EXECUTIVE SUMMARY

Funding recently has been awarded to scientists around the globe through the Grand Challenges Explorations program, an initiative funded by the Bill & Melinda Gates Foundation. The program seeks to foster concepts for contraceptive discovery platforms that can contribute to the development of new methods suitable for women and men living in limited resource settings.

  • Projects were evaluated on their development of long-term methods in the form of injectables, implants, or regular oral contraception. Projects that were variations of injectable formulations or implants using existing agents were not considered. Also excluded were methods used on an intermittent “on-demand” or pericoital use, such as vaginal gels.

What will contraceptive methods look like in the future? If current lines of research hold true, things may be radically different from the current options family planning clinicians now offer to male and female patients.

Funding recently has been awarded to scientists around the globe through the Grand Challenges Explorations program, an initiative funded by the Bill & Melinda Gates Foundation in Seattle. The program seeks to foster concepts for contraceptive discovery platforms that can contribute to the development of new methods suitable for women and men living in limited resource settings.

In its request for proposals, the program noted its desire for science aimed at developing new methods for long-term regular use in the form of injectables, implants, or regular oral contraception. Methods that looked to be variations of injectable formulations or implants using existing agents were not to be included. Also excluded were methods that would be used on an intermittent “on-demand” or pericoital use, such as vaginal gels.

Identifying a New Target

Paula Cohen, PhD, professor of genetics in the College of Veterinary Medicine at Cornell University in Ithaca, NY, will use her program funding in her efforts to determine whether meiosis the first stage of sperm formation is a potential target for the development of effective male contraceptives.

Why meiosis? By aiming at this early stage, a potential method would be accessible to compounds in the circulation, and its effect on fertility would be rapid and reversible. To examine the molecular mechanisms regulating meiotic entry, Cohen’s team will develop a spermatogonial stem cell culture system carrying fluorescent reporter proteins that signal cell state and meiotic entry. By using genome editing to mutate genes known to be involved in meiotic entry, and stem cell maintenance to test the system, scientists will attempt to switch one of the genes on and off on the spermatogonial stem cells. Once the system has been set up, scientists plan to screen for new genes involved in meiotic entry in an effort to identify potential candidates for the development of possible male contraceptives.

“The problem is, we know very little about meiosis, because it’s a very hard stage to target biologically or molecularly,” Cohen said in a press release. “Only recently have we started to gather the tools to be able to look at it.”

Focus on Female Fertility

In another potential approach, Francisco Diaz, PhD, associate professor of reproductive biology, and Pak Kin Wong, PhD, professor of biomedical engineering, both at Pennsylvania State University in University Park, will develop a high-throughput screening method to identify compounds able to block biological events essential for female fertility without affecting ovulation or hormone production. By blocking cumulus expansion (when cumulus cells release from the oocyte to enable it to enter the oviduct) and oocyte maturation (when the oocyte divides to produce the egg and a smaller polar body), Diaz’s team hopes to identify new contraceptives with fewer side effects.

To look at these two events, scientists will extract cumulus oocyte complexes from primed female mice and apply them to a microwell array prototype containing 1,024 wells coated with different test compounds and connected by microfluidic channels. The oocytes in the wells will be stimulated to undergo cumulus expansion. When cumulus cells are removed, then oocyte maturation will occur. Researchers will employ automated inverted microscopy to assess the ability of each compound to inhibit each step. The platform will be optimized first using known inhibitors, then tested using a library of 1,200 molecules approved by the Food and Drug Administration. The microfluidics device, developed in Wong’s laboratory, will analyze how test compounds influence polar body production. This device will help in developing a method to screen a large number of compounds for contraceptive activity by simultaneously assessing their effects on both cumulus expansion and oocyte maturation.

“Without cumulus expansion, transfer of the egg to the oviduct is prevented,” Diaz said in a press statement. “So, blocking cumulus expansion and trapping the oocyte in the ovary could be an attractive and novel target for contraceptive development.”

Zebrafish Under Investigation

Randall Peterson, PhD, L.S. Skaggs presidential endowed professor and dean of the College of Pharmacy at the University of Utah in Salt Lake City, is developing a zebrafish model for high-throughput screens to identify compounds that inhibit the formation of gametes. Researchers hope such compounds could lead to male and female contraceptives that last for weeks or months after only a single dose.

Unlike conventional drug discovery programs that use simplified, in vitro assays, the Peterson lab screens use living zebrafish, ensuring that the drug candidates discovered are active in vivo. In the current contraceptive line of research, scientists will generate transgenic zebrafish lines to express a selection of four fluorescently labeled markers for different stages of gametogenesis. These markers can be quantified rapidly to measure the effects of candidate compounds on blocking gamete production.

Other Lines Explored

Aurelien Forget, PhD, adjunct research associate in the School of Pharmacy and Medical Sciences at the University of South Australia in Adelaide, is working on a three-dimensional bioprinted model of the fallopian tube. This model will be used as a screening platform to identify compounds that specifically block sperm activation in the search for a contraceptive that targets male sperm. Such a method might be used before or after intercourse, and should avoid the side effects associated with current hormonal contraceptives. Since sperm must be activated in the oviduct before penetrating the cells and protein layer surrounding the egg for fertilization, scientists will isolate oviduct cell populations from mice to reproduce this process in vitro. Researchers will use a synthetic, printable extracellular matrix to build a three-dimensional oviduct that reproduces the four-layered structure. By assessing cell viability and function in their assembled oviduct, they hope to test the ability to capacitate mouse and human sperm.

Another Australian researcher, Darryl Russell, PhD, a research fellow at the University of Adelaide, is leading a scientific investigation of a scalable in vitro screening assay that can automatically evaluate adhesion in the cumulus-oocyte complex. By examining the adhesion process, which is required to release the oocyte from the ovary for fertilization, scientists hope to develop new contraceptives that would specifically block ovulation.

To achieve this target, researchers will isolate cumulus-oocyte complexes from mice, culture them with collagen, and test them in a 96-well plate format using an automated assay that measures electrical resistance. Scientists also will use short hairpin RNAs in mice cumulus-oocyte complexes to inhibit the genes that are activated when ovulation is stimulated. By analyzing the effect on adhesion using the quantitative assay, investigators hope to uncover the biochemical pathways required for ovulation that also may be a springboard for contraceptive development.