DURHAM — A large shareholder in Biocryst Pharmaceuticals Inc. argues that the drug company’s proposed merger with another drug company undervalues its assets and wants to scuttle the deal, according to a filing Friday with the Securities and Exchange Commission.

Dr. Jeffrey Jay of Great Point Partners LLC in Greenwich, Connecticut, owns 7.5 million shares of Durham-based Biocryst, or 7.6 percent of its stock.

In the filing, Jay argued that Biocryst’s stock is “is undervalued and represent a low-risk and high reward investment in the spectrum of such companies.” He later said that he is “strongly opposed to the merger with Idera.”

In February, BioCryst Pharmaceuticals signed a merger agreement with Exton, Pennsylvania-based Idera Pharmaceuticals.

But Jay, in the filing, said that the deal undervalues Biocryst.

“The merger is significantly unbalanced and represents a substantial transfer of highly valuable company assets to the shareholders of Idera in exchange for more speculative Idera assets of far more uncertain value,” said Jay in the filing.

In a letter to BioCryst’s board, Jay’s investment partner David Kroin wrote that the company’s lead drug, BCX-7353, has value of well over $1.5 billion, more than three times the current market capitalization of the company.

Kroin added, “Neither management team has provided guidance for cash synergies or an extended cash runway due to this merger.”

Durham-based BioCryst Pharmaceuticals develops small molecule drugs that block key enzymes involved in uncommon diseases. The company was founded in 1986.

As part of the deal, BioCryst chairman Robert Ingram will be the chairman of the combined company, and BioCryst CEO Jon P. Stonehouse will serve as a member of the board.

Each share of the BioCryst common stock will be exchanged for 0.50 shares of the new company stock and each share of Idera common stock will be exchanged for 0.20 shares of the new company stock.

BioCryst stockholders will own 51.6 percent of the combined company stock, and Idera stockholders will own 48.4 percent. The stock exchange is expected to be tax free to stockholders.

The company’s stock rose 9 cents, or 1.85 percent, to $4.96 on Friday. Idera’s shares rose 2 cents to $1.93 on Friday.

This story is from the North Carolina Business News Wire, a service of the UNC-Chapel Hill School of Media and Journalism