Intangible Assets

3 Months Ended

Dec. 31, 2022

Goodwill and Intangible Assets Disclosure [Abstract]

Intangible Assets

INTANGIBLE ASSETS

Intangible assets subject to amortization include patents and a license agreement capitalized as part of the Novartis RNAi asset acquisition in March 2015. The following table presents the components of intangible assets:

	Gross Carrying Amount		Accumulated Amortization		Impairment		Net Carrying Amount		Useful Lives
	(amounts in thousands)								(in years)
As of December 31, 2022
Patents	$	21,728	$	12,158	$	—	$	9,570	14
License	3,129		1,162		—		1,967		21
Total intangible assets, net	$	24,857	$	13,320	$	—	$	11,537
As of September 30, 2022
Patents	$	21,728	$	11,770	$	—	$	9,958	14
License	3,129		1,125		—		2,004		21
Total intangible assets, net	$	24,857	$	12,895	$	—	$	11,962

Intangible assets are reviewed annually for impairment and more frequently if potential impairment indicators exist. No impairment indicators were identified during the three months ended December 31, 2022 and 2021.

Intangible assets with definite useful lives are amortized on a straight-line basis over their useful lives. Intangible assets amortization expense for each of the three months ended December 31, 2022 and 2021 was $0.4 million. None of the intangible assets with definite useful lives are anticipated to have a residual value.

The following table presents the estimated future amortization expense related to intangible assets as of December 31, 2022:

	Amortization Expense
Year Ending September 30,	(in thousands)
2023 (remainder)	$	1,275
2024	1,700
2025	1,700
2026	1,700
2027	1,700
Thereafter	3,462
Total	$	11,537