Characterization of anastrozole effects, delivered by an intravaginal ring in cynomolgus monkeys

Advances in targeting estrogen synthesis and receptors in patients with endometriosis

INTRODUCTION

Endometriosis is an estrogen-dependent disease on the background of progesterone resistance. Increased estrogen production, low estrogen metabolization, and altered estrogen receptors (ERs) expression contribute to the hyperestrogenic milieu within endometriotic lesions. Since estrogens play a crucial role in the pathogenesis of the disease, inhibition of estrogen production is one of the main targets of available and emerging drugs.

AREAS COVERED

Firstly, we described the molecular alterations responsible for estrogen dependence. Secondly, we reviewed available and emerging treatments that interfere, through central (gonadotropin-releasing hormone analogs (GnRH-a), GnRH antagonists) or local mechanisms (aromatase inhibitors (AIs), inhibitors of steroid sulfatase (STS) and hydroxysteroid dehydrogenase type 1 (17β-HSD1)), with estrogen dependence. Finally, we focused on emerging treatments targeting ERs (selective estrogen receptor modulators (SERMs), estrogen receptors agonists, and antagonists).

EXPERT OPINION

Available treatments interfering with estrogen pathways exert a contraceptive effect, have hypoestrogenic side effects, and cannot prevent or definitively treat the disease. Preclinical and animal studies are focusing on emerging drugs targeting ERs in order to overcome limitations of available treatments. These treatments may represent a promising option, as they may produce a more specific inhibition of disease activity within endometriotic implants, avoiding prolonged hypoestrogenic status and limiting systemic side effects.

Evolution of drug-eluting biomedical implants for sustained drug delivery

In the field of drug delivery, the most commonly used treatments have traditionally been systemically delivered using oral or intravenous administration. The problems associated with this type of delivery is that the drug concentration is controlled by first pass metabolism, and therefore may not always remain within the therapeutic window. Implantable drug delivery systems (IDDSs) are an excellent alternative to traditional delivery because they offer the ability to precisely control the drug release, deliver drugs locally to the target tissue, and avoid the toxic side effects often experienced with systemic administration. Since the creation of the first FDA-approved IDDS in 1990, there has been a surge in research devoted to fabricating and testing novel IDDS formulations. The versatility of these systems is evident when looking at the various biomedical applications that utilize IDDSs. This review provides an overview of the history of IDDSs, with examples of the different types of IDDS formulations, as well as looking at current and future biomedical applications for such systems. Though there are still obstacles that need to be overcome, ever-emerging new technologies are making the manufacturing of IDDSs a rewarding therapeutic endeavor with potential for further improvements.

Sunitinib induces primary ectopic endometrial cell apoptosis through up-regulation of STAT1 in vitro

Background

Endometriosis (EMS) is a prevalent gynecological condition characterized by the growth of endometrial tissue outside the uterine cavity. This study aimed to clarify the targeted therapeutic effect of sunitinib in an endometriosis in vitro experiment.

Methods

Primary culture of ectopic endometrial cells and normal endometrial cells. Six tumor targeting drugs were selected to screen. MTT was used to determine the IC50, flow cytometry, and DAPI staining of the targeted drugs, in order to determine the apoptosis. The differential proteins after seeding were analyzed by protein spectrum, the correlation between the specific protein and cell apoptosis was determined by small molecule interference, and the expression of each related protein was detected by Western blot. Immunohistochemistry and ELISA were used to detect the expression of p‐PDGFR and p‐STAT1 in clinical samples, and the correlation between p‐STAT1 expression and ectopic focal size was analyzed by SPSS 19.

Results

Through the drug screening, it was found that sunitinib has a significant inhibitory effect on ectopic endometrial cells. It was determined that the IC50 of sunitinib on ectopic stromal endometrial cells was 3.32 μM, while the IC50 on normal endometrium was 7.9 μM. Meanwhile, the flow cytometry and DAPI nuclear dye that took out sunitinib had an inhibition effect on the ectopic endometrium at a concentration of 4 μM. Protein spectrum analysis was conducted on ectopic intimal cells after sunitinib treatment, and it was found that STAT1 is specifically expressed in ectopic endometrial cells. In vitro, and through fludarabine interference, it was revealed that sunitinib specifically inhibited the phosphorylation site Tyr751 of PDGFR, while the expression of STAT1, p‐STAT1, and caspase‐3 was significantly upregulated, and the expression of STAT1 and p‐STAT1 was positively correlated with the expression of caspase‐3. Finally, the expression of p‐PDGFR and p‐STAT1 in ectopic foal tissues was both higher than that in normal endometrium, and p‐STAT1 expression was positively with ectopic focal size.

Conclusion

The in vitro experiments revealed that sunitinib could upregulate the expression of STAT1 by inhibiting the phosphorylation site Tyr751 of PDGFR, thereby specifically inducing the apoptosis of the primary heterotopic mesenchymal endometrium.

Nanoparticle-Based Platform for Activatable Fluorescence Imaging and Photothermal Ablation of Endometriosis

Endometriosis is a painful disorder where endometrium-like tissue forms lesions outside of the uterine cavity. Intraoperative identification and removal of these lesions are difficult. This study presents a nanoplatform that concurrently delineates and ablates endometriosis tissues using real-time near-infrared (NIR) fluorescence and photothermal therapy (PTT). The nanoplatform consists of a dye, silicon naphthalocyanine (SiNc), capable of both NIR fluorescence imaging and PTT, and a polymeric nanoparticle as a SiNc carrier to endometriosis tissue following systemic administration. To achieve high contrast during fluorescence imaging of endometriotic lesions, nanoparticles are constructed to be non-fluorescent prior to internalization by endometriosis cells. In vitro studies confirm that these nanoparticles activate the fluorescence signal following internalization in macaque endometrial stromal cells and ablate them by increasing cellular temperature to 53 ^° C upon interaction with NIR light. To demonstrate in vivo efficiency of the nanoparticles, biopsies of endometrium and endometriosis from rhesus macaques are transplanted into immunodeficient mice. Imaging with the intraoperative Fluobeam 800 system reveals that 24 h following intravenous injection, nanoparticles efficiently accumulate in, and demarcate, endometriotic grafts with fluorescence. Finally, the nanoparticles increase the temperature of endometriotic grafts up to 47 °C upon exposure to NIR light, completely eradicating them after a single treatment.

Development of an intravaginal ring delivering simultaneously anastrozole and levonorgestrel: a pharmacokinetic perspective

Intravaginal rings (IVRs) are an option for continuous administration of drugs in women. As an attractive approach for the treatment of endometriosis-associated pelvic pain, IVRs delivering a combination of the aromatase inhibitor anastrozole (ATZ) and the progestin levonorgestrel (LNG) have been developed. This article describes the developmental pharmacokinetic (PK) aspects covering the characterization of in vitro release, preclinical IVR PK investigations in monkeys, and clinical PK considerations. An IVR for ATZ has been developed and investigated in healthy menstruating female cynomolgus monkeys showing effective in vivo release. PK data from the size-adapted IVR used in these animals can be translated into a human context as confirmed in human studies where predefined exposure levels of ATZ were reached. As ATZ may cause harm to the fetus, use of effective contraception has to be assured in women of childbearing potential. Therefore, the IVR delivers a low dose of LNG as a contraceptive. Although the daily dose differed strongly between both drugs (20 µg LNG/d to >1 mg ATZ/d), simultaneous delivery of ATZ and LNG in vitro and in vivo was observed with a high correlation between the in vitro release and PK profiles. The PK characteristics successfully guided the design of clinical studies investigating the drug–drug interaction (DDI) potential. No relevant DDI between both the investigated or other vaginally administered drugs were identified.

In Vitro Methods for Evaluating Drug Release of Vaginal Ring Formulations-A Critical Review

The vagina is a promising site for both local and systemic drug delivery and represents an interesting administration route for compounds with poor oral bioavailability. Whereas most of the currently marketed dosage forms were designed as immediate release formulations, intravaginal rings (IVRs) offer the possibility of a controlled vaginal drug delivery over several weeks or months. For a long time, the development of IVRs was limited to steroid-releasing formulations. Recently, IVRs have witnessed a surge of new interest as promising delivery systems for microbicides. Therefore, various novel IVR designs have been introduced. To ensure that only safe and effective IVRs will be administered to patients, it is important to properly distinguish between IVRs with desired and undesired release performance. In vitro methods for evaluating drug release of IVRs that present with sufficient predictive capacity for in vivo drug release, and discriminatory power with regard to IVRs quality, are an essential tool for this purpose. The objective of the present review article is to present the current status of in vitro drug release testing of IVRs and to critically discuss current compendial and non-official in vitro drug release methods with regard to their discriminatory power and in vivo predictivity.

Solid state 13C NMR spectroscopy provides direct evidence for reaction between ethinyl estradiol and a silicone elastomer vaginal ring drug delivery system

Steroid molecules have a long history of incorporation into silicone elastomer materials for controlled release drug delivery applications. Previously, based on in vitro release testing and drug content analysis, we demonstrated indirectly that the contraceptive progestin levonorgestrel (LNG) chemically and irreversibly binds to addition cure silicone elastomers, presumably via a hydrosilylation reaction between the levonorgestrel ethynyl group and the hydrosilane groups in the poly(dimethylsiloxane-co-methylhydrosiloxane) crosslinker of the silicone elastomer. Here, for the first time, we report that solid state ¹³C nuclear magnetic resonance (NMR) spectroscopy provides direct evidence for the irreversible binding of ethinyl estradiol (EE) - an estrogenic steroid molecule also containing an ethynyl functional group - to an addition cure silicone elastomer. By preparing silicone elastomer samples containing ¹³C-labelled EE, signals in the NMR spectra could readily be assigned to both the free and bound EE. Additional depolymerisation studies, performed on an addition cure silicone elastomer system from which the unbound EE fraction was completely extracted, further confirmed the presence of bound EE through the formation of coloured reaction mixtures resulting from the reaction of bound EE and trifluoroacetic acid (TFA). These methods will be particularly useful in the ongoing development of new steroid-releasing silicone drug delivery devices, including various vaginal ring devices for contraception, HIV prevention and multipurpose prevention technology applications.

The Effect of Drug Content Reduction on the In Vitro and In Vivo Properties of Levonorgestrel-Releasing Intravaginal Rings

Intravaginal rings (IVRs) are an option for continuous administration of drugs in women. However, a considerable amount of excess drug often remains in the ring upon removal. The current study focuses on comparing 2 IVRs releasing levonorgestrel (LNG). Both formulations were designed to release 40 μg of LNG daily, however, with a significant difference in the total amount of drug (10.6 vs. 176.9 mg). Numerical simulations and in vitro release rate testing were utilized in designing the IVRs and confirming the similarity of drug release. Moreover, a pharmacokinetic (PK) study was performed in 13 healthy Japanese women to investigate both formulations during the intended wearing period of 28 days. The primary PK metrics was the average concentration of LNG in plasma at defined time points under stable conditions. Statistical evaluation of the ratio of the main PK metrics indicated values almost in the bioequivalence range. Furthermore, drug content determinations for used and unused IVRs were analyzed for confirming the expected drug delivery in vivo. In summary, it was shown that with proper design, even major differences in the total drug content of IVR formulations might not result in significant effects in the in vitro and in vivo release properties.

"Per vaginam" topical use of hormonal drugs in women with symptomatic deep endometriosis: a narrative literature review

PURPOSE

We aim to provide a comprehensive overview of the role of the vagina as a route for drug delivery and absorption, with a particular focus on the use of vaginal hormonal compounds for the treatment of deep infiltrating symptomatic endometriosis.

METHODS

A MEDLINE search through PubMed was performed to identify all published studies in English language on vaginal hormonal treatments for symptomatic endometriosis.

RESULTS

Main advantages of the vaginal route include avoidance of the hepatic-first pass metabolic effect, the possibility of using lower therapeutic dosages, and the reduction of side effects compared with the oral administration. Studies on endometriosis treatment mainly focused on the use of vaginal danazol (n = 6) and the contraceptive vaginal ring (n = 2). One pilot study evaluated the efficacy of vaginal anastrozole in women with rectovaginal endometriosis. Most investigations evaluated the vaginal use of hormonal agents in women with deep infiltrating endometriosis/rectovaginal endometriosis. Overall, a substantial amelioration of pelvic pain symptoms associated with endometriosis was observed, particularly of dysmenorrhea. A significant reduction in rectovaginal endometriotic nodule dimensions measured at ultrasound examination was detected by some but not all authors.

CONCLUSIONS

The vaginal route represents a scarcely explored modality for drug administration. High local hormonal concentrations might achieve a greater effect on endometriotic lesions compared with alternative routes. Future studies should focus on the use of the vagina for delivering target therapies particularly in patients with deeply infiltrating rectovaginal lesions.

Model-Based Dose Selection for Intravaginal Ring Formulations Releasing Anastrozole and Levonorgestrel Intended for the Treatment of Endometriosis Symptoms

Pharmacokinetics (PK) of anastrozole (ATZ) and levonorgestrel (LNG) released from an intravaginal ring (IVR) intended to treat endometriosis symptoms were characterized, and the exposure-response relationship focusing on the development of large ovarian follicle-like structures was investigated by modeling and simulation to support dose selection for further studies. A population PK analysis and simulations were performed for ATZ and LNG based on clinical phase 1 study data from 66 healthy women. A PK/PD model was developed to predict the probability of a maximum follicle size ≥30 mm and the potential contribution of ATZ beside the known LNG effects. Population PK models for ATZ and LNG were established where the interaction of LNG with sex hormone-binding globulin (SHBG) as well as a stimulating effect of estradiol on SHBG were considered. Furthermore, simulations showed that doses of 40 μg/d LNG combined with 300, 600, or 1050 μg/d ATZ reached anticipated exposure levels for both drugs, facilitating selection of ATZ and LNG doses in the phase 2 dose-finding study. The main driver for the effect on maximum follicle size appears to be unbound LNG exposure. A 50% probability of maximum follicle size ≥30 mm was estimated for 40 μg/d LNG based on the exposure-response analysis. ATZ in the dose range investigated does not increase the risk for ovarian cysts as occurs with LNG at a dose that does not inhibit ovulation.