Therapeutic cancer vaccine
    Zensun is developing rhErbB3-f as a therapeutic cancer vaccine for patients with Her2 (ErbB2)-positive breast cancer. rhErbB3-f is a recombinant human ErbB3 receptor fragment produced by expression in E. coli. After purification and formulation with adjuvant, immunization with rhErbB3-f is expected to induce the production of specific anti-ErbB3 antibodies for treatment of breast cancer characterized by the overexpression of ErbB2.
    Scientists at Zensun have discovered that tumorigenesis and tumor growth are both closely related to the formation of the ErbB2-ErbB3 heterodimer. Thus, in the treatment of Her2-positive breast cancer, inhibition of ErbB3 should have the comparable effect on inhibiting tumor cell growth as that of inhibition of ErbB2, but would have the advantage of avoiding the severe cardiotoxicity seen in the treatments that targeting ErbB2. Based on this discovery, Zensun has developed the therapeutic cancer vaccine rhErbB3-f. Experimental animal data have shown that the rhErbB3-f vaccine can inhibit the growth of tumor cells by stimulating the immune system of the animal to generate anti-ErbB3 antibodies. The results of preclinical trials using orthotopic transplantation tumor models indicate that the rhErbB3-f vaccine can inhibit the occurrence of tumors and delay the development of breast cancer.
    In addition, the polyclonal antibody obtained from animals vaccinated with rhErbB3-f inhibited the growth of Her2 positive human breast cancer cells in vitro. Preclinical trials did not show any significant side effects associated with the drugs or immunizations. The rhErbB3-f vaccine has now completed a phase I clinical study in China, and the results show that the vaccine was safe and well-tolerated.
    Vaccine immunization has many advantages compared with treatment with a monoclonal antibody. For example, rhErbB3-f is obtained from E. coli, thus, compared with a monoclonal antibody, the production process is much simpler and has significantly lower costs. A detailed comparison is shown in Table 1.
Table 1. Comparison of rhErbB3-f with an anti-ErbB2 monoclonal antibody

HER2 positive breast cancer
    According to WHO data[1], breast cancer is the second most common cancer (11.9% of all tumors) and is the most common cancer in women, accounting for 25% of female cancer. It is estimated that breast cancer caused 522,000 deaths in women worldwide in 2012[2]. Although the incidence of breast cancer in China is lower than in Europe and the United States, it has been increasing over the past 30 years. In about 20-30% of all patients with breast cancer, the epidermal growth factor type II receptor (HER2, also called ErbB2) is highly expressed (positive). Her2 receptor overexpression results in tumor cell proliferation. Compared with other types of breast cancer, HER2-positive breast cancer is insensitive to some conventional treatments, and is more malignant, more likely to metastasize, and more likely to relapse; therefore patients suffering with Her2-positive breast cancer has a poorer prognosis and a shorter survival time.
[1] International Agency for Research on Cancer(IARC). GLOBOCAN, 2012.
[2]WHO. Health statistics and health information systems – Global Health Estimates (GHE), 2013.
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