6. Deferred Legal Fees and Intangible Assets

Deferred legal fees have been incurred in connection with patents for Oxtellar XR and Trokendi XR. As of March 31, 2017 and December 31, 2016, the Company had deferred legal fees of $11.3 million and $19.9 million, respectively.

The following sets forth the gross carrying amount and related accumulated amortization of the intangible asset, in thousands:

	Weighted-	March 31,			December 31,
	Average Life	2017			2016
	(unaudited)
Capitalized patent defense costs	5.9 - 11 years	$	31,172		$	17,773

Less accumulated amortization		(1,722		)	(1,283		)

		$	29,450		$	16,490

In March 2017, the Company entered into two settlements with various companies related to Trokendi XR patent litigation, at which time the Company reduced deferred legal fees by $12.6 million and transferred these amounts to intangible assets. The Company subsequently began amortizing the cost of litigation, and will continue to do so through the settlement date of January 1, 2023.

The net book value of intangible assets was $29.5 million as of March 31, 2017 and $16.5 million as of December 31, 2016. The

increase in intangible assets reflects the settlement of lawsuits related to Trokendi XR during the first quarter of 2017.

Amortization expense on intangible assets was approximately $439,000 and $142,000 for the three months ended March 31, 2017 and 2016, respectively.

There were no indicators of impairment identified at March 31, 2017 or March 31, 2016.