Compstatin control peptide

Background:Suppression of the platelet (PLT) storage lesion would maintain PLT quality over longer storage times. An increased storage period would greatly improve the ability of blood agencies and hospitals to manage PLT inventories and minimize product wastage. Activation of the complement system has been proposed to play a role in initiating or potentiating the PLT storage lesion. This study examines the effect of complement inhibition on the development of the PLT storage lesion.Study design and methods:Leukofiltered PLT concentrates (PCs) were split into miniunits containing the complement inhibitors N-acetylaspartylglutamic acid (NAAGA) or compstatin, a control peptide, or saline. Samples were collected up to Day 11 of storage. Complement activation was monitored as C3a generation. PLT quality was assessed by morphology, CD62 and CD63 expression, fibrinogen binding, pH, mean PLT volume, annexin V binding, and PLT viability. Caspase-3 activity served as a measure of PLT apoptosis.Results:At concentrations of NAAGA required to achieve approximately 50 percent complement inhibition, PLT activation, and caspase-3 activity were increased. Complement inhibition by compstatin was highly variable. Compstatin addition consistently resulted in a 37 to 55 percent inhibition of PLT caspase-3 activity, but PLT quality and viability were no different between compstatin PCs and control PCs over the storage time.Conclusions:Neither NAAGA nor compstatin provided complete inhibition of complement over the storage period. Addition of these small-peptide inhibitors to PCs did not slow PLT storage lesion development, in spite of the partial inhibition of caspase-3 activity in the compstatin-treated PCs.

Growing clinical evidence has implicated complement as a pivotal driver of COVID-19 immunopathology. Deregulated complement activation may fuel cytokine-driven hyper-inflammation, thrombotic microangiopathy and NET-driven immunothrombosis, thereby leading to multi-organ failure. Complement therapeutics have gained traction as candidate drugs for countering the detrimental consequences of SARS-CoV-2 infection. Whether blockade of terminal complement effectors (C5, C5a, or C5aR1) may elicit similar outcomes to upstream intervention at the level of C3 remains debated. Here we compare the efficacy of the C5-targeting monoclonal antibody eculizumab with that of the compstatin-based C3-targeted drug candidate AMY-101 in small independent cohorts of severe COVID-19 patients. Our exploratory study indicates that therapeutic complement inhibition abrogates COVID-19 hyper-inflammation. Both C3 and C5 inhibitors elicit a robust anti-inflammatory response, reflected by a steep decline in C-reactive protein and IL-6 levels, marked lung function improvement, and resolution of SARS-CoV-2-associated acute respiratory distress syndrome (ARDS). C3 inhibition afforded broader therapeutic control in COVID-19 patients by attenuating both C3a and sC5b-9 generation and preventing FB consumption. This broader inhibitory profile was associated with a more robust decline of neutrophil counts, attenuated neutrophil extracellular trap (NET) release, faster serum LDH decline, and more prominent lymphocyte recovery. These early clinical results offer important insights into the differential mechanistic basis and underlying biology of C3 and C5 inhibition in COVID-19 and point to a broader pathogenic involvement of C3-mediated pathways in thromboinflammation. They also support the evaluation of these complement-targeting agents as COVID-19 therapeutics in large prospective trials.

Emerging data indicate that complement and neutrophils contribute to the maladaptive immune response that fuels hyperinflammation and thrombotic microangiopathy, thereby increasing coronavirus 2019 (COVID-19) mortality. Here, we investigated how complement interacts with the platelet/neutrophil extracellular traps (NETs)/thrombin axis, using COVID-19 specimens, cell-based inhibition studies, and NET/human aortic endothelial cell (HAEC) cocultures. Increased plasma levels of NETs, tissue factor (TF) activity, and sC5b-9 were detected in patients. Neutrophils of patients yielded high TF expression and released NETs carrying active TF. Treatment of control neutrophils with COVID-19 platelet-rich plasma generated TF-bearing NETs that induced thrombotic activity of HAECs. Thrombin or NETosis inhibition or C5aR1 blockade attenuated platelet-mediated NET-driven thrombogenicity. COVID-19 serum induced complement activation in vitro, consistent with high complement activity in clinical samples. Complement C3 inhibition with compstatin Cp40 disrupted TF expression in neutrophils. In conclusion, we provide a mechanistic basis for a pivotal role of complement and NETs in COVID-19 immunothrombosis. This study supports strategies against severe acute respiratory syndrome coronavirus 2 that exploit complement or NETosis inhibition.