A Phase III Clinical Study to Evaluate SYN023's Efficacy and Safety

Summary

This is a Phase 3, blinded, randomized study of SYN023 compared to a China licensed Human Rabies Immunoglobulin (a Rabies immune globulin from human sources, HRIG) for the prevention of rabies as part of post-exposure prophylaxis (PEP). The trial will enroll the World Health Organization (WHO) Category III rabies exposure subjects. The subject's death and rabies data will be reviewed by Data and safety monitoring board (DSMB) to confirm the safety. Besides, rabies vaccine would be administered after Study Drug in each group. This trial is proposed to further the licensure of SYN023 to provide an effective PEP alternative available to those exposed persons who need such a product. A placebo-controlled rabies trial is unethical thus HRIG is selected as the control group. Rabies immune globulin from equine and human sources (HRIG) have been evaluated in many trials and HRIG is the standard of care in China.

Timeline

Start

2020-09-23

Primary completion

2022-06-24

Completion

2022-12-16

Publications

• Results McClain JB, Chuang A, Reid C, Moore SM, Tsao E. Rabies virus neutralizing activity, pharmacokinetics, and safety of the monoclonal antibody mixture SYN023 in combination with rabies vaccination: Results of a phase 2, randomized, blinded, controlled trial. Vaccine. 2021 Sep 24;39(40):5822-5830. doi: 10.1016/j.vaccine.2021.08.066. Epub 2021 Sep 3.
• Results Ding Y, Wu M, Zhang H, Zhu X, Hu Y, Li X, Liu J, Tsao E, Liu M, Li C. Safety, pharmacokinetics and pharmacodynamics of SYN023 alone or in combination with a rabies vaccine: An open, parallel, single dose, phase 1 bridging study in healthy Chinese subjects. Antiviral Res. 2020 Dec;184:104956. doi: 10.1016/j.antiviral.2020.104956. Epub 2020 Oct 19.
• Liu X, Zha Y, Wang Z, Jiang Y, Zhang X, Guo J, Li J, Zhang Q, Tsao E. The pharmacokinetics and safety comparison of Zamerovimab and Mazorelvimab monoclonal antibodies vs. HRIG in category III rabies post-exposure prophylaxis: a stratified analysis by wound characteristics. Biologicals. 2025 Nov;92:101852. doi: 10.1016/j.biologicals.2025.101852. Epub 2025 Aug 13.
• Liu X, Li J, Zha Y, Wang Z, Jiang Y, Zhang X, Guo J, Yu J, Li X, Zhang Q, Reid C, McClain JB, Tsao E. The efficacy and safety of SYN023 (Zamerovimab and Mazorelvimab injection), the recombinant humanized anti-rabies virus monoclonal antibody mixture, combined with rabies vaccine in a WHO category III rabies post-exposure population: A randomized, double-blind, positive control, phase III clinical trial. Vaccine. 2025 Aug 13;61:127289. doi: 10.1016/j.vaccine.2025.127289. Epub 2025 Jun 5.

Drugs

Indications