Catalyst Biosciences Presents Four Posters at the International Society for Thrombosis and Haemostasis (ISTH) 2021 Virtual Congress

SOUTH SAN FRANCISCO, Calif., July 19, 2021 (GLOBE NEWSWIRE) — Catalyst Biosciences, Inc. (NASDAQ: CBIO) today presented four posters at the International Society for Thrombosis and Haemostasis (ISTH) 2021 Virtual Congress, being held July 17-21, 2021. The first poster, entitled: “Subcutaneous Marzeptacog Alfa (Activated) Effectively Treats Bleeding in FVII Deficient Rats Both When Administered Prior To or After Bleeding Has Started,” was presented by Tom Knudsen, DVM, Ph.D., senior vice president, corporate development, Catalyst Biosciences, who also presented the second and third posters. The study was conducted using an animal model to investigate the effect of subcutaneous (SQ) marzeptacog alfa (MarzAA) on tail vein transection (TVT) bleeding in FVII deficient rats. The data demonstrated that SQ MarzAA corrects the bleeding phenotype in FVII deficient rats when administered prior to or even after bleeding has started in a TVT bleeding model. The second poster, entitled: “Dose Selection for Subcutaneous Marzeptacog Alfa (Activated) in Subjects with Factor VII Deficiency Using Population Pharmacometric Clinical Trial Simulations,” highlighted work done in support of the dose selection for SQ MarzAA in planned clinical trials. The objective of the study was to conduct simulations using a MarzAA-specific, population pharmacokinetic (PK) model in a large population following different dose levels of MarzAA. The simulations indicated that hemostasis may be achieved with the proposed trial doses and sufficient exposure levels may be sustained in two-thirds or more of subjects for 24 hours even after a single SQ MarzAA dose of 20 µg/kg, and almost all subjects at higher doses. The third poster, entitled: “Dose Selection of Marzeptacog Alfa (Activated) in Children with Hemophilia: A Population Pharmacokinetic Exposure Matching Strategy,” presented data using clinical trial simulation to support pediatric trial dose selection for SQ MarzAA in children with Hemophilia A or B with inhibitors. The population pharmacokinetics simulation supported selecting a 60 µg/kg SQ dose of MarzAA in a pediatric clinical trial, similar to the dose in the ongoing clinical trial in adult and adolescent subjects. The fourth poster, entitled: “Mitigation of Injection Site Reactions After Subcutaneous Administration of Dalcinonacog Alfa (DalcA) in Hemophilia B Using Preclinical Models,” was presented by Natacha Le Moan, Ph.D., senior director, translational research, Catalyst Biosciences. The study was conducted to investigate the mechanism of injection site reactions (ISR) by examining cutaneous cellular and proteomic changes after SQ DalcA administration in the ex vivo human HypoSkin® biopsy platform and in vivo minipig model. The data demonstrated that formulation buffer composition affects DalcA MRGPRX2 (Mas-related Gprotein coupled receptor X2)-mediated cell activation in vitro. The activation of the MRGPRX2 receptor triggers vascular permeability, pain and itching and has been implicated in ISRs. An optimal formulation buffer reducing MRGPRX2 activation was selected to minimize the risk of ISRs upon DalcA administration. “Our scientific teams have built a tremendous body of knowledge around MarzAA and DalcA, and we are pleased to have presented some of that at ISTH,” said Nassim Usman, Ph.D., president and chief executive officer of Catalyst. “The data support our approach in our ongoing trials of MarzAA in hemostasis, where we are enrolling patients in the Crimson 1 Phase 3 registrational study as well as in a Phase 1/2 trial.” A copy of the presentation materials can be accessed on the Scientific Presentations and Publications section of the Catalyst website. 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 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 development. Forward-Looking StatementsThis press release contains forward-looking statements that involve substantial risks and uncertainties. Forward-looking statements include statements about the potential uses and benefits of MarzAA and DalcA, as well as statements about ongoing clinical trials. 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 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, 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, the risk that Biogen will terminate Catalyst’s agreement, the risk that potential adverse effects may arise from the testing or use of MarzAA, including the generation of neutralizing antibodies, 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, [email protected]