Pfizer Inc. (PFE) has temporarily halted enrollment of new patients in a clinical trial of an experimental lung-cancer drug, saying the drug was associated with a higher rate of adverse events, including fatalities, than those who didn't get the drug.

The drug is figitumumab, also known as CP-751,871. It was in a Phase 3, or late-stage, trial in patients with a form of the disease known as non-adenocarcinoma non-small cell lung cancer.

The trial began around March 2008 and was projected to have about 820 patients before ending in 2011, according to a U.S. government clinical-trial database. Some of the patients were given figitumumab in addition to the drugs paclitaxel and carboplatin, while others would get paclitaxel and carboplatin only.

Pfizer said in a written statement Friday that an independent committee monitoring drug safety found there were more serious adverse events, including deaths, in people who received the Pfizer drug. Pfizer didn't immediately disclose the number of such events.

It was the latest research setback for Pfizer, which has struggled to bring successful new drugs to market to offset lost revenue from patent expirations for current best-sellers. Pfizer is in the process of acquiring Wyeth (WYE) partly to beef up its research efforts.

Pfizer is temporarily halting new enrollment of patients in the trial, but currently enrolled patients may continue their treatment in accordance with the trial design and in consultation with their doctors. The company will work with the drug-safety committee to analyze the data before issuing further guidance.

A separate study, which tests figitumumab with the drug Tarceva, continues to enroll new patients, Pfizer said.

Figitumumab belongs to a class of drugs known as IGF-1R inhibitors, which block a substance in the body known as insulin-growth factor.

The Pfizer trial's halt was reported earlier by CNBC.

Pfizer shares rose 29 cents to $16.99 in recent trading Friday.

- Peter Loftus; Dow Jones Newswires; 215-656-8289; peter.loftus@dowjones.com