Preclinical Evaluation of Novel Sperm Ion-Channel-based Non-Hormonal Contraceptive Candidates
Poster #: 182
Session/Time: A
Author:
Maimoona S. Bhutta, PhD
Mentor:
Gustavo F. Doncel, MD, PhD
Research Type: Basic Science
Abstract
INTRODUCTION:
With nearly half of all pregnancies being unintended, there is an urgent need for new contraceptive methods providing safe, effective, and user-friendly options for women globally. Hence, developing non-hormonal contraceptives (NHCs) that target key proteins essential for sperm function after ejaculation, while providing safe and effective on-demand contraception for women, would be a game-changer. We evaluated two novel NHC candidates, MB-C8, a Ca2+ channel (CatSper), and YLT-992, a K+ channel (SLO3) inhibitor that block sperm-specific ion channels required for hyperactivated motility following capacitation, a required step in fertilization.
METHODS:
Safety and efficacy of NHC active pharmaceutical ingredients (APIs) were evaluated using in vitro functionality assays with human and rabbit sperm to assess their impact on sperm viability, motility, and motion using computer-assisted sperm analysis. The protective effect of seminal plasma (SP) was assessed testing the inhibitory activity of NHC APIs in human and rabbit semen after a 2min exposure. To determine whether sperm immobilizing effects of both APIs were reversible, all samples were washed and underwent swim-up to separate motile from non-motile spermatozoa. Additionally, safety of NHC APIs was investigated using ex vivo viability assays in human cervicovaginal (CV) tissue explants obtained from surgical resections. APIs demonstrating >80% efficacy in human and rabbit sperm, as well as complete safety in human CV tissue, were advanced to a pilot in vivo rabbit contraceptive efficacy test (RCET).
RESULTS:
MB-C8 and YLT-992 significantly inhibited human sperm hyperactivity (HA) in a dose-dependent manner, without affecting sperm and CV explant viability. MB-C8 concentrations >3.1µM (p<0.0001) and >6.3µM (p<0.0001) irreversibly inhibited human sperm HA and progressive motility (PM) within 30sec of treatment, respectively. Similarly, in rabbit sperm, 10µM MB-C8 irreversibly inhibited both HA (p=0.0121) and PM (p<0.0001) after a short exposure. This inhibitory effect against human or rabbit sperm HA was maintained even in the presence of seminal plasma and persisted after washing. Following ex vivo mixing of semen with 10µM MB-C8 in a RCET, no implantation sites (100% contraceptive efficacy) were observed without affecting follicle development or ovulation, highlighting its potential as an on-demand NHC candidate. For YLT-992, 0.01µM specifically inhibited human sperm HA by 90% (p<0.0001) with no change in PM (p=0.93) or general motility (p=0.71) after 2hrs of incubation. These effects were maintained in presence of human seminal plasma and even after the compound was washed off, indicating a lack of reversibility. However, YLT-992 was specific for human sperm and ineffective in inhibiting rabbit sperm HA or motility.
CONCLUSION:
We validated the potential of MB-C8 and YLT-992 as promising NHC candidates due to their significant inhibition of sperm HA, a critical step for fertilization. Furthermore, zero implantation sites in a rabbit model highlight the exceptional contraceptive efficacy of MB-C8. Continued preclinical studies are needed to confirm long-term safety of both NHC APIs. Ultimately, NHCs that specifically target sperm function without affecting female reproductive tract physiology could significantly improve contraceptive technologies, providing women with safer and more acceptable options for preventing unplanned pregnancies.
With nearly half of all pregnancies being unintended, there is an urgent need for new contraceptive methods providing safe, effective, and user-friendly options for women globally. Hence, developing non-hormonal contraceptives (NHCs) that target key proteins essential for sperm function after ejaculation, while providing safe and effective on-demand contraception for women, would be a game-changer. We evaluated two novel NHC candidates, MB-C8, a Ca2+ channel (CatSper), and YLT-992, a K+ channel (SLO3) inhibitor that block sperm-specific ion channels required for hyperactivated motility following capacitation, a required step in fertilization.
METHODS:
Safety and efficacy of NHC active pharmaceutical ingredients (APIs) were evaluated using in vitro functionality assays with human and rabbit sperm to assess their impact on sperm viability, motility, and motion using computer-assisted sperm analysis. The protective effect of seminal plasma (SP) was assessed testing the inhibitory activity of NHC APIs in human and rabbit semen after a 2min exposure. To determine whether sperm immobilizing effects of both APIs were reversible, all samples were washed and underwent swim-up to separate motile from non-motile spermatozoa. Additionally, safety of NHC APIs was investigated using ex vivo viability assays in human cervicovaginal (CV) tissue explants obtained from surgical resections. APIs demonstrating >80% efficacy in human and rabbit sperm, as well as complete safety in human CV tissue, were advanced to a pilot in vivo rabbit contraceptive efficacy test (RCET).
RESULTS:
MB-C8 and YLT-992 significantly inhibited human sperm hyperactivity (HA) in a dose-dependent manner, without affecting sperm and CV explant viability. MB-C8 concentrations >3.1µM (p<0.0001) and >6.3µM (p<0.0001) irreversibly inhibited human sperm HA and progressive motility (PM) within 30sec of treatment, respectively. Similarly, in rabbit sperm, 10µM MB-C8 irreversibly inhibited both HA (p=0.0121) and PM (p<0.0001) after a short exposure. This inhibitory effect against human or rabbit sperm HA was maintained even in the presence of seminal plasma and persisted after washing. Following ex vivo mixing of semen with 10µM MB-C8 in a RCET, no implantation sites (100% contraceptive efficacy) were observed without affecting follicle development or ovulation, highlighting its potential as an on-demand NHC candidate. For YLT-992, 0.01µM specifically inhibited human sperm HA by 90% (p<0.0001) with no change in PM (p=0.93) or general motility (p=0.71) after 2hrs of incubation. These effects were maintained in presence of human seminal plasma and even after the compound was washed off, indicating a lack of reversibility. However, YLT-992 was specific for human sperm and ineffective in inhibiting rabbit sperm HA or motility.
CONCLUSION:
We validated the potential of MB-C8 and YLT-992 as promising NHC candidates due to their significant inhibition of sperm HA, a critical step for fertilization. Furthermore, zero implantation sites in a rabbit model highlight the exceptional contraceptive efficacy of MB-C8. Continued preclinical studies are needed to confirm long-term safety of both NHC APIs. Ultimately, NHCs that specifically target sperm function without affecting female reproductive tract physiology could significantly improve contraceptive technologies, providing women with safer and more acceptable options for preventing unplanned pregnancies.