Novavax RSV Vaccine Fails to Hit Primary Endpoint in Phase III Trial

illustration of RSV

Shares of Maryland-based Novavax are down 66 percent in morning trading after the company announced its respiratory syncytial virus (RSV) vaccine called ResVax failed to hit its primary endpoint in a Phase III trial.

In the late-stage PREPARE trial, ResVax, an aluminum adjuvanted RSV fusion (F) protein recombinant nanoparticle vaccine, was being tested in infants with RSV lower respiratory tract infection (LRTI). Data from the Phase III trial showed that ResVax failed to meet the primary objective of prevention of medically significant RSV LRTI through 90 days of life. However, the company said the trial did show efficacy against a secondary objective of RSV LRTI hospitalization. That makes ResVax the first RSV vaccine to show Phase III efficacy, the company said. Data also showed that the drug fared well against RSV LRTI with severe hypoxemia, an abnormally low level of oxygen in the blood.

Stanley C. Erck, president and chief executive officer of Novavax, said while the study did not meet is pre-specified endpoints for success, the data from the trial indicate that ResVax protects infants from some of the most serious consequences of RSV, including RSV LRTI hospitalizations and RSV LRTI with severe hypoxemia. The trial did show that ResVax reduced all-cause LRTI hospitalizations by 25 percent and all-cause LRTI severe hypoxemia by 39 percent in infants observed through the first 180 days of life. Also, the data demonstrated that mothers vaccinated from 28 up to 33 weeks of pregnancy, showed vaccine efficacy rates against RSV LRTI hospitalization of 53 percent and severe RSV hypoxemia of 70 percent through the first 90 days of their infants’ lives. That was compared with 26 percent and 44 percent for mothers vaccinated after 33 weeks of pregnancy, the company said.

“The potential to prevent these most serious outcomes during infants’ most vulnerable months of life could have a profound impact upon the global burden of RSV disease,” Erck said in a statement.

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The company plans to meet with regulatory officials in the U.S. and in Europe to discuss a path forward for ResVax.

RSV is the most common cause of viral pneumonia in young children, which is the leading cause of death in children under the age of five worldwide. In the United States, RSV is the leading cause of hospitalization of infants, with an estimated number of annual cases of about 76,000. Keith Klugman, director of the Bill & Melinda Gates Foundation’s Pneumonia Program, said ResVax shows promise in the fight against RSV. The Gates Foundation financially supported the Phase III trial.

“We are very encouraged that the Novavax maternal RSV vaccine reduced severe RSV hypoxemia by 60 percent in the first months of life and believe this vaccine has great potential for reducing RSV-associated deaths in young babies,” Klugman said in a statement.

Novavax intends to present additional results from the Prepare trial at an upcoming medical meeting.

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