Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2022	Apr. 29, 2022
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2022
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q1
Trading Symbol	CBIO
Entity Registrant Name	Catalyst Biosciences, Inc.
Entity Central Index Key	0001124105
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		31,477,053
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity File Number	000-51173
Entity Tax Identification Number	56-2020050
Entity Address, Address Line One	611 Gateway Blvd.
Entity Address, Address Line Two	Suite 710
Entity Address, City or Town	South San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94080
City Area Code	650
Local Phone Number	871-0761
Entity Interactive Data Current	Yes
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	DE
Document Quarterly Report	true
Document Transition Report	false
Title of 12(b) Security	Common Stock