A bifunctional C5 antibody-CR1 fusion protein may have a higher yield and superior complement-inhibiting activity compared with the standard C5 antibody therapy used to treat paroxysmal nocturnal hemoglobinuria (PNH), according to a new article posted on Research Square. The study has not yet been peer-reviewed.

The researchers used transient transfection expression to generate candidate fusion proteins and purified them via protein A affinity chromatography. The bioactivities of the candidate proteins were evaluated by in vitro classical pathway- and alternative pathway-mediated hemolysis assays. They also used flow cytometry to calculate C3b deposition.

Furthermore, the study authors tested the pharmacokinetic and pharmacodynamic characteristics of optimized fusion proteins in wild-type and human C5 transgenic mice, as well as cynomolgus monkeys. Next, they used collagen antibody-induced arthritis model mice to evaluate the therapeutic effects of the final product for PNH and other complement-associated diseases.

According to the results, a bifunctional complement inhibitory fusion protein with a higher yield and superior classic and alternative pathway inhibitory activities was generated through the mutated short consensus repeat 1 to 5 fragment of CR1 to the N-terminal of the heavy chain of the C5 antibody, modifying surface charge and attaching linkers. The final product showed the capability to inhibit C3 fragment deposition and therapeutic potential for collagen antibody-induced arthritis, as well as 1 week of in vivo bioactivity.

Read more about PNH treatment

“CR1 was initially chosen to construct this anti-C5 antibody fusion protein since several CR1 derivatives had been evaluated in pre-clinical and clinical trials, such as TP-10 (phase I) in patients undergoing cardiac surgery, IBI302 (phase II) in wet [age-related macular degeneration] clinical trials, and CSL-40 in pre-clinical studies,” Gong and colleagues wrote.

The widely used C5 antibody is inefficient in blocking the alternative pathway of the complement system and unable to reduce the deposition of C3b on the cell surface produced by C3 activation. It may even increase C3b deposition, which is often associated with extravascular hemolysis in PNH patients treated with C5 antibody. On the other hand, CR1 alone has poor druggability due to its low yield and short pharmacokinetics.


Gong Y, Chai X, Jia J, et al. Bi-functional C5 antibody-CR1 fusion for complement inhibition. Research Square. Published online April 4, 2023. doi:10.21203/rs.3.rs-2763376/v1