Is Lenacapavir safe while breastfeeding?

Summary of use during breastfeeding

Infant exposure to lenacapavir during breastfeeding is minimal.[1] If a mother requires lenacapavir, it is not a reason to discontinue breastfeeding. Achieving and maintaining viral suppression with antiretroviral therapy decreases breastfeeding transmission risk to less than 1%, but not zero. Individuals with HIV who are on antiretroviral therapy with a sustained undetectable viral load and who choose to breastfeed should be supported in this decision. If a viral load is not suppressed, banked pasteurized donor milk or formula is recommended.[2,3] Extended postnatal prophylaxis of breastfed infants with lenacapavir should continue until breastfeeding is stopped.[4]

Effects on the breastfed infant

In a 2-year study, mothers received lenacapavir subcutaneous lenacapavir 927 mg in two 1.5 mL injections every 26 weeks following a 600 mg oral loading dose. No adverse effects of lenacapavir were observed in their breastfed infants, although the intensity of breastfeeding was not recorded.[1]

Effects on milk supply

Relevant published information was not found as of the revision date.

Levels in milk

Maternal Levels. In a study of lenacapavir prophylaxis for HIV, mothers received subcutaneous lenacapavir 927 mg in two 1.5 mL injections every 26 weeks following a 600 mg oral loading dose. In 102 mothers, the median breastmilk concentration of lenacapavir was 31.8 mcg/L (IQR 121.4 to 53.2 mcg/L).[1]

Infant Levels. The manufacturer reports a study in which the median infant-to-mother plasma ratio for lenacapavir in infants (n = 10) who were breastfed by participants receiving lenacapavir from 0 to less than 13 weeks after delivery was 0.06 (range 0.01 to 0.20).

In a study of HIV prophylaxis, women received subcutaneous lenacapavir 927 mg in two 1.5 mL injections every 26 weeks following a 600 mg oral loading dose. In 98 breastfed infants who were 10 to 187 days postpartum, the median plasma concentration was 1.63 mcg/L (IQR 0.87 to 2.85 mcg/L). The median infant-to-maternal plasma ratio for lenacapavir was 0.02, or 5% of the maternal serum concentrations (n = 98). However, the authors point out that results were not categorized by breastfeeding exclusivity or intensity, and these data might not capture peak exposures for exclusively breastfed infants during maternal peak plasma concentrations.[1]

The manufacturer the median infant-to-mother plasma ratio for lenacapavir in infants (n=10) who were breastfed by individuals receiving lenacapavir from 0 to less than 13 weeks after delivery was 0.06 (range: 0.01 to 0.20).