Protalix Biotherapeutics, an Israeli biotech with a novel manufacturing platform, said in a terse statement that it had retained Citigroup to assist it with reviewing a “broad array of product partnering, technology sharing, and other strategic alternatives.” It declined to provide further information.

Protalix issued the statement following reports in the Israeli newspaper Calcalist that Pfizer had approached the company about buying it. Pfizer is Protalix’s partner on the Gaucher disease drug Elelyso, which the U.S. Food and Drug Administration approved in 2012.

The newspaper speculated that Merck and Novartis may also be interested in making a bid for the company. Protalix, the newspaper reported, was seeking a $1 billion price tag, but said its largest shareholder might settle for between $700 million to $800 million.

On February 5, the day of the news, the stock rose to as high as $6.73 and ended the day up 15 percent to close at $6.15 on unusually heavy trading volume of 7.5 million shares.

Protalix has a proprietary manufacturing platform known as ProCellEx. The process uses plant cells rather than mammalian, bacterial, or yeast-based expression to produce biologics. The company uses large flexible plastic containers for culturing and harvesting cells instead of the more common steel tanks. The approach provides a highly scalable means of production that has significantly lower capital and production costs and, the company says, enables penetration of certain patent-protected markets.