The biotech is responding to practices that were criticized for contributing to overuse of its flagship anemia drug at the same time safety concerns were growing, The New York Times reports.

Specifically, Amgen will no longer offer rebates to oncology clinics for their use of Aranesp, although larger discounts will be offered at the time of purchase. But discounts will not be offered on two other drugs, Neulasta and Neupogen, based on a doctor’s purchase of Aranesp, the paper writes.

Critics have said that by providing hundreds of millions of dollars in discounts and rebates each year to cancer clinics, Amgen provided an incentive for doctors to use more of the drug. Oncology practices typically buy the drugs they use and then are reimbursed for them by patients and insurers. If the doctors pay less for the drugs because of discounts and rebates, they can make a higher profit.

Amgen’s pricing policies are not unique, but criticism has intensified as new studies suggested that Aranesp and Procrit, a similar drug sold by Johnson & Johnson, may harm cancer patients using the drugs to treat anemia caused by chemotherapy. The studies indicated high doses might worsen cancer, hasten death and cause cardiovascular problems, the Times writes.

Amgen maintained that its pricing policies have not caused overuse of the Aranesp. “Nevertheless, we believe these contracting changes, along with other modifications, help to clear up those possible misperceptions,” according to a statement given the paper.

Amgen has begun briefing cancer clinics and patient advocacy groups about the changes, which will take effect Octocber 1. “It’s a step in the right direction,” Nancy Roach, chairwoman of the board of the Colorectal Cancer Coalition, tells the Times.

Because of the new safety concerns, the FDA has put stronger warnings on the labels of Aranesp and Procrit while Medicare has restricted reimbursement for use of the drugs. Sales of both products, while still in the billions of dollars annually, have fallen sharply.

Congress has been investigating Amgen’s pricing. In a letter to Amgen in March, John Dingell and Bart Stupak, both Democrats of Michigan, said they were concerned that Amgen’s “bundling” practices “have helped fuel excessive and dangerous off-label use of Aranesp.” Dingell chairs the House Energy and Commerce Committee and Stupak heads the subcommittee on oversight and investigations. And Senator Chuck Grassley of the Senate Finance Committee wrote Amgen, noting the biotech provided nearly $800 million in rebates to more than 6,000 facilities in 2006.

Amgen once offered discounts and rebates to doctors based on how much Aranesp they bought. In response to criticism that this was leading to overuse of the drug, it quietly changed its policy in February to offer the discounts and rebates based on the share of a clinic’s anemia drug purchases represented by Aranesp as opposed to Procrit. This change was meant to show that its contracts were aimed at competing with J&J, not increasing overall use of anemia drugs, the Times writes.

In its newest change Amgen will stop offering rebates, which attracted more criticism than discounts at the time of purchase. However, an Amgen spokeswoman tells the Times bigger discounts will be offered at the time of purchase to doctors who buy at least 50 percent of their anemia drugs from Amgen rather than J&J. The net effect could be the same total discounts to the doctors.

Amgen also used to offer extra discounts on two other drugs, Neulasta and Neupogen, to doctors who bought more Aranesp. Both drugs help protect cancer patients from infections by bolstering their white blood cell counts.

Amgen has a near monopoly on white cell boosters. Johnson & Johnson sued Amgen, saying this “bundling” violated antitrust laws because doctors were forced to buy Aranesp to get the indispensable white cell boosters at an affordable price. A lawsuit was settled last month, with Amgen agreeing to pay J&J $200 million but not admitting any wrongdoing.

Amgen changed its contract in February so that the extra discounts on Neulasta and Neupogen were based on Aranesp’s share of a clinic’s anemia drug purchases. But now it is ending the bundling altogether.

Peter Eisenberg, an oncologist in Marin County, California, tells the Times he welcomed the end of bundling. His practice, California Cancer Care, had been buying the drugs separately because it refused to accept Amgen’s terms. “Our practice probably gave up a million bucks over two years, probably more, in rebates by not signing a contract,” he tells the paper.