ABSTRACT
AIMS: To characterize the pharmacokinetics (PK) of recombinant human C1 inhibitor (rhC1INH) in healthy volunteers and hereditary angioedema (HAE) patients. METHODS: Plasma levels of C1INH following 294 administrations of rhC1INH in 133 subjects were fitted using nonlinear mixed-effects modelling. The model was used to simulate maximal C1INH levels for the proposed dosing scheme. RESULTS: A one-compartment model with Michaelis-Menten elimination kinetics described the data. Baseline C1INH levels were 0.901 [95% confidence interval (CI): 0.839-0.968] and 0.176 U ml(-1) (95% CI: 0.154-0.200) in healthy volunteers and HAE patients, respectively. The volume of distribution of rhC1INH was 2.86 l (95% CI: 2.68-3.03). The maximal rate of elimination and the concentration corresponding to half this maximal rate were 1.63 U ml(-1) h(-1) (95% CI: 1.41-1.88) and 1.60 U ml(-1) (95% CI: 1.14-2.24), respectively, for healthy volunteers and symptomatic HAE patients. The maximal elimination rate was 36% lower in asymptomatic HAE patients. Peak C1INH levels did not change upon repeated administration of rhC1INH. Bodyweight was found to be an important predictor of the volume of distribution. Simulations of the proposed dosing scheme predicted peak C1INH concentrations above the lower level of the normal range (0.7 U ml(-1)) for at least 94% of all patients. CONCLUSIONS: The population PK model for C1INH supports a dosing scheme on a 50 U kg(-1) basis up to 84 kg, with a fixed dose of 4200 U above 84 kg. The PK of rhC1INH following repeat administration are consistent with the PK following the first administration.
Subject(s)
Complement C1 Inactivator Proteins/pharmacokinetics , Hereditary Angioedema Types I and II/blood , Models, Biological , Clinical Trials as Topic , Complement C1 Inactivator Proteins/administration & dosage , Complement C1 Inactivator Proteins/therapeutic use , Complement C1 Inhibitor Protein , Computer Simulation , Hereditary Angioedema Types I and II/drug therapy , Humans , Recombinant Proteins/administration & dosage , Recombinant Proteins/pharmacokinetics , Recombinant Proteins/therapeutic useABSTRACT
BACKGROUND: Recombinant human C1-inhibitor (rhC1INH) purified from milk of transgenic rabbits is used for the treatment of acute attacks in patients with hereditary angioedema (HAE) due to C1-inhibitor (C1INH) deficiency. OBJECTIVE: The objective was to investigate the risk of rhC1INH inducing IgE antibodies or eliciting anaphylactic reactions. METHODS: In subjects treated with rhC1INH, we retrospectively analysed the frequency and clinical relevance of pre-exposure and potentially newly induced IgE antibodies against rabbit and other animal allergens including cow's milk by the ImmunoCAP(®) Specific IgE blood test system. RESULTS: 130 HAE patients and 14 healthy subjects received 300 administrations of rhC1INH, 65 subjects (47.4 %) on one occasion; 72 (52.6 %) on at least two occasions (range 2-12; median 2). Five subjects had pre-existing anti-rabbit epithelium IgE; the subject with the highest levels and a previously undisclosed rabbit allergy developed an anaphylactic reaction upon first exposure to rhC1INH, whereas the other four subjects with lower pre-existing IgE levels (Class 1-3), did not. No other anaphylactic reactions were identified in any of the subjects exposed to rhC1INH. Analysis of post-exposure samples revealed that the risk of inducing new or boosting existing IgE responses to rabbit or cow's milk allergens was negligible. CONCLUSION: The propensity of rhC1INH to induce IgE antibodies following repeated administration of rhC1INH is low. Subjects with substantially elevated anti-rabbit epithelium IgE antibodies and/or clinical allergy to rabbits may have an increased risk for an allergic reaction. No other risk factors for allergic reactions to rhC1INH have been identified.
