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* Final Phase III results due by late September
* Sanofi hopes to deliver first doses in late 2015
* Sanofi has spent over 1.3 bln euros on project
* Sales could top 1 bln euros but project is risky -analysts
By Natalie Huet and Noëlle Mennella
NEUVILLE-SUR-SAONE, France, March 25 (Reuters) - Sanofi expects final clinical results for its vaccine againstdengue by late September, the French drugmaker's project leaderhas told Reuters, and has already gambled on starting productiondespite some disappointing early trials data.
Sanofi has invested more than one billion euros in theproject and is hoping to become the first drugmaker to sell sucha shot next year after two decades of research on the world'sfastest-growing tropical disease, for which there is nopreventative treatment.
Sanofi Pasteur, the French drugmaker's vaccine unit, hasmade a big industrial bet: it started producing the vaccine lastJuly to keep a lead over competitors and ensure it is ready toship doses, assuming it finally gets approved by regulators.
The investment highlights the time-consuming andcapital-intensive nature of the vaccines business.
Sanofi is upbeat - but based on clinical trial results sofar, many analysts believe approval is far from assured. All arewaiting for the upcoming data to determine whether the vaccinewill be a blockbuster.
"Today we are confident our vaccine can have an impact onpublic health and we are gearing up for its success," GuillaumeLeroy, who heads the dengue vaccine project at Sanofi Pasteur,said in an interview.
Leroy said the results of a final clinical trial on 30,000children in Latin America and southeast Asia would starttrickling in from mid-year. He said as soon as his team coulddraw reliable preliminary findings it would unveil these.
By the end of the third quarter, Sanofi will have fullconsolidated clinical results that it hopes to present at aconference on tropical diseases in November.
If the data is positive, Sanofi hopes to sell the vaccinearound late 2015 in at least one country affected by thedisease, most likely one of the 10 that took part in the trials.
"It's hard to predict which one could be first, but one caneasily imagine it'll be one of the bigger countries, such asBrazil, Mexico, Malaysia, maybe the Philippines," Leroy said.
Dengue fever - also known as "breakbone fever" because ofthe severe pain it can cause - is an infectious mosquito-bornedisease that thrives in tropical regions. It infects 50 to 100million people each year, according to the World HealthOrganization - and some experts put the number at triple thatlevel.
Most patients survive dengue but it kills an estimated20,000 people each year, many of them children.
RISKY BET, POTENTIAL BLOCKBUSTER
For now, Sanofi's project is still a huge gamble.
Sanofi started working on the vaccine 20 years ago and hasinvested over 1 billion euros ($1.38 billion) in research anddevelopment, plus more than 300 million euros into a dedicatedproduction plant outside of Lyon in southeast France.
The sparkling white facility, which was the first investmentapproved by Chief Executive Chris Viehbacher when he took thehelm in 2008, will be able to produce up to 100 million dosesper year from late 2017, Leroy said.
In this new unit, lab workers dressed from head to toe inprotective gear cultivate living cells and bring them intocontact with the virus to make pouches of antigens for each ofdengue's four serotypes to be mixed together later on.
Coming up with a vaccine that can protect against the fourstrains of the disease has puzzled scientists for over 70 years,since the movement of troops during World War II helped denguespread across the Pacific and become a worldwide pandemic.
"These serotypes vary from one country to the next and fromone season to the next," Leroy explained. "Predicting theirincidence is very difficult."
Data released in late 2012 from a trial in Thailand showedSanofi's vaccine failed to protect against one the disease'sfour strains, which happened to be the most prevalent in thecountry at the time.
Following those disappointing results some analysts cut itschances to around 50 percent - but even if it is not perfect,medical experts believe it is likely to be used to some degree.
Analyst forecasts show the vaccine could reap annual peaksales of 1 billion euros within a few years of launch,significantly boosting Sanofi's vaccines business, whichgenerated sales of 3.7 billion euros in 2013.
"From a vaccines perspective this clearly is exciting,because it's an area of unmet medical need, and Sanofi arepotentially first in class," said Citi analyst Peter Verdult.
Rivals such as Takeda, Merck & Co,GlaxoSmithKline and Novartis are also workingon dengue vaccines, but these have not reached Phase III trials.
Verdult said success for Sanofi would hinge on the strengthof the final data and on pricing, which he sees likely between$10 and $50 a dose, though he noted Sanofi has sponsored healtheconomic studies suggesting cost effectiveness up to $100.
"Clearly if the data shows efficacy on only three of thefour strains, it's going to be a lot more difficult for them tocharge the higher end of that range," he noted.
The vaccine, which is given in three shots six months apart,is currently being tested in 10,000 children aged 2-14 insoutheast Asia and in 20,000 children aged 9-16 in LatinAmerica. So far, the trial shows the vaccine is well tolerated,with no significant side effects reported, Leroy said.($1 = 0.7255 Euros) (Editing by Ben Hirschler and Giles Elgood)
