Selecting the appropriate animal model for testing the safety of women’s health therapies, such as intravaginal rings and gels, is crucial for the successful development of the therapy. While nonhuman primates are physiologically the most similar to humans, and therefore advantageous for late-stage evaluation of efficacy, there are several other animal model options suitable for safety and pharmacokinetic (PK) studies of women’s health drugs and devices.
Scientists have been studying topical microbicides as a form of prevention of HIV-1 infection. While rodents and rabbits are anatomically and physiologically different from humans, they are still extremely useful in preclinical safety and PK studies. It is important to note that rabbits and rodents, with the exception of humanized mice, are not susceptible to HIV-1 infection. Thus, these species cannot be utilized in efficacy testing. Pigs are also an appropriate animal model for safety studies of topical gels.
Scientists have also been developing intravaginal rings (IVRs) as a way to deliver pharmaceutical products. The devices are intended to be worn continuously, providing controlled release of active pharmaceutical ingredients. Due to the size of the device, many preclinical studies have been performed in nonhuman primates and sheep. Sheep have a body mass and cervicovaginal canal size similar to women, which allows PK and tox properties to be evaluated without issues of scaling. As further research and development continues in this space, many IVR studies have shown that, through surgical implantation of ring segments, rabbits are an appropriate animal model for early-stage PK and dosing studies.
It is important to note that while this area of study has been progressing in recent years, there is still no standardized and validated animal model for microbicides – whether delivered topically or via intravaginal rings. If you aren’t sure which animal model would best suit your study needs, we are always here to help.