American Bioscience and American Pharmaceutical Partners to Present Six Abstracts on Applications of Nanoparticle Albumin Bound (nab(TM)) Tumor Targeting Technology at the 97th American Association of Cancer Research Annual Meeting.

SCHAUMBURG, Ill. & LOS ANGELES -- American Pharmaceutical Partners, Inc. (NASDAQ:APPX):

--Pre-clinical Dose-Ranging Study: Improved Activity of ABRAXANE(R) vs. Taxotere(R)

--nab(TM) Tumor-Targeting Technology Applied to Docetaxel Injection (Taxotere) Increased Activity and Decreased Toxicity in a Pre-clinical Study

--Importance of SPARC Expression in Tumor Response to Taxanes Described in Patients with Head-and-Neck Cancer

American Pharmaceutical Partners, Inc. (NASDAQ:APPX) and American Bioscience Inc. (ABI) today announced the presentation of data at the 97th Annual Meeting of the American Association of Cancer Research (AACR) that further highlights its proprietary nanoparticle albumin-bound (nab(TM)) tumor-targeting technology.

ABRAXANE(R) for Injectable Suspension (paclitaxel protein-bound particle for injection) (albumin bound) in a pre-clinical dose-ranging study across various tumor models showed improved activity versus solvent-based docetaxel injection (Taxotere(R)). Taxanes (paclitaxel and docetaxel, Taxol(R) and Taxotere, respectively) are among the most widely used chemotherapeutic agents, however conventional forms of these agents cannot be administered without the combination of toxic solvents. Solvents cause significant additional side effects beyond those associated with the chemotherapeutic agent.

Data presented (Poster #5437; Title: Improved effectiveness of ABRAXANE versus Taxotere in multiple different xenografts as a function of HER2 and SPARC status) at AACR investigated the potential of improved safety and activity of ABRAXANE vs. Taxotere (docetaxel injection) in the pre-clinical setting. The dose ranging study found that ABRAXANE was nontoxic up to 120mg/kg. In contrast, Taxotere showed a dose dependent weight loss for 15-50 mg/kg with the maximum tolerated dose at 15 mg/kg. ABRAXANE was more active than Taxotere with demonstrated tumor growth inhibition at 15 mg/kg in four of five models. The study suggests that ABRAXANE, which uses tumor targeting technology, nab(TM), was more effective, or equally effective, at a submaximum tolerated dose (MTD) compared with Taxotere at its MTD in four of five models, concluding that a clinical study of ABRAXANE versus Taxotere was warranted.

ABI's nanoparticle albumin-bound (nab) tumor-targeting technology exploits the natural properties of a human protein, albumin, for drug delivery. By wrapping albumin around active drug and creating particles of approximately 130 nanometers, ABI has found a way to eliminate the need for solvents and deliver higher concentrations of chemotherapy without the solvent-related toxicities compared with solvent-based taxanes. The FDA approval of ABRAXANE validated the nab technology and in a phase three trial, ABRAXANE showed higher tumor response rates and greater safety than Taxol.

A second pre-clinical study (Poster #5438; Title: Enhanced efficacy and safety of nanoparticle albumin-bound nab-docetaxel versus Taxotere) applied nab technology to docetaxel and in pre-clinical models of colon cancer compared nab-docetaxel with Taxotere (docetaxel injection). The study suggested that nab-docetaxel showed significantly greater antitumor activity against colon tumor versus Taxotere (p<0.0001) and despite a 50 percent higher dose demonstrated equivalent safety to Taxotere.

The Role of SPARC Expression and Tumor Response to nab(TM) Therapies

ABI has identified a biological pathway specific to tumors through which tumors preferentially accumulate albumin-bound compounds. This accumulation of albumin appears to be facilitated through a tumor's secretion of a protein called SPARC, which acts like a magnet, and attracts, binds to, and leads to high concentrations of albumin in the tumor. Much research has suggested that a common denominator in most solid tumors that are difficult to treat, including in breast, lung, ovarian, head-and-neck, melanoma, gastric, esophageal, glioma and cervical tumors, is the presence of the protein SPARC. The over-expression of the SPARC protein (SPARC positive) has been associated with poor prognosis in many of these tumors.

A retrospective analysis presented on April 4 at AACR (Poster 3495; Title: SPARC Expression in Head and Neck Cancer Correlates with Tumor Response to Nanoparticle Albumin-bound Paclitaxel) supports the importance of SPARC and its interaction with albumin-bound compounds. This study examined tumor response to nab paclitaxel in patients with SPARC-positive, head-and-neck cancer vs. patients with SPARC-negative, head-and-neck cancer. Nearly all (83 percent) of the patients with head-and-neck cancer who had tumors that expressed SPARC responded to nab-paclitaxel compared with a significantly lower response -- only 25 percent -- in the patients who had tumors that were SPARC negative. In this study with ABRAXANE in 54 patients with head-and-neck cancer, a high overall response rate (ORR) of 78 percent was reported.

Details of the other presentations by ABI at AACR are as follows:

April 5, 2006, Experimental and Molecular Therapeutics 43,
8 a.m.-12 p.m..
ABI-007, nanoparticle albumin bound paclitaxel, enhanced tumor
radioresponse (Abstract Number: 5439)

April 4, 2006, Experimental and Molecular Therapeutics 31,
8 a.m.-12 p.m.
Anti-angiogenic and antitumor activity of nanoparticle albumin
bound (nab) thiocolchicine dimer (IDN5404) with a novel dual mechanism
of action on tubulin and topoisomerase-1 (Abstract Number: 3823)

April 2, 2006, Chemistry 2. 1 p.m.-5:p.m.
Preparation and Evaluation of Novel Derivatives of Geldanamycin
(Abstract Number 1121)

About ABRAXANE(R)

The U.S. Food and Drug Administration approved ABRAXANE(R) for Injectable Suspension (paclitaxel protein-bound particles for injectable suspension) (albumin-bound) in January 2005 for the treatment of breast cancer after failure of combination chemotherapy for metastatic disease or relapse within six months of adjuvant chemotherapy. Prior therapy should have included an anthracycline unless clinically contraindicated. For the full prescribing information for ABRAXANE(R) please visit www.abraxane.com.

In the randomized metastatic breast cancer study, the most important adverse events included neutropenia (all cases 80%; severe 9%), anemia (all 33%; severe 1%), infections (24%), sensory neuropathy (any symptoms 71%; severe 10%), nausea (any 30%; severe 3%), vomiting (any 18%; severe 4%), diarrhea (any 26%; severe <1%), myalgia/arthralgia (any 44%; severe 8%), and mucositis (any 7%; severe <1%). Other adverse reactions included asthenia (any 47%; severe 8%), ocular/visual disturbances (any 13%; severe 1%), fluid retention (any 10%; severe 0%), alopecia (90%), hepatic dysfunction (elevations in bilirubin 7%, alkaline phosphatase 36%, AST (SGOT) 39%), and renal dysfunction (any 11%; severe 1%). Thrombocytopenia (any 2%; severe <1%), hypersensitivity reactions (any 4%; severe 0%), cardiovascular reactions (severe 3%), and injection site reactions (1%) were uncommon.

About American BioScience, Inc.

American BioScience, Inc. (ABI) is a privately held biotechnology company focused on the discovery, development and delivery of next-generation therapeutics including biologically active molecules already existing within the human biological system, for the treatment of life-threatening diseases. ABI owns a majority interest in American Pharmaceutical Partners, Inc.

About American Pharmaceutical Partners

American Pharmaceutical Partners, Inc. is a specialty drug company that develops, manufactures and markets injectable pharmaceutical products, focusing on the oncology, anti-infective and critical care markets. Abraxis Oncology, the proprietary division of APP, is devoted entirely to developing and promoting innovative, next-generation cancer therapies such as ABRAXANE, recently launched for the treatment of metastatic breast cancer. For more information, visit APP's website at www.appdrugs.com and www.abraxisoncology.com.

FORWARD-LOOKING STATEMENT

The statements contained in this press release that are not purely historical are forward-looking statements within the meaning of Section 21E of the Securities Exchange Act of 1934, as amended. Because these forward-looking statements, whether expressed or implied, involve risks and uncertainties, there are important factors that could cause actual results to differ materially from those in the forward-looking statements. These factors include, without limitation, the uncertainties regarding the costs and time involved in bringing our Illinois manufacturing facility to a fully operational status, the adverse impact of production delays on the sales and marketing of our products, the costs associated with the ongoing launch of ABRAXANE, the market adoption and demand of ABRAXANE, marketing approvals and launches of other products, the impact of pharmaceutical industry regulation, the impact of competitive products and pricing, the availability and pricing of ingredients used in the manufacture of pharmaceutical products, the ability to successfully manufacture products in a time-sensitive and cost effective manner, the acceptance and demand of new pharmaceutical products, the impact of patents and other proprietary rights held by competitors and other third parties. Additional relevant information concerning risks can be found in APP's Form 10-K for the year ended December 31, 2005, APP's information statement filed on March 13, 2006 and other documents it has filed with the Securities and Exchange Commission.

Taxol(R) is a registered trademark of Bristol-Meyers Squibb Company. Taxotere(R) is a registered trademark of Aventis Pharmaceuticals, Inc.