Lassa fever

SciClone Pharmaceuticals, Inc. (NASDAQ: SCLN) today announced that its proprietary immunomodulatory compound SCV-07 was effective in preclinical studies, significantly reducing lesions in a model of human papillomavirus (HPV) and increasing survival in a model of Lassa fever.

These data were presented yesterday at the International Union of Microbiological Societies (IUMS) conference in San Francisco, California. The HPV model study was conducted by Neil D. Christensen, Ph.D., Associate Professor of Pathology, and Microbiology and Immunology at Pennsylvania State University. The Lassa fever model study was conducted in the laboratory of Dr. C.J. Peters, Professor, Department of Pathology, University of Texas Medical Branch at Galveston.

"These data underscore the broad applicability of SCV-07, as they demonstrate activity in two dramatically different models of viral infection," said Cynthia Tuthill, Ph.D., Vice President of Scientific Affairs, SciClone Pharmaceuticals, Inc. "We look forward to initiating phase 1 clinical studies of SCV-07 in healthy volunteers later this year. We anticipate proceeding to a phase 2 study in a viral or infectious disease indication in 2006."

In the HPV model study, animals treated with SCV-07 showed a marked reduction in papilloma size and volume of both treated and untreated papillomas, indicating that subcutaneously administered SCV-07 works systemically to treat all papillomas occurring on the animal. Untreated animals did not experience reduction in papilloma size or volume. HPV is one of the most common sexually-transmitted infections worldwide and can cause genital warts. Certain strains of the virus can lead to cervical cancer, which affects approximately 50,000 women annually in the United States.

In a model of Lassa fever, SCV-07 decreased the severity of the disease and significantly increased the survival of the animals, compared to animals in the untreated control group. Occasional epidemics of Lassa fever in Africa have had human fatality rates as high as 50%. The Lassa virus is classified as a category A (highest) biothreat agent by the National Institute of Allergy and Infectious Diseases (NIAID).

Earlier studies indicate that SCV-07 stimulates the body's immune response by promoting T-cell differentiation into T helper 1 (Th1) cells, a critical process in the body's fight against infection. SciClone acquired the worldwide rights, outside of Russia, to SCV-07 from Verta, Ltd., a biotechnology company located in St. Petersburg, Russia.

About SciClone

SciClone Pharmaceuticals is a biopharmaceutical company engaged in the development of therapeutics to treat life-threatening diseases. SciClone's lead product ZADAXIN is currently being evaluated in two phase 3 hepatitis C clinical trials in the United States and one phase 3 hepatitis C trial in Europe. ZADAXIN is also being evaluated in other late-stage clinical trials for the treatment of hepatitis B and certain cancers. The company's other drug development candidate is SCV-07, which is being evaluated for the treatment of viral and infectious diseases. For more information about SciClone, visit www.sciclone.com.

The information in this press release contains forward-looking statements including our expectations and beliefs regarding the progress of preclinical and clinical trials for SCV-07, and the fact that the experimental or clinical data described may imply certain actual results in larger patient populations. Words such as "expects," "plans," "believe," "may," "will," "anticipated," "intended" and variations of these words or similar expressions are intended to identify forward-looking statements. In addition, any statements that refer to expectations, goals, projections or other characterizations of future events or circumstances, including any underlying assumptions, are forward-looking statements. These statements are not guarantees of future performance and are subject to risks, uncertainties and assumptions that are difficult to predict. Therefore, our actual results could differ materially and adversely from those expressed in any forward-looking statements as a result of various factors, including the progress or failure of preclinical and clinical trials for SCV-07, the statistical significance of data obtained from SCV-07 preclinical and clinical trials, enrollment in clinical trials for SCV-07, competition with other studies for the enrollment of patients meeting a particular patient profile, maintenance of the sufficiency and eligibility of the enrolled patient population, unanticipated delays or additional expenses incurred during SCV-07 preclinical studies, future actions of our collaborative partner, unexpected adverse results to patients, and the fact that experimental data and clinical results derived from studies with a limited group of patients may not be predictive of the results of larger studies, as well as other risks and uncertainties described in SciClone's filings with the Securities and Exchange Commission.

Corporate contact: Becky Horner Investor Relations SciClone Pharmaceuticals, Inc. 650-358-3437