Compstatin analog Cp40 inhibits complement dysregulation in vitro in C3 glomerulopathy

Abstract

C3 glomerulopathy (C3G) defines a group of untreatable ultra-rare renal diseases caused by uncontrolled activation of the alternative complement pathway. Nearly half of patients progress to end stage renal failure within 10 years. Cp40, a second-generation compstatin analog in clinical development, is a 14 amino-acid cyclic peptide that selectively inhibits complement activation in humans and non-human primates by binding to C3 and C3b. We hypothesized that by targeting C3 Cp40 would provide an effective treatment for C3G. By investigating its effects in vitro using multiple assays of complement activity, we show that Cp40 prevents complement-mediated lysis of sheep erythrocytes in sera from C3G patients, prevents complement dysregulation in the presence of patient-derived autoantibodies to the C3 and C5 convertases, and prevents complement dysregulation associated with disease-causing genetic mutations. In aggregate, these data suggest that Cp40 may offer a novel and promising therapeutic option to C3G patients as a disease-specific, targeted therapy. As such, Cp40 could represent a major advance in the treatment of this disease.

Keywords: C3 glomerulonephritis; C3 glomerulopathy; Complement dysregulation; Compstatin; Dense deposit disease.

Conflict of interest statement

Conflicts of interest

J.D.L. and D.R. are the inventors of patents and/or patent applications that describe the use of complement inhibitors for therapeutic purposes. J.D.L. is the founder of Amyndas Pharmaceuticals, which is developing complement inhibitors for clinical applications. The remaining authors declare no competing financial interests.

Copyright © 2015 Elsevier GmbH. All rights reserved.

Figures

Figure 1

Cp40 restores complement control in both DDD and C3GN. (a) In vitro hemolysis is prevented in patients with DDD and C3GN (blue, 0μM Cp40; red, 5μM Cp40; green, 10μM Cp40). Shown are the mean values and SEMs of three experiments. (b) Identified disease drivers. C3Nef: C3 Nephritic factors; C4Nef: C4 Nephritic factors; FHAA: Factor H autoantibodies.

Figure 2

Cp40 prevents abnormal C3 breakdown as assayed by immunofixation electrophoresis (IFE). (a) IFE gel: incubation of PNS with patient sera generates large amounts of iC3b under Mg2+-EGTA conditions (G) but not under EDTA conditions (D). The addition of Cp40 (final 10μM) prevents lysis. Purple dashed line, normal cutoff. (b) Percent C3 conversion, C3 conversion was quantified as: %iC3b(G) − %iC3b(D) or %iC3b(G+CP40) − %iC3b(D).

Figure 3

Cp40 abrogates complement dysregulation induced by C3Nefs in vitro. (a) Illustration of C3Nef assay (C3Nefs, green Y). Cp40 is introduced at time points as indicated by the diamonds. (b) Cp40 inhibits C3Nef-mediated complement dysregulation in patients who are C3Nef positive (n=13).

Figure 4

Cp40 abrogates complement dysregulation induced by C4Nefs in vitro. (a) Illustration of C4Nef assay (C4Nefs, purple Y). Cp40 is introduced at time points as indicated by the diamonds. (b) Cp40 prevents formation of C5 convertase (C4b2a3b), thus inhibiting C4Nef-mediated complement dysregulation in patients who are C4Nef positive (n=3).