GameStop, AMC extend gains but broader meme stock rally shows signs of fizzling

GameStop and AMC logged further gains in premarket trading as the broader meme stock frenzy fizzled early on its third day, with Blackberry shares flat and Koss edging lower.Brick-and-mortar video game retailer GameStop was up 10.16% at 6:40 a.m. E.T., while movie theatre chain AMC rose 9.20%.Other so-called "meme stocks" were mixed in pre-trading. Shares of one-time popular smartphone maker BlackBerry were up just 0.58% and headphones manufacturer Koss fell 4.39% at 06:42 a.m. E.T.The meme stock craze resu ...