Clinical Efficacy, Pharmacokinetics, and Safety of the Available Medical Options in the Treatment of Endometriosis-Related Pelvic Pain: A Scoping Review

BACKGROUND

In this scoping review, we sought to identify published studies evaluating the drugs currently used in the treatment of endometriosis-related pelvic pain, with reflection on their chemical properties, pharmacokinetics, safety profile, and clinical efficacy.

METHODS

A literature search was conducted with the use of the PubMed and EMBASE electronic databases, focusing on identifying articles published in English between January 1990 and 2023.

RESULTS

Based on the included studies, current therapy options for the treatment of endometriosis-related pain identified and reviewed in this article were: (1) non-steroidal anti-inflammatory drugs; (2) combined oral contraceptive (COCs); (3) progestins; (4) gonadotropin-releasing hormone agonists and antagonists; (5) aromatase inhibitors (AIs); (6) selective estrogen and progesterone receptor modulators; and (7) levonorgestrel-intrauterine device.

CONCLUSIONS

Based on the published evidence, clinicians should consider NSAIDs, COCs, and progestins as the first-line medical therapies. Compared with second-line options, such as GnRH agonists/antagonists or AIs, the abovementioned first-line options are well tolerated, efficacious, and exhibit lower overall price. Future research priorities should be to identify novel target therapies and to evaluate the effects of available drugs through different routes of administration.

Aromatase inhibitors in the pharmacotherapy of endometriosis

INTRODUCTION

Endometriosis is a benign chronic inflammatory disease responsible for debilitating pain and decreased quality of life. The traditional treatment is based on estroprogestins, progestins, GnRH analogues and surgery. Recently aromatase inhibitors (AIs) demonstrated good efficacy in controlling symptoms and size of endometriotic implants, mostly because they suppress extraovarian estrogen synthesis, which can enhance the hypoestrogenic state ameliorating symptoms of endometriosis.

AREAS COVERED

Phase I, II, III and IV trials, on the use of AIs used for the treatment of endometriosis have been retrieved. The pharmacokinetics and pharmacodynamics of third generation non-steroidal AIs have also been investigated. a MEDLINE search using the following MeSH keywords: "endometriosis", "aromatase inhibitors", "therapy", "treatment" has been performed. The timeframe was from 2010 up to November 2022 including reviews, systematic reviews, reports, case series, and retrospective or prospective trials.

EXPERT OPINION

AIs have shown good clinical efficacy in combination with hormonal therapy in disease control, and they represent a promising second line therapy in selected patients yet more research is needed on alternative drug delivery systems and better control of adverse effects. In postmenopausal women in which surgery is contraindicated, AIs represent an excellent treatment option. Their application in routine clinical practice remains limited by adverse effects.

A Systematic Review of Systematic Reviews on the Use of Aromatase Inhibitors for the Treatment of Endometriosis: The Evidence to Date

Endometriosis is a chronic gynecologic condition that affects around 6-10% of reproductive age women. This clinical entity is characterized with pelvic pain, dysmenorrhea, dyspareunia, and infertility which are the most often presenting symptoms. Aromatase P450 is the key enzyme for ovarian estrogen biosynthesis and there is evidence that endometriotic lesions express aromatase and are able to synthesize their own estrogens. Aromatase inhibitors (AIs) are potent drugs that suppress the estrogen synthesis via suppression of aromatase. We performed a systematic review of systematic reviews and narrative reviews on the use of aromatase inhibitors in the medical management of endometriosis. We searched: PubMed (1950-2022), Google Scholar (2004-2022), Cochrane Library (2010-2022) and Researchgate (2010-2022). The search included the following medical subject headings (MeSH) or keywords: "Aromatase Inhibitors" AND "Endometriosis" AND "Systematic reviews" OR "Systematic review" AND "Reviews" OR "Reviews" AND "Endometriosis". The electronic database search yielded initially 12,106 studies from the different databases. Further assessment of the studies resulted in exclusion of (n = 12,015) studies due to duplicates and irrelevance; Finally, 24 studies were selected for inclusion, 5 were Systematic reviews and 19 were Narrative reviews. The 5 systematic reviews were assessed by AMSTAR-2 criteria and were found to have low quality. Narrative reviews were assessed with SANRA criteria and were found to have high-quality aromatase inhibitors are potent drugs that can manage the endometriosis-related symptoms in cases where initial medical management has failed to show positive results. However, their use is limited by the adverse effects that are linked with menopausal symptoms. aromatase inhibitors can be administered as an alternative treatment in patients. Future studies with randomized design are required to reach safer conclusions and further investigation. These studies should define the therapeutic dose, new add-back therapy modalities. Future directions should examine the most-appropriate way of administration and the duration of therapy.

Fused deposition modeling three-dimensional printing of flexible polyurethane intravaginal rings with controlled tunable release profiles for multiple active drugs

We designed and engineered novel intravaginal ring (IVR) medical devices via fused deposition modeling (FDM) three-dimensional (3D) printing for controlled delivery of hydroxychloroquine, IgG, gp120 fragment (encompassing the CD4 binding site), and coumarin 6 PLGA-PEG nanoparticles (C6NP). The hydrophilic polyurethanes were utilized to 3D-print reservoir-type IVRs containing a tunable release controlling membrane (RCM) with varying thickness and adaptable micro porous structures (by altering the printing patterns and interior fill densities) for controlled sustained drug delivery over 14 days. FDM 3D printing of IVRs were optimized and implemented using a lab-developed Cartesian 3D printer. The structures were investigated by scanning electron microscopy (SEM) imaging and in vitro release was performed using 5 mL of daily-replenished vaginal fluid simulant (pH 4.2). The release kinetics of the IVR segments were tunable with various RCM (outer diameter to inner diameter ratio ranging from 1.12 to 2.61) produced from FDM 3D printing by controlling the printing perimeter to provide daily zero-order release of HCQ ranging from 23.54 ± 3.54 to 261.09 ± 32.49 µg/mL/day. IgG, gp120 fragment, and C6NP release rates demonstrated pattern and in-fill density-dependent characteristics. The current study demonstrated the utility of FDM 3D printing to rapidly fabricate complex micro-structures for tunable and sustained delivery of a variety of compounds including HCQ, IgG, gp120 fragment, and C6NP from IVRs in a controlled manner.

Is intracrinology of endometriosis relevant in clinical practice? A systematic review on estrogen metabolism

Endometriosis is a chronic, multifactorial, estrogen-dependent disease. The abnormal endocrine microenvironment of endometriosis lesions is considered a main feature and multiple enzymatic pathways leading to local increased synthesis of estrogens have been identified. However, the relevance of intracrinology in clinical practice is still lacking. Medline, Embase, Scopus database were systematically searched for studies reporting on local estrogens metabolism of endometriotic lesions. The main enzymatic pathways involved in the intracrinology of endometriosis such as aromatase (CYP19A1), 17β-hydroxysteroid dehydrogenase (HSD17B) type 1, type 2 and type 5, steroid sulfatase (STS), estrogen sulfotransferase (SULT1E1) were assessed with a critical perspective on their role in disease endocrine phenotyping, drug resistance and as therapeutic targets. Overall, studies heterogeneity and missing clinical data affect the interpretation of the clinical role of these enzymes. Although the use of some drugs such as aromatase inhibitors has been proposed in clinical practice for two decades, their potential clinical value is still under investigation as well as their modality of administration. A closer look at new, more realistic drug targets is provided and discussed. Altered expression of these key enzymes in the lesions have far reaching implication in the development of new drugs aimed at decreasing local estrogenic activity with a minimal effect on gonadal function; however, given the complexity of the evaluation of the expression of the enzymes, multiple aspects still remains to be clarified.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022311329, identifier CRD42022311329.

Computational Models for Diagnosing and Treating Endometriosis

Endometriosis is a common but poorly understood disease. Symptoms can begin early in adolescence, with menarche, and can be debilitating. Despite this, people often suffer several years before being correctly diagnosed and adequately treated. Endometriosis involves the inappropriate growth of endometrial-like tissue (including epithelial cells, stromal fibroblasts, vascular cells, and immune cells) outside of the uterus. Computational models can aid in understanding the mechanisms by which immune, hormone, and vascular disruptions manifest in endometriosis and complicate treatment. In this review, we illustrate how three computational modeling approaches (regression, pharmacokinetics/pharmacodynamics, and quantitative systems pharmacology) have been used to improve the diagnosis and treatment of endometriosis. As we explore these approaches and their differing detail of biological mechanisms, we consider how each approach can answer different questions about endometriosis. We summarize the mathematics involved, and we use published examples of each approach to compare how researchers: (1) shape the scope of each model, (2) incorporate experimental and clinical data, and (3) generate clinically useful predictions and insight. Lastly, we discuss the benefits and limitations of each modeling approach and how we can combine these approaches to further understand, diagnose, and treat endometriosis.

Pearl Index study with levonorgestrel-releasing intravaginal rings: using pharmacokinetic results to investigate treatment compliance as a potential contributor for contraceptive failure

STUDY QUESTION

What is the reason for insufficient contraceptive efficacy of levonorgestrel (LNG) delivered by intravaginal ring (IVR) releasing comparable amounts of LNG as approved progestogen-only pills (POPs)?

SUMMARY ANSWER

The pharmacokinetic (PK) evaluation in a subpopulation indicated that the steady-state concentration of plasma LNG was markedly lower in the participants in the USA compared to those in Japan suggesting non-compliance in the US participants which may explain a clearly higher Pearl Index (PI) in USA (8.2, unadjusted PI) compared to Japan (1.4, unadjusted PI).

WHAT IS KNOWN ALREADY

Contraceptive efficacy of LNG in POPs has been demonstrated following different routes of administration (e.g. orally, implants, intrauterine systems), and the PK is well-characterized including a target exposure needed for contraception. Exposure above this target concentration was reached in Phase 1 studies using IVR delivering 40 µg LNG per day.

STUDY DESIGN, SIZE, DURATION

The primary objective of this multicenter, open-label, single-arm study conducted in the USA and in Japan was to assess the contraceptive efficacy of an LNG-containing IVR during a planned treatment period of 1 year in healthy women 18-35 years of age. The study was planned to be conducted in 1600 participants (1300 in the USA, 300 in Japan). The study was prematurely terminated after approximately one-third of the planned exposure was reached due to a high number of pregnancies (28) in the US study population.

PARTICIPANTS/MATERIALS, SETTING, METHODS

In total, 1471 participants were treated (1166 participants in the USA and 305 participants in Japan). The PI as a measure of contraceptive efficacy was calculated from the frequency of unintended pregnancies during treatment. LNG exposure in the systemic circulation was assessed during treatment in 136 participants (PK subgroups: 106 in the USA and 30 in Japan).

MAIN RESULTS AND THE ROLE OF CHANCE

The PK evaluation in the PK subgroups indicated that the steady-state concentration of plasma LNG after 6 months was markedly lower in the participants in the USA (geometric mean 91.2 ng/l) compared to those in Japan (263.8 ng/l). This PK finding cannot be explained by the regional differences in body weight observed between the PK subgroups, thus suggesting non-compliance in the US participants. In 15.7% of the samples collected in the USA and 3.5% samples in Japan, the LNG concentration at steady state was below the lower limit of quantification (10 ng/l), which is not expected with the required continuous use of the IVR documented in most of the eDiaries.

LIMITATIONS, REASONS FOR CAUTION

The planned duration of treatment was 12 months, but due to the premature termination of the study none of the participants completed the 12-month treatment. All data collected until the study termination were considered, but it is to be noted that the amount of missing data limits the conclusions that can be drawn from the data.

WIDER IMPLICATIONS OF THE FINDINGS

The results of this study triggered the termination of the project, because the objective to show sufficient contraceptive efficacy of the LNG IVR was not met. The choice of a user-dependent contraceptive method with an LNG dose that is not inhibiting ovulation is not advisable for women who may have compliance issues.

STUDY FUNDING/COMPETING INTEREST(S)

The study was funded by Bayer AG and all authors are employees of Bayer AG.

TRIAL REGISTRATION NUMBER

NCT02403401.

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.

Aromatase inhibitors for the treatment of endometriosis: a systematic review about efficacy, safety and early clinical development

INTRODUCTION

Pharmacotherapy has a key role in endometriosis treatment and management, however, a significant proportion of patients have only intermittent or limited benefits with current treatment options. Therefore, novel therapeutic approaches are necessary.

AREAS COVERED

This systematic review provides an overview of the efficacy and safety of aromatase inhibitors (AIs) as monotherapies and combination therapies for endometriosis. A systematic literature search was performed from January 1990 to April 2020 in the electronic database MEDLINE, EMBASE, The Cochrane Library, and Web of Science.

EXPERT OPINION

Based on the critical role of estrogens and the rate-limiting step in the production of the estrogens represented by the aromatase enzyme, AIs are a potential therapeutic option for women affected by endometriosis. Nevertheless, further research is needed to clarify the efficacy of AIs in this setting. Adverse effects need to be investigated to clarify the preventive role of add-back therapy. On that basis, AIs should be adopted only as second-line therapy in patients who are refractory to standard treatments in the setting of scientific research. Further studies should define best dosages, appropriate add-back therapies, administration routes, treatment length, and which patients may benefit more from AIs.

Novel drug delivery methods for improving efficacy of endometriosis treatments

INTRODUCTION

Pharmacotherapy has a key role in the management of endometriosis. However, a significant proportion of patients gains only intermittent or limited benefits. In this regard, alternative and novel drug delivery methods are of paramount importance to improve efficacy and compliance of available treatments and develop alternative medical approaches.

AREAS COVERED

This review aims to provide the reader with a complete overview of available evidence about alternative and novel drug delivery methods for endometriosis pharmacotherapy and highlight new research lines.

EXPERT OPINION

Progestins and estroprogestins, which represent the first-line therapy, are already available in different formulations, being employed for contraception. Nevertheless, evidence on their adoption is still limited for some drug delivery methods, such as vaginal rings, patches, and subcutaneous implants. Further research is needed to define better their clinical utility in patients with endometriosis. Nanotechnologies have been investigated as novel drug delivery methods able to target the drug at the disease level. However, data are very limited and preliminary, and further research is needed to consider a possible clinical application in endometriosis.

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.

Absence of Drug-Drug Interaction of Anastrozole on Levonorgestrel Delivered Simultaneously by an Intravaginal Ring: Results of a Phase 2 Trial

Intravaginal rings (IVRs) are an established option for continuous administration of drugs in women. The combination of anastrozole (ATZ) and levonorgestrel (LNG) in an IVR with an intended 4-week wearing period has been considered for long-term treatment of endometriosis-associated pelvic pain. A randomized, parallel-group, multicenter phase 2b study to assess the efficacy and safety of different dose combinations in women with symptomatic endometriosis has recently been performed. This paper will focus on the investigation of pharmacokinetic (PK) effects of ATZ on LNG using data collected from this study. Two hundred sixteen patients were randomized to the treatment group with IVRs releasing LNG 40 μg/day alone or in combination with ATZ 300 μg/day, 600 μg/day, or 1050 μg/day for 12 weeks. PK blood samples were taken before dosing and before IVR replacement or removal (days 28, 56, and 84). The primary PK parameter was the plasma concentration in apparent steady state of ATZ and LNG at the end of each IVR wearing period. Results of PK analysis demonstrate that ATZ concentrations increased proportionally with increasing dose (geometric mean values of 7.85, 15.48, and 22.61 μg/L at 300, 600, and 1050 μg/day nominal release, respectively). All point estimates for LNG concentration in apparent steady state ratios between the mono and combination IVR groups were close to 1, and the 90% confidence interval limits were in the 0.80 to 1.25 range (1.01 [0.85-1.19], 1.03 [0.88-1.20], 0.94 [0.80-1.10]). In conclusion, our data indicate there is no evidence of drug-drug interaction of ATZ on LNG.

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.

Absence of Effect of Intravaginal Miconazole, Clindamycin, Nonoxynol-9, and Tampons on the Pharmacokinetics of an Anastrozole/Levonorgestrel Intravaginal Ring

A study was performed to investigate the effect of an intravaginally administered antimycotic, an antibiotic, and a spermicide plus the co-usage of tampons on the pharmacokinetics (PK) of levonorgestrel (LNG) and anastrozole (ATZ) administered as an intravaginal ring (IVR) releasing 1050 μg ATZ per day and 40 μg LNG per day. In this parallel-group, randomized, open-label study, healthy premenopausal women received an IVR as the main treatment. Comedications were administered on 3 consecutive evenings during treatment with IVR on days 9-11 (group A, 400 mg miconazole; group B, 100 mg clindamycin; group C, 75 mg nonoxynol-9); tampon co-usage (group D) was performed on days 20-23. The primary PK parameter was the average plasma concentration (C_av,ss ) of ATZ and LNG at defined intervals, mainly prior to, during, and up to 7 days after the start of comedication. Fifty-two subjects were included, and at least 11 subjects per group completed the treatments. Overall, the medications and comedications were safe and well tolerated. Very similar ATZ and LNG plasma levels were observed across all groups. The calculated ratios of C_av,ss confirmed the absence of PK interactions because all relevant point estimates and 90% confidence intervals were within the range of 0.800-1.250, which is typically used in bioequivalence studies. These results demonstrate the absence of PK interactions between ATZ/LNG released from IVR and the tested antibiotic, antimycotic, spermicide, and tampons. Therefore, no restrictions for the use of the IVR are needed to continue the clinical program intended to treat endometriosis symptoms.

"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.

Fetal safety profile of aromatase inhibitors: Animal data

Aromatase inhibitors (AIs) are a class of drugs that act by blocking the production of estrogens from androgens. The current review concentrates on the prenatal developmental toxicity of AIs in experimental models. Available data indicate that AIs may affect pregnancy at human therapeutic or lower doses. The window of vulnerability to AIs is not limited to organogenesis, but also includes the preimplantation stage and fetal periods. Decreased embryo/fetal survival was the prominent treatment-related effect. Morphological anomalies noted in fetuses exposed to AIs included skeletal anomalies, abnormal head morphology, increased ano-genital distance in female fetuses, and minor urinary tract system anomalies. Placental enlargement was consistently reported in rats and non-human primates after maternal treatment with several AIs. In conclusion, data from basic scientific research suggest that low intensity exposure to AIs applied during a wide gestational window can profoundly affect prenatal development.