Red Robin Gourmet Burgers (RRGB) - Get Red Robin Gourmet Burgers, Inc. Report  said CEO Denny Marie Post retired Wednesday and the board has formed a search committee to seek her successor.

Shares of the restaurant chain fell 8.3% to $25.88 in trading Thursday.

Pattye Moore, chairman, was appointed interim chief executive, the company said in a statement.

"The board intends to move quickly on the search process as the company continues to execute our turnaround plan in this challenging and rapidly evolving casual-dining landscape," Moore said.

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Same-store sales at Red Robin declined 4.5% in the fourth quarter, and Moore noted that "through the first three periods of the fiscal first quarter ... comparable-restaurant revenue, using constant currency rates, has decreased 3.6%.

"This reflects, in part, the challenging weather that affected several regions of the U.S.. The weather impact for these periods, estimated to be 100 to 150 basis points, primarily drove sales performance below our expectations," Moore added.

The stock also was downgraded to neutral from buy at Bank of America Merrill Lynch.

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