Sequential administration of anti-complement component C5 eculizumab and type-2 anti-CD20 obinutuzumab for the treatment of early antibody-mediated rejection after kidney transplantation: A proof of concept.

Kidney transplant (KT) candidates with donor-specific antibodies (DSA) exhibit exceedingly high antibody-mediated rejection (ABMR) and allograft loss rates. Currently, treatment of ABMR remains an unmet clinical need. We report the use of the anti-C5 eculizumab and the type-2 anti-CD20 obinutuzumab in two patients with early ABMR. Eculizumab (900 mg IV) led to complete inhibition of the terminal complement cascade (unremarkable AP50 and CH50 activity) and prompt stoppage of complement-dependent antibody-mediated allograft injury (clearance of intra-graft C4d and C5b-9 deposition). Despite complement inhibition, obinutuzumab (1000 mg IV) determined full and long-lasting peripheral B-cell depletion, with significant reduction in all DSA. Graft function improved, remaining stable up to three years of follow-up. No signs of active ABMR and rebound DSA were detected. Obinutuzumab B-cell depletion and inhibition of DSA production were not affected by complement blockage. Further studies are needed to confirm the potential benefit of obinutuzumab in association with complement inhibitors.

Role of C5 inhibitors in neuromyelitis optica spectrum disorders with seropositive anti-aquaporin-4 antibody: A systematic review and meta-analysis.

BACKGROUND: Neuromyelitis optica spectrum disorder (NMOSD) is an autoimmune disorder characterized by relapses of inflammation and demyelination primarily affecting the optic nerve and the spinal cord. C5 complement inhibition is an effective therapeutic approach in the treatment of NMOSD. In this systematic review and meta-analysis, we aimed to determine the role of C5 inhibitors in the treatment of patients with seropositive anti-aquaporin-4 antibody (AQP4+IgG) NMOSD. METHODS: This systematic review follows the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline. Relevant articles were systematically searched through Medline, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), and Web of Science databases until October 6th, 2023. We included randomized clinical trials (RCTs) that investigated the treatment with C5 inhibitors compared to placebo in patients with seropositive NMOSD. The primary endpoint was the rates of first adjudicated relapse. Secondary endpoints included different disability and quality of life measures. The random-effects model was used for all statistical analyses. RESULTS: Two RCTs with a total of 201 patients were included. C5 inhibitors demonstrated significant reduction of first adjudicated relapse (risk ratio (RR) = 0.05, 95 % CI 0.01-0.15) and Hauser Ambulation Index (HAI) (mean difference (MD): -0.79, 95 % CI -1.27 to -0.31). There was no significant difference between the two groups in Expanded Disability Status Scale (EDSS) (MD -0.23, 95 % CI -0.54-0.08). C5 inhibitors significantly improved the mean change in EQ-5D index (MD 0.08, 95 % CI 0.01-0.14; P = 0.02); however, no significant difference was shown in the mean change in EQ-5D VAS (MD 3.79, 95 % CI -1.61 to 9.19; P = 0.17). Safety measures were comparable between C5 inhibitors and placebo. CONCLUSION: NMOSD Patients with AQP4+IgG receiving C5 inhibitors have lower rate of relapses and improved levels of disability and quality of life. Real-world studies are warranted to establish the long-term safety of C5 inhibitors.

Upregulation of Checkpoint Ligand Programmed Death-Ligand 1 in Patients with Paroxysmal Nocturnal Hemoglobinuria Explained by Proximal Complement Activation.

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare hemolytic disease driven by impaired complement regulation. Mutations in genes encoding the enzymes that build the GPI anchors are causative, with somatic mutations in the PIG-A gene occurring most frequently. As a result, the important membrane-bound complement regulators CD55 and CD59 are missing on the affected hematopoietic stem cells and their progeny, rendering those cells vulnerable to complement attack. Immune escape mechanisms sparing affected PNH stem cells from removal are suspected in the PNH pathogenesis, but molecular mechanisms have not been elucidated. We hypothesized that exuberant complement activity in PNH results in enhanced immune checkpoint interactions, providing a molecular basis for the potential immune escape in PNH. In a series of PNH patients, we found increased expression levels of the checkpoint ligand programmed death-ligand 1 (PD-L1) on granulocytes and monocytes, as well as in the plasma of PNH patients. Mechanistically, we demonstrate that complement activation leading to the decoration of particles/cells with C3- and/or C4-opsonins increased PD-L1 expression on neutrophils and monocytes as shown for different in vitro models of classical or alternative pathway activation. We further establish in vitro that complement inhibition at the level of C3, but not C5, inhibits the alternative pathway-mediated upregulation of PD-L1 and show by means of soluble PD-L1 that this observation translates into the clinical situation when PNH patients are treated with either C3 or C5 inhibitors. Together, the presented data show that the checkpoint ligand PD-L1 is increased in PNH patients, which correlates with proximal complement activation.

Complement ratios C3bc/C3 and sC5b-9/C5 do not increase the sensitivity of detecting acute complement activation systemically.

BACKGROUND: Complement activation plays an important pathogenic role in numerous diseases. The ratio between an activation product and its parent protein is suggested to be more sensitive to detect complement activation than the activation product itself. In the present study we explored whether the ratio between the activation product and the parent protein for C3 (C3bc/C3) and for C5 (sC5b-9/C5) increased the sensitivity to detect complement activation in acute clinical settings compared to the activation product alone. MATERIALS AND METHODS: Samples from patients with acute heart failure following ST-elevated myocardial infarction (STEMI) and from patients with out-of-hospital cardiac arrest (OHCA) were used. C3, C3bc and C5, sC5b-9 were analysed in 629 and 672 patient samples, respectively. Healthy controls (n = 20) served to determine reference cut-off values for activation products and ratios, defined as two SD above the mean. RESULTS: Increased C3bc/C3- and sC5b-9/C5 ratios were vastly dependent on C3bc and sC5b-9. Thus, 99.5 % and 98.1 % of the increased C3bc/C3- and sC5b-9/C5 ratios were solely dependent on increased C3bc and sC5b-9, respectively. Significantly decreased C3 and C5 caused increased ratios in only 3/600 (0.5 %) and 4/319 (1.3 %) samples, respectively. Strong correlations between C3bc and C3bc/C3-ratio and between sC5b-9 and sC5b-9/C5-ratio were found in the STEMI- (r = 0.926 and r = 0.786, respectively) and the OHCA-population (r = 0.908 and r = 0.843, respectively; p < 0.0001 for all). Importantly, sC5b-9 identified worse outcome groups better than sC5b-9/C5-ratio. CONCLUSION: C3bc and sC5b-9 were sensitive markers of complement activation. The ratios of C3bc/C3 and sC5b-9/C5 did not improve detection of complement activation systemically.

Microfluidic Assays for Probing Neutrophil-Borrelia Interactions in Blood During Lyme Disease.

Human neutrophils are highly sensitive to the presence of Borrelia burgdorferi (Bb), the agent of Lyme disease (LD), in tissues. Although Bb is also found in the blood of LD patients, far less is known about how neutrophils respond to Bb in the presence of blood. In this study, we employed microfluidic tools to probe the interaction between human neutrophils and Bb and measured the activation of human neutrophils in blood samples from patients. We found that neutrophils migrate vigorously toward Bb in the presence of serum, and this process was complement-dependent. Preventing complement factor 5 cleavage or blocking complement receptors decreased neutrophil's ability to interact with Bb. We also found that spiking Bb directly into the blood from healthy donors induced spontaneous neutrophil motility. This response to Bb was also complement-dependent. Preventing complement factor 5 cleavage decreased spontaneous neutrophil motility in Bb-spiked blood. Moreover, we found that neutrophils in blood samples from acute LD patients displayed spontaneous motility patterns similar to those observed in Bb-spiked samples. Neutrophil motility was more robust in blood samples from LD patients than that measured in healthy and ill controls, validating the utility of the microfluidic assay for the study of neutrophil-Bb interactions in the presence of blood.

Alternative Pathway Involvement in Protoporphyria Patients Related to Sun Exposure.

The homeostasis of tissues in a chronic disease is an essential function of the alternative pathway (AP) of the complement system (CS). However, if not controlled, it may also be detrimental to healthy cells with a consequent aggravation of symptoms. The protoporphyria (PP) is a rare chronic disease that causes phototoxicity in visible light with local skin pain and general malaise. In order to establish if there is a systemic involvement of the CS during sun exposure, we designed a non-invasive method with a serum collection in winter and summer from 19 PP and 13 controls to detect the levels of CS protein: Properdin, Factor H (FH), and C5. Moreover, the global radiation data were collected from the regional agency of environmental protection (ARPA). The results show growing values for every protein in patients with PP, compared to control, in both seasons, in particular in summer compared to winter. To reinforce the evidence, we have estimated the personal exposure of patients based on the global radiation data. The main factors of the AP increased over the season, confirming the involvement of the AP in relation to light exposure. The systemic response could justify the general malaise of patients after long light exposure and can be exploited to elucidate new therapeutic approaches.

Complement-5 Inhibition Deters Progression of Fulminant Hepatitis to Acute Liver Failure in Murine Models.

BACKGROUND & AIMS: Acute liver failure (ALF) is a life-threatening condition with limited treatment alternatives. ALF pathogenesis seemingly involves the complement system. However, no complement-targeted intervention has been clinically applied. In this study, we aimed to investigate the potential of Complement-5 (C5)-targeted ALF treatment. METHODS: ALF was induced in C5-knockout (KO, B10D2/oSn) mice and their wild-type (WT) counterparts (B10D2/nSn) through intraperitoneal lipopolysaccharide (LPS) and d-galactosamine (D-GalN) administration. Thereafter, monoclonal anti-C5 antibody (Ab) or control immunoglobulin was administered intravenously. Furthermore, a selective C5a-receptor (C5aR) antagonist was administered to WT mice to compare its efficacy with that of anti-C5-Ab-mediated total C5 inhibition. We clarified the therapeutic effect of delayed anti-C5-Ab administration after LPS/D-GalN challenge. We also assessed the efficacy of anti-C5-Ab in another ALF model, using concanavalin-A. RESULTS: Liver injury was evident 6 hours after LPS/D-GalN administration. C5-KO and anti-C5-Ab treatment significantly improved overall animal survival and significantly reduced serum transaminase and high-mobility group box-1 release with decreased histological tissue damage. This improvement was characterized by significantly reduced CD41+ platelet aggregation, maintained F4/80+ cells, and less infiltration of CD11+/Ly6-G+ cells with lower cytokine/chemokine expression. Furthermore, C5-KO and anti-C5-Ab downregulated tumor necrosis factor-α production by macrophages before inducing marked liver injury. Moreover, single-stranded-DNA cells and caspase activation were reduced, indicating significant attenuation of apoptosis. Anti-C5-Ab treatment protected the liver more effectively than the C5aR antagonist, and its delayed doses were hepatoprotective. In addition, anti-C5-Ab treatment was effective against concanavalin-A-induced ALF. CONCLUSIONS: C5 inhibition effectively suppresses progression to ALF in mice models of fulminant hepatitis, serving as a new potential treatment strategy for ALF.

One-year outcomes from a phase 3 randomized trial of ravulizumab in adults with paroxysmal nocturnal hemoglobinuria who received prior eculizumab.

Ravulizumab every 8 weeks showed non-inferiority to eculizumab every 2 weeks in a 26-week, phase 3, randomized controlled trial in adults with paroxysmal nocturnal hemoglobinuria (PNH) who were clinically stable on eculizumab (NCT03056040). We report results from the first 26 weeks of the extension period in which patients continued ravulizumab (n = 96) or switched from eculizumab to ravulizumab (n = 95). At week 52, mean (SD) lactate dehydrogenase levels increased 8.8% (29%) with ravulizumab-ravulizumab and 5.8% (27%) with eculizumab-ravulizumab from primary evaluation period baseline. During the extension period, four patients (ravulizumab-ravulizumab, n = 3; eculizumab-ravulizumab, n = 1) experienced breakthrough hemolysis, but none associated with serum free C5 ≥ 0.5 µg/mL. Mean Functional Assessment of Chronic Illness Therapy (FACIT)-Fatigue scores remained stable through week 52. During the extension period, proportions of patients avoiding transfusion remained stable (ravulizumab-ravulizumab, 86.5%; eculizumab-ravulizumab, 83.2%); 81.2% and 81.1%, respectively, had stabilized hemoglobin. All patients maintained serum free C5 levels < 0.5 µg/mL. Adverse events were generally similar between groups, and rates were lower in the extension period. Adults with PNH on stable eculizumab therapy who received ravulizumab over 52 weeks experienced durable efficacy, with consistent efficacy in patients who received eculizumab during the primary evaluation period and then switched to ravulizumab. Ravulizumab was well tolerated.

CompLement C5 Antibodies for decreasing brain injury after aneurysmal Subarachnoid Haemorrhage (CLASH): study protocol for a randomised controlled phase II clinical trial.

BACKGROUND: The inflammatory response after aneurysmal subarachnoid haemorrhage (aSAH) has been associated with early brain injury, delayed cerebral ischaemia, poor functional outcome, and case fatality. In experimental SAH studies, complement C5 antibodies administered shortly after SAH reduced brain injury with approximately 40%. Complement component C5 may be a new therapeutic target to reduce brain injury and hereby improve the outcome after aSAH. We aim to investigate the pharmacodynamic efficacy and safety of eculizumab (complement C5 antibody) in patients with aSAH. METHODS: A randomised, controlled, open-label, phase II clinical trial with blinded outcome assessment. Eculizumab (1200 mg) is administered intravenously < 12 h, on day 3 and on day 7 after ictus. Patients in the intervention group receive prophylactic antibiotics for 4 weeks, and those with a central line or an external ventricular shunt and a positive fungal or yeast culture also receive prophylactic antifungal therapy for 4 weeks. The primary outcome is C5a concentration in the cerebrospinal fluid (CSF) on day 3 after ictus. Secondary outcomes include the occurrence of adverse events, inflammatory parameters in the blood and CSF, cerebral infarction on magnetic resonance imaging, and clinical and cognitive outcomes. We aim to evaluate 26 patients with CSF assessments, 13 in the intervention group and 13 in the comparator group. To compensate for early case fatality and inability to obtain CSF, we will include 20 patients per group. DISCUSSION: The CLASH trial is the first trial to investigate the pharmacodynamic efficacy and safety of eculizumab in the early phase after aSAH. TRIAL REGISTRATION: Netherlands Trial Register NTR6752 . Registered on 27 October 2017 European Clinical Trials Database (EudraCT) 2017-004307-51.

Complement C3 vs C5 inhibition in severe COVID-19: Early clinical findings reveal differential biological efficacy.

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.

Mild Clinical Course of COVID-19 in 3 Patients Receiving Therapeutic Monoclonal Antibodies Targeting C5 Complement for Hematologic Disorders.

BACKGROUND Patients receiving immunosuppressive therapies might be more susceptible to COVID-19. Conversely, an exaggerated inflammatory response to the SARS-CoV-2 infection might be blunted by certain forms of immunosuppression, which could be protective. Indeed, there are data from animal models demonstrating that complement may be a part of the pathophysiology of coronavirus infections. There is also evidence from an autopsy series demonstrating complement deposition in the lungs of patients with COVID-19. This raises the question of whether patients on anti-complement therapy could be protected from COVID-19. CASE REPORT Case 1 is a 39-year-old woman with an approximately 20-year history of paroxysmal nocturnal hemoglobinuria (PNH), who had recently been switched from treatment with eculizumab to ravulizumab prior to SARS-CoV-2 infection. Case 2 is a 54-year-old woman with a cadaveric renal transplant for lupus nephritis, complicated by thrombotic microangiopathy, who was maintained on eculizumab, which she started several months before she developed the SARS-CoV-2 infection. Case 3 is a 60-year-old woman with a 14-year history of PNH, who had been treated with eculizumab since 2012, and was diagnosed with COVID-19 at the time of her scheduled infusion. All 3 patients had a relatively mild course of COVID-19. CONCLUSIONS We see no evidence of increased susceptibility to SARS-CoV-2 in these patients on anti-complement therapy, which might actually have accounted for the mild course of infection. The effect of anti-complement therapy on COVID-19 disease needs to be determined in clinical trials.

Isolation of antigen-specific, disulphide-rich knob domain peptides from bovine antibodies.

As a novel alternative to established surface display or combinatorial chemistry approaches for the discovery of therapeutic peptides, we present a method for the isolation of small, cysteine-rich domains from bovine antibody ultralong complementarity-determining regions (CDRs). We show for the first time that isolated bovine antibody knob domains can function as autonomous entities by binding antigen outside the confines of the antibody scaffold. This yields antibody fragments so small as to be considered peptides, each stabilised by an intricate, bespoke arrangement of disulphide bonds. For drug discovery, cow immunisations harness the immune system to generate knob domains with affinities in the picomolar to low nanomolar range, orders of magnitude higher than unoptimized peptides from naïve library screening. Using this approach, knob domain peptides that tightly bound Complement component C5 were obtained, at scale, using conventional antibody discovery and peptide purification techniques.

Eculizumab for the treatment of myasthenia gravis.

INTRODUCTION: Acetylcholine receptor antibody-positive generalized myasthenia gravis (gMG) is effectively treated with symptomatic and immunosuppressive drugs but a proportion of patients has a persistent disease and severe adverse events (AEs). The unmet medical needs are specific immunosuppression and AE lowering. Eculizumab blocks C5 protecting neuromuscular junction from the destructive autoantibody effects. Phase II (Study C08-001) and III (ECU-MG-301) studies, with the open-label extension (ECU-MG-302), demonstrated eculizumab efficacy and safety in refractory gMG patients. AREAS COVERED: We provide an overview of eculizumab biological features, clinical efficacy, and safety in gMG patients, highlighting our perspective on the drug positioning in the MG treatment algorithm. EXPERT OPINION: Eculizumab has the potential to significantly change the immunosuppressive approach in gMG offering the opportunity to avoid or delay corticosteroids' use due to its speed and selective mechanism of action. Eculizumab prescription will depend on: 1. ability to modify the natural disease course; 2. sustainability in the clinical practice (cost/effectiveness ratio); 3. drug-induced AE reduction. At present we are missing a controlled study on its use as a first-line treatment. We think that immunosuppression in MG will change significantly in the next years by adopting more focused 'Precision Medicine' approaches, and Eculizumab seems to satisfy such a promise.

Complement Inhibitor Therapy for Myasthenia Gravis.

Complement activation as a driver of pathology in myasthenia gravis (MG) has been appreciated for decades. The terminal complement component [membrane attack complex (MAC)] is found at the neuromuscular junctions of patients with MG. Animals with experimental autoimmune MG are dependent predominantly on an active complement system to develop weakness. Mice deficient in intrinsic complement regulatory proteins demonstrate a significant increase in the destruction of the neuromuscular junction. As subtypes of MG have been better defined, it has been appreciated that acetylcholine receptor antibody-positive disease is driven by complement activation. Preclinical assessments have confirmed that complement inhibition would be a viable therapeutic approach. Eculizumab, an antibody directed toward the C5 component of complement, was demonstrated to be effective in a Phase 3 trial with subsequent approval by the Federal Drug Administration of the United States and other worldwide regulatory agencies for its use in acetylcholine receptor antibody-positive MG. Second- and third-generation complement inhibitors are in development and approaching pivotal efficacy evaluations. This review will summarize the history and present the state of knowledge of this new therapeutic modality.

C3(H2O) prevents rescue of complement-mediated C3 glomerulopathy in Cfh-/- Cfd-/- mice.

Therapeutic complement inhibition is a major focus for novel drug development. Of upstream targets, factor D (FD) is appealing because it circulates in plasma at low concentrations and has a single function: to cleave factor B to generate C3 convertase of the alternative pathway (AP). Mice with a targeted deletion of factor H (FH; Cfh-/- mice) develop C3 glomerulopathy (C3G) due to uncontrolled AP activity. To assess the impact of FD inhibition, we studied Cfh-/- Cfd-/- mice. We show that C3G in Cfh-/- mice is not rescued by removing FD. We used serum from Cfh-/- Cfd-/- mice to demonstrate that residual AP function occurs even when both FD and FH are missing and that hemolytic activity is present due to the action of C3(H2O). We propose that uncontrolled tick-over leads to slow activation of the AP in Cfh-/- Cfd-/- mice and that a minimal threshold of FH is necessary if tissue deposition of C3 is to be prevented. The FD/FH ratio dictates serum C3 level and renal C3b deposition. In C3G patients with chronic renal disease, the FD/FH ratio correlates inversely with C3 and C5 serum levels, suggesting that continuous AP control may be difficult to achieve by targeting FD.

Inhibition of complement pathway activation with Pozelimab, a fully human antibody to complement component C5.

Complement is a key component of the innate immune system. Inappropriate complement activation underlies the pathophysiology of a variety of diseases. Complement component 5 (C5) is a validated therapeutic target for complement-mediated diseases, but the development of new therapeutics has been limited by a paucity of preclinical models to evaluate the pharmacokinetic (PK) and pharmacodynamic (PD) properties of candidate therapies. The present report describes a novel humanized C5 mouse and its utility in evaluating a panel of fully human anti-C5 antibodies. Surprisingly, humanized C5 mice revealed marked differences in clearance rates amongst a panel of anti-C5 antibodies. One antibody, pozelimab (REGN3918), bound C5 and C5 variants with high affinity and potently blocked complement-mediated hemolysis in vitro. In studies conducted in both humanized C5 mice and cynomolgus monkeys, pozelimab demonstrated prolonged PK and durable suppression of hemolytic activity ex vivo. In humanized C5 mice, a switch in dosing from in-house eculizumab to pozelimab was associated with normalization of serum C5 concentrations, sustained suppression of hemolytic activity ex vivo, and no overt toxicity. Our findings demonstrate the value of humanized C5 mice in identifying new therapeutic candidates and treatment options for complement-mediated diseases.

Pharmacokinetic and pharmacodynamic effects of ravulizumab and eculizumab on complement component 5 in adults with paroxysmal nocturnal haemoglobinuria: results of two phase 3 randomised, multicentre studies.

Ravulizumab, a novel long-acting complement component 5 (C5) inhibitor administered every 8 weeks (q8w), was non-inferior to eculizumab for all efficacy outcomes in two randomised, open-label, phase 3 trials in C5 inhibitor-naïve (Study 301) and eculizumab-experienced (Study 302) adult patients with paroxysmal nocturnal haemoglobinuria (PNH). This pre-specified analysis characterised ravulizumab pharmacokinetics (PK), pharmacodynamics (PD; free C5 levels), and PD differences between medications (Study 301, n = 246; Study 302, n = 195). Ravulizumab PK parameters were determined using non-compartmental analysis. Serum free C5 was quantified with a Gyros-based fluorescence assay (ravulizumab) and an electrochemiluminescence ligand-binding assay (eculizumab). Ravulizumab PK parameters were numerically comparable in both studies; the median time to maximum concentrations ranged from 2·3 to 2·8 and 2·3 to 2·6 h in studies 301 and 302, respectively. Ravulizumab steady-state serum concentrations were achieved immediately after the first dose and sustained throughout treatment. For ravulizumab, the mean (SD) post hoc terminal elimination half-life was 49·7 (8·9) days. Serum free C5 concentrations <0·5 µg/ml were achieved after the first ravulizumab dose and sustained throughout treatment in both studies. In a minority of patients, free C5 concentrations <0·5 µg/ml were not consistently achieved with eculizumab in either study. Ravulizumab q8w was more consistent in providing immediate, complete, sustained C5 inhibition than eculizumab every-2-weeks in patients with PNH.

Soluble pattern recognition molecules: Guardians and regulators of homeostasis at airway mucosal surfaces.

Maintenance of homeostasis at body barriers that are constantly challenged by microbes, toxins and potentially bioactive (macro)molecules requires complex, highly orchestrated mechanisms of protection. Recent discoveries in respiratory research have shed light on the unprecedented role of airway epithelial cells (AEC), which, besides immune cells homing to the lung, also significantly contribute to host defence by expressing membrane-bound and soluble pattern recognition receptors (sPRR). Recent evidence suggests that distinct, evolutionary ancient, sPRR secreted by AEC might become activated by usually innocuous proteins, commonly referred to as allergens. We here provide a systematic overview on sPRR detectable in the mucus lining of AEC. Some of them become actively produced and secreted by AECs (like the pentraxins C-reactive protein and pentraxin 3; the collectins mannose binding protein and surfactant proteins A and D; H-ficolin; serum amyloid A; and the complement components C3 and C5). Others are elaborated by innate and adaptive immune cells such as monocytes/macrophages and T cells (like the pentraxins C-reactive protein and pentraxin 3; L-ficolin; serum amyloid A; and the complement components C3 and C5). Herein we discuss how sPRRs may contribute to homeostasis but sometimes also to overt disease (e.g. airway hyperreactivity and asthma) at the alveolar-air interface.

The complement C5 inhibitor crovalimab in paroxysmal nocturnal hemoglobinuria.

Complement C5 inhibition is the standard of care (SoC) for patients with paroxysmal nocturnal hemoglobinuria (PNH) with significant clinical symptoms. Constant and complete suppression of the terminal complement pathway and the high serum concentration of C5 pose challenges to drug development that result in IV-only treatment options. Crovalimab, a sequential monoclonal antibody recycling technology antibody was engineered for extended self-administered subcutaneous dosing of small volumes in diseases amenable for C5 inhibition. A 3-part open-label adaptive phase 1/2 trial was conducted to assess safety, pharmacokinetics, pharmacodynamics, and exploratory efficacy in healthy volunteers (part 1), as well as in complement blockade-naive (part 2) and C5 inhibitor-treated (part 3) PNH patients. Twenty-nine patients were included in part 2 (n = 10) and part 3 (n = 19). Crovalimab concentrations exceeded the prespecified 100-µg/mL level and resulted in complete and sustained terminal complement pathway inhibition in treatment-naive and C5 inhibitor-pretreated PNH patients. Hemolytic activity and free C5 levels were suppressed below clinically relevant thresholds (liposome assay <10 U/mL and <50 ng/mL, respectively). Safety was consistent with the known profile of C5 inhibition. As expected, formation of drug-target-drug complexes was observed in all 19 patients switching to crovalimab, manifesting as transient mild or moderate vasculitic skin reactions in 2 of 19 participants. Both events resolved under continued treatment with crovalimab. Subcutaneous crovalimab (680 mg; 4 mL), administered once every 4 weeks, provides complete and sustained terminal complement pathway inhibition in patients with PNH, warranting further clinical development (ClinicalTrials.gov identifier, NCT03157635).