(M-497) State-of-the-Art 3D-Printed Intravaginal Ring AnelleO PRO: Sustained Progesterone Supplementation for the Treatment of Infertility

Infertility, defined as the inability to get pregnant after one year of unprotected intercourse, remains a global unmet medical need. In the United States alone, infertility affects upwards of 19% of women aged 15-49. A further 26% of women have difficult maintaining or carrying a pregnancy to term¹. Assisted Reproductive Technology (ART) encompasses all fertility treatments including the main type, in vitro fertilization (IVF). Exogenous progesterone supplementation is a well established in ART and critical for conception and maintaining pregnancy^2-4.  Current progesterone supplementation options are limited to a twice daily vaginal gel, (Crinone^®), a vaginal insert administered 2-3 times per day (Endometrin^®), or daily intramuscular (IM) injection (Makena^®). Gels and inserts are messy, lead to vaginal discharge, and require multiple applications. Alternatively, the IM injection is painful, requires assistance for administration, and has several known side effects⁵. Collectively, these drawbacks lead to suboptimal patience compliance and ultimately hinder the ability to become pregnant.

We propose an alternative method to progesterone supplementation: a 3D-printed 28-day intravaginal ring (IVR). IVRs are noted for their high patient compliance given ease of self-administration, discreetness, and long acting duration⁶. 3D-printing enables rational design and fabrication using a silicone-polyurethane material. Impregnation of progesterone is a separate post-processing step that allows for tuned drug loading. By controlling design and loading, we demonstrate the ability to target device performance. We characterized AnelleO PRO IVRs by in vitro release, accelerated stability, in vivo mouse safety, and in vivo sheep pharmacokinetic studies.

AnelleO PRO rings were designed using computationally aided design (CAD) software (Rhino, Robert McNeel & Associates and Magics, Materialise). Rings were designed to mimic the dimensions of the commercially available Estring^® with an outer diameter (OD) of 54.0 mm and cross-sectional diameter (CS) of 7.6 mm. Several designs were explored using a unit cell approach, as shown in Fig. 1A. IVRs were 3D-printed with Digital Light Synthesis (DLS, Carbon) in a proprietary silicone-polyurethane resin. Progesterone was incorporated homogenously into the rings in a separate, post-processing step resulting in the final AnelleO PRO device.

AnelleO PRO IVRs were characterized in a number of ways to evaluated device performance. In vitro release studies were conducted in simulated vaginal fluid (SVF). Steady-state release rates and maximum release duration were quantified. Accelerated stability studies (40°C/75% relative humidity) were conducted to evaluate the effect of long-term storage on ring mechanical properties and drug release kinetics. The safety of the proprietary resin was explored in vivo using mouse-sized rings (3 mm OD) in which BALB/c (n=5 per time) were surgically implanted with placebo IVRs and monitored for external abnormalities. Plasma was collected pre (day 0), and post IVR implantation (day 3, 7, 14, 30, and 60) and assayed for systemic inflammatory responses (IL-6, TNF-alpha). Additionally, histological examination of vaginal tissues was conducted to assess damage and cellular infiltration. Finally, pharmacokinetic studies were conducted in vivo with sheep using human-sized IVRs (n=4). Plasma, vaginal secretions, and vaginal biopsies were collected over the course of 6 weeks.

AnelleO PRO rings were fabricated using a variety of designs to explore the effect of theoretical specific surface area (SSA, mm^-1) and drug loading on release kinetics (Fig. 1B-1C). Results showed that PRO release kinetics can be fine-tuned by changing IVR design and/or PRO loading to release PRO in 6 weeks to 6 months. PRO release kinetics can be controlled by changing drug loading. Faster release kinetics were obtained with lower drug loading (solid 3.8 wt% PRO) compared to significantly slower release kinetics observed at higher drug loading (17.2 wt% PRO).

Safety studies in BALB/c female were surgically implanted with IVRs (3 mm OD) and monitored over 60 days. Minimal macrophages with add-mixed lymphocytes were observed on Day 3, mainly around the suture area. By later timepoints, no macrophages or lymphocytes were present indicating that the rings were well-tolerated.

Pharmacokinetic studies were conducted in vivo using sheep (n=4) implanted with AnelleO PRO solid IVRs (1.2 g PRO/IVR 54 mm OD) and monitored for 6 weeks. Plasma levels were above the minimum required progesterone dose for successful IVF (6-10 ng/mL) for the first 2 weeks, then dropped slightly (~2-6 ng/mL) and were maintained at those levels for the study duration (6 weeks). PRO levels ranged between ~1000-12000 ng/mL in vaginal fluids and between ~5-90 ng/g in vaginal biopsies. Based on the quantified residual PRO extracted from PRO-IVRs (241 ± 27 mg) post in vivo sheep PK, 80% of the total PRO loaded was released over 6 weeks.

1.         Centers for Disease Control and Prevention, 2020 Assisted Reproductive Technology: Fertility Clinical and National Summary Report. 2022, US Dept of Health and Human Services.

2.         Schindler, A. E.;  Campagnoli, C.;  Druckmann, R.;  Huber, J.;  Pasqualini, J. R.;  Schweppe, K. W.; Thijssen, J. H., Classification and pharmacology of progestins. Maturitas 2003, 46 Suppl 1, S7-S16.

3.         Szekeres-Bartho, J.; Balasch, J., Progestagen therapy for recurrent miscarriage. Hum Reprod Update 2008, 14 (1), 27-35.

4.         Rai, P.;  Rajaram, S.;  Goel, N.;  Ayalur Gopalakrishnan, R.;  Agarwal, R.; Mehta, S., Oral micronized progesterone for prevention of preterm birth. Int J Gynaecol Obstet 2009, 104 (1), 40-3.

5.         Current clinical irrelevance of luteal phase deficiency: a committee opinion. ASRM pages 2015, 103 (4), e27-e32.

6.         Wieder, D.R.; Pattimakiel, L. Examining the efficacy, safety, and patient acceptiability of the combined contraceptive vaginal ring (NuvaRing®). Int. J.Women’s Health 2010, 2, 401-409.