Journal Article

SAT-432 Pharmacokinetics (PK) and Exposure-Response Relationship of Teprotumumab, an Insulin-Like Growth Factor-1 Receptor (IGF-1R) Blocking Antibody, in Active Thyroid Eye Disease (TED)

Ramanathan, Srini, Xin, Yan, Sile, Saba, Holt, Robert, Kovalenko, Maria, Bhatt, Nivedita, Chamberlain, Jason, Sun, Rui, Xu, Fengyan, Gao, Yuying

2020

Overview

Introduction: Teprotumumab treatment resulted in statistically and clinically meaningful improvements across multiple facets of active TED and was generally well-tolerated in Phase 2 and 3 trials.1,2 An initial intravenous infusion of 10 mg/kg followed by 20 mg/kg every 3 weeks was selected based on in vitro activity and clinical PK profile, to maintain pharmacologically active exposures and >90% saturation of IGF-1R over dosing intervals and to achieve efficacy at a well-tolerated dose for this vision-threatening disease. Methods: Population PK analysis were performed on data from a Phase 1 oncology study (n=60)3 and Phase 2 and 3 trials in active TED (N=83)2,3 and covariate effect on PK was assessed. Exposure-response relationship was evaluated in TED studies for key efficacy endpoints (proptosis response rate, % patients with a clinical activity score value of 0 or 1, and diplopia responder rate) and selected safety variables (hyperglycemia and muscle spasms). Results: Teprotumumab PK was linear in TED patients and consistent with other immunoglobulin G1 monoclonal antibodies (IgG1 mAbs), with low systemic clearance (0.334 L/day), low volume of distribution (3.9 L for central compartment and 4.2 L for peripheral compartment), and long elimination half-life (19.9 days). 4,5 Model-predicted mean (± standard deviation) steady-state area under the concentration curve (AUCss), peak (Cmax,ss), and trough (Cmin,ss) concentrations in TED patients were 131 (± 30.9) mg∙hr/mL, 643 (± 130) µg/mL and 157 (± 50.6) µg/mL, respectively, suggesting low inter-subject variability. Population PK analysis indicated no significant impact of baseline age, gender, race, weight, smoking status, renal impairment (mild/moderate), and hepatic function (total bilirubin, aspartate and alanine aminotransferases) on teprotumumab PK. Female patients had 15% higher Cmax,ss but similar AUC compared to male patients, which is not considered clinically relevant. Exposure-response analysis from the TED dose regimen indicated no meaningful correlations between exposures (AUCss, Cmax,ss and Cmin,ss) and key efficacy endpoints or selected safety variables, supporting the demonstrated, favorable benefit-risk profile of the TED dose regimen.2 Conclusion: Teprotumumab PK was characterized in TED patients by long elimination half-life, low systemic clearance and low volume of distribution, consistent with other IgG1 mAbs. There was no meaningful exposure-response relationship at the selected TED dose regimen for both efficacy and safety endpoints, supporting the teprotumumab dose regimen used in TED patients. Reference: (1) Smith TJ, et al. N Engl J Med 2017;376:1748-1761. (2) Douglas RS, et al. AACE 2019 late-breaking abstract. (3) ClinicalTrials.gov: NCT00400361. (4) Dirks NL et al. Clin Pharmacokinet. 2010;49(10):633-59. (5) Ryman JT et al. CPT Pharmacometrics Syst Pharmacol. 2017;6(9):576-88.

• Publisher: Oxford University Press
• Subject: Thyroid