STEROIDAL AND NONSTEROIDAL SULFAMATES AS POTENT INHIBITORS OF STEROIDSULFATASE

Synthetic routes to potent steroidal and nonsteroidal sulfamate-based active site-directed inhibitors of the enzyme steroid sulfatase, a top ical target in the treatment of postmenopausal women with hormone-depe ndent breast cancer, are described. Novel compounds were examined for estrone sulfatase (E1-STS) inhibition in intact MCF-7 breast cancer ce lls and placental microsomes. Reaction of the sodium salt of estrone w ith sulfamoyl chloride gave estrone 3-O-sulfamate (EMATE, 2) which inh ibits E1-STS activity potently (> 99% at 0.1 mu M in intact MCF-7 cell s, IC50 = 65 PM) in a time-and concentration-dependent manner, suggest ing that EMATE is an active site-directed inhibitor. EMATE is also act ive in vivo orally. 5,6,7,8-Tetrahydronaphthalene 2-O-sulfamate (7) an d its N-methylated derivatives (8 and 9) were synthesized, and 7 inhib its the E1-STS activity in intact MCF-7 cells by 79% at 10 mu M. 4-Met hylcoumarin 7-O-sulfamate (COUMATE) and its derivatives (14, 16, and 1 8) were prepared to extend this series of nonsteroidal inhibitors, and COUMATE reduces the E1-STS activity in placental microsomes by >90% a t 10 mu M. Although the orally active COUMATE is less potent than EMAT E as an active site-directed inhibitor, it has the important advantage of being nonestrogenic. Analogues (20, 22, 24, 26, 27, 31, 33, 39, an d 44) of COUMATE were synthesized to study its structure-activity rela tionships, and sulfamates of tetralones (46 and 48) and indanones (49, 51, and 53) were also prepared. While most of these compounds were fo und to inhibit E1-STS activity less effectively than COUMATE, one anal ogue, 3,4-dimethylcoumarin 3-O-sulfamate (24), was found to be some 12 -fold more potent than COUMATE as an E1-STS inhibitor in intact MCF-7 cells (IC50 = 30 nM for 24, cf. 380 nM for COUMATE). Hence, highly pot ent sulfamate-based inhibitors of steroid sulfatase, such as EMATE, CO UMATE, and 24, possess therapeutic potential and will allow the import ance of estrogen formation in breast tumors via the E1-STS pathway to be assessed. A pharmacophore for active site-directed sulfatase inhibi tion is proposed.