Celgene Corp. has filed suit against the U.S. Patent and Trademark Office to keep EntreMed Inc. from getting a crucially needed patent on a potential new anti-cancer drug.

The civil action, disclosed yesterday by EntreMed, represents yet another blow to the struggling Rockville company, which analysts say is short on cash and time.

"This is not good - by any means," said associate analyst Peter McDonald, who follows EntreMed for Gerard Klauer Mattison in New York. "The company has had enough problems as it is."

According to EntreMed, Celgene's lawsuit asks the Patent and Trademark Office to reject EntreMed's request for a patent on ENMD 0995, a drug in early stage testing that has shown promise in combating a form of cancer known as multiple myeloma. James E. Rogan, the patent office director, and EntreMed are named as defendants.

Celgene, based in Warren, N.J., could not be reached for comment yesterday. EntreMed declined yesterday to comment on the U.S. District Court lawsuit, or anything else about the company.

"On the advice of legal counsel, we are not discussing the matter at this time," said Amy Finan, an EntreMed spokeswoman.

EntreMed has recently been articulating a shift in strategic focus - from complex protein drugs that can be delivered only by injection, to so-called small-molecule drugs that can be taken orally, and are cheaper to make. ENMD 0995 - derived from the infamous drug thalidomide - is a small-molecule drug.

Thalidomide acquired its notoriety because of the birth defects it caused in newborns, after doctors prescribed it to prevent morning sickness. Since that time, however, researchers are finding other uses for the drug: It has been used to combat leprosy and has found increasing use as a cancer-fighter.

ENMD 0995, EntreMed's latest drug candidate, entered Phase I clinical trials last week. The Food and Drug Administration granted ENMD 0995 "orphan drug" status, which helps companies develop pharmaceutical remedies for diseases that affect fewer than 200,000.

Multiple Myeloma is one such disease, afflicting only about 14,000 people annually, according to the Multiple Myeloma Research Foundation. The disease, which is the second-most prevalent form of blood cancer, came to prominence several years ago when former Democratic vice presidential candidate Geraldine A. Ferraro revealed she had been stricken.

EntreMed has said that tests in animals suggest its ENMD 0995 thalidomide derivative is more effective and less toxic than other thalidomide-based multiple myeloma treatments.

Quantifying just what this drug could mean to EntreMed financially would be difficult even without the Celgene litigation, said McDonald, the Gerard Klauer analyst.

But the company clearly has pinned its future on this and a few other drug candidates, and the Celgene lawsuit makes that figure even tougher to predict, McDonald said.

In a prepared statement, EntreMed said it "will vigorously defend its patent rights in this lawsuit. We are confident in our patent position for a number of reasons."

Those reasons are based largely on the dates it filed for patent protection, compared with the later dates on which Celgene filed. But there are many nuances to these filings, McDonald said, meaning it takes more than just the dates to decide a patent dispute.

"These patent fights can drag on for a long time," he said.

And time is something EntreMed definitely appears to lack, according to McDonald.

Despite the cost cuts it has made, and jobs it has slashed, the company could be out of cash when the year comes to an end, McDonald said.

Normally, a firm facing EntreMed's financial plight would take on a partner with deeper pockets.

The new partner would receive a share of the new drug's future sales but also share in the risk the drug may fail.

But many potential partners will be scared off by the storm cloud of patent litigation, McDonald said, perhaps forcing EntreMed to forge on alone.

"It's coming down to its last act. This is just another hiccup in what has proven to be not a good time [for EntreMed]."

Sun staff writer Julie Bell contributed to this article.