AMC’s stock tumbles after prospectus filed for sale of up to 40 million shares

Shares of AMC Entertainment Holdings Inc. tumbled Thursday after the movie-theater operator disclosed an equity-distribution agreement in which the company could sell up to 40 million common shares.

The sales could represent up to 7.7% of the 519.2 million common shares outstanding as of Aug. 4.

AMC’s stock AMC sank 19.5% in morning trading….