Sonus Pharmaceuticals Initiates Phase 1 Clinical Trial for Company's Second Anti-cancer Drug, TOCOSOL(R) Camptothecin.

BOTHELL, Wash. -- Sonus Pharmaceuticals, Inc. (NASDAQ:SNUS) today announced the initiation of a Phase 1 clinical study for its second oncology product candidate, TOCOSOL([R])Camptothecin, a novel camptothecin drug. Formulated with the Company's proprietary vitamin E-based TOCOSOL technology, TOCOSOL Camptothecin is a New Chemical Entity that is a conjugate of SN-38. SN-38 is the active ingredient in irinotecan, a commercially available camptothecin analog. Preclinical data, presented at the AACR-NCI-EORTC 2005 conference, suggest that TOCOSOL Camptothecin may be more efficacious and better tolerated than irinotecan.

The single-agent Phase 1 study of TOCOSOL Camptothecin is expected to enroll up to 61 patients with advanced solid tumors at two leading cancer centers in the United States, including the Sarah Cannon Research Institute (SCRI), Nashville, Tennessee; and Fox Chase Cancer Center, Philadelphia, Pennsylvania. The study will investigate the safety profile of TOCOSOL Camptothecin at different doses in order to determine the maximum tolerated dose in humans. The Phase 1 study is also designed to observe anti-tumor effects of TOCOSOL Camptothecin as well as to characterize the pharmacokinetics of the drug.

"TOCOSOL Camptothecin has shown impressive results in preclinical studies," said Howard A. Burris III, M.D., Chief Medical Officer and Director of Drug Development, SCRI. "This promising compound may have the ability to improve outcomes in patients treated with camptothecin-based drugs."

"Moving our second TOCOSOL drug candidate into clinical development marks a significant milestone for Sonus. Based on the strength of preclinical data, we believe that TOCOSOL Camptothecin may offer a more efficacious, safer and easier to administer formulation of a camptothecin drug," said Richard Daifuku, M.D., Ph.D., Acting Chief Medical Officer and Vice President of Preclinical and Clinical Research, Sonus Pharmaceuticals. "Additionally, TOCOSOL Camptothecin is the first New Chemical Entity invented by Sonus scientists, which serves to further demonstrate the versatility of our proprietary TOCOSOL technology and our growing capabilities in drug development."

About TOCOSOL Camptothecin

TOCOSOL Camptothecin is a new entry in the same drug class as the approved camptothecin analogs, irinotecan and topotecan. These products are used in the treatment of colorectal, lung, ovarian and cervical cancers and have estimated annual sales of over $1 billion. Camptothecins are among the most important classes of anti-cancer drugs introduced in recent years; however, the commercially available products have demonstrated toxicities that may limit their clinical utility. TOCOSOL Camptothecin is designed to overcome the limitations of the marketed camptothecin analogs with the potential to provide improved anti-tumor efficacy, better patient tolerance, reduced duration of administration and improved convenience of use.

About Sonus Pharmaceuticals

The Company's lead oncology product candidate, TOCOSOL Paclitaxel, is currently in a Phase 3 pivotal trial in metastatic breast cancer. TOCOSOL Paclitaxel is a ready-to-use, injectable formulation of paclitaxel that may reduce treatment-limiting side effects and improve anti-tumor activity. Submission of the New Drug Application for TOCOSOL Paclitaxel is expected by the end of 2007. In October 2005, Sonus entered into a licensing agreement with Schering AG for the development and commercialization of TOCOSOL Paclitaxel. Located near Seattle, Sonus Pharmaceuticals, Inc. is focused on the development of oncology drugs that provide better therapeutic alternatives for cancer patients, including improved efficacy, safety and tolerability, and are more convenient to use. For additional information on Sonus, including news releases, please visit www.sonuspharma.com.

Safe Harbor 

Certain statements made in this press release are forward-looking such as those, among others, relating to the development, safety and efficacy of therapeutic drugs and potential applications for these products. As discussed in Sonus Pharmaceuticals' filings with the Securities and Exchange Commission, including its Annual Report on Form 10-K filed on March 16, 2006 and Quarterly Reports on Form 10-Q filed on May 10, 2006 and August 9, 2006, actual results could differ materially from those projected in the forward-looking statements as a result of the following factors, among others: the Company's products will require extensive clinical testing and approval by regulatory authorities; such approvals are lengthy and expensive and may never occur; risks that the Company will not be able to complete the Phase 3 clinical trial for TOCOSOL Paclitaxel; risks that clinical studies with TOCOSOL Paclitaxel will not be successful; risks that the FDA may not approve the TOCOSOL Paclitaxel New Drug Application; risks that the Phase 1 clinical trial for TOCOSOL Camptothecin will not be successful; risks of successful development of therapeutic drugs; and risks that the Company may not be successful in obtaining funding from third parties or completing a financing necessary to support the costs and expenses of clinical studies as well as research and development activities. The Company undertakes no obligation to update the forward-looking statements contained herein or to reflect events or circumstances occurring after the date hereof.