(473b) Engineering Muco-Inert Nanoparticles for Improved Vaginal Drug Delivery during Pregnancy

Introduction: Vaginal drug delivery is the preferred route for targeting the female reproductive tract. By avoiding the harsh gastrointestinal environment and hepatic first-pass effect, local tissue concentration can be increased [1]. Additionally, the uterine-first-pass effect leads to accumulation of vaginally administered drugs in the uterus [2]. Vaginal formulations have been demonstrated to have some efficacy in prevention of preterm birth (PTB), though the optimal formulation for vaginal drug delivery has yet to be explored. Key barriers to effective vaginal drug delivery, including the protective mucus that acts as a barrier and facilitates clearance, must be considered [3]. By identifying physicochemical properties for optimal nanoparticle penetration of CVM, improved vaginal drug absorption can be achieved. Here, we characterized the structural and barrier properties of cervicovaginal mucus (CVM) during pregnancy using fluorescent probe nanoparticles of various sizes and surface coatings. We further utilize these design criteria to formulate drug nanoparticles that can penetrate the vaginal mucus barrier for more effective prevention of PTB.

Methods: 500 CVM samples (spaced monthly) were self-collected by 100 pregnant women. CVM microstructure was characterized by a quantitative multiple particle tracking method. Fluorescently-labeled nanoparticles with and without mucoinert coatings were added to CVM. Particle motions due to thermal energy were recorded and quantified to estimate the mesh spacing of mucin proteins comprising CVM. Further, these nanoparticles were administered vaginally to pregnant mice and the in vivo distribution was imaged. Several drugs were formulated into nanosuspensions via wet milling. The size and zeta potential of the formulations were measured. Drug levels the female reproductive tract tissues were analyzed using LC-MS/MS methods. Finally, these formulations were tested in a murine model of PTB. Pregnant mice were challenged with an intra-uterine (IU) lipopolysaccharide (LPS) injection on embryonic day 15 (E15, out of 19 day gestation). Treatment was dosed vaginally daily from E15-18. Mice were checked every

Results: Similar to what was observed previously in CVM from non-pregnant women, nanoparticles with mucoinert coatings have increased mobility in CVM from pregnant women. However, CVM from pregnant women causes a significant reduction in mobility of nanoparticles, particularly for nanoparticles 500nm in size or greater, as pregnancy progresses. Mucoinert nanoparticles ~250nm in size were slowed, but a significant fraction were still highly mobile in CVM. This inferred reduction in pore size in CVM is likely due to increasing progesterone levels throughout pregnancy. Pharmacokinetic studies revealed that nanosuspensions with a size <300 nm and a zeta potential between 0 mV to -5 mV were better able to deliver drugs to the female reproductive tract tissues. Additionally, vaginally delivered drugs were shown to target the female reproductive tract as compared to systemically administered formulations. We were able to formulate Trichostatin A, progesterone, hydroxyprogesterone caproate, vorinostat, and several other drugs into nanosuspensions. Progesterone and its analogs are prescribed for the prevention of PTB clinically. Surprisingly, progestins were only able to prevent PTB in our model when in the presence of a histone deacetylase inhibitor. Analysis of cervical and myometrial tissues revealed anti-inflammatory effects from the combination dosing.

Conclusion: Here, we gained valuable insight for engineering targeted vaginal drug treatments for pregnant women. We have demonstrated the first prevention of preterm birth in this animal model, and are able to bring the dams to deliver live pups. Effectively delivering drugs to target tissues can help to reveal mechanism behind disease. Our technology has allowed us to better target the female reproductive tract and understand mechanisms of preterm birth.

1. Ensign, R. Cone, J. Hanes, JCR 2014, 0:500-5:14
2. De Ziegler, C. Bulletti, B. De Monstier, A.S. Jääskeläinen, Ann N Y Acad Sci, 1997; 828:291-9.
3. Yu, J. Chisholm, W.J. Choi, A. Anonuevo, S. Pulicare, W. Zhong, M. Chen, C. Fridley, S.K. Lai, L.M. Ensign, J.S. Suk, J. Hanes, Adv Healthc Mater, 5 (2016) 2745-2750.
4. J.C. Condon, P. Jeyasuria, J.M. Faust, J.W. Wilson, C.R. Mendelson, PNAS 2003, 100.16, 9518-9523.