HOUSTON, Jan. 7, 2005 – Thirty-eight US Oncology, Inc.-affiliated cancer-care sites nationwide continue to play a significant role in the clinical research of Abraxane™, approved today by the U.S. Food and Drug Administration (FDA). Abraxane (paclitaxel protein-bound particles for injectable suspension), a next generation taxane, and the first in a new class of albumin-bound nanotechnology, was approved for the treatment of metastatic breast cancer. US Oncology conducted a Phase II clinical trial of Abraxane in patients with metastatic breast cancer who were resistant to taxane drugs and continue to participate in the ongoing clinical development of the drug. Clinical trials of Abraxane have shown that the new drug is superior to solvent-based paclitaxel (commonly marketed as Taxol®) in response rate and time to tumor progression.

“Abraxane is a significant advance in how paclitaxel is delivered and provides a much-needed new option for breast cancer patients,” said Dr. Joyce A. O’Shaughnessy, co-director, US Oncology Breast Cancer Research, and director of Breast Cancer Prevention, at Baylor-Charles A. Sammons Cancer Center in Dallas, Texas. “With this human protein nanoparticle form of paclitaxel, patients no longer require steroid premedication to avoid the sometimes life-threatening allergic reactions which occur with current solvent-based paclitaxel therapy.

“In our trials with weekly Abraxane, we saw fewer side effects than observed with solvent-based paclitaxel, and, even more encouraging, we saw a significant response to Abraxane in some women whose cancer had progressed through treatment with taxanes. Women taking Abraxane also spent less time in the clinic receiving their chemotherapies,” said Dr. Joanne Blum, medical oncologist at Baylor-Sammons and principal investigator of the US Oncology clinical trial of Abraxane.

To date, the formulation of insoluble tumor-fighting agents, such as paclitaxel, has required the use of solvents which, in addition to other side effects, cause severe allergic reactions called hypersensitivity reactions. For instance, in Taxol, paclitaxel must be dissolved in the solvent Cremophor-EL® so that it can be administered to patients. To reduce the risk of allergic toxicities when receiving Taxol, patients must undergo premedication using steroids and anti-histamines and be given the drug using slow infusions.

Abraxane - developed by American Bioscience and to be marketed by Abraxis Oncology, a division of American Pharmaceutical Partners (NASDAQ:APPX) - is an innovation in cancer treatment. Abraxane is engineered using a proprietary process (protein bound nanoparticle technology) to create tiny particles (nanoparticles) in which the active chemotherapeutic drug, paclitaxel, is bound to a naturally occurring protein called albumin. By using this nanotechnology, the active component (paclitaxel) can be delivered into the body without the need for solvents such as Cremophor-EL.

Because Abraxane is solvent-free, solvent-related toxicities are eliminated, premedication is not required and administration can occur more rapidly. In a randomized Phase III trial, the response rate of Abraxane was almost twice that of the solvent-containing drug Taxol. Because Abraxane does not contain solvents, higher doses of paclitaxel could be given which may account in part for its increased anti-tumor activity. In addition, albumin is a protein that normally transports nutrients to cells and has been shown to accumulate in rapidly growing tumors. Therefore, Abraxane’s increased effectiveness may also be due to preferential delivery of albumin-bound paclitaxel to cancer cells.

“We are proud to have been a part of the clinical trials for Abraxane, as it is a much-needed new option for women with metastatic breast cancer,” said Dr. Atul Dhir, president of the cancer information research group. “Our participation in these trials is an example of US Oncology’s continuing commitment to advancements in treatment for breast cancer.”

Over the past 11 years, more than 16,000 patients of US Oncology-affiliated practices have taken part in clinical trials involving chemotherapy, immunotherapy, stem cell transplantation and gene therapy. The company has contributed to the development of 18 approved cancer-fighting drugs.