Research and License Agreements	12 Months Ended
Dec. 31, 2017
Revenue Recognition [Abstract]
Research and License Agreement	10. Research and License Agreements In February 2004, the Company entered into a research services agreement (the Research Agreement) with the University of Basel (the University) for biological evaluation of selectin antagonists. Certain patents covering the rivipansel compound remain subject to provisions of the Research Agreement. Under the terms of the Research Agreement, the Company will owe a 10% payment to the University for all future milestone and royalty payments received from Pfizer with respect to rivipansel. A milestone license fee of $2.0 million was recorded in the year ended December 31, 2015 for the payment due to the University of Basel representing 10% of the $20.0 million non-refundable milestone payment that the Company received from Pfizer in August 2015. The accrued license and milestone fee of $2.0 million was paid in February 2016. There were no payments recorded for the years ended December 31, 2017 or 2016. In October 2011, the Company and Pfizer entered into a licensing agreement (the Pfizer Agreement) that provides Pfizer an exclusive worldwide license to rivipansel for vaso-occlusive crisis associated with sickle cell disease and for other diseases for which the drug candidate may be developed. The Company was responsible for completion of the Phase 2 trial, after which Pfizer assumed all further development and commercialization responsibilities. Upon execution of the Pfizer Agreement, the Company received an up-front payment of $22.5 million. The Pfizer Agreement also provides for potential milestone payments of up to $115.0 million upon the achievement of specified development milestones, including the dosing of the first patients in Phase 3 clinical trials for up to two indications and the first commercial sale of a licensed product in the United States and selected European countries for up to two indications; potential milestone payments of up to $70.0 million upon the achievement of specified regulatory milestones, including the acceptance of the Company’s filings for regulatory approval by regulatory authorities in the United States and Europe for up to two indications; and potential milestone payments of up to $135.0 million upon the achievement of specified levels of annual net sales of licensed products. Pfizer has the right to terminate the Pfizer Agreement by giving prior written notice. The Company has determined that each potential future clinical, development and regulatory milestone is substantive. Although sales-based milestones are not considered substantive, they are still recognized upon achievement of the milestone (assuming all other revenue recognition criteria have been met) because there are no undelivered elements that would preclude revenue recognition at that time. The Company is also eligible to receive royalties on future sales contingent upon annual net sales thresholds. In addition, the Company and Pfizer have formed a joint steering committee, or JSC, that will oversee and coordinate activities as set forth in the research program. The $22.5 million up-front payment was recognized over a period of 1.5 years. In May 2014, the Company received a non-refundable payment of $15.0 million from Pfizer as a partial milestone payment owed to the Company upon the dosing of the first patient in the Phase 3 clinical trial. The dosing of the first patient in a Phase 3 clinical trial of rivipansel in June 2015 triggered the remaining $20.0 million of the scheduled milestone payment under the Pfizer Agreement. During the year ended December 31, 2015, the Company recorded revenue of $20.0 million pursuant to the Pfizer Agreement in the Company’s statement of operations. There was no revenue recognized under the Pfizer Agreement for the years ended December 31, 2017 and 2016. The Company assessed this arrangement in accordance with Topic 606 and concluded that the contract counterparty, Pfizer, is a customer. The Company identified the following performance obligations under the contract: (1) an exclusive worldwide license to rivipansel for vaso-occlusive crisis associated with sickle cell disease and for other diseases for which the drug candidate may be developed; and (2) research and development (R&D) services to develop the rivipansel compound for commercial use related to the Phase 2 clinical trial and delivery of data to Pfizer. In addition to the rivipansel license and R&D services, management also considered whether the Company’s participation in the JSC constituted a promise. The JSC was formed solely for communication purposes between Pfizer and the Company relating to Pfizer’s progress in further developing rivipansel for commercial use. The Company’s involvement in the JSC is limited to attending the JSC meetings on a semi-annual basis to receive progress updates from Pfizer; Pfizer is responsible for calling and organizing the meetings. Given the minimal level of involvement by the Company, participation in the JSC is not considered a significant aspect of the arrangement and the related costs, such as employee time, are not material. Therefore, management views the Company’s participation in JSC as administrative only and did not further evaluate its participation in the JSC in identifying the performance obligations in the contract. Under the Agreement, in order to evaluate the appropriate transaction price, the Company determined that the up-front amount constituted the entirety of the consideration to be included in the transaction price and to be allocated to the performance obligations based on the Company’s best estimate of their relative stand-alone selling prices. The transaction price of the upfront fee is equal to the $22.5 million received. The fixed upfront consideration is recognized under ASC 606 based on when control of the combined performance obligation is transferred to the customer, which corresponds with the service period (through March 2013). None of the clinical, regulatory milestones has been included in the transaction price, as all milestone amounts were fully constrained. Event driven milestones are a form of variable consideration as the payments are variable based on the occurrence of future events. As part of its evaluation of the constraint, the Company considered numerous factors, including that receipt of the milestones is outside the control of the Company and contingent upon success in future clinical trials and the licensee’s efforts. Recognition of event driven milestones should be recognized when the variable consideration is no longer constrained. There are no changes in accounting necessary for the $15.0 million milestone payment recognized in May 2014 or the $20.0 million milestone payment recognized in June 2015 as a result of Pfizer dosing the first patient in the Phase 3 clinical trial of rivipansel. Future event milestones will be recognized when the constraint no longer applies. Any consideration related to sales-based milestones (including royalties) will be recognized when the related sales occur as they were determined to relate predominantly to the license granted to Pfizer and therefore have also been excluded from the transaction price. The Company will re-evaluate the transaction price in each reporting period and as uncertain events are resolved or other changes in circumstances occur. In evaluation of the Agreement, there were no significant financing components identified, no non-cash consideration was paid by Pfizer and no consideration was paid by the Company to Pfizer as part of the arrangement.

10. Research and License Agreements

In February 2004, the Company entered into a research services agreement (the Research Agreement) with the University of Basel (the University) for biological evaluation of selectin antagonists. Certain patents covering the rivipansel compound remain subject to provisions of the Research Agreement. Under the terms of the Research Agreement, the Company will owe a 10% payment to the University for all future milestone and royalty payments received from Pfizer with respect to rivipansel. A milestone license fee of $2.0 million was recorded in the year ended December 31, 2015 for the payment due to the University of Basel representing 10% of the $20.0 million non-refundable milestone payment that the Company received from Pfizer in August 2015. The accrued license and milestone fee of $2.0 million was paid in February 2016. There were no payments recorded for the years ended December 31, 2017 or 2016.

In October 2011, the Company and Pfizer entered into a licensing agreement (the Pfizer Agreement) that provides Pfizer an exclusive worldwide license to rivipansel for vaso-occlusive crisis associated with sickle cell disease and for other diseases for which the drug candidate may be developed. The Company was responsible for completion of the Phase 2 trial, after which Pfizer assumed all further development and commercialization responsibilities. Upon execution of the Pfizer Agreement, the Company received an up-front payment of $22.5 million. The Pfizer Agreement also provides for potential milestone payments of up to $115.0 million upon the achievement of specified development milestones, including the dosing of the first patients in Phase 3 clinical trials for up to two indications and the first commercial sale of a licensed product in the United States and selected European countries for up to two indications; potential milestone payments of up to $70.0 million upon the achievement of specified regulatory milestones, including the acceptance of the Company’s filings for regulatory approval by regulatory authorities in the United States and Europe for up to two indications; and potential milestone payments of up to $135.0 million upon the achievement of specified levels of annual net sales of licensed products. Pfizer has the right to terminate the Pfizer Agreement by giving prior written notice.

The Company has determined that each potential future clinical, development and regulatory milestone is substantive. Although sales-based milestones are not considered substantive, they are still recognized upon achievement of the milestone (assuming all other revenue recognition criteria have been met) because there are no undelivered elements that would preclude revenue recognition at that time. The Company is also eligible to receive royalties on future sales contingent upon annual net sales thresholds. In addition, the Company and Pfizer have formed a joint steering committee, or JSC, that will oversee and coordinate activities as set forth in the research program. The $22.5 million up-front payment was recognized over a period of 1.5 years. In May 2014, the Company received a non-refundable payment of $15.0 million from Pfizer as a partial milestone payment owed to the Company upon the dosing of the first patient in the Phase 3 clinical trial. The dosing of the first patient in a Phase 3 clinical trial of rivipansel in June 2015 triggered the remaining $20.0 million of the scheduled milestone payment under the Pfizer Agreement. During the year ended December 31, 2015, the Company recorded revenue of $20.0 million pursuant to the Pfizer Agreement in the Company’s statement of operations. There was no revenue recognized under the Pfizer Agreement for the years ended December 31, 2017 and 2016.

The Company assessed this arrangement in accordance with Topic 606 and concluded that the contract counterparty, Pfizer, is a customer. The Company identified the following performance obligations under the contract: (1) an exclusive worldwide license to rivipansel for vaso-occlusive crisis associated with sickle cell disease and for other diseases for which the drug candidate may be developed; and (2) research and development (R&D) services to develop the rivipansel compound for commercial use related to the Phase 2 clinical trial and delivery of data to Pfizer. In addition to the rivipansel license and R&D services, management also considered whether the Company’s participation in the JSC constituted a promise. The JSC was formed solely for communication purposes between Pfizer and the Company relating to Pfizer’s progress in further developing rivipansel for commercial use. The Company’s involvement in the JSC is limited to attending the JSC meetings on a semi-annual basis to receive progress updates from Pfizer; Pfizer is responsible for calling and organizing the meetings. Given the minimal level of involvement by the Company, participation in the JSC is not considered a significant aspect of the arrangement and the related costs, such as employee time, are not material. Therefore, management views the Company’s participation in JSC as administrative only and did not further evaluate its participation in the JSC in identifying the performance obligations in the contract.

Under the Agreement, in order to evaluate the appropriate transaction price, the Company determined that the up-front amount constituted the entirety of the consideration to be included in the transaction price and to be allocated to the performance obligations based on the Company’s best estimate of their relative stand-alone selling prices. The transaction price of the upfront fee is equal to the $22.5 million received. The fixed upfront consideration is recognized under ASC 606 based on when control of the combined performance obligation is transferred to the customer, which corresponds with the service period (through March 2013). None of the clinical, regulatory milestones has been included in the transaction price, as all milestone amounts were fully constrained. Event driven milestones are a form of variable consideration as the payments are variable based on the occurrence of future events. As part of its evaluation of the constraint, the Company considered numerous factors, including that receipt of the milestones is outside the control of the Company and contingent upon success in future clinical trials and the licensee’s efforts. Recognition of event driven milestones should be recognized when the variable consideration is no longer constrained. There are no changes in accounting necessary for the $15.0 million milestone payment recognized in May 2014 or the $20.0 million milestone payment recognized in June 2015 as a result of Pfizer dosing the first patient in the Phase 3 clinical trial of rivipansel. Future event milestones will be recognized when the constraint no longer applies.

Any consideration related to sales-based milestones (including royalties) will be recognized when the related sales occur as they were determined to relate predominantly to the license granted to Pfizer and therefore have also been excluded from the transaction price. The Company will re-evaluate the transaction price in each reporting period and as uncertain events are resolved or other changes in circumstances occur. In evaluation of the Agreement, there were no significant financing components identified, no non-cash consideration was paid by Pfizer and no consideration was paid by the Company to Pfizer as part of the arrangement.