Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Mar. 20, 2023	Jun. 30, 2022
Document and Entity Information
Document Type	10-K
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Dec. 31, 2022
Entity File Number	001-37990
Entity Registrant Name	LEAP THERAPEUTICS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	27-4412575
Entity Address, Address Line One	47 Thorndike Street
Entity Address, Address Line Two	Suite B1-1
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02141
City Area Code	617
Local Phone Number	714-0360
Title of 12(b) Security	Common Stock, par value $0.001
Trading Symbol	LPTX
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		118,750,386
Entity Public Float			$ 93.8
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	FY
Entity Central Index Key	0001509745
Amendment Flag	false
ICFR Auditor Attestation Flag	false
Auditor Name	EisnerAmper LLP
Auditor Firm ID	274
Auditor Location	Iselin, New Jersey