Inhibition of FT enzyme activity in leukemic bone marrow samples by day 8 of R115777 administration.

Results are expressed as percent residual FT activity relative to day 0 (baseline) values. FT enzyme activity was not reproducibly inhibited in patients receiving R115777 100 mg bid. Beginning at 300 mg bid, however, R115777 suppressed FT activity relative to baseline values in all marrow samples studied.