WHI-05, a novel bromo-methoxy substituted phenyl phosphate derivative of zidovudine, is a dual-action spermicide with potent anti-HIV activity

Heterosexual transmission of HIV to women is the fastest-growing mode of transmission. In a systematic effort to develop a microbicide capable of preventing HIV transmission as well as providing fertility control, novel phenyl phosphate derivatives of 3'-azido-3'-deoxythymidine (zidovudine, ZDV) have been identified that exhibit potent anti-MN and spermicidal activities. This study reports the synthesis, characterization, and preclinical formulation of compound WHI-05, 5-bromo-6-methoxy-5,6-dihydro-3'-azidothymidine-5'-(p-methoxyphenyl) methoxyalaninyl phosphate. The anti-HIV activities of WHI-05 and ZDV were compared by measuring p24 antigen production and reverse transcriptase activity as markers of viral replication using human peripheral blood mononuclear cells (PBMC) infected with both ZDV-sensitive and ZDV-resistant strains of HN. The sperm immobilizing activity (SIA) of WHI-05 was compared with that of ZDV and nonoxynol - P (N - 9). by computer-assisted sperm analysis (CASA). The effect of WHI-05 on sperm membrane-integrity was examined by high resolution, low voltage scanning electron microscopy (HR-LVSEM). The in vitro cytotoxicity profile of WHI-05 versus N - 9. were compared using normal human vaginal, ectocervical, and endocervical epithelial cells. The in vivo vaginal tolerance, absorption, and toxicity of a 2% WHI-05 gel-microemulsion was tested in the rabbit. Whereas ZDV displayed potent anti-MN activity but lacked SIA, WHI-05 elicited both potent anti-MN activity and SIA. WHI-05 inhibited the replication of ZDV-sensitive as well as ZDV-resistant strains of HIV in PBMC. CASA combined with MR-LVSEM demonstrated that WHI-05-induced SIA was not associated with membrane damage. Unlike, N - 9 the spermicidal activity of WHI-05 was not associated with cytotoxicity to reproductive tract epithelial cells. Repetitive intravaginal application of a 2% WHI-05 gel-microemulsion did not damage the vaginal epithelium or cause local inflammation in the rabbit model. As a potent anti-MN agent that has spermicidal activity and is devoid of mucosal toxicity, WHI-05 shows a unique clinical potential to become the active ingredient for a vaginal contraceptive for women who are at high risk for acquiring HIV by heterosexual vaginal transmission. CONTRACEPTION 1999;59:319331 (C) 1999 Elsevier Science Inc. All rights reserved.