Pharmacokinetics/pharmacodynamics by race: Analysis of a peginterferon β-1a phase 1 study

Background: Black/African American participants are underrepresented in clinical trials for multiple sclerosis but can experience a greater burden of disease than other racial groups in the United States. A phase 1, open-label, crossover study that demonstrated bioequivalence of subcutaneous and intramuscular injection of peginterferon β-1a in healthy volunteers enrolled similar proportions of Black and White participants, enabling a post hoc subgroup analysis comparing these groups.

Methods: Peginterferon β-1a (125 μg) was administered by subcutaneous or intramuscular injection, followed by a washout period before a second injection using the alternative method. The primary pharmacokinetic and pharmacodynamic endpoints were maximum observed concentration (C_max) and area under the concentration-time curve from hour 0 to infinity (AUC_inf) of study drug and serum concentration of neop-terin, respectively. Safety and tolerability were included as secondary endpoints.

Findings: This analysis included 70 (51.5%) Black and 59 (43.3%) White participants. Peginterferon β-1a C_max was 29.8% higher in Black than in White participants following subcutaneous administration but was similar following intramuscular administration. Mean AUC_inf was 31.0% and 11.8% greater in Black than in White participants with subcutaneous and intramuscular administration, respectively. Pharmacodynamics and safety signals were similar between groups, although Black participants reported numerically fewer adverse events.

Conclusions: No clinically meaningful differences were identified between Black and White participants related to peginterferon β-1a administration, supporting the approved dose of 125 μg/mL peginterferon β-1a. Future clinical studies should include sufficiently diverse populations to ensure accurate assessments of treatment response.

Funding: Funding for medical writing support was provided by Biogen (Cambridge, MA, USA).