Note 4. Intangible assets, net

Intangible assets were as follows:

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Amortization expense related to intangible assets, all of which are classified as finite-lived, was $0.1 million and $0.7 million, and $0.5 million and $1.5 million for the three and nine months ended February 28, 2022 and 2021, respectively. The Company recognized an impairment charge of $10.0 million related to the ProstaGene, LLC intangible asset acquisition during the quarter ended February 28, 2021. Refer to Note 8, Acquisition of Patents and Intangibles, of the 2021 Form 10-K for further information.

The following table summarizes the estimated aggregate future amortization expense related to the Company’s intangible assets with finite lives as of February 28, 2022:

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