Peginterferon beta-1a concentrations in breast milk of lactating multiple sclerosis patients

Peginterferon beta-1a is an interferon beta-1a formulation that has been pegylated, resulting in a longer half-life than other interferon beta formulations. We examined concentrations of peginterferon beta-1a in breast milk of lactating patients with multiple sclerosis (MS) receiving peginterferon beta-1a as their postpartum disease-modifying therapy.

After completion of titration to a full dose of peginterferon beta-1a and following a single full dose peginterferon beta-1a injection (125 µg), breast milk samples (≥10 mL) were collected by 5 women on days 1-14 post injection. Peginterferon beta-1a concentrations in breast milk samples were measured by a qualified enzyme-linked immunosorbent assay (detection threshold: 15 pg/mL). Mean and median daily concentrations and median maximum concentration (C_max), time of C_max (T_max), time of last measurable concentration (T_last), area under the concentration-time curve (AUC_last), and relative infant dose (RID) were determined.

After receiving a single full dose peginterferon beta-1a injection, the maximum breast milk concentration recorded in an individual patient was 126.2 pg/mL (0.00013 µg/mL) on day 6. The remaining patients all had maximum breast milk concentrations <72 pg/mL. The geometric mean of C_max was 48.9 pg/mL and the median T_max and T_last were 4 and 7 days, respectively. The median AUC_last was 210.9 day*pg/mL. Among the 5 study patients, the mean breast milk concentration across all study days was 35.95 pg/mL, with an estimated RID of 0.0054% of the maternal dose.

Minimal concentrations of peginterferon beta-1a were detected in the breast milk samples. These findings may be useful for clinicians considering postpartum MS treatment options.