CBIO Catalyst Biosciences Inc

Catalyst Biosciences, Inc. (NASDAQ: CBIO) today announced the publication of preclinical data from its study of CB 2679d-GT in Hemophilia B mice in Blood, the peer-reviewed, official journal of the American Society of Hematology. The paper, entitled: "Gene Therapy for Hemophilia B Using CB 2679d-GT: A Novel Factor IX Variant with Higher Potency than Factor IX Padua," demonstrated superiority of the Company's CB 2679d-GT gene therapy candidate over that of the R338L-Padua variant, which is currently used in clinical trials.

The study, conducted at the Vrije Universiteit Brussel, Brussels, Belgium, by the team of Thierry VandenDriessche and Marinee Chuah in collaboration with Catalyst Biosciences, showed gene therapy with CB 2679d-GT safely and effectively achieved sustained factor IX (FIX) levels and significantly outperformed the R338L-Padua variant in hemophilia B mice. A significantly reduced bleeding time and total blood loss with CB 2679d-GT gene therapy compared to mice treated with R338L-Padua demonstrated a more rapid and robust hemostatic correction. Thus, CB 2679d-GT could potentially allow for lower and safer vector doses in future human trials.

"The data demonstrate the strong potential of our gene therapy candidate," said Grant Blouse, Ph.D., Senior Vice President, Translational Research at Catalyst Biosciences. "We are thrilled to have the study results published in Blood to share with the medical and scientific communities

Thierry VandenDriessche, the lead investigator at Vrije Universiteit Brussel, Belgium, said, "Collectively, these data support the efficacy and safety of CB 2679d-GT as a promising novel alternative to R338L-Padua for hemophilia B gene therapy. Its potential to obtain higher FIX activity levels and superior hemostatic efficacy following AAV directed gene therapy in hemophilia B patients than what is currently achievable with the R338L-Padua variant validates further clinical development."

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 subcutaneously (SQ) administered next-generation engineered coagulation Factor VIIa (FVIIa) for the treatment of episodic bleeding in subjects with rare bleeding disorders. Our complement pipeline includes a preclinical C3-degrader program partnered with 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 development.

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, and the superiority of CB 2679d-GT over the Padua variant. 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 that additional human trials will not replicate the results from earlier trials, that potential adverse effects may arise from the testing or use of the Company’s product candidates, including the generation of neutralizing antibodies, the risk that clinical trials and studies may be delayed as a result of COVID-19, competitive products and other factors, that trials may not have satisfactory outcomes, 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, the risk that Biogen will terminate Catalyst's agreement, 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 on March 4, 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, Inc.investors@catbio.com