Shares of movie-chain operator AMC Entertainment AMC, +35.58% climbed 20% in premarket trading, after jumping 36% on Thursday, and more than doubled over the last four days. On Twitter, financial analytics group Ortex said new losses generated for short sellers of the meme stock were “up to $500 million in the pre-market alone. Total losses in $AMC this week are $1.75 bilion so far. Retail investors on social media fueled the rise of AMC earlier in the year. Videogames retailer GameStop GME, +4.77%, also a popular meme stock this year, was up 2.7% in premarket.