China's medicines authority (China State Food & Drug Administration, SDFA) approved the cancer therapy after it achieved promising results in a clinical trial on October 16, 2003. The treatment, called Gendicine, has been launched commercially by SiBiono GeneTech Co. of Shenzhen, Guangdong province. Gendicine was approved for the treatment of head and neck squamous cell carcinoma. The gene therapy product is an adenovirus vector carrying the p53 tumour-suppressor gene. Gendicine is similar to Advexin developed by the Texas-based Introgen Therapeutics. Advexin is still waiting for FDA approval.
The results of the Gendicine clinical trial are published in Human Gene Therapy, says Zhaohui Peng, the SiBiono company's founder and head. Gendicine's approval was announced earlier but has gone largely unnoticed outside China (see also China approves first gene therapy. There were concerns about the approval among researchers elsewhere in the world as to quality of the trials performed and thereby the safety and efficacy of the treatment (Controversial Chinese gene-therapy drug entering unfamiliar territory). The available clinical data and conclusions drawn were obtained from a relatively small number of patients in clinical trials. There have been more patients treated, but the clinical data of these patients are hard to access, partly due to the fact that they were published only in Chinese journals. Furthermore, it seemed that approval had been made on the basis of tumour shrinkage rather than extension of patient lifetime (An update on gene therapy in China). Despite these concerns, patients have flown to China to undergo therapy (see Medical Tourism)
Gendicine enters the tumour cells by way of receptor-mediated endocytosis and begins to over-express genes coding for the p53 protein needed to fight the tumour. Ad-p53 seems to act by stimulating the apoptotic pathway in tumour cells, which increases the expression of tumour suppressor genes and immune response factors (such as the ability of natural killer (NK) cells to exert "bystander" effects). It also decreases the expression of multi-drug resistance, vascular endothelial growth factor and matrix metalloproteinase-2 genes and blocking transcriptional survival signals.
p53 mutation status of the tumour cells and response to Ad-p53 treatment are not closely correlated. Ad-p53 appears to act synergistically with conventional treatments such as chemo- and radiotherapy. This synergy still exists in patients with chemotherapy and radiotherapy-resistant tumors. Gendicine produces fewer side effects than conventional therapy.