the participant (or to the embryo or fetus, if the 
participant is or may become pregnant during treatment) . 
To help prevent injury to unborn children, upon 
recommendation by the attending physician, the 
participants should practice adequate methods of birth 
control throughout the period of their involvement in 
this clinical research study. 
Extensive study of this vector marking procedure has been 
undertaken in mice, monkeys, and in man at the NIH as 
well as at many other institutions. A variant of this 
vector is currently in use for treatment of patients at 
the NIH. No adverse effects have been observed in all of 
this extensive study because the vector is modified so 
that it cannot cause an infection in the cells of the 
body. It only marks a small number of blood cells in the 
autologous marrow. 
Risks, however, which may not yet been observed, are 
possible. These are "theoretical risks" since they have 
not yet been seen. It is possible that the vector could 
change the cells which are marked so as to grow in an 
abnormal pattern, and even cause cancer or leukemia. 
However, this has not been seen and the probability of 
this happening is probably less than one in a million. 
This probably is a risk which is lower than damage to the 
cells by chemotherapy and irradiation. The marker could 
also produce a protein which might inactivate certain 
antibiotics but alternative antibiotics are available so 
that this does not constitute a risk or threat for 
patients during therapy. 
5. POTENTIAL BENEFITS: The potential benefit to be gained from 
this treatment is attaining a functioning bone marrow which 
may in turn prolong life expectancy. The identification of 
the course of relapse may be of benefit to patients on future 
protocols but this research may not be of immediate benefit. 
6. ALTERNATE PROCEDURES OR TREATMENTS: Alternate drugs and 
treatments currently available include hydroxyurea, myleran, 
interferons, and intensive chemotherapy combinations, most of 
which contain daunorubicin and ara-c (at conventional doses) . 
The only curative therapy for CML is bone marrow 
transplantation from a compatible sister or brother donor or 
unrelated donor. If a compatible donor is not available, this 
therapy is designed to remove the leukemia cells from the 
patient's own marrow so as to use it in a transplant. This 
therapy is hoped to be better than the treatments previously 
available for this disease. It is possible that it would be 
less effective and/or more toxic. The patient may have 
storage and then decline therapy. The patient may decline to 
have marking but still have the bone marrow transplant. 
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Recombinant DNA Research, Volume 14 
