Novavax shares slump as RSV vaccine fails in Phase 3 trial
- Shares in Novavax sunk by nearly 70% by value Thursday after the biotech announced a Phase 3 study of its experimental vaccine ResVax failed to achieve its main goal.
- The trial featured 4,636 pregnant women, two-thirds of whom were randomly selected to receive the company's vaccine while the remaining one-third were given placebo. Topline results showed the vaccine did not meet the primary endpoint of preventing medically significant respiratory syncytial virus (RSV) lower respiratory tract infections in infants three months after delivery.
- ResVax is the lead clinical candidate for the Gaithersburg, Maryland-based company. In a statement, CEO Stanley Erck focused on study data suggesting the vaccine could still help prevent some of the most serious consequences of RSV, namely hospitalization and severe hypoxemia. That argument did little to prevent Thursday morning's stock sell-off, however.
RSV is a prevalent respiratory virus and one of the most common cause of bronchiolitis and pneumonia in children under the age of one in the U.S., according to the Centers for Disease Control and Prevention.
AstraZeneca's Synagis (palivizumab) is the only approved medicine for preventing serious lower respiratory tract disease caused by RSV, first gaining U.S. approval in 1998. The space has proved challenging for other companies: A candidate from Regeneron fell short in Phase 3 testing in 2017 and Johnson & Johnson last year paused clinical work on its RSV antiviral drug, lumicitabine.
AstraZeneca has been pushing MEDI8897 forward in partnership with Sanofi as a potential successor to Synagis. Late last year, AstraZeneca agreed to divest the U.S. rights to Synagis to Sobi in a $1.5 billion deal that gave the Swedish drugmaker an opportunity to get in on future earnings from the drug.
And then there's Novavax with ResVax.
The study's primary endpoint focused on lower respiratory tract infections. Infants born to women in the vaccine group posted an incidence rate of about 1.5% compared to the control group's rate of 2.4%, according to data released Thursday. That improvement, of about 40%, was not enough to meet statistical muster for declaring success.
The improvement rates for some of the secondary endpoints, such as on RSV hospitalizations and cases with severe hypoxemia, were modestly better at 44% and 48% respectively. That's what company leaders focused on Thursday, particularly when using a pre-specified exploratory and post-hoc analyses.
In particular, the company emphasized the vaccine showed a statistically significant improvement in hospitalization rates for the per-protocol population.
However, U.S.-specific data showed placebo beating the vaccine, according to a geographic analysis on the primary endpoint.
The vaccine's efficacy rate in the U.S. for lowering incidence rates for lower respiratory tract infections was -33%. That means the control group had a lower incident rate, about 1.7%, compared to the vaccine's rate of 2.3% for U.S.-based infants.
In slides, the company blamed that disparity on negative effects of late gestational age of immunization and short intervals to birth, saying both are more common in the U.S.
Novavax still plans to push forward with ResVax development, which has been supported in part by funding from the Bill & Melinda Gates Foundation. The group awarded up to $89 million in grants to Novavax in 2015.
"The vaccine is not dead," the company's R&D head Greg Glenn said in an interview. "We see it going forward, and just how, in what form ... I just can't speculate at this point."
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