For the first time, scientist demonstrate an effective way to deliver drugs to the placenta – a feat that’s almost impossible to accomplish without harm to the baby. Key to this discovery was the scientists’ realization that the placenta has properties similar to tumors, and thus, drug delivery mechanisms that work in tumors could also work for the placenta. The team hopes this proof-of-concept study will pave the way for future therapies to prevent premature births and other pregnancy-related complications.
The placenta is a complex organ that develops in the uterus of pregnant women. It attaches to the uterine wall, and provides oxygen and nutrients to the growing baby via the umbilical cord that extends from it. In addition, the placenta keeps waste products from accumulating in the baby’s blood.
Given the important roles, the health of the placenta is crucial to the well-being of both mother and baby. In some instances when the placenta is not functioning properly, doctors are forced to induce early delivery – a procedure that significantly raises the risks of infant mortality and related complications.
Drugs available to treat complications in utero are severely limited because of their potential harm to the growing baby. The difficulty remained: how to exclusively target the organ without side-effects to the nearby tissues. In this sense, the team of researchers realized the problem is much similar to treating tumors without collateral damage to the body.
"Placentas behave like well-controlled tumors," said Lynda Harris, researcher at the University of Manchester in England, and senior study author. "They grow quickly, produce growth hormones and evade the immune system. A lot of cancer research focuses on finding ways of delivering drugs to kill the tumor without affecting the rest of the body. We had the idea that if we could selectively target the placenta in the same way, we could deliver other drugs to help improve placental function and therefore treat pregnancy complications."
Indeed, they cloaked a growth hormone in tumor-homing peptides, which are short chains of simple amino acids. The peptides act as a chaperone to guide the drug to only the placenta organ. In mouse studies, the team showed this method was effective at increasing the growth of undersized fetuses. Additionally, the drug did not accumulate in the mother mouse’s organs nor the fetus, suggesting the drug was highly specific to only the placenta.
"Our findings emphasize the similarities between placentas and tumors," said Erkki Ruoslahti, a distinguished adjunct professor at UC Santa Barbara. "That similarity makes it possible to take some of the existing tumor-homing peptides and make use of them in targeting drugs to the placenta. This paper shows that it is possible to increase the delivery of drugs into the placenta via these peptides."
Of note, the study demonstrated proof-of-concept for the targeted delivery of drugs to the placenta based on methods established in cancer therapies. "Only one drug for use during pregnancy has been licensed in the last 20 years," said Harris. "By developing this platform, we have opened up the possibility that any number of new drugs can be adapted and then used safely to treat common and serious pregnancy complications."
Additional source: UC Santa Barbara press release