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Kasia Kready




Grad Student


Harvard University


Systems Biology


Kasia Kready, Kailyn Doiron, Katherine Redfield Chan, Jeffrey Way, Quincey Justman, Camille E. Powe, Pamela Silver

Principal Investigator


A long-acting prolactin to combat lactation insufficiency


Human infants are born to breastfeed. While 50% of lactating persons struggle to make enough milk, there are no governmentally-approved drugs to enhance lactation1. Here, we engineer a variant of the naturally-occurring driver of lactation, the hormone Prolactin, to increase its serum half-life and produce a viable drug candidate. Our engineered variant, Prolactin-eXtra Long-acting (Prolactin-XL), is comprised of endogenously active human prolactin fused to an engineered human IgG Fc domain designed to overcome the unique drug development challenges specific to the lactating person-infant dyad. Our Prolactin-XL has a serum half-life of 70.9h in mice, 2,625-fold longer than endogenously active prolactin alone (70.9h v. 0.027h). We demonstrate that Prolactin-XL increases milk production and restores growth of pups fed by dams with pharmacologically-ablated lactation. We show that Prolactin-XL-enhanced lactation is accompanied by reversible, lactocyte-driven changes in mammary gland morphology. This work establishes long-acting prolactins as a potentially powerful pharmacologic means to combat insufficient lactation.

Research Context

Breastfeeding also touches the lives of almost everyone on the planet in some way. Lactating persons who struggle to make enough milk predominantly identify as women, but men, neonates of both sexes, trans people, adoptive parents, and post-menopausal women can all lactation. Prolactin even drives milk production in some non-mammals such as male emperor penguins and in pigeons and flamingos of both sexes. This underscores the diverse biological contexts where milk production is not coupled to pregnancy and female sexes. Lactation has broad implications across general healthcare, but it is also uniquely a women’s health research project and gender biology project. Although we focus mostly on therapeutics for lactating parents, this work has implications for sex difference & similarity research . Our Prolactin-XL and homologous fusions are powerful tools to study enhancing lactation across almost all mammals and almost all sexes, with few exceptions.