Brodalumab is a recombinant fully human monoclonal immunoglobulin IgG2 antibody that binds with high affinity to human IL-17RA and blocks the biological activities of the pro-inflammatory cytokines IL-17A, IL-17F, IL-17A/F heterodimer and IL-25, resulting in inhibition of the inflammation and clinical symptoms associated with psoriasis. IL-17RA is a protein expressed on the cell surface and is a required component of receptor complexes utilized by multiple IL-17 family cytokines. IL-17 family cytokine concentrations have been reported to be increased in psoriasis. IL-17A, IL-17F and IL-17A/F heterodimer have pleiotropic activities including the induction of pro-inflammatory mediators such as IL-6, GROα, and G-CSF from epithelial cells, endothelial cells and fibroblasts that promote tissue inflammation. Blocking IL-17RA inhibits IL-17 cytokine-induced responses resulting in normalization of inflammation in the skin.
Elevated levels of IL-17A, IL-17C and IL-17F gene expression are found in psoriatic plaques. Elevated levels of expression of IL-12B and IL-23A, the genes for the two subunits of IL-23, an upstream activator of IL-17A and IL-17F expression, are also found in psoriatic plaques. Treatment with brodalumab in psoriasis patients has been shown to decrease levels of IL-17A and markers of cell proliferation and epidermal thickness in lesional skin biopsies to non-lesional skin biopsy levels up to 12 weeks post-treatment.
Based on population pharmacokinetic modelling, the estimated accumulation ratio after 20 weeks of dosing is 2.5-fold. In moderate to severe plaque psoriasis patients following a single subcutaneous administration of brodalumab at 210 mg, the mean maximum serum concentration (Cmax) was 13.4 mcg/ml (standard deviation [SD] = 7.29 mcg/ml). The median time to maximum concentration (Tmax) was 3.0 days (range: 2.0 to 4.0 days) and the mean area under the concentration time curve to the last measurable concentration (AUClast) was 111 mcg*day/ml (SD = 64.4 mcg*day/ml). The subcutaneous bioavailability of brodalumab estimated by population pharmacokinetic modelling was 54.7% (relative standard error [RSE] = 4.25%).
The observed pharmacokinetic parameters during steady-state (weeks 10-12) were: mean steady-state area under the concentration time curve over the dosing interval (AUCtau) was 227.4 mcg*day/ml (SD = 191.7 mcg*day/ml) corresponding to average concentration (Cav,ss) of 16.2 mcg/ml, mean Cmax was 20.9 mcg/ml (SD = 17.0 mcg/ml) and Week 12 mean minimum serum concentration (Ctrough) was 9.8 mcg/ml (SD = 11.2 mcg/ml).
Based on population pharmacokinetic modelling, the estimated mean steady-state volume of distribution of brodalumab was approximately 7.24 L.
As an IgG2 human monoclonal antibody brodalumab is expected to be degraded into small peptides and amino acids via catabolic pathways in a manner similar to endogenous IgG.
Following subcutaneous administrations of 210 mg, brodalumab exhibits non-linear pharmacokinetics typical for a monoclonal antibody that undergoes target-mediated drug disposition.
Brodalumab clearance decreases with increasing dose and exposure increases in a greater than doseproportional manner. For a 3-fold increase in SC brodalumab dose from 70 to 210 mg, the steady-state serum brodalumab Cmax and AUC0-t increased approximately 18- and 25-fold, respectively.
Following a single subcutaneous administration of brodalumab 210 mg in plaque psoriasis patients, the apparent clearance (CL/F) is 2.95 L/day.
Population pharmacokinetic modelling predicted that serum brodalumab concentrations dropped below the quantification limit (0.05 mcg/ml) 63 days after discontinuation of steady-state dosing of brodalumab 210 mg administered every 2 weeks in 95% of the patients. However, brodalumab concentrations below LLOQ (Lower Limit of Quantification) were associated with IL-17 receptor occupancy up to 81%.
Based on population pharmacokinetic modelling the estimated half-life of brodalumab was 10.9 days at steady-state after every other week subcutaneous dose of 210 mg.
Population pharmacokinetic modelling indicated that exposure decreased as body weight increased. No dose adjustment is recommended.
Population pharmacokinetic modelling indicated that age did not have an effect on brodalumab pharmacokinetics, which was co-based on 259 (6%) patients being 65-74 years old and on 14 (0.3%) patients being ≥75 years old, within a total PK population of 4271 plaque psoriasis patients.
No pharmacokinetic data are available in patients with impaired renal or hepatic function. Renal elimination of intact brodalumab, an IgG monoclonal antibody, is expected to be low and of minor consequence. Brodalumab is expected to be mainly eliminated via catabolism and hepatic impairment is not expected to influence clearance.
The pharmacokinetics of brodalumab was similar between Japanese and non-Japanese patients with psoriasis.
Population pharmacokinetic analysis indicated that gender did not have an effect on brodalumab pharmacokinetics.
A population pharmacokinetic/pharmacodynamic model, developed using all available data indicated that at a dose of 210 mg every 2 weeks, 90% of all patients would be predicted to maintain a trough concentration greater than the estimated IC90 value of 1.51 mcg/ml. Based on an exploratory descriptive analysis, no relationship was observed between exposure and incidence of serious infections and infestations, candida infections, viral infections, and suicidal ideation and behaviour events. Exposure-response analysis indicates that higher brodalumab concentrations are related to better PASI and sPGA response.
Non-clinical data reveal no special hazard for humans based on conventional studies of repeated dose toxicity (including safety pharmacology endpoints and assessment of fertility-related endpoints), and toxicity to reproduction and development.
Carcinogenicity studies with brodalumab have not been conducted. However, there were no proliferative changes in cynomolgus monkeys administered weekly subcutaneous doses of brodalumab at 90 mg/kg for 6 months (AUC exposure 47-fold higher than in human patients receiving brodalumab 210 mg every 2 weeks). The mutagenic potential of brodalumab was not evaluated; however, monoclonal antibodies are not expected to alter DNA or chromosomes.
In cynomolgus monkeys there were no effects on male and female reproductive organs and on sperm count, motility and morphology following administration of brodalumab at dose levels up to 90 mg/kg once weekly for 6 months, (AUC exposure up to 47-fold higher than in human patients receiving brodalumab 210 mg every 2 weeks).
In cynomolgus monkeys, no effects on embryo-foetal or postnatal (up to 6 months of age) development were observed when brodalumab was dosed subcutaneously throughout pregnancy at exposure levels up to 27-fold higher than those achieved in human patients receiving brodalumab 210 mg every 2 weeks based on the area under the concentration curve (AUC). Serum concentrations in monkey infants and in foetal rabbits indicated considerable passage of brodalumab from the mother to the foetus at the end of pregnancy.
In cynomolgus monkeys, after weekly subcutaneous dosing of brodalumab at dose levels up to 90 mg/kg for 6 months, brodalumab-related effects were limited to injection site reactions and mucocutaneous inflammation that was consistent with pharmacologic modulation of host surveillance to commensal microflora. There were no effects on peripheral blood immunophenotyping and the Tcell dependent antibody response assay. In a local tolerance test in rabbits, moderate to severe edema was observed after subcutaneous injection of a formulation containing brodalumab at the clinical concentration of 140 mg/ml.
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