SAN FRANCISCO—To make sense of Sanofi's Dengvaxia experiences, look no further than the old adage: Learn from your mistakes. It's no secret that Sanofi has had a rough time marketing its world-first dengue vaccine, and at the J.P. Morgan Healthcare Conference, vaccine head David Loew told FiercePharma the company gleaned some lessons from the troubled launch. First mistake: The company was “overly optimistic” with its early sales forecasts for the shot, a mistake driven by the huge number of dengue cases in emerging countries. The need for a vaccine is obvious, but affordability is a problem, Loew said. Those same countries can't necessarily afford to mount broad vaccination campaigns, and most patients aren't able to foot the bill out of pocket.

Regulatory issues were another piece of the problem, Loew said. Dengvaxia was the first vaccine where Sanofi focused on launching in emerging markets first, before the U.S. and Europe—an approach it called "flipping the model" for a drug launch. But launching a new shot without FDA or EMA approvals is “really hard,” because other regulatory authorities often look to those agencies for their own guidelines.

“You really want to have FDA and EMA (approvals) right from the start,” he said.

Those were some expensive lessons: Sanofi spent 20 years and $1.5 billion developing Dengvaxia, and finally started rolling it out in 2016. And then it hit a safety snag. In late 2017, the company reported that the vaccine can cause more serious dengue cases if given to people who haven’t been infected before. The disclosure triggered a scandal in the Philippines, where officials had started a mass vaccination campaign. Virtual Roundtable ESMO Post Show: Highlights from the Virtual Conference Cancer experts and pharma execs will break down the headline-making data from ESMO, sharing their insights and analysis around the conference’s most closely watched studies. This discussion will examine how groundbreaking research unveiled over the weekend will change clinical practice and prime drugs for key new indications, and panelists will fill you in on the need-to-know takeaways from oncology’s hottest fields. Register today. Save Your Spot Sanofi execs originally projected €200 million in first-year Dengvaxia sales, but the shot delivered just €55 million in 2016. In 2017, sales sank to €3 million. WHO ended up recommending the vaccine be used "exclusively or almost exclusively" in people with a prior dengue infection, confirmed by a diagnostic test. Sanofi meanwhile, had started working with regulators to change the vaccine’s official label and mounted an effort to develop a diagnostic. On Monday, Loew said he can’t provide an update on the diagnostic work.