License and royalty revenue	3 Months Ended
Mar. 31, 2018
License And Royalty Revenue [Abstract]
License and royalty revenue	9. License and royalty revenue Novartis Pharma AG On April 26, 2017, the Company entered into a worldwide license agreement with Novartis Pharma AG, or Novartis. Under the terms of the agreement, Novartis non-exclusively licensed certain patent rights related to lentiviral vector technology to develop and commercialize CAR T cell therapies for oncology, including Kymriah (formerly known as CTL019), Novartis’s anti-CD19 CAR T therapy. At contract inception, financial terms of the agreement included a $7.5 million payment upon execution, $7.5 million of potential future milestone payments associated with regulatory approvals, and $1.1 million of payments for each subsequently licensed product, as well as low single digit royalty payments on net sales of covered products. In August 2017, Novartis received FDA approval for Kymriah and paid the Company $2.5 million as a result of the achievement of a related milestone. Given this arrangement is within the scope of Topic 606, the Company assessed this arrangement in accordance with Topic 606 and concluded that at the date of contract inception, only one performance obligation, consisting of the license which was satisfied at contract inception, was identified. Accordingly, the nonrefundable license fee of $7.5 million was recognized as revenue upon contract execution and the $2.5 million regulatory milestone was also recognized as revenue upon milestone achievement given there were no other unsatisfied performance obligations in the arrangement. This accounting conclusion was unchanged from its historical treatment under ASC 605. Because the single performance obligation was previously satisfied, all regulatory milestones will be recognized as revenue in full in the period in which the associated milestone is achieved. Regulatory approvals are not within the Company’s control or the licensee’s control and are generally not considered probable of being achieved until those approvals are received. As such, these milestones are constrained and excluded from the transaction price until such time as regulatory approvals are received. The Company began recognizing royalty revenue from sales of Kymriah in the fourth quarter of 2017. As the license was deemed to be the predominant item to which the royalties relate, the Company recognizes royalties from the sales of Kymriah when the related sales occur. For the three months ended March 31, 2018, the Company recognized royalty revenue of $0.3 million. The associated cost of license revenue was less than $0.1 million for the same period. For the three months ended March 31, 2017, there was no license and royalty revenue, or cost of license and royalty revenue, recognized. Orchard Therapeutics Limited (formerly GlaxoSmithKline Intellectual Property Development Limited) On April 28, 2017, the Company entered into a worldwide license agreement with GlaxoSmithKline Intellectual Property Development Limited, or GSK. Under the terms of the agreement, GSK non-exclusively licensed certain patent rights related to lentiviral vector technology to develop and commercialize gene therapies for Wiscott-Aldrich syndrome and metachromatic leukodystrophy, two rare genetic diseases. Financial terms of the agreement include a nonrefundable upfront payment of $3.0 million as well as $1.3 million of potential milestone payments for each marketing authorization for each indication in any country as well as low single digit royalties on net sales of covered products. This license agreement was assigned by GSK to Orchard Therapeutics Limited, effective as of April 11, 2018. Given this arrangement is within the scope of Topic 606, the Company assessed this arrangement in accordance with Topic 606 and concluded that at the date of contract inception, only one performance obligation, consisting of the license which was satisfied at contract inception, was identified. Accordingly, the entire nonrefundable license fee of $3.0 million was recognized as revenue upon contract execution given there were no other unsatisfied performance obligations in the arrangement. This accounting conclusion was unchanged from its historical treatment under ASC 605. Because the single performance obligation was previously satisfied, all regulatory milestones will be recognized as revenue in full in the period in which the associated milestone is achieved. Regulatory approvals are not within the Company’s control or the licensee’s control and are generally not considered probable of being achieved until those approvals are received. As such, these milestones are constrained and excluded from the transaction price until such time as regulatory approvals are received. There was no revenue recognized under this arrangement in the three months ended March 31, 2018 and 2017.

9. License and royalty revenue

Novartis Pharma AG

On April 26, 2017, the Company entered into a worldwide license agreement with Novartis Pharma AG, or Novartis. Under the terms of the agreement, Novartis non-exclusively licensed certain patent rights related to lentiviral vector technology to develop and commercialize CAR T cell therapies for oncology, including Kymriah (formerly known as CTL019), Novartis’s anti-CD19 CAR T therapy. At contract inception, financial terms of the agreement included a $7.5 million payment upon execution, $7.5 million of potential future milestone payments associated with regulatory approvals, and $1.1 million of payments for each subsequently licensed product, as well as low single digit royalty payments on net sales of covered products. In August 2017, Novartis received FDA approval for Kymriah and paid the Company $2.5 million as a result of the achievement of a related milestone.

Given this arrangement is within the scope of Topic 606, the Company assessed this arrangement in accordance with Topic 606 and concluded that at the date of contract inception, only one performance obligation, consisting of the license which was satisfied at contract inception, was identified. Accordingly, the nonrefundable license fee of $7.5 million was recognized as revenue upon contract execution and the $2.5 million regulatory milestone was also recognized as revenue upon milestone achievement given there were no other unsatisfied performance obligations in the arrangement. This accounting conclusion was unchanged from its historical treatment under ASC 605. Because the single performance obligation was previously satisfied, all regulatory milestones will be recognized as revenue in full in the period in which the associated milestone is achieved. Regulatory approvals are not within the Company’s control or the licensee’s control and are generally not considered probable of being achieved until those approvals are received. As such, these milestones are constrained and excluded from the transaction price until such time as regulatory approvals are received.

The Company began recognizing royalty revenue from sales of Kymriah in the fourth quarter of 2017. As the license was deemed to be the predominant item to which the royalties relate, the Company recognizes royalties from the sales of Kymriah when the related sales occur. For the three months ended March 31, 2018, the Company recognized royalty revenue of $0.3 million. The associated cost of license revenue was less than $0.1 million for the same period. For the three months ended March 31, 2017, there was no license and royalty revenue, or cost of license and royalty revenue, recognized.

Orchard Therapeutics Limited (formerly GlaxoSmithKline Intellectual Property Development Limited)

On April 28, 2017, the Company entered into a worldwide license agreement with GlaxoSmithKline Intellectual Property Development Limited, or GSK. Under the terms of the agreement, GSK non-exclusively licensed certain patent rights related to lentiviral vector technology to develop and commercialize gene therapies for Wiscott-Aldrich syndrome and metachromatic leukodystrophy, two rare genetic diseases. Financial terms of the agreement include a nonrefundable upfront payment of $3.0 million as well as $1.3 million of potential milestone payments for each marketing authorization for each indication in any country as well as low single digit royalties on net sales of covered products. This license agreement was assigned by GSK to Orchard Therapeutics Limited, effective as of April 11, 2018.

Given this arrangement is within the scope of Topic 606, the Company assessed this arrangement in accordance with Topic 606 and concluded that at the date of contract inception, only one performance obligation, consisting of the license which was satisfied at contract inception, was identified. Accordingly, the entire nonrefundable license fee of $3.0 million was recognized as revenue upon contract execution given there were no other unsatisfied performance obligations in the arrangement. This accounting conclusion was unchanged from its historical treatment under ASC 605. Because the single performance obligation was previously satisfied, all regulatory milestones will be recognized as revenue in full in the period in which the associated milestone is achieved. Regulatory approvals are not within the Company’s control or the licensee’s control and are generally not considered probable of being achieved until those approvals are received. As such, these milestones are constrained and excluded from the transaction price until such time as regulatory approvals are received. There was no revenue recognized under this arrangement in the three months ended March 31, 2018 and 2017.