Respiratory Syncytial Virus (RSV) is the most commonly occurring lower respiratory tract viral infection in young children and usually isn't serious, but in premature infants and babies under six months old, the infection can be severe, and even fatal.
There is no vaccine, but there is a biologic drug — an antibody against the virus, called Palivizumab — that is used to help prevent RSV infections in preemies born before 29 weeks of gestation, but half the treated infants still end up in the hospital with an RSV infection.
And there are several other problems with Palivizumab: Doctors only recommend it in pre-term infants, it is given in five monthly injections, and the medication is very expensive. The recommended pediatric dose is 15 mg per month. The wholesale price of the drug is $780.15 for a 50 mg vial.
Luckily for preemies and infants everywhere, scientists at Medimmune, LLC and Dartmouth College developed a new antibody that could help prevent RSV. The antibody is called MEDI8897 and so far, it has some definite advantages over Palivizumab.
In most parts of the US, Respiratory Syncytial Virus season — the peak infection months — runs from late October to late January. Most kids catch RSV before they turn two, sometimes more than once. Otherwise healthy children usually only experience fever, cough, and flu-like symptoms.
In premature infants and young babies, though, the infection can cause bronchiolitis — inflammation of the small airways in the lung — and pneumonia.
RSV infections are very serious in premature and very young infants because their immune systems are still developing. So, scientists are working on ways to prevent the infection from occurring in the first place.
Researcher Qing Zhu and colleagues engineered MEDI8897 to provide RSV protection throughout the winter season with a single dose of the antibody. Lab studies performed by the scientists have shown it to be more potent against the virus than Palivizumab.
Becuase it's more potent than Palivizumab, it takes 150 times less antibody to inactivate the virus in the lab. When it was tested in rats with RSV, about 5 ug/ml MEDI8897 was needed to clear 90% of the virus from the rats, while it took 50 ug/ml Palivizumab to achieve the same result.
When MEDI8897 was given preventatively to rats, the amount of virus in their nose after four days was 10–100 times less than in rats given Palivizumab.
The results of the lab studies on MEDI8897 showed a significant improvement over Palivizumab, but the most promising result of MEDI8897 is that it has already moved from the lab to clinical trials in humans.
The antibody has completed one clinical trial in adults in a Phase I trial for safety, tolerability, and pharmacokinetics — measures of how long the antibody stays in the blood. It was given intravenously at 3 doses and intramuscularly at 3 doses. All doses were well tolerated, except at the highest intramuscular dose.
Two new clinical trials are now underway: A Phase II study of different doses in healthy pre-term infants for safety, tolerability, and pharmacokinetics; and a new trial is recruiting that will study the ability of different doses in healthy pre-term infants to prevent RSV infections.
The development plan for MEDI8897 includes a proposed Phase III trial in healthy full-term and late preterm infants. The scientific results will drive how quickly the development and testing proceeds.
The single dose MEDI8897 appears to provide better protection against RSV than Palivizumab and the development and testing in humans is proceeding quickly. If the the positive results continue, we may have a way to keep 100,000 infants a year from being hospitalized with life-threatening RSV infections.
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