MJM 1997 3: 126-132
Copyright © 1997 by MJM
CROSSROADS: WHERE MEDICINE AND THE HUMANITIES MEET
Human Germline Gene Therapy
Torsten O. Nielsen*, M.D.C.M., Ph.D.
The idea of human germline gene therapy introducing genetic changes into early embryos which become incorporated into all cells of the body and, as such, are passed on to future generations - has elicited considerable ethical, scientific, and political controversy. Technological advances have turned what until recently was fanciful science fiction into a theoretical and practical possibility. Human germline interventions raise unique ethical concerns which must be addressed, such as its possible use for eugenics. The basic technology of germline gene therapy is being successfully applied in animal experiments for the investigation of gene function, proving to be exceptionally valuable in dissecting the genetic controls of development and in creating models for the study of human diseases. However, while transgenic animal research provides a powerful tool for studying gene function, human germline gene therapy is unlikely ever to be a procedure with significant clinical utility, and is probably not worth pursuing, considering the danger posed by its comparative usefulness for eugenic enhancement. From a medical perspective, uses for this technology in the treatment of genetic disease are limited, and more efficient alternative procedures (such as preimplantation diagnosis followed by selective reimplantation) will likely become available. ETHICAL CONSIDERATIONS In the 1980s, initial discussion about human gene therapy sometimes evoked strong opposition, based on claims that it entails playing God, or violates “natural law” (1). A background paper submitted to the Canadian parliament stated bluntly that “there is a feeling among segments of the general public that the *To whom correspondence should be addressed: Capital Health Region, Postgraduate Education Office, #186 – 2334 Trent St., Victoria, British Columbia, Canada, V8R 4Z3
genetic manipulation of humans is simply not an acceptable activity” (2). However, the public is thought to dramatically overestimate the risks of that which is unfamiliar, hard to understand, or outside public scrutiny (3). Technophobia regarding human gene therapy has, to a degree, subsided, and the debate has evolved to focus more on the potential benefits of such treatment. A U.S. government poll in the late 1980s found that fully 84% of Americans supported the genetic manipulation of human cells to cure fatal genetic diseases (4). Somatic cell gene therapy, for recognized genetic disorders, is broadly considered to be acceptable in principle, gaining the approval of all international policy bodies which have studied the issue (5) as it “poses no new ethical problems” (6), and is not morally different from, for instance, organ transplantation. Because safety and efficacy in humans is not fully established, somatic cell gene therapy is currently employed only under strict criteria (2); an example of a current protocol yielding encouraging results is the replacement of the adenosine deaminase gene in lymphocyte progenitor cells, to cure children of severe combined immunodeficiency (7). The acceptance of somatic cell gene therapy means that questions about germline gene therapy can focus on its unique and crucial differences: the effects are permanent and passed on to future generations who cannot give their consent, and human germline interventions are extremely difficult to study experimentally. The major argument raised in favour of developing germline gene therapy derives from the ethical principle of beneficence (3): up to 2% of newborns suffer from some kind of genetic defect (5), including many of the 1See Commentary in Letters to the Editor (page 78)
Vol. 3 No. 2
Human Germline Gene Therapy
most miserable diseases known (8), such as LeschNyhan syndrome. Germline interventions may in some...