| Document and Entity Information - USD ($) | 12 Months Ended | ||
| Dec. 31, 2021 | Mar. 31, 2022 | Jun. 30, 2021 | |
| Cover [Abstract] | |||
| Document Type | 10-K/A | ||
| Amendment Flag | true | ||
| Document Period End Date | Dec. 31, 2021 | ||
| Document Fiscal Year Focus | 2021 | ||
| Document Fiscal Period Focus | FY | ||
| Trading Symbol | CBIO | ||
| Entity Registrant Name | Catalyst Biosciences, Inc. | ||
| Entity Central Index Key | 0001124105 | ||
| Current Fiscal Year End Date | --12-31 | ||
| Entity Well-known Seasoned Issuer | No | ||
| Entity Current Reporting Status | Yes | ||
| Entity Voluntary Filers | No | ||
| Entity Filer Category | Accelerated Filer | ||
| Entity Shell Company | false | ||
| Entity Small Business | true | ||
| Entity Emerging Growth Company | false | ||
| Entity Common Stock, Shares Outstanding | 31,477,053 | ||
| Entity Public Float | $ 135,045,079 | ||
| ICFR Auditor Attestation Flag | true | ||
| Entity Interactive Data Current | Yes | ||
| Title of 12(b) Security | Common stock, par value $0.001 per share | ||
| Security Exchange Name | NASDAQ | ||
| Entity File Number | 000-51173 | ||
| Entity Incorporation, State or Country Code | DE | ||
| 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 | ||
| Document Annual Report | true | ||
| Document Transition Report | false | ||
| Auditor Firm ID | 274 | ||
| Auditor Name | EisnerAmper LLP | ||
| Auditor Location | Philadelphia, Pennsylvania | ||
| Amendment Description | EXPLANATORY NOTE Catalyst Biosciences, Inc. (the “Company”) is filing this Amendment No. 1 on Form 10-K/A (“Amendment”) to amend its Annual Report on Form 10-K for the year ended December 31, 2021 (the “Form 10-K”), which was originally filed with the Securities and Exchange Commission (“SEC”) on March 31, 2022. The purpose of this Amendment is to file the information required by Items 10, 11, 12, 13 and 14 of Part III of Form 10-K. Except as described above, no other amendments are being made to our annual report on Form 10-K filed on March 31, 2022. In addition, as required by Rule 12b-15 under the Securities Exchange Act of 1934, as amended (the “Exchange Act”), new certifications by the Company’s principal executive officer and principal financial officer are filed herewith as exhibits 31.03 and 31.04 to this Amendment pursuant to Rule 13a-14(a) of the Exchange Act. The Company is not including certifications pursuant to Section 1350 of Chapter 63 of Title 18 of the United States Code (18 U.S.C. 1350) as no financial statements are being filed with this Amendment. |
