Atypical Post-Injection Reactions with Delayed Onset Following Glatiramer Acetate 40 mg: Need for Titration?

Area of Science:

• Neuroimmunology
• Pharmacovigilance
• Multiple Sclerosis Therapeutics

Background:

• Glatiramer acetate (GA) 20 mg/day (GA20) is linked to immediate post-injection reactions (PIRs).
• Glatiramer acetate 40 mg three times weekly (GA40) offers dosing convenience but has higher concentration per injection.
• Atypical PIRs observed with GA40 necessitated systematic monitoring.

Purpose of the Study:

• To characterize the nature and frequency of atypical post-injection reactions (PIRs) in multiple sclerosis (MS) patients receiving glatiramer acetate 40 mg (GA40).
• To compare the onset and duration of atypical PIRs with typical PIRs.
• To identify factors associated with the occurrence of atypical PIRs with GA40.

Main Methods:

• Prospective collection of clinical practice data from relapsing-remitting MS patients treated with GA40.
• Descriptive statistics, Mann-Whitney, Chi-squared tests, and Cox regression models were employed.
• Analysis focused on characterizing atypical PIRs and their association with patient history and GA exposure.

Main Results:

• 26.6% of patients on GA40 experienced PIRs, with 22.0% reporting atypical PIRs.
• Atypical PIRs showed significantly delayed onset (median 30 min vs 1 min) and longer duration (median 120 min vs 6 min) compared to typical PIRs.
• Previous GA20 exposure was associated with a lower risk of atypical PIRs (HR=0.35), while experiencing PIRs with GA20 increased the risk with GA40 (HR=5.75).

Conclusions:

• Atypical PIRs, particularly gastrointestinal symptoms and shivering, are common with GA40, characterized by delayed onset and prolonged duration.
• Further studies are needed to confirm prevalence and explore the role of nocebo responses.
• Initial dose titration may potentially mitigate the frequency of PIRs.