4. Positive pregnancy test within 24 hours of study infusion or an unwillingness to undergo pregnancy testing in females of child-bearing potential. Females capable of child-bearing must agree not to become pregnant from the time of study enrollment until at least 3 months after completion of study infusion. If a woman is sexually active and has no history of hysterectomy or tubal ligation, she must agree to use hormonal or barrier birth control with spermicidal gel.