Intangible assets are related to certain capitalized milestone and sublicense payments. The following table presents intangible assets (in thousands):

	December 31,
	2020			2019
Intangible assets	$	19,773		$	19,773
Less accumulated amortization		(19,773	)		(17,273	)
Total	$	-		$	2,500

We recorded cost of sales - amortization of intangible assets related to capitalized sublicense payments to Merck, Sharp & Dohme Corp. (“Merck”) that we capitalized upon FDA approval of HEPLISAV-B in November 2017. See Note 10. Cost of sales – amortization of intangible assets for the year ended 2020 and 2019 was $2.5 million and $9.2 million, respectively. At December 31, 2020, intangible assets related to Merck has been fully amortized. No impairment of intangible assets has been identified during the years presented.

In May 2019, we announced a strategic restructuring to focus on our vaccine business and curtail our investment in our immuno-oncology programs. In July 2020, we sold assets related to our immuno-oncology compound, SD-101, which included intellectual property, clinical and non-clinical data, regulatory filings, clinical supply inventory and certain contracts to Surefire Medical Inc. d/b/a TriSalus Life Sciences (“TriSalus”). Pursuant to the Asset Purchase Agreement, we received $5 million upon closing of the transaction and $4 million in December 2020 as reimbursement for certain clinical trial expenses. In addition, we could receive up to an additional $250 million upon the achievement of certain development, regulatory, and commercial milestones and low double-digit royalties based on potential future net sales of product containing SD-101 compound. In connection with our agreement with Symphony Dynamo, Inc. and Symphony Dynamo Holdings LLC (“Holdings”) in November 2009, we paid $2.5 million to Holdings in August 2020. See Note 9.

For the year ended December 31, 2020, we recognized a gain on sale of SD-101 assets of $6.9 million, based on the amount of consideration received, net of any transaction costs. The $2.5 million payment to Holdings was included in selling, general and administrative expense in our consolidated statement of operations.