Contributions
Abstract: S500
Type: Oral Presentation
Presentation during EHA22: On Saturday, June 24, 2017 from 17:00 - 17:15
Location: Room N104
Background
Paroxysmal nocturnal hemoglobinuria (PNH) and atypical hemolytic uremic syndrome (aHUS) are well-characterized diseases of complement dysregulation. The only approved therapeutic for these diseases is Soliris® (Eculizumab, Alexion), a monoclonal antibody that binds and inhibits the cleavage of complement C5. Soliris® requires lifelong intravenous administration by a medical professional every two weeks. An orally bioavailable small molecule inhibitor of complement C5 to treat these and other complement mediated diseases represents a potential paradigm shift in the treatment of diseases of complement dysregulation.
Aims
To demonstrate the utility of an orally available, small molecule Complement C5 inhibitor for the treatment of complement mediated disorders.
Methods
Surface Plasmon Resonance (SPR) and Fluorescent Polarization assays (FP) were used to evaluate the affinity and specificity of the binding interaction between complement C5 and small molecule inhibitors. Determination of binding site, mechanism of action and potency were achieved by X-ray crystallography studies, Wieslab ELISA, and a sheep erythrocyte hemolysis based assay. The ability of the small molecules to prevent the hemolysis of PNH erythrocytes was evaluated using a modified Ham test. Pharmacokinetic studies were performed in rodents.
Results
Here we describe a series of first in class, orally bioavailable small molecules that bind to C5 with high affinity and inhibit its cleavage into C5a and C5b. These molecules demonstrate desirable drug-like properties with molecular weights under 500 amu and tPSA<100 Å2. A high-resolution co-crystal structure with C5 shows a unique binding site on the 188 kDa C5 protein, and specific binding of these molecules to C5 has been demonstrated by surface plasmon resonance (SPR) and fluorescence polarization (FP) assays. The position of the binding site suggests that these molecules will inhibit C5 cleavage in patients with the R885H/C polymorphism, which confers resistance to eculizumab. The molecules inhibit the terminal complement complex activity with single digit nanomolar IC50 as measured by inhibition of hemolysis in a highly sensitive antibody-sensitized sheep erythrocytes assay. In addition, they inhibit MAC deposition on complement-activating surfaces and prevent the cleavage of C5 to C5a and C5b as confirmed by ELISAs that directly detect generation of C5a and MAC. This series of inhibitors prevents the complement-mediated hemolysis of PNH erythrocytes (Type III) in a dose-dependent manner.
Conclusion
The results presented here highlight, for the first time, the feasibility of an oral, potent small molecule inhibitor of C5. The development of an orally available complement C5 inhibitor has the potential to provide a new therapeutic modality to treat both rare and common conditions where terminal complement cascade inhibition is desired.
Session topic: 11. Bone marrow failure syndromes incl. PNH - Biology
Keyword(s): Paroxysmal nocturnal hemoglobinuria (PNH), Oral, Complement
Abstract: S500
Type: Oral Presentation
Presentation during EHA22: On Saturday, June 24, 2017 from 17:00 - 17:15
Location: Room N104
Background
Paroxysmal nocturnal hemoglobinuria (PNH) and atypical hemolytic uremic syndrome (aHUS) are well-characterized diseases of complement dysregulation. The only approved therapeutic for these diseases is Soliris® (Eculizumab, Alexion), a monoclonal antibody that binds and inhibits the cleavage of complement C5. Soliris® requires lifelong intravenous administration by a medical professional every two weeks. An orally bioavailable small molecule inhibitor of complement C5 to treat these and other complement mediated diseases represents a potential paradigm shift in the treatment of diseases of complement dysregulation.
Aims
To demonstrate the utility of an orally available, small molecule Complement C5 inhibitor for the treatment of complement mediated disorders.
Methods
Surface Plasmon Resonance (SPR) and Fluorescent Polarization assays (FP) were used to evaluate the affinity and specificity of the binding interaction between complement C5 and small molecule inhibitors. Determination of binding site, mechanism of action and potency were achieved by X-ray crystallography studies, Wieslab ELISA, and a sheep erythrocyte hemolysis based assay. The ability of the small molecules to prevent the hemolysis of PNH erythrocytes was evaluated using a modified Ham test. Pharmacokinetic studies were performed in rodents.
Results
Here we describe a series of first in class, orally bioavailable small molecules that bind to C5 with high affinity and inhibit its cleavage into C5a and C5b. These molecules demonstrate desirable drug-like properties with molecular weights under 500 amu and tPSA<100 Å2. A high-resolution co-crystal structure with C5 shows a unique binding site on the 188 kDa C5 protein, and specific binding of these molecules to C5 has been demonstrated by surface plasmon resonance (SPR) and fluorescence polarization (FP) assays. The position of the binding site suggests that these molecules will inhibit C5 cleavage in patients with the R885H/C polymorphism, which confers resistance to eculizumab. The molecules inhibit the terminal complement complex activity with single digit nanomolar IC50 as measured by inhibition of hemolysis in a highly sensitive antibody-sensitized sheep erythrocytes assay. In addition, they inhibit MAC deposition on complement-activating surfaces and prevent the cleavage of C5 to C5a and C5b as confirmed by ELISAs that directly detect generation of C5a and MAC. This series of inhibitors prevents the complement-mediated hemolysis of PNH erythrocytes (Type III) in a dose-dependent manner.
Conclusion
The results presented here highlight, for the first time, the feasibility of an oral, potent small molecule inhibitor of C5. The development of an orally available complement C5 inhibitor has the potential to provide a new therapeutic modality to treat both rare and common conditions where terminal complement cascade inhibition is desired.
Session topic: 11. Bone marrow failure syndromes incl. PNH - Biology
Keyword(s): Paroxysmal nocturnal hemoglobinuria (PNH), Oral, Complement