II’. I'rencli Anderson 
words, somatic cell gene therapy. Attempts to correct a patient’s 
reproductive cells (i.c., germ line gene therapy) or to alter or improve 
a ‘normal’ person by gene manipulation (i.e., enhancement or eugenic 
genetic engineering) are controversial areas. However, somatic cell 
gene therapy for a patient suffering a serious genetic disorder would 
be ethically acceptable if carried out under the same strict criteria 
that cover other new experimental medical procedures. The tech- 
niques now being developed by clinical investigators for human 
application are for somatic cell, not germ line, gene therapy. 
What criteria should be satisfied prior to the time that somatic 
cell gene therapy is tested in a clinical trial? Three general require- 
ments, first presented in 1980 (Anderson and Fletcher, 1980), arc 
that it should be shown in animal studies that (i) the new gene can 
be put into the correct target cells and will remain there long enough 
to be effective: (ii) the new gene will be expressed in the cells at an 
appropriate level; and (iii) the new gene will not harm the cell or, 
by extension, the animal. These three requisites, summarized as 
delivery, expression, and safety, will each be examined in turn. 
These criteria arc very similar to those required prior to the use 
of any new drug, therapeutic procedure, or surgical operation. The 
requirements simply state that the new treatment should get to the 
area of disease, correct it, and do more good than harm. Some flexi- 
bility is necessary since the criteria might be altered for a critically 
ill patient for whom no further conventional therapy is available. 
The exact definitions of what is ‘long enough to be effective’, what 
level is ‘an appropriate level’, and how much harm is meant by ‘harm’, 
are questions for ongoing discussion as more is learned about gene 
therapy. Ultimately, local Institutional Review Boards and the 
National Institutes of Health (NIH), the latter through its newly 
created Working Group on Human Gene Therapy, must decide if a 
given protocol is ready for human application. Once the criteria are 
satisfied, that is, when the probable benefits for the patient are 
expected to exceed the possible risks, then attempts to cure human 
genetic disease by treatment with somatic cell gene therapy would 
be ethical. The goal of biomedical research is, and has always been, 
to alleviate human suffering. Gene therapy is a proper and logical 
part of that effort. 
Delivery 
At present, the only human tissue that can be used effectively for 
gene transfer is bone marrow. No other cells (except, perhaps, skin 
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