In May 2017, the Company closed on a business combination and recorded an initial purchase price allocation including goodwill. During the nine months ended September 30, 2018 and prior to the end of the measurement period for accounting for the business combination, the Company recorded adjustments to the purchase price allocation resulting in a net decrease in tax refunds receivable, with a corresponding net increase in goodwill, of $490,676. As goodwill related to this transaction had previously been determined to be fully impaired, the Company recognized an impairment charge of $490,676 as a result of these purchase price allocation adjustments during the nine months ended September 30, 2018. The purchase price allocation was considered final in May 2018, and no further adjustments were recorded.

	September 30, 2019
	Estimated Useful Lives	Gross Carrying Value		Accumulated Amortization			Impairment			Net Book Value
Internally developed patents	6-10 years	$	743,956	$	(440,994	)	$	—		$	302,962
Acquired licenses	16-20 years		285,000		(265,273	)		—			19,727
Total intangible assets subject to amortization			1,028,956		(706,267	)		—			322,689
IPR&D assets	Indefinite		13,418,967		—			(1,000,000	)		12,418,967
Total		$	14,447,923	$	(706,267	)	$	(1,000,000	)	$	12,741,656

	December 31, 2018
	Estimated Useful Lives	Gross Carrying Value		Accumulated Amortization			Impairment			Net Book Value
Internally developed patents	6-10 years	$	718,559	$	(317,172	)	$	—		$	401,387
Acquired licenses	16-20 years		285,000		(253,430	)		—			31,570
Total intangible assets subject to amortization			1,003,559		(570,602	)		—			432,957
IPR&D assets	Indefinite		37,868,978		—			(24,450,011	)		13,418,967
Total		$	38,872,537	$	(570,602	)	$	(24,450,011	)	$	13,851,924

Amortization expense of intangible assets subject to amortization was $28,084 and $15,972 for the three months ended September 30, 2019 and 2018, and $135,664 and $45,426 for the nine months ended September 30, 2019 and 2018, respectively. Amortization expense was classified as research and development expenses in the accompanying unaudited consolidated statements of operations and comprehensive loss.

The development activities under the SparVax-L NIAID contract were completed during the third quarter of 2019, with no future funding identified. As a result of the contract completion and the US government’s funding prioritization of only single dose anthrax vaccine candidates, the Company abandoned the project and concluded that the full remaining net book value of the SparVax-L IPR&D asset was impaired during the three months ended September 30, 2019. An impairment charge of $1,000,000 was expensed for the three and nine months ended September 30, 2019.