SciClone Pharmaceuticals : Voluntary Announcement - Official Initiation of the Clinical Study on COVID-19 Inactivated Vaccine Combined with Thymalfasin (Trade Name ZADAXIN)

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SciClone Pharmaceuticals (Holdings) Limited

賽生藥業控股有限公司 *

(Incorporated in the Cayman Islands with limited liability)

(Stock Code: 6600)

VOLUNTARY ANNOUNCEMENT

BUSINESS UPDATE

Official Initiation of the Clinical Study on COVID-19

Inactivated Vaccine Combined with Thymalfasin (Trade Name ZADAXIN)

This announcement is made by SciClone Pharmaceuticals (Holdings) Limited (the "Company" or "SciClone Pharmaceuticals", together with its subsidiaries, the "Group") on a voluntary basis. The purpose of this announcement is to keep the shareholders and potential investors of the Company informed on the latest business plans and development of the Group.

The Company is pleased to announce that a clinical study for COVID-19 inactivated vaccine combined with Thymalfasin (Trade Name ZADAXIN) was officially initiated on April 25, 2021. With participation of 15 hospitals within the People's Republic of China, the clinical study is sponsored by the Company, and led by Professor Zhang Wenhong (張文宏教授) from Huashan Affiliated Hospital of Fudan University (復旦大學附屬華山醫院) and Professor Gao Zhiliang (高志良教授) from the Third Affiliated Hospital of Sun Yat-sen University (中山大學附屬 第三醫院). It is a prospective, open and randomized controlled study which mainly evaluates

the safety, tolerance, and immunogenicity of COVID-19 inactivated vaccine combined with Thymalfasin (Trade Name ZADAXIN) in healthy adults. The clinic study is expected to recruit 200 subjects nationwide.

About Thymalfasin (Trade Name ZADAXIN):

Thymalfasin, scientifically known as thymosin alpha 1 ("Tα1"), is a thymic hormone drug that naturally circulates in the blood. It is the only substance with the same chemical structure and configuration as natural Tα1 in the human body. It can boost the immunity of patients, enhance their quality of life, and improve the remission rate and survival rate.

Zadaxin, our proprietary product, is a Thymalfasin synthesized and prepared by the Company. Zadaxin has been approved as a vaccine enhancer for the treatment of patients with chronic hepatitis B and immune impairment. In addition to official indications, Zadaxin is also listed as a drug for treatments of sepsis (2014), pancreatic cancer (2019 and 2020), liver cancer (2017, 2018 and 2019), COVID-19 (2020) and lymph cancer (2021) in the treatment guidelines issued by the National Health Commission and professional associations including the Chinese Medical Association and the Chinese Society of Clinical Oncology. Over the past decades, Zadaxin has gained recognition among doctors and patients as a trusted branded product especially for its potential benefits in treating SARS and COVID-19.

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Thymalfasin (Trade Name ZADAXIN) works as immunomodulator by promoting T lymphocytes maturation, increasing the secretion of various lymphokines by activated T cells and the level of lymphokines receptor on T cells, as well as activating CD4 cells to enhance allogeneic and autologous human mixed lymphocyte response. Incomplete or weakened antibody response to T-cell-dependent antigens may be a factor for the insufficient efficacy of some vaccines, while Thymalfasin can enhance the immune response of patients to viral vaccines by enhancing the antibody response of T-cell-dependent B cells and increasing the production of specific antibodies.

In view of the mechanism of action of Thymalfasin (Trade Name ZADAXIN) and previous clinical studies, the combination with Thymalfasin (Trade Name ZADAXIN) may help increase the level of SAR-Cov-2 neutralizing antibody and prolong the antibody protection time while carrying out mass vaccination under the threat of COVID-19 pandemic.

The clinical study may or may not be able to successfully prove that Thymalfasin (Trade Name ZADAXIN) can enhance the antibody protection level of COVID-19 inactivated vaccine. Shareholders and potential investors of the Company are advised to exercise caution when dealing in the shares of the Company.

About SciClone Pharmaceuticals:

The Company is a biopharmaceutical company with an integrated platform for product development and commercialization. The Company strategically focuses on some of the largest and fast- growing therapeutic areas with unmet medical needs in China, primarily including oncology and severe infection. With its product development and commercialization strength, the Company has established a good track record in terms of balanced and high-quality products on the market in key therapeutic areas and in developing and commercializing portfolios of pipeline products with better potential.

For more information about the Company, please visit www.sciclone.com.

By order of the Board

SciClone Pharmaceuticals (Holdings) Limited

ZHAO Hong

Executive Director, Chief Executive Officer and

President

Hong Kong, 26 April 2021

As at the date of this announcement, the board of directors comprises Mr. Zhao Hong as executive director, Mr. Li Zhenfu, Dr. Daniel Luzius Vasella, Ms. Lin Shirley Yi-Hsien, Ms. Li Quan, Mr. Shi Cen and Ms. Wang Xiaozhuo as non-executive directors, and Dr. Liu Guoen, Dr. Chen Ping, Mr. Gu Alex Yushao and Ms. Wendy Hayes as independent non-executive directors.

*  for identification purpose only

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