By Randall Osborne

West Coast Editor

Filing a shelf registration even as the company awaits the outcome of patent cases that could deplete its cupboards, Transkaryotic Therapies Inc. (TKT) aims to sell up to $500 million in securities.

"We have no current plans [to sell]," said Justine Koenigsberg, manager of corporate communications for Cambridge, Mass.-based TKT, adding that the registration is not related to the firm's ongoing patent litigation with Amgen Inc., of Thousand Oaks, Calif., or with Genzyme General, also of Cambridge.

The court skirmish with Amgen is over erythropoietin (EPO) marketed by Amgen under the name Epogen. It is a glycoprotein hormone that regulates the level of red blood cells in circulation by stimulating their production in the bone marrow.

The fight with Genzyme, which involves a race to market, is over competing products to treat Fabry's disease. Genzyme's enzyme replacement therapy is called Fabrazyme. The firm's marketing request has been accepted for priority review, and Genzyme expects approval in mid-January. TKT's enzyme replacement therapy is Replagal, also in line for priority review.

Decisions in the court cases are pending.

Also Thursday, TKT disclosed it has adopted a shareholders' rights plan. Often called a "poison pill," the plan kicks in if any party buys 20 percent of the company's stock, and is designed to protect shareholders from a hostile takeover.

"No one has approached the company," Koenigsberg told BioWorld Today, and the plan is not in any response to any such intention.

The plan declares a dividend of one preferred stock purchase right per each common share owned at the end of business Dec. 26.

If exercised, each right entitles shareholders to buy a fractional share of preferred stock for $289. If someone buys 20 percent or more of TKT, each right would let the holder (other than the 20 percent buyer) acquire company shares with a market value of twice the exercise price of the right.

As of Sept. 30, TKT had 22.69 million shares of common stock and 10,000 shares of Series A preferred stock outstanding. Its stock (NASDAQ: TKTX) fell $2.50 Thursday to close at $35.25.