The following purchased assets were accounted for as asset acquisitions as substantially all of the fair value of the assets acquired were concentrated in a group of similar assets and/or the acquired assets were not capable of producing outputs due to the lack of employees and early stage of development. Because the assets had not yet received regulatory approval, the fair value attributable to these assets was recorded as in process research and development (“IPR&D”) expenses in the Company’s consolidated statement of operations for the years ended December 31, 2019, 2018, and 2017.

The Company accounts for contingent consideration payable upon achievement of certain regulatory, development or sales milestones in such asset acquisitions when the underlying contingency is resolved.

On October 2, 2017, the Company, entered into a license agreement with Pulmokine, Inc. under which it was granted an exclusive worldwide license and sublicense to certain intellectual property rights owned or controlled by Pulmokine to develop and commercialize GB002 and certain backup compounds for the treatment, prevention and diagnosis of any and all disease or conditions. The Company also has the right to sublicense its rights under the license agreement, subject to certain conditions. The assets acquired are in the early stages of the FDA approval process, and the Company intends to further develop the assets acquired through potential FDA approval as evidenced by the milestone arrangement in the contract. The development activities cannot be performed without significant cost and effort by the Company. The agreement will remain in effect from the effective date, unless terminated earlier, until, on a licensed product-by-licensed product and country-by-country basis, the later of ten years from the date of first commercial sale or when there is no longer a valid patent claim covering such licensed product or specified regulatory exclusivity for the licensed product in such country. The Company is obligated to make future development and regulatory milestone payments of up to $63.0 million, commercial milestone payments of up to $45.0 million, and sales milestone payments of up to $190.0 million. The Company is also obligated to pay tiered royalties on sales for each licensed product, at percentages ranging from the mid-single digits to the high single-digits. The Company made an upfront payment in the year ended December 31, 2017, recorded as IPR&D of $5.5 million. As of December 31, 2019, no milestones had been accrued as the underlying contingencies had not yet been resolved.

On January 4, 2018, the Company acquired AA Biopharma Inc. pursuant to a merger agreement, and with the acquisition acquired the rights to GB001 and certain backup compounds. In connection with the merger agreement, the Company issued an aggregate of 20,000,000 shares of Series Seed Convertible Preferred Stock and 1,101,278 shares of Common Stock to the AA Biopharma shareholders. The Company recorded IPR&D of $19.3 million in connection with the acquisition of AA Biopharma.

On June 24, 2018, the Company entered into a license agreement with Aerpio Pharmaceuticals, Inc. (“Aerpio”) under which the Company was granted an exclusive worldwide license and sublicense to certain intellectual property rights owned or controlled by Aerpio to develop and commercialize GB004, and certain other related compounds for all applications. The Company also has the right to sublicense its rights under the license agreement, subject to certain conditions. The Company is obligated to make future development and regulatory milestone payments of up to $55.0 million, commercial milestone payments of up to $85.0 million and sales milestone payments of up to $260.0 million. The Company is also obligated to pay tiered royalties on sales for each licensed product, at percentages ranging from a high single-digit to mid-teens, subject to certain customary reductions. The Company made an upfront payment of $20.0 million, which represented the purchase consideration for an asset acquisition. As of December 31, 2019, no milestones had been accrued as the underlying contingencies had not yet been resolved.

On September 21, 2018, the Company acquired Adhaere Pharmaceuticals, Inc. pursuant to a merger agreement for an upfront payment of $7.5 million in cash, and with the acquisition acquired the rights to GB1275 and certain backup compounds. The Company is obligated to make future regulatory, development and sales milestone payments of up to $62.0 million and pay tiered royalties on worldwide net sales, at percentages ranging from low to mid-single digits, subject to customary reductions. The Company recorded IPR&D of $7.5 million in connection with the acquisition of Adhaere. In May 2019, the Company made a milestone payment of $1.0 million in connection with the filing of the Investigational New Drug application for the GB1275 program. As of December 31, 2019, no other milestones had been accrued as the underlying contingencies had not yet been resolved.

The Company recorded the following IPR&D expense on the consolidated statements of operations (in thousands):

	Years Ended December 31,
	2019		2018		2017
GB002	$	—	$	—	$	5,500
GB001		—		19,148		—
GB004		—		20,000		—
GB1275		1,000		7,501		—
Other preclinical programs		2,600		3,010		—
Total in process research and development	$	3,600	$	49,659	$	5,500