6. Intangible Assets and In-Process R&D

Intangible assets at December 31, 2019 consist of the rights to trade secrets and know-how related to the manufacturing of the EyeGate Ocular Bandage Gel (“OBG”). During the third quarter of 2018, the Company entered into an intellectual property license agreement with SentrX Animal Care, Inc. (“SentrX”) with respect to certain rights relating to the manufacturing of EyeGate OBG product. The intangible assets were recorded at $250,000, representing the upfront payment paid to SentrX. Additionally, SentrX is eligible to receive milestone payments totaling up to $4.75 million, upon and subject to the achievement of certain specified development and commercial milestones. These future milestone payments to SentrX will increase the carrying value of the intangible assets. The Company’s intangible assets are amortized on a straight-line basis over the estimated useful lives. Additionally, in-process R&D at December 31, 2019 and 2018 consists of projects acquired from the acquisition of Jade that have not reached technological feasibility and which have no alternative future use. Once the R&D process is complete, the Company will amortize the R&D asset over its remaining useful life. The Company periodically evaluates these assets for impairment.

Intangible assets and in-process R&D at December 31, 2019 and 2018 consists of the following:

Amortization expense on intangible assets was $25,000 and $6,250 for the years ended December 31, 2019 and 2018, respectively.