Malaysia calls for phase 4 Dengvaxia study before considering full approval

Already struggling to meet initial expectations, Sanofi Pasteur's dengue vaccine Dengvaxia will have to undergo phase 4 testing in Malaysia before the endemic country agrees to sign off on a full approval.

Malaysia’s National Pharmaceutical Regulatory Agency’s Drug Control Authority, which conditionally approved the vaccine, said in a notice that "[i]f the study fails to verify the clinical benefit or are not conducted with due diligence, DCA may withdraw" Dengvaxia's registration.

The French vaccinemaker will conduct the two-year trial jointly with the country’s Ministry of Health, aiming to further assess the vaccine’s effectiveness and safety. Before the readout, the vaccine will only be available to eligible trial volunteers 9 to 45 years old. It won't be covered by Malaysia’s National Immunisation Programme, meaning that participants will need to pay to get vaccinated.

The agency also doesn't shy away from the concern that the vaccine might result in a more severe dengue infection for infection-naïve children under 9 when they’re later exposed to the virus naturally. That sentiment echoes a Science study last year that found the vaccine could make infections worse if it's used in areas of low dengue prevalence.

The first-to-market dengue vaccine got off to a bumpy start after it was first licensed in Mexico in December 2015 for use in individuals 9 to 45 years old living in endemic areas. The company expected €200 million in sales for last year, but the shot brought in just €55 million. Execs said economic and political turmoil in Latin America hurt the launch.

Dengvaxia is now approved in 14 counties, mainly Asian and Latin American countries where dengue poses a noticeable threat, and boasts a World Health Organization endorsement. But its sales still haven't picked up to the levels Sanofi would like for a shot it spent $1.5 billion and 20 years to develop.

What's more, there might not be much time left for Dengvaxia to make its mark as the world's only dengue vaccine. Japan's Takeda just finished enrolling children for a large phase 3 study of its dengue candidate, TAK-003, in eight countries. The drugmaker wants to determine if its version can protect kids against any serotype regardless of previous exposure to the virus. Initial results are expected next year.