Compare pharmacokinetic (PK) profiles and safety outcomes of subcutaneous (SC) and intramuscular (IM) peginterferon beta-1a in Black/African American (AA) and White participants.

Characterizing the impact of peginterferon beta-1a route of administration on PK parameters and safety outcomes across racial groups is needed to better inform treatment decisions for all with multiple sclerosis (MS).

Healthy volunteer participants were randomised 1:1 to receive a single dose of peginterferon beta-1a 125 mcg (IM followed by SC or vice versa) with 28-day washout periods between doses. Blood samples were collected from ≤2 hours predose to 504 hours postdose. PK parameters (maximum serum concentration [C_max] and area under the curve from time zero to infinity [AUC_inf]) and adverse events (AEs) were compared between Black/AA and White participants.

Participants (n=136) in this study were Black/AA (n=70; 51.5%), White (n=59; 43.4%), Asian (n=3; 2.2%), and other (n=4; 2.9%). Analyses focused on Black/AA and White participants. Mean C_max was 22.3% higher following SC (1.59 ng/mL vs 1.30 ng/mL) and 2.7% higher following IM (1.50 ng/mL vs 1.46 ng/mL) administration in Black/AA than White participants. Similarly, AUC_inf was 29.4% higher with SC (193.83 h×ng/mL vs 149.78 h×ng/mL) and 12.8% higher with IM (194.46 h×ng/mL vs 172.40 h×ng/mL) administration in Black/AA than White participants. Incidence of AEs was lower for Black/AA than White participants with SC (63.8% [44/69] vs 75.9% [44/58]) and IM (54.5% [36/66] vs 79.7% [47/59]) dosing. No serious AEs were reported.

Black/AA participants had slightly higher PK parameters than White participants but a lower incidence of AEs following IM or SC administration, indicating that dose adjustment is not needed for different racial groups. This study is the first comparing PK profiles of an MS disease-modifying therapy between racial groups.