Insider trading, kickbacks to doctors and false reports to federal regulators are some of the allegations shareholders are levying against Amgen Inc. as a cluster of lawsuits moves toward consolidation at the end of the month.

The investors are seeking several hundred million dollars to recoup market losses they claim were caused by the Thousand Oaks-based biotechnology giant by failing to disclose adverse facts about the company's anemia drugs, Aranesp and Epogen.

One suit filed by the Public Employees Retirement Association of Colorado claims Amgen misled investors with inaccurate finance statements that did not include information that the company marketed the medicines for unapproved, off-label uses, gave doctors kickbacks to overprescribe the drugs in dangerous amounts, and did not reveal negative studies that showed problems with the drugs.

By disseminating "misleading information" and failing to disclose material facts, "the market price of Amgen's securities was artificially inflated," they allege. Had it been known, they would not have purchased the securities or paid so much for them.

Amgen Communications Director Mary Klem said the company does not comment about ongoing litigation, but denied the allegations have veracity.

"We absolutely do not believe any of the allegations are true and plan to vigorously defend ourselves," she said.

Shareholder lawsuits are common, as seen in the Supreme Court case involving Tellabs, a technology company based in Naperville, Ill.

Investors sued the company, claiming they were misled when the company engaged in a scheme to inflate Tellabs' stock price from December 2000 to June 2001. The suit said the company's chief executive provided false assurances of robust demand for the company's products.

Investors lost in that case last month when the Supreme Court justices imposed a strict standard for shareholder lawsuits seeking to recover losses from companies accused of fraudulent business practices.

The 8-1 opinion written by Justice Ruth Bader Ginsburg will make it harder for groups of investors to file lawsuits alleging they lost money because company officials violated U.S. securities laws. A lawsuit will survive only if the facts alleged in it are "cogent and compelling" in pointing to an intent to deceive investors, Ginsburg wrote.

The standard will be applied at the very start of a securities fraud case, meaning that many lawsuits may be tossed out at the earlier stages of a court battle.

The business community argued that the Tellabs case is the kind of meritless claim that Congress intended to prohibit when it reformed securities law 12 years ago.

Investors criticize Amgen

Aranesp and Epogen are two of Amgen's principal products, with sales producing nearly half of its $14.3 billion revenue in 2006.

The FDA approved Aranesp for treating anemia in chemotherapy and kidney disease patients and Epogen for treating anemia in patients undergoing kidney dialysis. By law, drug companies must not promote drugs for "off-label" uses they aren't approved for, but the shareholders, citing a May 9 article in The New York Times, claim Amgen paid hundreds of millions of dollars in kickbacks to doctors to entice them to promote off-label uses.

Shareholders involved in the suits say Amgen's off-label uses included promoting the drugs for cancer patients not undergoing chemotherapy who were less anemic than the drug was approved for.

The company also is accused of taking advantage of lax policies in the Medicare and Medicaid programs that permitted reimbursement for off-label uses of the drugs.

"Amgen established and deployed reimbursement teams' to help medical providers properly code and bill Medicare for all different uses of Epogen and Aranesp," the Public Employees Retirement Association of Colorado suit states.

Accusations on anemia drug

The shareholders also allege that Amgen officers unloaded their own stock after a 2006 clinical study of cancer patients taking Aranesp "discovered that more deaths occurred in patients taking Aranesp than in taking a placebo."

Investors say they didn't find out about the study until four months later.

The Colorado lawsuit states, "Dennis Fenton, Amgen's executive vice president of operations, sold 100,000 shares of Amgen stock for over $7 million. Defendants Richard Nanula, Amgen's (former) chief financial officer, sold 30,000 shares for over $2 million.

"The timing and size of this insider selling was highly suspicious in light of the material, adverse information about Amgen known to defendants but not disclosed to the public."

Also accused of "highly suspicious insider selling" is Chief Executive Officer Kevin Sharer, who sold more than 70 percent of his holdings, 1.2 million shares for $96 million.

Shareholders involved in the various lawsuits include Teachers Retirement System of the State of Kentucky; city of Boca Raton Police & Firefighters Retirement System; Kentucky Teachers Retirement System; General Retirement System of the city of Detroit; Maine State Retirement System; and Connecticut Retirement Plans and Trust Funds.

Named as defendants are Amgen Inc., Sharer, Nanula and other current and former officers and board members.

The claims have been filed in federal court in Los Angeles. Judge Philip S. Gutierrez has scheduled a July 30 hearing on the consolidation issue.

— The Associated Press contributed to this report.