Shares of Raptor Pharmaceuticals (RPTP) spiked in pre-market trading after reports suggested that several companies are considering bids for the biopharmaceutical company.

SHIRE: According to a report on Wednesday from Spain's Intereconomia, Shire (SHPG) offered to acquire Novato, California-based Raptor for $800M. The report noted that a merger of the companies would create one of the largest companies dedicated to combat rare or "orphan diseases."

Raptor Chief Executive Julie Smith told Bloomberg in a phone interview that the company does not comment on "speculation or rumors," and said she would call the Shire report "a rumor."

RETROPHIN: Separately, people familiar with the matter said Retrophin (RTRX), which was founded by Martin Shkreli, is also considering an acquisition of Raptor, Bloomberg reported on Wednesday evening. According to the people, who said Raptor has attracted interest from other drugmakers, a deal would boost growth in treatments for rare diseases.

No final agreement has been reached, the people said. Controversial entrepreneur Shkreli left Retrophin, which develops drugs for "catastrophic" diseases, in 2014 and is no longer associated with the company, the report noted.

WHAT'S NOTABLE: In April, Reuters reported that Raptor reached out to investment banks to advise it on a sale. At the time, Reuters' sources noted that Raptor's move was "exploratory" and might not lead to a sale. The report said that while the pharmaceutical industry was interested in orphan drugs because of their strong patent protection, it is also difficult for small companies like Raptor to raise cash for research because of volatile markets.

PRICE ACTION: Raptor Pharmaceuticals was up 17%, or $1.20, to $8.10 in pre-market trading.