After product testing and regulatory approval "the first commercial batches" should be available in February, Rajiah Meir, Sanofi's communications manager for Saudi Arabia, told AFP.
On Wednesday the company formally inaugurated its factory at King Abdullah Economic City, an industrial and residential development on the Red Sea.
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Meir said the plant will initially produce antibiotics, cardiovascular drugs, diabetic medication and medicine to protect against blood clots.
Sanofi is one of the first multinational pharmaceutical groups to produce in the kingdom, a company press release said.
The 35,000-square-metre (376,600-square-foot) plant, whose construction began two years ago, will export throughout the Gulf, the company's website says.
Sanofi declined to reveal its investment in the facility, or the number of initial employees, but it said 100 additional jobs will come next year.