Science, medicine, and the future : Gene therapy

Introduction

In the eight years since the first human gene transfer experiment, in which a patient with malignant melanoma received genetically modified autologous T cells,1 about 30 gene therapy companies have been launched, three major gene therapy journals have been established, more than 200 human gene therapy protocols have been approved, and over 2000 patients have received gene therapy. As yet, however, only a handful of patients with rare conditions have benefited from gene therapy, and early optimism about this new treatment has given way to disillusionment. In this article I look at the current status of gene therapy research and discuss the key problems that must be overcome to realise the enormous potential of gene therapy to treat not just single gene disorders but many common diseases such as arthritis, cancer, hypertension, atherosclerosis, diabetes, and asthma.

Scope of gene therapy

Gene therapy is a term that can be applied to any clinical therapeutic procedure in which genes are intentionally introduced into human somatic cells. There are two main approaches: in vivo gene therapy, in which genes are delivered directly to target cells in the body, and ex vivo gene therapy, in which the target cells are genetically modified outside the body and then reimplanted (fig 1).

Gene transfer into human cells is not a new concept: viral genes are introduced into human cells when a viral vaccine is administered to protect against disease. However, the clinical goals of gene therapy are different and often depend on the prolonged survival of genetically engineered cells or tissues in the patient. The key technologies …