Jan. 27 (Bloomberg) -- AstraZeneca Plc was asked by U.S. regulators to strengthen warnings on its antipsychotic drug Seroquel about potential side effects that can lead to diabetes, according to court documents.

The U.S. Food and Drug Administration wants AstraZeneca, the U.K.’s second-largest drugmaker, to highlight on Seroquel’s warning label that some users experienced “significant weight gain,” lawyers for consumers suing the company said in a court filing yesterday. The first trial over claims that Seroquel caused diabetes is set to begin Feb. 2 in Orlando, Florida.

Letters sent by regulators to the London-based company last month “reveal FDA directives to AstraZeneca” to expand Seroquel’s warning label, Richard Laminack, a lawyer for two former Seroquel users, said in the federal court filing.

AstraZeneca faces about 9,000 lawsuits with more than 15,000 plaintiffs in the U.S. over claims that Seroquel causes diabetes and other health problems. Seroquel, which generated sales of $4.03 billion in 2007, is the company’s second-biggest seller after the ulcer treatment Nexium.

“This warning will reduce the attractiveness of using this drug, given the risk of developing a serious condition,” said Navid Malik, an analyst at London-based Matrix Corporate Capital LLP. He doesn’t have a rating on the stock.

AstraZeneca Shares

AstraZeneca fell 115 pence, or 3.9 percent, to 2,832 pence in London trading, the biggest drop in two months. The company’s American depositary receipts, each representing one ordinary share, declined 83 cents, or 2 percent, to $39.99 in New York Stock Exchange composite trading.

Johnson & Johnson, maker of the rival antipsychotic Risperdal, rose 99 cents, or 1.8 percent, to $57.54. Eli Lilly & Co., maker of the antipsychotic Zyprexa, rose $1.04, or 2.8 percent, to $38.61.

Seroquel’s label has “always provided accurate and appropriate information and warnings,” Tony Jewell, a spokesman for AstraZeneca in Wilmington, Delaware, said in an e-mailed statement. “We continue to work with the FDA to share accurate information with the public as more scientific data becomes available about the medicine.”

Jewell declined to comment on whether the FDA had requested stronger Seroquel warnings and said communications with the agency were confidential.

Weight Gain

Studies linking Seroquel, Zyprexa and similar antipsychotic treatments to weight gain and diabetes prompted the FDA to require that all makers of such medicines warn doctors about risks in 2003 and 2004.

Obesity is a known risk factor for type-two diabetes, a metabolic disorder in which the body stops responding to insulin properly, according to the Centers for Disease Control and Prevention in Atlanta.

Evidence uncovered in pre-trial exchanges of information shows that FDA officials advised AstraZeneca executives in letters of Dec. 18 and Dec. 22 that the “significant weight gain” reference should be added to the label’s “warnings and precautions section,” according to Laminack’s filing. It had been listed under “vital signs” on the label, the lawyer said.

The FDA also wants “data for Seroquel-induced weight change and glucose changes” moved up into the label’s warning section, according to the filing.

Karen Riley, an FDA spokeswoman, said she couldn’t immediately comment on whether the agency had asked AstraZeneca to toughen Seroquel’s warning.

Expert Witnesses

The FDA’s calls for stronger warnings “mirror” the contentions of consumers’ expert witnesses, who are seeking to testify in Linda Guinn’s trial, Laminack said in the filing. U.S. District Judge Anne Conway hasn’t ruled whether jurors will be allowed to hear those experts.

“Seroquel and Zyprexa are among the worst offenders affecting hazardous weight gain and glucose changes,” Laminack claimed in the filing.

Lilly agreed to pay at least $1.2 billion to settle lawsuits filed by about 31,000 patients who used Zyprexa. The Indianapolis-based company said this month it would pay an additional $1.42 billion to resolve claims by state and federal officials that it marketed the drug for unapproved uses. Lilly also agreed to plead guilty to a criminal charge.

AstraZeneca officials have said they will fight each Seroquel case and don’t plan to settle.

The drugmaker gave the FDA letters to plaintiffs on Jan. 21, Laminack said in the filing. Guinn’s lawyers asked Conway to punish AstraZeneca for failing to hand over the letters promptly by delaying the Feb. 2 trial for a month, giving them more time to gather information about the FDA’s contacts with the company over the label.

AstraZeneca should be sanctioned for “efforts to hide or delay the truth” in the Seroquel cases, the consumers’ lawyers said in court papers.

The case is Guinn v. Astra USA Inc., 07-10291-ACC, U.S. District Court, Middle District of Florida (Orlando).

To contact the reporters on this story: Margaret Cronin Fisk in Southfield, Michigan, at mcfisk@bloomberg.net; Jef Feeley in Wilmington, Delaware, at jfeeley@bloomberg.net.

Last Updated: January 27, 2009 16:22 EST