The health scandal came to light in 2007 when a doctor raised the alert on heart risks linked to Mediator, a drug destined for overweight people with diabetes but that was also widely prescribed to others as an appetite-suppressant.
The drug, which may have caused up to 1,800 deaths, was later banned in France where millions of people took it.
It is also banned in the United States, Spain and Italy.
In the latest court ruling in more than a decade of legal proceedings, the Paris appeals court upheld verdicts of "aggravated fraud" and "involuntary manslaughter and injuries".
It ordered Servier to pay a 9-million-euro ($9.8- million) fine and pay back more than 415 million euros ($455 million) to the national social security agency and health insurance companies, much higher damages than in an initial ruling in 2021.
Jean-Philippe Seta, former right-hand man of one of the late founders of the group, was handed a four-year sentence, including one year to be served with an electronic bracelet, and a 90,000-euro ($98,000) fine.
Charles-Joseph Oudin, one of the lawyers for the more than 7,000 civil parties in the lawsuit, was delighted.
"It's a huge victory for the victims I represent and that I have been defending since the first complaint in November 2010," he said.
Wednesday's verdict is the latest in a long legal battle.
Eight years after the scandal erupted, a French court in 2015 found Servier negligent for the first time for having left "defective" medicine on the market.
Known by its lab name as benfluorex, Mediator was initially licensed to reduce levels of fatty proteins called lipids, with the claim that it helped diabetics control their level of blood sugar.
But it also suppressed appetite, which meant it gained a secondary official use to help obese diabetics lose weight.
In the end, it was widely sold on prescription for even non-diabetics who wanted to slim down.
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