Stocks to Watch: CSX, Aclaris, Alnylam, Rigel

Companies with shares expected to trade actively in Friday's session include CSX Corp. (CSX), Aclaris Therapeutics Inc. (ACRS), Alnylam Pharmaceuticals Inc. (ALNY) and Rigel Pharmaceuticals Inc. (RIGL).

CSX shares dropped 12% premarket Friday on news that Chief Executive Hunter Harrison was taking a medical leave for an undisclosed illness. The veteran railroad executive's absence puts into question whether or not he will be able to carry out a turnaround at CSX, whose stock had been energized after he was installed.

Aclaris shares rose 1% premarket after the company said it received U.S. Food and Drug Administration approval for its skin-treatment Eskata. Eskata treats non-cancerous skin growths called raised seborrheic keratoses, which affects more than 83 million Americans, according to the company.

Alnylam's stock rose 5% premarket after the company said the U.S. Food and Drug Administration lifted its clinical hold on studies for its hemophilia treatment, fitusiran. Alnylam and the FDA had previously reached an agreement to mitigate risk during studies of the drug, which Alnylam is developing with a unit of Sanofi (SNY).

Rigel shares rose 3.6% premarket after the company said its longtime chief financial officer, Ryan Maynard, would resign at the end of the month. Rigel CEO Raul Rodriguez said recent financing positions the company to prepare for the potential launch of one of its treatments, making it the right time for a transition.

Hess Corp. (HES) is up 5.5% before the bell on the news the energy company is facing fresh pressure from activist investor Elliott Management, which is hoping to either remove CEO John B. Hess or push him to consider selling all or part of the company.

Adobe Systems Inc. (ADBE) rose 2% in premarket action after beating forecasts with its earnings out late Thursday.

Costco Wholesale Corp. (COST) is up 2.7% after the retailer reported fiscal first-quarter earnings and sales above Wall Street forecasts.

Write to Cara Lombardo at cara.lombardo@wsj.com

(END) Dow Jones Newswires

December 15, 2017 09:11 ET (14:11 GMT)