A Novel pH Dependent C5 Monoclonal Antibody with Better Developability

Introduction:

Dysregulation of complement system is the driver of many immune disorder diseases, including paroxysmal nocturnal hemoglobinuria (PNH), atypical hemolytic uremic syndrome (aHUS), and etc. All pathways of complement activation converge at the cleavage of C5, which leads to the generation of membrane attack complex (MAC). The approval of Eculizumab, anti-C5 monoclonal antibody, opened the complement-inhibitor era and proved C5 to be a feasible therapeutic target with manageable risk. Eculizumab and Crovalimab are currently approved for treatment of patients with PNH, yet treatment limitations include hemolysis breakthrough for non-sufficient C5 inhibition, lack of efficacy in patients with C5 mutational variants, and the burden of regular intravenous infusions. The next-generation C5 inhibitor emerges as a new/existing C5 monoclonal antibody engineered to have pH dependence (to reduce dosing frequency), and other new approached to target C5 in complement system. Here we report the results of a novel pH dependent C5 monoclonal antibody-LP-005, to prevent the hemolysis of red blood cells (RBCs) from PNH patients in vitro experiment.

Methods:

The sequence of Ravulizumab and Crovalimab were obtained from INN. LP-005 was generated using hybridoma method and multidimentionally optimized in variable and content regions. All antibodies were expressed by NHK293 cells.

For antibody affinity test, Fortebio Octet K2 was used, different C5 antibodies were first loaded on the AHC sensors and serial diluted recombinant human C5 have been run for global-fit analysis.

For antibody biological function test, antibody-sensitized sheep RBCs hemolysis (classic pathway/CP activity) inhibition assay have been run in 1% normal human serum (NHS) with antibodies serial diluted by GVB++ buffer. Antibody-sensitized chicken RBC hemolysis (CP activity) inhibition assay have been run in 6.25% NHS with antibodies serial diluted by GVB++ buffer. Ex vivo inhibition of PNH patients (with more than 70% CD59 deficiency) RBCs hemolysis by anti-C5 antibodies was performed using ABO blood group-compatible serum (20%) under conditions of robust alternative pathway (AP) specific activation (GVB0 + MgEGTA, pH7.3). CD59 deficiency on RBCs of PNH patients has been analyzed by flow cytometry using APC-conjugated anti-human CD59 (negative) and PE-conjugated anti-human CD47 antibodies (positive).

Antibody stability test was conducted, antibodies were treated at 66℃ and 67.5℃ for 1hr, and C5 binding activity was then tested using by ELISA.

Results:

In the present study, we report a novel humanized anti-C5 monoclonal antibody, named LP-005. LP-005, Ravulizumab and Crovalimab exhibits different binding kinetics to C5 (Table 1), however, there is no clear correlation between their binding affinity and complement inhibition activity (NHS-induced CP and AP hemolysis).

In antibody-sensitized sheep RBCs hemolysis inhibition assay (CP), LP-005 shows an IC50 of 0.41 nM, whereas Ravulizumab and Crovalimab has IC50 of 0.99 nM and 0.4 nM respectively (Figure 1).

For AP induced helmolysis assay, PNH patient’s RBCs with more than 70% CD59 absence was used, however, little difference was found between LP-005 and Ravulizumab hemolysis inhibition activity. Moreover, Crovalimab showed incomplete and less efficient inhibition compared with Ravulizumab and LP-005 (Figure 2).

The thermal stability study showed that LP-005 is comparable to Crovalimab and is more stable than Ravulizumab (Figure 3).

Conclusion:

In summary, LP-005 is a novel anti-C5 monoclonal antibody with higher bioactivity in CP induced hemolysis compared to Ravulizumab, and comparable activity in AP induced hemolysis using PNH patient’s RBCs. LP-005 is also engineered to increase FcRn binding property as well as thermal stability, which has the potential to be a good drug candidate with improved pharmacokinetic properties of decreasing doses frequency during clinical practice as well as a more robust manufacture process during drug development.