Net revenue from our partners in connection with our collaboration and license agreements consisted of the following (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2020		2019		2020		2019
License Agreement with Pfizer	$	5,735	$	—	$	6,339	$	—
Strategic Collaboration with Novartis		278		10,722		589		167,784
Collaboration and License Agreement with PTC Therapeutics		—		6,036		—		6,036
Total net revenue from partners	$	6,013	$	16,758	$	6,928	$	173,820

The following table presents the balance of our receivables and contract liabilities related to our collaboration and license agreements associated with our partners (in thousands):

	June 30, 2020		December 31, 2019
Receivables included in "Accounts receivable"	$	513	$	3,550
Contract liabilities included in "Deferred revenue"		263		1,322

During the three and six months ended June 30, 2020, we recognized the following revenue as a result of the change in the contract liability balances related to our collaboration and license agreements associated with our partners (in thousands):

Three Months Ended

June 30, 2020

Six Months Ended

June 30, 2020

Revenue recognized in current period from:

Amounts included in deferred revenue at the beginning

of the period

455

1,059

In October 2019, we entered into a license agreement with Pfizer, or the Pfizer License Agreement, for the development and commercialization of vupanorsen (previously referred to as AKCEA-ANGPTL3-L_Rx). Under the terms of the Pfizer License Agreement, we granted Pfizer an exclusive license to further develop, manufacture and commercialize vupanorsen worldwide, subject to our potential participation in co-commercialization. We are responsible for completing a Phase 2 clinical trial and providing limited quantities of active pharmaceutical ingredient, or API, for vupanorsen.

We received a $250.0 million upfront payment in the fourth quarter of 2019 from Pfizer. We issued 6,873,344 shares of our common stock to Ionis as payment of the $125.0 million sublicense fee due under our development, commercialization and license agreement related to our cardiometabolic franchise, or Cardiometabolic License Agreement, with Ionis and recorded it as a research and development expense in our condensed consolidated statement of operations.

At commencement of the Pfizer License Agreement, we identified the following three distinct performance obligations:

We concluded that the three performance obligations were distinct because Pfizer has full use of the obligations without any continuing involvement from us. Further, Pfizer, or another third party, could provide these obligations without our assistance.

We determined the transaction price for the Pfizer License Agreement to be the $250.0 million upfront payment we received from Pfizer. None of the development or regulatory milestone payments under this agreement were included in the upfront transaction price. We concluded that such future payments pursuant to the Pfizer License Agreement will be recognized when it is probable that Pfizer will achieve the related development or regulatory milestones.

Based on the distinct performance obligations under the Pfizer License Agreement, we allocated the $250.0 million transaction price based on the relative stand-alone selling prices of each of our performance obligations as follows:

We are recognizing revenue related to each of our performance obligations as follows:

During the second quarter of 2020, Pfizer exercised its option to purchase additional vupanorsen API in accordance with the Pfizer License Agreement. We concluded that the option to purchase additional API did not constitute a material right as the API is being sold at its stand-alone selling price, and thus is not offered at a discount. Accordingly, we recognized $5.3 million of revenue relating to this option upon the delivery of vupanorsen API in the second quarter of 2020. Pfizer has the option to purchase additional vupanorsen API in the future at agreed upon terms and conditions pursuant to the Pfizer License Agreement.

We are eligible to receive up to $1.3 billion in milestone payments, including up to $205.0 million for the achievement of development milestones, up to $250.0 million for the achievement of regulatory milestones and up to $850.0 million for the achievement of commercialization milestones. We will achieve the next milestone payment of $75.0 million when Pfizer advances vupanorsen_. We are also eligible to receive tiered royalties in the mid-teens to low twenty percent range on net sales of vupanorsen. Pfizer will reduce these royalties upon the expiration of certain patents or if a generic competitor negatively impacts the product in a specific country. We will share any milestone payments and royalties equally with Ionis.

During the three and six months ended June 30, 2020, we recognized $0.5 million and $1.1 million, respectively, of revenue related to our Pfizer License Agreement that was in our beginning deferred revenue balance. Our condensed consolidated balance sheets at June 30, 2020 and December 31, 2019 included deferred revenue of $0.3 million and $1.3 million, respectively, related to our development activities obligation under the Pfizer License Agreement.

In January 2017, we initiated a strategic collaboration with Novartis Pharma AG, or Novartis, for the development and commercialization of AKCEA-APO(a)-L_Rx and AKCEA-APOCIII-L_Rx. Under the terms of the Novartis collaboration, we agreed to complete a Phase 2 clinical trial, conduct an end-of-Phase 2 meeting with the U.S. Food and Drug Administration, or FDA, and provide initial quantities of API for each medicine.

In February 2019, Novartis exercised its exclusive option to license AKCEA-APO(a)-L_Rx.Novartis is responsible for conducting and funding all future development, regulatory and commercialization activities for AKCEA-APO(a)-L_Rx. Novartis has full use of the license without any continuing involvement from us, therefore making the license distinct from other performance obligations. Accordingly, we recognized the related license fee of $150.0 million in full in February 2019 upon exercise. We issued 2,837,373 shares of our common stock to Ionis to satisfy the $75.0 million sublicense fee due to Ionis for Novartis’ option exercise under our Cardiometabolic License Agreement with Ionis.

In the second quarter of 2019, we completed the development services performance obligation for AKCEA-APO(a)-L_Rx and all revenue allocated to this revenue stream was fully recognized as of June 30, 2019.

We are eligible to receive up to $675.0 million in additional milestone payments, including $25.0 million for the achievement of a development milestone, up to $290.0 million for the achievement of regulatory milestones and up to $360.0 million for the achievement of commercialization milestones. In connection with Novartis’ exercise of its option to exclusively license AKCEA-APO(a)-L_Rx, we and Novartis established a more definitive co-commercialization framework under which we and Novartis may negotiate the co-commercialization of AKCEA-APO(a)-L_Rx in select markets. Included in this framework is an option by which Novartis could solely commercialize AKCEA-APO(a)-L_Rx in exchange for Novartis paying us increased commercial milestone payments based on sales of AKCEA-APO(a)-L_Rx.

We will earn the next milestone payment of $25.0 million under this collaboration if Novartis reaches a specific level of enrollment related to the Phase 3 clinical trial for AKCEA-APO(a)-L_Rx. We are also eligible to receive tiered royalties in the mid-teens to low twenty percent range on net sales of AKCEA-APO(a)-L_Rx. Novartis will reduce these royalties upon the expiration of certain patents or if a generic competitor negatively impacts the product in a specific country. We will share any milestone payments and royalties equally with Ionis. AKCEA-APO(a)-L_Rx was recently granted Fast Track Designation by the FDA as a potential treatment for people at significant risk for cardiovascular disease due to elevated levels of lipoprotein(a), or Lp(a).

In December 2019, Novartis elected not to exercise its option to license AKCEA-APOCIII-L_Rx and terminated the strategic collaboration solely in relation to AKCEA-APOCIII-L_Rx.As a result, the development services performance obligation relating to AKCEA-APOCIII-L_Rx was satisfied and all revenue allocated to the development services revenue stream was fully recognized as of December 31, 2019.

As a result of Novartis’ election not to exercise its option, we retain the rights to further develop and commercialize AKCEA-APOCIII-L_Rx. We are no longer entitled to any future license fees, milestone payments or royalties from Novartis relating to AKCEA-APOCIII-L_Rx. In the second quarter of 2020, we repurchased $2.3 million of AKCEA-APOCIII-L_Rx API from Novartis to be used to further develop AKCEA-APOCIII-L_RX. This amount is included in research and development expense on our condensed consolidated statement of operations.

In August 2018, we entered into a collaboration and license agreement with PTC Therapeutics International Limited, or the PTC License Agreement, to commercialize TEGSEDI and WAYLIVRA in Latin America and certain Caribbean countries, or the PTC Territory. In addition, in April 2019, we entered into a supply agreement with PTC Therapeutics International Limited, or PTC Therapeutics, providing them the option to purchase product from us subject to terms as described in the agreement. During the three and six months ended June 30, 2020, we did not recognize any revenue from our collaboration with PTC Therapeutics.

In May 2019, we received a $6.0 million milestone payment from PTC Therapeutics as a result of regulatory approval of WAYLIVRA in Europe. We paid Ionis a $3.0 million sublicense fee under our Cardiometabolic License Agreement and recorded it as a cost of license in our condensed consolidated statement of operations. In October 2019, we received a $4.0 million milestone payment from PTC Therapeutics as a result of regulatory approval of TEGSEDI in Brazil. We paid Ionis a $2.4 million sublicense fee under our development, commercialization, collaboration and license agreement with Ionis dated March 2018, or the TTR License Agreement, and recorded it as a cost of license in our condensed consolidated statement of operations. We did not include these milestone payments in the upfront transaction price as we concluded that such future payments pursuant to the PTC License Agreement will be recognized when it is probable that PTC Therapeutics will achieve the related regulatory milestones. After receiving regulatory approval for WAYLIVRA and TEGSEDI, we deemed the milestones probable and recognized $6.0 million and $4.0 million as license revenue during the second and fourth quarter of 2019, respectively.

We are eligible to receive an additional $4.0 million milestone payment upon receiving regulatory approval of WAYLIVRA in Brazil and royalties in the mid-twenty percent range on net sales of TEGSEDI and WAYLIVRA in the PTC Territory.

PTC Therapeutics’ obligation to pay royalties to us begins on the earlier of 12 months after the first commercial sale of TEGSEDI or WAYLIVRA in Brazil or the date that PTC Therapeutics recognizes revenue of at least $10.0 million in cumulative net sales of TEGSEDI or WAYLIVRA in the PTC Territory. PTC Therapeutics will reduce these royalties upon the expiration of certain patents or if a generic competitor negatively impacts the market share of TEGSEDI or WAYLIVRA in the PTC Territory. Milestone payments and royalties that we are eligible to receive from PTC Therapeutics for TEGSEDI are split 60% to Ionis and 40% to Akcea in accordance with our TTR License Agreement. All WAYLIVRA milestone payments and royalties that we are eligible to receive from PTC Therapeutics are split equally with Ionis in accordance with our Cardiometabolic License Agreement. PTC Therapeutics is solely responsible for the commercialization of the products in the PTC Territory at its sole cost and expense, including the pursuit and maintenance of applicable regulatory approvals. Unless earlier terminated, the PTC License Agreement will continue in effect until the date on which the royalty term and all payment obligations with respect to all products in all countries in the PTC Territory have expired.