Sheep Postcoital Testing to Evaluate Antibody-Based, Nonhormonal Contraceptive Tablet [ID 1459]

INTRODUCTION: Efficacy of on-demand nonhormonal contraception that targets and disables progressively motile sperm (PMS) can be studied through surrogate postcoital testing (PCT) in sheep models, due to similarities to human reproductive tract size and anatomy. We utilized PCT to assess the contraceptive potential of anti-sperm antibody in tablet form in vivo in sheep. METHODS: Pooled semen from five prescreened human male donors was collected and evaluated for adequate motility prior to use. Ewes (n=6) were given a quick-dissolving tablet delivering active anti-sperm antibody, a placebo tablet, or phosphate-buffered saline (PBS) as a control measure. Coital simulation included mixing tablet/PBS in the sheep vagina for 5 minutes with 15 strokes with a test tube, instilling 1 mL of semen for 2 minutes, mixing with five test tube strokes, and retrieving the semen/drug/vaginal secretion mixture for microscopic examination. Progressively motile sperm were counted via video analysis for pooled and sheep samples, reported as #PMS/high powered field (hpf), and analyzed with ANOVA ( P <.05 significant). RESULTS: Pooled semen had 13.4±3.1 PMS/hpf. Control sheep (PBS) had 3.7±2.6 PMS/hpf. Sheep given the antibody tablet had 0.04±0.05 PMS/hpf, whereas the placebo had 2.7±2.0 PMS/hpf ( P <.001). The antibody tablet reduced the fraction of PMS by ∼99%. CONCLUSIONS/IMPLICATIONS: In clinical studies, less than 1.0 PMS/hpf has been a threshold for effective contraception; therefore, the results from this study indicate that suitably formulated tablets delivering anti-sperm antibody could serve as an effective nonhormonal contraceptive.