Martin Shkreli, the brash pharmaceutical executive whose abrupt fiftyfold increase in the price of an old infectious disease drug sparked an uproar, has acquired a majority of the shares of a publicly traded biotechnology company that was about to go out of business.

The company, KaloBios Pharmaceuticals, had said on Friday that it would wind down its operations after having suffered various setbacks in developing drugs.

But in a statement late Wednesday, KaloBios said that a group led by Mr. Shkreli had acquired more than half of its outstanding shares and that the company was in discussions with Mr. Shkreli about possibly continuing to operate.

Shares of KaloBios soared more than 800 percent after hours Wednesday, to more than $19, after Mr. Shkreli’s stock purchases were reported in a filing with the Securities and Exchange Commission. The shares had closed at $2.07 in regular trading.