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One of last week's biggest losers was Rite Aid (NYSE:RAD). Shares of the drugstore chain plummeted 13.9% on the week, falling on concerns that regulators may not approve its pending acquisition by Walgreens Boots Alliance (NASDAQ:WBA).

Most of Rite Aid's drop took place on Friday, when Bloomberg reported that the Federal Trade Commission may not clear the final regulatory hurdle separating Walgreens from its purchase of Rite Aid. Walgreens stock took a 2.1% hit on the news, but Rite Aid suffered a 12.3% retreat.   

Antitrust concerns seemed to be dissolving last year, when Fred's (NASDAQ:FRED) had secured a deal to pick up 865 Rite Aid stores in territories where a Walgreen-Rite Aid pairing would dominate the market. That side deal would seemingly surpass the divestiture that regulators were demanding. There were concerns that the smallish Fred's wouldn't be able to finance the asset purchase, but obviously that won't even be a factor if Rite Aid isn't acquired. Fred's stock experienced a 3.5% hit on Friday's news.

There's never an easy way out

Rite Aid stock has been one of the market's biggest winners since bottoming out at a mere $0.20 eight years ago. Even after last week's drop, it's still a juicy 37-bagger off those all-time lows. 

Rite Aid seemed as if it was on the brink of disappearing, but the drugstore chain turned things around. It would score 14 straight profitable quarters -- according to data from S&P Global Market Intelligence -- before proving mortal in last year's May quarter.

Walgreens struck a $17.2 billion deal to pick up Rite Aid in late 2015, offering Rite Aid investors an all-cash transaction of $9 a share. The market knew it would take some time given Walgreens Boots Alliance's size, but now we're in 2017 and the FTC is still weighing in on the proposed pairing. Bloomberg's report points to Fred's $950 million asset deal as a potential sticking point. 

Not everyone is convinced that this deal is falling apart. Cowen analyst Charles Rhyee issued a note following Friday's report, arguing that the story could've been leaked by the losing side of what seems to be a split staff at the FTC in this matter. With litigation as a possible path if the union is disrupted, Rhyee still feels that the deal will more than likely close. 

At least one Wall Street pro is concerned. Evercore ISI analyst Ross Muken also weighed in, suggesting that Rite Aid stock could plunge to $3.50 or below if the buyout falls apart. Rite Aid's stock will obviously take a hit if the FTC nixes the transaction. Friday's plunge bears that out. However, Rite Aid stock closed above $6 the day before the transaction was announced. This isn't a materially different Rite Aid being run today. 

Rite Aid's fate may be riding on the Walgreens deal, but it was too strong a turnaround story for investors to ignore if things don't close as planned in the coming months.