FAIR VALUE MEASUREMENTS - Transfers (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
FAIR VALUE MEASUREMENTS
Assets, transfer from level 1 to level 2	$ 0	$ 0
Assets, transfer from level 2 to level 1	$ 0	$ 0

Amount of transfers of assets measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2.

No definition available.

Name:	aplt_FairValueAssetsLevel1ToLevel2TransfersAmount1
Namespace Prefix:	aplt_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant