Catalyst Biosciences : Investor presentation – January 26, 2021

Nasdaq: CBIO

CATALYST

BIOSCIENCES

Corporate Overview

26 January 2021

CatalystBiosciences.com

© Catalyst Biosciences

Forward looking statements

Certain information contained in this presentation and statements made orally during this presentation include forward-looking statements that involve substantial risks and uncertainties. All statements included in this presentation, other than statements of historical facts, are forward- looking statements. Forward-looking statements include,

without limitation, statements about the product candidates of Catalyst Biosciences, Inc. (the "Company") and the benefits of its protease engineering platform, potential markets for and advantages of MarzAA and DalcA; plans to enroll a pivotal Phase 3 registration study of MarzAA; the initiation of a Phase 1/2 trial in patients with FVII Deficiency, Glanzmann Thrombasthenia, and patients treated with Hemlibra; MarzAA as possibly the first prophylactic for FVII Deficiency and Glanzmann Thrombasthenia; the potential for MarzAA and DalcA to effectively and therapeutically treat hemophilia subcutaneously; projected complement market opportunity, solution to

fundamental shortcomings in current treatment options, plans to enroll the CB 4332 observational trial in the Company's complement program in mid-2021, and ongoing updates related to CB 4322 and the C4b degrader.

Actual results or events could differ materially from the plans, intentions, expectations and projections disclosed in the forward-looking statements. Various important factors could cause actual results or events to differ materially, including, but not limited to, the risk that trials and studies may be delayed as a result of COVID-19 and other factors, that trials may not have satisfactory outcomes, that human trials will not replicate the results from earlier trials, the risk that costs required to develop or manufacture the Company's products will be higher than anticipated, including as a result of delays in development and manufacturing resulting from COVID-19 and other factors, the risk that Biogen will terminate its agreement with the Company, competition and other risks described in the "Risk Factors" section of the

Company's Annual Report on Form 10-K filed with the Securities and Exchange Commission ("SEC") on February 20, 2020, Quarterly Report on Form 10-Q filed with the SEC on November 5, 2020, and in other filings with the SEC. The forward-looking statements in this presentation represent the Company's view as of the date of this presentation and the Company does not assume any obligation to update any forward-looking statements, except as required by law.​

© Catalyst Biosciences

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The Protease Medicines Company

Harnessing the catalytic power of proteases

Late-stage asset in Phase 3

Robust complement portfolio

Clinical-stage hemophilia assets Novel differentiated protease medicines

© Catalyst Biosciences

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Catalyst's protease platform generates differentiated therapeutics

Unique expertise in protease biology enables design of optimized protease therapeutics

Discovery platform

Our proteases

Protease

scaffold

Structure guided

design

Molecular evolution

Engineered

regulation

Pharmacokinetic

improvement

• Functionally enhance natural proteases in the complement & coagulation cascades
• Engineer novel protein degraders in the complement cascade
• Modulate or target biological activation or inactivation

Therapeutic

protease

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