What happened 

Shares of GNC Holdings Inc. (NYSE:GNC) jumped as much as 31.5% in trading Thursday after a large investment got the go-ahead to move forward. The stock was holding up nicely, at a 27% gain on the day, at 11:05 a.m. EDT. 

So what

The Committee on Foreign Investment in the United States approved Harbin Pharmaceutical Group Holding's $300 million investment in GNC, which will make it the company's biggest investor. The companies are also forming a joint venture in China to manufacture, market, and sell products there. 

Supplements on a black table, with full measuring cups next to them.

Image source: Getty Images.

Under the February 2018 agreement, Harbin will get $300 million of convertible preferred shares, which convert to common stock at $5.35 per share. The preferred shares will come with a 6.5% annual coupon. GNC says it will use the money to repay outstanding debt and for corporate purposes. 

Now what

GNC is only worth about $300 million at its current stock price, so this is a massive investment for the company, leaving Harbin with about 40% of the company's stock once converted. The challenge now is making this investment into a financial turnaround, which will be easier with a smaller debt load. But after nearly two years of losses, there's reason to be cautious with GNC shares until a turnaround materializes. 

Travis Hoium has no position in any of the stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.