Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2021	Nov. 01, 2021
Document and Entity Information
Entity Registrant Name	Onconova Therapeutics, Inc.
Entity Central Index Key	0001130598
Document Type	10-Q
Document Period End Date	Sep. 30, 2021
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Quarterly Report	true
Document Transition Report	false
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Interactive Data Current	Yes
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		20,890,563
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Title of 12(b) Security	Common Stock, par value $.01 per share
Trading Symbol	ONTX
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	22-3627252
Entity File Number	001-36020
Entity Address, Address Line One	12 Penns Trail
Entity Address, City or Town	Newtown
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	18940
City Area Code	267
Local Phone Number	759-3680