8. INTANGIBLE ASSETS

In August 2019, the Company received FDA approval of WAKIX® (pitolisant) for the treatment of excessive daytime sleepiness (“EDS”) in adult patients with narcolepsy. This event triggered a milestone payment of $75,000 under the provisions of the 2017 LCA (defined below) which the Company capitalized as an intangible asset. The Company determined a useful life of 10 years for such intangible asset, and, as of December 31, 2023, the remaining useful life was 5.8 years.

In October 2020, the Company received FDA approval for the New Drug Application (“NDA”) for WAKIX® for the treatment of cataplexy in adult patients with narcolepsy. This event triggered a milestone payment of $100,000 under the provisions of the 2017 LCA which the Company capitalized as an intangible asset and paid in January of 2021. The Company determined a useful life of 9 years for such intangible asset, and, as of December 31, 2023, the remaining useful life was 5.8 years.

In February 2022, the Company attained $500,000 in life-to-date aggregate net sales of WAKIX in the United States. This event triggered a final $40,000 payment under the provisions of the 2017 LCA which the Company capitalized as an intangible asset and paid in March of 2022. The Company determined a useful life of 7.6 years for such intangible asset, and, as of December 31, 2023, the remaining useful life was 5.8 years.

Amortization expense was $23,845, $22,966 and $18,424 for the years ended December 31, 2023, 2022 and 2021, respectively, and is recorded in general and administrative expenses in the consolidated statements of operations and comprehensive income (loss).

Future annual amortization expense for the unamortized intangible assets is as follows:

​

​

The gross carrying amount and net book value of the intangible asset is as follows:

​

​