Synthesis and evaluation of 7 alpha-iodo-5 alpha-dihydrotestosterone as a potential radioligand for androgen receptor.

ABSTRACT

7 alpha-Iodo-17 beta-hydroxy-5 alpha-androstan-3-one (7 alpha-iodo-5 alpha-dihydrotestosterone, 7 alpha-IDHT) has been synthesized as a potential radioligand for the detection and measurement of androgen receptor and for imaging of androgen-receptor-containing tissues when labeled with the gamma-emitting radionuclides 125I and 123I, respectively. In vitro binding studies show that 7 alpha-IDHT binds with high affinity to the rat and human androgen receptor (RBA = 74) compared to R1881 (RBA = 100). Further, this compound showed high specificity for the androgen receptor. 7 alpha-IDHT showed only a marginal affinity for the progestin receptor and even less affinity for the estrogen receptor. No binding was detected to the glucocorticoid receptor. These characteristics make 7 alpha-IDHT a potentially ideal agent for imaging and evaluation of androgen-receptor-containing tissues.