NEW YORK (CNN/Money) - Johnson & Johnson has reportedly filed an antitrust suit charging that biotech company Amgen illegally drove J&J's drug Procrit out of the market using illegal market leverage.

The New York Times reported that the suit was filed Tuesday in Federal District Court in Trenton, N.J. The paper reported that the suit charges Amgen was bundling sales of its drugs in a way that forces cancer clinics to buy Amgen's Aranesp rather than Procrit.

"We believe the allegations are not legitimate and we intend to fight this," Amgen spokeswoman Mary Klem told the paper.

Both drugs are versions of erythropoietin, a protein that bolsters the body's production of red blood cell, according to the report. It says that the lawsuit estimates that combined sales to American cancer clinics are expected to be $2.8 billion in 2005. The clinics use the drugs to treat anemia caused by chemotherapy.

Amgen also produces two other drugs, Neulasta and Neupogen, that increase production of infection-fighting white blood cells, used to treat a different side effect of chemotherapy. The paper, citing the lawsuit, says that Amgen has about 98 percent of the market for those white cell boosters, while J&J does not sell a similar product.

The lawsuit accuses Amgen of giving cancer clinics bigger discounts on Neulasta and Neupogen if they buy more Aranesp. Without the discounts, the suit contends, clinics would lose money on Neulasta when reimbursed by Medicare.

"Forcing physicians who treat cancer patients to abandon Procrit as the only economically viable way to gain access to another badly needed drug for their patients is not, by any measure, in the public interest," the lawsuit argues, according to the Times report.

Procrit's market share in cancer clinics has fallen to 34 percent, from 55 percent in the first quarter of 2004, according to the report.

Ronald Renaud, an analyst at J. P. Morgan who recommends Amgen stock, was quoted by the paper saying that the suit amounted to Johnson & Johnson "grasping at straws."

"We maintain that the most significant driver behind Aranesp's success has been the less frequent dosing when compared to Procrit," Renaud wrote in a note to clients. "Keeping a cancer patient from having to return to the oncologist's office any more than necessary is a powerful incentive to use both Aranesp and Neulasta."

For a look at the projected boom in sale of cancer-treating drugs, click here.