Multi-brand restaurant company Inspire Brands has closed the acquisition of American fast-food chain Sonic Drive-In for $2.3bn.

The deal, which was announced in September this year, makes Inspire Brands the fifth largest restaurant company in the US. Its network has now grown to more than 8,300 restaurants, with annual system-wide sales of more than $12bn.

Sonic currently operates more than 3,600 drive-in restaurants, serving approximately three million customers every day.

Inspire Brands CEO Paul Brown said: “We are thrilled to officially welcome Sonic to the Inspire family. Sonic and its franchisees have created one of the most successful and distinctive brands in the restaurant industry.

“Inspire’s commitment to strategic investments and culture of collaboration will significantly benefit our guests, team members, and franchisees.”

“We look forward to helping further drive innovation and long-term growth at Sonic and across our growing family of brands.”

Sonic president Claudia San Pedro will lead the business. The company’s former chairman and CEO Cliff Hudson will serve as its senior advisor until March 2019 to support the transition process.

Pedro said: “This is an important and exciting milestone for Sonic. Inspire’s commitment to strategic investments and culture of collaboration will significantly benefit our guests, team members, and franchisees.”

Headquartered in Atlanta, Georgia, the restaurant company owns various major restaurant brands including Arby’s, Buffalo Wild Wings and Rusty Taco globally. It is owned by affiliates of Roark.

In August this year, Inspire Brands re-acquired 12.3% ownership interest from QSR chain Wendy’s for $450m.