Applications of Recombinant Adenovirus-p53 Gene Therapy for Cancers in the Clinic in China

Suppression of TP53 function is nearly ubiquitous in human cancers, and a significant fraction of cancers have mutations in the TP53 gene itself. Therefore, the wild-type TP53 gene has become an important target gene for transformation research of cancer gene therapy. In 2003, the first anti-tumor gene therapy drug rAd-p53 (recombinant human p53 adenovirus), trade name Gendicine™, was approved by the China Food and Drug Administration (CFDA) for treatment of head and neck squamous cell carcinoma (HNSCC) in combination with radiotherapy. The recombinant human TP53 gene is delivered into cancer cells by an adenovirus vector constructed to express the functional p53 protein. Although the only currently approved used of Gendicine is in combination with radiotherapy for treatment of HNSCC, clinical studies have been carried out for more than 20 other applications of Gendicine in treating cancer, including treatment of advanced lung cancer, advanced liver cancer, malignant gynecological tumors, and soft tissue sarcomas. Currently more than 30,000 patients have been treated with Gendicine. This review provides an overview of the clinical applications of Gendicine in China. We summarize a total of 48 studies with 2,561 patients with solid tumors, including 34 controlled clinical studies and 14 open clinical studies, i.e., clinical studies without a control group. There are 11 studies for head and neck cancer, 10 for liver cancer, 6 for malignant gynecological tumors, 4 for non-small cell lung cancer, 4 for soft tissue sarcoma, 4 for malignant effusion, 2 for gastrointestinal tumors, and 7 for other types of cancer. In all the reported clinical studies, the most common side effect was self-limited fever. Intratumoral injection and intra-arterial infusion were the most common routes of administration. Overall, Gendicine combined with chemotherapy, radiotherapy, or other conventional treatment regimens demonstrated significantly higher response rates compared to standard therapies alone. Some of the published studies also showed that Gendicine combination regimens demonstrated longer progression-free survival times than conventional treatments alone. To date, Gendicine has been clinically used in China for treatment of cancers other than HNSCC for more than ten years, mainly for patients with advanced or unresectable malignant tumors. However, the establishment of standard treatment regimens using TP53 gene therapy is still needed in order to advance its use in clinical practice.

The First Approved Gene Therapy Product for Cancer Ad-p53 (Gendicine): 12 Years in the Clinic

Gendicine (recombinant human p53 adenovirus), developed by Shenzhen SiBiono GeneTech Co. Ltd., was approved in 2003 by the China Food and Drug Administration (CFDA) as a first-in-class gene therapy product to treat head and neck cancer, and entered the commercial market in 2004. Gendicine is a biological therapy that is delivered via minimally invasive intratumoral injection, as well as by intracavity or intravascular infusion. The wild-type (wt) p53 protein expressed by Gendicine-transduced cells is a tumor suppressor that is activated by cellular stress, and mediates cell-cycle arrest and DNA repair, or induces apoptosis, senescence, and/or autophagy, depending upon cellular stress conditions. Based on 12 years of commercial use in >30,000 patients, and >30 published clinical studies, Gendicine has exhibited an exemplary safety record, and when combined with chemotherapy and radiotherapy has demonstrated significantly higher response rates than for standard therapies alone. In addition to head and neck cancer, Gendicine has been successfully applied to treat various other cancer types and different stages of disease. Thirteen published studies that include long-term survival data showed that Gendicine combination regimens yield progression-free survival times that are significantly longer than standard therapies alone. Although the p53 gene is mutated in >50% of all human cancers, p53 mutation status did not significantly influence efficacy outcomes and long-term survival rate for Ad-p53-treated patients. To date, Shenzhen SiBiono GeneTech has manufactured 41 batches of Gendicine in compliance with CFDA QC/QA requirements, and 169,571 vials (1.0 × 10¹² vector particles per vial) have been used to treat patients. No serious adverse events have been reported, except for vector-associated transient fever, which occurred in 50-60% of patients and persisted for only a few hours. The manufacturing accomplishments and clinical experience with Gendicine, as well as the understanding of its cellular mechanisms of action and implications, could provide valuable insights for the international gene therapy community and add valuable data to promote further developments and advancements in the gene therapy field.