Catalyst Biosciences Announces Presentations at the International Society on Thrombosis and Haemostasis

Catalyst Biosciences, Inc. (NASDAQ: CBIO) today announced four poster presentations on marzaptacog alfa (activated) (MarzAA) and dalcinanonog alfa (DalcA) at the upcoming International Society on Thrombosis and Haemostatis (ISTH) Virtual Congress being held from July 17-21, 2021.

Poster TitleDose selection for subcutaneous marzaptacog alfa (activated) in subjects with Factor VII deficiency using population pharmacometrics clinical trial simulationsAuthorTom Knudsen, D.V.M., Ph.D., vice president, corporate development, Catalyst Biosciences

Poster titleDose selection of marzaptacog alfa (activated) in children with Hemophilia: a population pharmacokinetic exposure matching strategyAuthorTom Knudsen, D.V.M., Ph.D., vice president, corporate development, Catalyst Biosciences

Poster titleSubcutaneous marzaptacog alfa (activated) is effective treatment of bleeding in FVII deficient ratsAuthorTom Knudsen, D.V.M., Ph.D., vice president, corporate development, Catalyst Biosciences

Poster titleMitigation of injection site reactions after subcutaneous administration of dalcinanonog alfa (DalcA) in Hemophilia B using preclinical modelsAuthorNatacha Le Moan, senior director, translational research, Catalyst Biosciences

A copy of the presentation materials can be accessed on the Events and Presentations section of the Catalyst website once the congress begins.

About Catalyst Biosciences, the Protease Medicines companyCatalyst is a research and clinical development biopharmaceutical company focused on addressing unmet medical needs in rare disorders of the complement and coagulation systems. Our protease engineering platform has generated two late-stage clinical programs, including MarzAA, a SQ-administered next-generation engineered rFVIIa for the episodic treatment of bleeding in subjects with rare bleeding disorders and dalcinonacog alfa (DalcA) a SQ-administered next-generation engineered rFIX for prophylaxis of bleeding in subjects with Hemophilia B. Our complement pipeline includes a preclinical C3-degrader program licensed to Biogen for dry age-related macular degeneration, an improved complement factor I protease for SQ replacement therapy in patients with CFI deficiency, and C4b-degraders designed to target disorders of the classical complement pathway, as well as other complement programs in discovery.

Forward-Looking Statements This press release contains forward-looking statements that involve substantial risks and uncertainties. Forward-looking statements include statements about the potential benefits of products based on Catalyst's engineered protease platform. 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 the one or both of the clinical trials of MarzAA may be delayed or terminated as a result of COVID-19, competitive products and other factors, that trials may not have satisfactory outcomes, that additional human trials will not replicate the results from earlier trials, that potential adverse effects may arise from the testing or use of MarzAA, including the generation of neutralizing antibodies, 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 trial enrollment, development and manufacturing resulting from COVID-19 and other factors, competition and other risks described in the "Risk Factors" section of the Company's Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission on May 6, 2021, and in other filings with the Securities and Exchange Commission. The Company does not assume any obligation to update any forward-looking statements, except as required by law.

Contact:Ana KaporCatalyst Biosciences, [e-mail]