinical trials for any product in combination with Roche’s portfolio of therapeutics, for which Roche will have the right to lead the conduct of such Phase 1 clinical trials. Pursuant to the Roche agreement, the parties will share the costs of Phase 1 development for each collaboration program. In addition, Roche will be responsible for post-Phase 1 development costs for each licensed product for which it retains global commercialization rights, and the Company and Roche will share post-Phase 1 development costs for each licensed product for which the Company retains commercialization rights in the United States.

Subject to the terms of the Roche agreement, the Company received an upfront cash payment of $45.0 million and will be eligible to receive up to approximately $965.0 million in contingent option fees and milestone payments related to specified research, pre-clinical, clinical, regulatory and sales-based milestones. Of the total contingent payments, up to approximately $215.0 million are for option fees and milestone payments for research, pre-clinical and clinical development events prior to licensing across all five potential collaboration programs, including contingent milestone payments for initiation of each of the collaboration programs for which the parties will work together to select targets (pre-option exercise milestones). In addition, for any licensed product for which Roche retains worldwide commercialization rights, the Company will be eligible to receive tiered royalties ranging from low double-digits to high-teens on future net sales of the licensed product. For any licensed product for which the Company retains commercialization rights in the United States, the Company and Roche will be eligible to receive tiered royalties ranging from mid-single-digits to low double-digits on future net sales in the other party’s respective territories in which it commercializes the licensed product. The upfront cash payment and any payments for milestones, option fees and royalties are non-refundable, non-creditable and not subject to set-off.

The Roche agreement will continue until the date when no royalty or other payment obligations are or will become due, unless earlier terminated in accordance with the terms of the Roche agreement. Prior to its exercise of its first option, Roche may terminate the Roche agreement at will, in whole or on a collaboration target-by-collaboration target basis, upon 120 days’ prior written notice to the Company. Following its exercise of an option, Roche may terminate the Roche agreement at will, in whole, on a collaboration target-by-collaboration target basis, on a collaboration program-by-collaboration program basis or, if a licensed product has been commercially sold, on a country-by-country basis, (i) upon 120 days’ prior written notice if a licensed product has not been commercially sold or (ii) upon 180 days’ prior written notice if a licensed product has been commercially sold. Either party may terminate the Roche agreement for the other party’s uncured material breach or insolvency and in certain other circumstances agreed to by the parties. In certain termination circumstances, the Company is entitled to retain specified licenses to be able to continue to exploit the licensed products.

The Company determined that there were five deliverables under the Roche agreement: (i) a non-transferable, sub-licensable and non-exclusive license to use the Company’s intellectual property and collaboration compounds to conduct research activities;(ii) conducting research and development activities through Phase 1 clinical trials under the research plan; (iii) providing pre-clinical and clinical supply of collaboration compounds; (iv) participation on a joint research committee (JRC) and joint development committee (JDC); and (v) regulatory responsibilities under Phase 1 clinical trials.

The Company determined that the license did not have value to Roche on a stand-alone basis due to the specialized nature of the research activities to be provided by the Company that are not available in the marketplace and the fact that the license is to perform research and development only. Therefore, the license has limited value without the performance of the research and development activities and is not separable. The pre-clinical and clinical supply activities are integral to the performance of the research and development activities and can only be used for the performance of such activities, and the regulatory responsibilities are dependent on the research and development activities. The Company determined that the best estimate for the selling price of the JRC and JDC participation was inconsequential. Accordingly, the Company combined the license, pre-clinical and clinical supply, JRC and JDC participation and regulatory responsibilities deliverables with the research and development activities, the last item to be delivered in the arrangement, as one unit of accounting. The Company is recognizing the total allocable arrangement consideration consisting of the upfront payment of $45.0 million as revenue on a straight-line basis over the Company’s best estimate of the period it expects to perform research and development activities. The Company expects the services to be delivered ratably.

The Company evaluated whether the option fees that may be received in connection with the Roche agreement are substantive. The Company concluded that the option fees were substantive due to the uncertainty around whether the goals of the collaboration will be achieved, and therefore the options are not a deliverable in the current arrangement. If Roche elects to exercise the options, the exercises and related contingent deliverables would be accounted for as a separate arrangement.

The Company evaluated whether the milestones that may be received in connection with the Roche agreement are substantive milestones. Pre-option exercise milestones, of up to $215.0 million, that are expected to be achieved as a result of the Company’s efforts during the performance of the research and development activities are considered substantive and are recognized as revenue upon the achievement of the milestone, assuming all other revenue recognition criteria are met. The development event milestones are not considered substantive because the Company does not contribute effort to the achievement of such milestones as they are expected to be achieved after the performance of the research and development activities. Consideration received with respect to these milestones will be added to the total arrangement consideration that has been allocated to the identified units of accounting. As a result, that amount is recognized as revenue ratably over the period starting from the effective date of the agreement to the date that the Company will complete all of its obligations, with a cumulative catch-up from the effective date through the date of achievement of the milestone. If the consideration is received after the completion of all of the Company’s obligations, the amount will be recognized as revenue immediately.

During both the three months ended September 30, 2017 and 2016, the Company recognized revenue under the Roche agreement of $1.4 million, which represents a portion of the $45.0 million upfront payment. During the nine months ended September 30, 2017 and 2016, the Company recognized revenue under the Roche agreement of $4.2 million and $3.0 million, respectively, which represents a portion of the $45.0 million upfront payment.

Alexion

In March 2015, the Company entered into a research, development and commercialization agreement (Alexion agreement) with Alexion to research, develop and commercialize one or more drug candidates targeting the ALK2 kinase for the treatment of fibrodysplasia ossificans progressiva (FOP). On July 26, 2017, the Company received written notice from Alexion of its election to terminate the Alexion agreement for convenience, and the termination became effective on October 24, 2017.

Under the terms of the Alexion agreement, the Company and Alexion agreed to collaborate to research, develop and commercialize one or more drug candidates targeting the ALK2 kinase for the treatment of FOP, which is a rare genetic disease caused by mutations in the ALK2 gene, ACVR1. Effective upon the termination, the Company’s exclusivity obligations under the Alexion agreement terminated, including without limitation, the Company’s exclusivity obligations with respect to (i) the treatment of FOP, heterotopic ossification or diffuse intrinsic pontine glioma, (ii) ALK2, including both wild type and mutated forms, and (iii) certain molecules related to the foregoing. In addition, the research term and all licenses granted to Alexion terminated, and certain licenses granted by Alexion to the Company survived and became perpetual, irrevocable and non-terminable. The Company plans to evaluate opportunities to continue advancing this research program and is currently conducting research and pre-clinical development activities directed toward identifying a development candidate.

Pursuant to the Alexion agreement, the Company was responsible for research and pre-clinical development activities related to any drug candidates, and Alexion was responsible for all clinical development, manufacturing and commercialization activities related to any drug candidates. In addition, Alexion was responsible for funding 100% of the Company’s research and development costs incurred under the research plan, including pass-through costs and a negotiated yearly rate per full-time equivalent for the Company’s employees’ time and their associated overhead expenses. As a result of the termination of the Alexion agreement, the Company will not be entitled to receive payment from Alexion for any research and development expenses incurred after the effective date of termination.

Prior to termination, the Company had received an aggregate amount of $18.8 million in upfront and milestone payments. The Company received a $15.0 million non‑refundable upfront payment in March 2015 upon execution of the Alexion agreement and was eligible to receive over $250.0 million in payments upon the successful achievement of pre‑specified pre‑clinical, clinical, regulatory and commercial milestones as follows: (i) up to $6.0 million in pre‑clinical milestone payments for the first licensed product, (ii) up to $83.0 million and $61.5 million in development milestone payments for the first and second licensed products, respectively, and (iii) up to $51.0 million in commercial milestone payments for each of the first and second licensed products. Prior to termination, the Company had received an aggregate amount of $3.8 million in pre-clinical milestone payments. As a result of the termination of the Alexion agreement, the Company will not be entitled to receive payment from Alexion for any additional milestones. Prior to termination, Alexion was required to pay the Company tiered royalties, ranging from mid‑single to low‑double digit percentages, on a country‑by‑country and licensed-product‑by‑licensed product basis, on worldwide net product sales of licensed products. Prior to termination, the royalty term for each licensed product in each country was the period commencing with first commercial sale of such licensed product in such country and ending on the later of (i) the expiration of the last‑to‑expire valid claim of specified patents covering such licensed product, (ii) the expiration of the applicable regulatory exclusivity period, and (iii) 10 or 15 years from specified commercial sales. There are no refund provisions in the Alexion agreement.

The Company determined that there were three deliverables under the Alexion agreement: (i) an exclusive license to research, develop, manufacture and commercialize the licensed products and the compounds in the field in the territory, (ii) conducting research and development activities under the research plan and (iii) participation on a joint steering committee (JSC) and joint project team (JPT).

The Company determined that the license did not have value to Alexion on a stand-alone basis due to the specialized nature of the research services to be provided by the Company that are not available in the marketplace. Therefore, the deliverables are not separable and, accordingly, the license, undelivered research and development activities and JSC and JPT participation are a single unit of accounting. When multiple deliverables are accounted for as a single unit of accounting, the Company bases its revenue recognition model on the final deliverable. Under the Alexion agreement, the last deliverable that was anticipated to be completed was the Company’s research and development activities and participation on the JSC and JPT, which were expected to be delivered over the same performance period. The Company is recognizing the remaining deferred revenue balance related to the upfront payment and non-substantive milestone payment previously received under the Alexion collaboration utilizing the proportional performance model over the remaining period of performance, which ended October 24, 2017.

The Company evaluated whether the milestones that it was eligible to receive in connection with the Alexion agreement were substantive or non-substantive milestones. The Company concluded that the first pre-clinical milestone payment received from Alexion was non-substantive due to the certainty at the date the Alexion agreement was entered into that the milestone event would be achieved. In the second quarter of 2015, the Company achieved the first pre-clinical milestone under the Alexion agreement and received a $1.8 million payment from Alexion. The Company is recognizing revenues from the related milestone payment over the remaining period of performance.

The remaining non-refundable pre-clinical milestones that the Company was eligible to achieve as a result of the Company’s efforts prior to termination were considered substantive and would have been recognized as revenue upon the achievement of the milestone, assuming all other revenue recognition criteria were met. The Company has recognized and received an aggregate of $2.0 million in substantive milestones through September 30, 2017. Milestones that were expected to be achieved after the period of substantial involvement were not considered substantive because the Company would not contribute effort to the achievement of such milestones. These milestones would have been recognized as revenue upon achievement of the milestone, assuming all other revenue recognition criteria were met, as there would have been no undelivered elements remaining and no continuing performance obligations.

During the three and nine months ended September 30, 2017, the Company recognized revenue under the Alexion agreement of $6.7 million and $15.6 million, respectively, which represents $3.4 million and $9.3 million, respectively, of reimbursable research and development costs, a portion of the $15.0 million upfront payment and the $1.75 million non-substantive milestone payment previously received under the collaboration. During the three and nine months ended September 30, 2016, the Company recognized revenue under the Alexion agreement of $4.8 million and $17.0 million, respectively, which represents $3.5 million and $11.0 million, respectively, of reimbursable research and development costs, the $1.75 million milestone payment recognized in the nine months ended September 30, 2016, which was recognized upon achievement, as well as a portion of the $15.0 million upfront payment and the $1.75 million non-substantive milestone payment previously received. During the nine months ended September 30, 2017, the Company received $9.5 million related to reimbursable research and development costs under the Alexion agreement. As of September 30, 2017, the Company has recorded unbilled accounts receivable of $3.4 million related to reimbursable research and development costs for activities performed during the three months ended September 30, 2017.