MADRID — Emmanuelle Bercot’s “150 Milligrams” (“La Fille de Brest”) will open the 64th San Sebastian Festival, the highest-profile movie event in the Spanish-speaking world.

The Sept. 16 opening-night berth marks another step up in status for France’s Bercot, who is fast emerging as one of Europe’s most prominent writer-director-actresses after her annus mirabilis at Cannes last year, when “La Tete Haute” (“Standing Tall”), her fifth feature as a director, opened the festival and “Mon Roi” (“My King”) won her the award for best actress.

“150 Milligrams,” sold by Wild Bunch, marks the company’s fourth high-profile title to date at the Spanish festival, which closes with Jerome Salle’s “The Odyssey.” Wild Bunch is also handling world sales on one of San Sebastian’s most-anticipated competition contenders, Bertrand Bonello’s youth terrorist thriller “Nocturama,” plus Oliver Stone’s “Snowden,” which screens out of competition.

Wild Bunch’s slate in San Sebastian reflects its ability to produce, finance or sell major festival-friendly, art-house, foreign-language or crossover titles.

Based on real events, “150 Milligrams,” dubbed a French “Erin Brockovich,” turns on a woman’s battle in France to expose the effects of a killer anti-diabetic drug, Mediator. Haut et Court, which produced Cannes Palme d’Or winner plus the original French TV series “The Returned,” produces.