SciClone Pharmaceuticals, Inc. (NASDAQ: SCLN) and its partner Sigma-Tau S.p.A., announced additional topline results in a clinical study evaluating the potential of ZADAXIN® (thymalfasin) to enhance immune response to the MF59 adjuvanted H1N1 influenza monovalent vaccine, Focetria™ from Novartis. According to investigators, ZADAXIN treatment given with the H1N1 vaccine led to a statistically significant (p value=0.04) increase in the percentage of subjects who seroconverted, also when evaluated 42 days after vaccination, compared to those who received the H1N1 vaccine alone. In addition, the improvement in titers seen in ZADAXIN-treated patients was maintained at this later timepoint.

"The seroconversion results that we have seen to date in this study are very encouraging and continue to demonstrate the value that ZADAXIN may have in offering the public a more powerful vaccine regimen against the H1N1 virus," said Friedhelm Blobel, Ph.D., SciClone's president and chief executive officer. "It is our hope that ZADAXIN will ultimately provide the enhancement benefits to H1N1 vaccines for patients with compromised or weakened immune systems. If this study continues to show positive data, we may also explore the potential of ZADAXIN to improve the response to vaccines with other flu or virus strains."

Findings showed that, when measured 42 days following vaccination, 93% of patients in the low-dose ZADAXIN arm and 94% of patients in the high-dose ZADAXIN arm achieved seroconversion, compared to only 77% of patients in the vaccine-only arm of the study. This increased seroconversion with ZADAXIN compares favorably with that seen at 21 days following vaccination, which the companies reported in January 2010 as being 89% and 88% in the two ZADAXIN groups, compared to only 56% in patients treated with the vaccine alone, which was a highly statistically significant increase (p value < 0.01). A higher seroconversion rate is indicative of the robustness of the immune response and may lead to more durable protection. Seroconversion -- a significant rise in specific antibody titers against H1N1 influenza -- is defined as a four fold or greater change in titers from baseline.

The randomized, three-arm open label study is designed to evaluate efficacy based on the proportion of patients achieving seroconversion. The ongoing study, which has a planned duration of six months, is being conducted in patients with end-stage renal disease who are on chronic dialysis. One cohort of patients received the H1N1 vaccine only. The other groups received thymalfasin at either a low dose (3.2 mg) or a high dose (6.4 mg). Thymalfasin was given twice, the first injection seven days prior to vaccination and the second on the day of vaccination with Focetria. All patients who did not achieve an antibody titer of at least 1:40 on day 21 received a second H1N1 vaccination on that day. Dosing regimens were based on preclinical results obtained in ferret and mouse models conducted in Europe and the U.S. All patients are being followed for six months, to measure the durability of the protective titers, the second key parameter for the assessment of the immunogenicity of a vaccination.

"To witness seroconversion rates in the ZADAXIN treatment arms in the range of 93-94% at 42 days compared to just 77% with vaccine alone is very promising, especially in an immunocompromised population of patients on chronic dialysis," said Professor Trevor Jones, group R&D director, Sigma-Tau. "We are pleased with the ongoing progress of this study and the positive data that it continues to produce."

The Company will announce further data on the study after all patients have reached 184 days post vaccination and final topline results are available.

ZADAXIN has an excellent safety profile, with a long track record of patient use. Approximately 100,000 patients worldwide have used ZADAXIN in both commercial and clinical settings, alone and in combination with various antiviral and anticancer drugs.

About thymalfasin (ZADAXIN)

ZADAXIN, scientifically referred to as thymalfasin or thymosin alpha 1, is SciClone's synthetic preparation of thymalfasin, a peptide produced by the thymus gland which circulates in the blood naturally and is instrumental in immune responses. Published scientific and clinical studies have shown that thymalfasin helps stimulate and direct the body's immune system to improve response to vaccines, and to eradicate infectious diseases like HCV and HBV, as well as certain cancers.

Within the immune system, thymalfasin stimulates stem cell differentiation and increases production of antibodies and disease-fighting T cells, including CD4, CD8, and natural killer cells, while simultaneously slowing the breakdown and removal of these T cells. The increase in production of antibodies after thymalfasin treatment leads to an increase in response to vaccines, providing enhanced protection against infection; the increases in T-helper cells allows the immune system to tag and identify invasive agents and cancerous cells for removal.

ZADAXIN is currently approved in more than 30 countries worldwide to treat a variety of indications. In clinical studies, more than 4,000 patients being treated with vaccines or infected with viral hepatitis B or hepatitis C, primary immunodeficiency diseases, or various cancers have been treated with ZADAXIN with virtually no drug-related side effects.

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SciClone Pharmaceuticals
Sigma-tau

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