In a year in which dengue has almost quadrupled in Cambodia, the world’s
first vaccine against dengue has shown the ability to protect against disease
caused by three of four virus strains, in a keenly awaited clinical trial in
Thailand.
The developer, French drugmaker
Sanofi SA, said yesterday the proof of efficacy was a key milestone in the
70-year quest to develop a viable dengue shot, adding the results also
confirmed the safety profile of the vaccine candidate.
Dengue is endemic in Southeast
Asia and, like Cambodia, countries worldwide have had very little success in
controlling it, World Health Organization Cambodia epidemiologist Steve Bjorge
told the Post.
“The only control is larvicide
and sanitation of the environment,” Bjorge said, pointing out that as yet there
was no cure for the disease. “An effective vaccine would be a real help.”
Cambodia dengue numbers in the
first half of the year compared to those in 2011 have almost quadrupled, with
15,600 cases reported compared to 4,604 for the same time last year. The death
toll is now at 60, and a premature rainy season caught health officials off
guard.
The mosquito-borne disease, also
known as “breakbone fever”, is a threat to nearly 3 billion people and is
caused by four different types of virus, none of which confers immunity from
the others.
Sanofi’s vaccine generated an
antibody response for all four dengue virus types, but evidence of protection
was only demonstrated against three of the four strains circulating in
Thailand.
Sanofi said researchers were
carrying out analyses to understand the lack of protection for the fourth
serotype.
“It’s a surprise,” company
spokesman Pascal Barollier said. “We need to get to the bottom of the data to
find out why it is reacting this way and wait for ongoing Phase III trials to
see if it is linked to some specific situation in Thailand.”
The Phase IIb study involving
4,002 Thai children aged four to 11 years was conducted during a dengue
epidemic, which might be an explanation for the unexpected outcome.
Deutsche Bank analyst Mark Clark
said the lack of protection against the fourth virus type meant a commercial
launch was more likely in 2015 than in 2014, as Sanofi awaits Phase III data
rather than filing early in some countries.
“More positively, given that
protection against at least three of the four viral types has been
demonstrated, the data supports the likelihood of launch for this huge unmet
clinical need,” Clark wrote in a research note.
The company’s vaccine unit Sanofi
Pasteur has already invested 350 million euros ($423 million) in a new French
factory to make the three-dose vaccine and believes its product could generate
more than 1 billion euros in yearly sales.
But uptake of the vaccine will
depend on precisely how well doctors believe it can protect populations at risk
in fast-expanding tropical cities from Rio to Manila, as well as travellers to
such areas.
Sanofi, which reports
second-quarter results today, gave no details on the level of protection in a
brief statement. The full data are now being reviewed by scientific experts and
public health officials, with detailed results to be published later this year.
Large-scale late-stage Phase III
clinical studies with 31,000 participants are under way with Sanofi’s vaccine
in 10 countries in Asia and Latin America.
Reuters
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