Mean C4 Levels Research Articles

Safety, tolerability, and activity of the active C1s antibody riliprubart in cold agglutinin disease: a phase 1b study

AbstractCold agglutinin disease is a rare autoimmune hemolytic anemia characterized by complement pathway-mediated hemolysis. Riliprubart (SAR445088, BIVV020), a second-generation classical complement inhibitor, is a humanized monoclonal antibody that selectively inhibits only the activated form of C1s. This Phase 1b study evaluated the safety, tolerability, and effect on hemolysis of riliprubart in adult patients with cold agglutinin disease. On day 1, 12 patients received a single IV dose of either 30 mg/kg (n = 6) or 15 mg/kg (n = 6) of riliprubart and were subsequently followed for 15 weeks. Riliprubart was generally well tolerated; there were no treatment-emergent serious adverse events, or treatment-emergent adverse events leading to death or permanent study discontinuation. There were no reports of serious infections, encapsulated bacterial infections including meningococcal infections, hypersensitivity, or thromboembolic events. Rapid improvements in hemoglobin (day 5) and bilirubin (day 1) were observed in both treatment cohorts. Mean hemoglobin levels were maintained at >11.0 g/dL from day 29 and mean levels of bilirubin were normalized by day 29; both responses were maintained throughout the study. Improvements in clinical markers closely correlated with a sustained reduction in the 50% hemolytic complement (CH50) throughout the study. Mean C4 levels, an in vivo marker of treatment activity, increased 1 week after treatment with either dose of riliprubart and were sustained throughout the study. In conclusion, a single IV dose of riliprubart was well tolerated, and led to rapid classical complement inhibition, control of hemolysis, and improvement in anemia, all of which were sustained over 15 weeks. This trial was registered at www.ClinicalTrials.gov as #NCT04269551.

Hydralazine-associated vasculitis: Overlapping features of drug-induced lupus and vasculitis.

Hydralazine is an antihypertensive medication that has been associated with drug-induced lupus erythematosus (DIL) as well as ANCA-associated vasculitis (AAV). Although rare, early diagnosis is critical since drug cessation is the mainstay of therapy. This retrospective study aims to characterize the clinical, laboratory, and histopathologic features of this disease. Once approval was obtained from the Institutional Review Board at the University of Iowa, all patients carrying a diagnosis of vasculitis (ICD9 code: 447.6 or ICD10 code: I77.6, I80, L95, M30, or M31) and positive ANCA lab results over the past 15 years were identified. Age, gender, comorbid conditions, medications taken over the prior 6 months, laboratory data, including electrolytes, urine studies and serologies, chest x-rays, CT scans, and pathologic biopsy records were abstracted from the electronic medical record. 323 cases of AAV were identified, of which 12 were exposed to hydralazine, all at the time of diagnosis. The average duration of hydralazine therapy was 22 months and mean cumulative dose was 146g. Patients were typically older (70.3 years old) with slight female preponderance (7 females). Eleven patients presented with dyspnea, fatigue, and unintentional weight loss. Five had polyarthralgias and 8 had lower extremity petechiae. All 12 patients were both ANA and ANCA positive. ANA titers ranged from 1:160 and 1:2560. Ten were of diffuse pattern while 2 were nucleolar. ANCA titers ranged from 1:320 to 1:2560. Eleven had a pANCA pattern while one had cANCA. All 12 patients were positive for histone and 11 were positive for myeloperoxidase antibodies. Eleven also had dsDNA antibodies, and 4 had anti-cardiolipin IgG or IgM antibodies. Nine patients were also hypocomplementemic (mean C3 level: 88.4mg/dL; mean C4 level: 16.5mg/dL). All patients had variable levels of proteinuria (1+ to 3+) and eleven had active urine sediment. Urine protein:creatinine ratios ranged from 0.2 to 1.7. Of the 6 patients who underwent kidney biopsy, all 6 showed pauci-immune crescentic glomerulonephritis. Seven patients had bilateral pulmonary interstitial infiltrates and four had pleural effusions on CT scan. Four had pericardial effusions as demonstrated by echocardiography. Hydralazine-associated vasculitis is a drug-associated autoimmune syndrome that presents with interstitial lung disease, hypocomplementemia, and pauci-immune glomerulonephritis. Patients have elements of both DIL and DIV, as manifested by high ANA and ANCA titers as well as the presence of histone and MPO antibodies. Further research is needed to understand the etiopathogenesis of this condition.

Serum C4 levels in patients with systemic lupus erythematosus in remission

Twenty-six patients with systemic lupus erythematosus (SLE) showing systemic lupus activity measure (SLAM) and SLE disease activity index (SLEDAI) scores ≤2, as well as a lower C4 concentration than the mean C4 levels of healthy controls, were selected to evaluate the C4 levels of SLE patients in remission. Serum complement (CH50), complement components (C4, C3, and B), complement split products (C4d, iC3b, and Bb), phenotypic expression of C4 allotype, C4 production by peripheral blood monocytes, peripheral blood lymphocyte subpopulation, and interferon-gamma (IFN-γ) production were examined. In patients with SLE in remission, the C4 consumption (C4d/C4) was found to increase, and this was considered to be the most important factor for determining the serum concentration of C4. However, the relevance of the C4 allotypic expression was minimal. The IFN-γ-stimulated production of C4 by peripheral blood monocytes in SLE patients in remission was also less than that of the healthy controls. The IFN-γ-stimulated production of C4 in SLE patients in remission correlated with the peripheral blood CD4-positive cells. Less IFN-γ was produced by lymphocytes of SLE in remission than by those of healthy adults. We conclude that the serum C4 levels in SLE patients in remission reflect the degree of C4 consumption as well as the disease state, rather than genetic influences such as a C4A defect.

Inactivation of heamolytic complement by house dust allergen in the serum of children with atopic diseases.

Purified house dust allergen has been employed for screening the susceptibility to inactivation of haemolytic complement in the blood serum of atopic children and control subjects. Fluid phase complement in the control group of children was more sensitive to allergen-induced inactivation than observed in a normal adult population. Though the mean complement sensitivity indices in all groups of patients were below the valve for the control group, there was considerable statistical overlap. The serum complement sensitivities were in no way related to the clinical manifestations. The results of the complement test were not correlated to the total IgE levels, the RAST scores nor the skin reactions with house dust allergen. Some evidence for the in vivo involvement of the complement system in childhood atopic allergy was provided: the mean C3 proactivator level was significantly lower in atopic children, than in the control group; the mean C4 level in children with bronchial asthma and in children with atopic dermatitis was significantly depressed. A significant positive correlation between the serum C4 levels and allergen-complement sensitivities in children with both bronchial asthma and atopic dermatitis was observed.