Comparison of estrogenic components used for hormonal contraception.

Attempts have been made over the years to replace ethinyl estradiol (EE) in combined oral contraceptives (COCs) with the less potent natural estrogen estradiol (E2), or its prodrug, E2 valerate (E2V), to improve their safety and tolerability. Recently, a COC incorporating a novel weak natural estrogen, estetrol (E4), combined with drospirenone, has become available. We present a comparative analysis of the three prevailing estrogens used in COCs, focusing on their structure-function relationships, receptor-binding affinity, potency, metabolism, pharmacokinetic parameters, and pharmacodynamics. The binding affinity of EE to estrogen receptor (ER)α is twice that of E2, whereas its affinity for ERß is about one-half that of E2. E4 has a lower binding affinity for the ERs than E2. The high potency of EE is notable in its dramatic increase in estrogen-sensitive hepatic globulins and coagulation factors. EE and E2 undergo extensive and comparable metabolism, while E4 produces only a very limited number of metabolites. E4 has the highest bioavailability among the three estrogens, with E2 having <5%. Studies demonstrate consistent ovulation inhibition, although a higher dose of E4 (15 mg) in COCs is required to achieve follicular suppression compared to E2 (1-3 mg) and EE (0.01-0.035 mg). E2 and E4 in COCs may be less stimulatory of coagulant proteins than EE. Studies with E2/dienogest suggest a comparable risk of venous thromboembolism to EE/levonorgestrel, while data assessing risk with an E4-based COC are insufficient. Nevertheless, the E4-based formulation shows promise as a potential alternative to EE and E2 due to its lower potency and possibly fewer side effects.

Role of membrane estrogen receptor alpha (ERα) in the rapid regulation of male sexual behavior.

The activation of male sexual behavior depends on brain estrogen synthesis. Estrogens act through nuclear and membrane receptors producing effects within hours/days or seconds/minutes, respectively. In mice, estrogen receptor alpha (ERα) is the main estrogen receptor (ER) controlling the activation of male sexual behavior. Although neuroestrogens rapidly modulate mouse sexual behavior, it is not known whether these effects involve membrane ERα (mERα). This study combines two complementary approaches to address this question. C451A-ERα mice carry an ERα that cannot signal at the membrane, while estetrol (E4) is a natural estrogen acting as an agonist on nuclear ERα but as an antagonist on membrane ERα. In wild-type males, E4 decreased the number of mounts and intromissions after 10 min. In C451A-ERα males, E4 also altered sexual performance but after 30 min. E4 did not affect time spent near the female in both wild-type and C451A-ERα mice. However, regardless of genotype, the aromatase inhibitor 1,4,6-Androstatriene-3,17-dione (ATD) decreased both sexual performance and the time spent near the female after 10 and 30 min, confirming the key role of aromatization in the rapid control of sexual behavior and motivation. In conclusion, the shift in timing at which the effect of E4 is observed in mice lacking mERα suggests a role for mERα in the regulation of rapid effects of neuroestrogens on sexual performance, thus providing the first demonstration that E4 acts as an antagonist of a mER in the brain. The persisting effect of ATD on behavior in C451A-ERα mice also suggests the implication of another ER.

The benefits of estetrol addition to drospirenone for contraception.

Ethinylestradiol and drospirenone combined oral contraceptive formulations have been marketed for >20 years. Drospirenone has antimineralocorticoid and anti-androgenic effects that may offer several health benefits. Recently, 2 new drospirenone-containing oral contraceptives entered the market, 1 as a progestin-only pill containing 4 mg drospirenone and the other as a combined oral contraceptive containing 15 mg estetrol and 3 mg drospirenone. Estetrol has a unique differential effect on nuclear and membrane estrogen α-receptors when compared with other estrogens, leading to low impact on the liver, breast, and hemostasis parameters and a beneficial effect on the endometrium, vagina, cardiovascular system, bone, and brain. Phase 3 clinical studies demonstrated that the Pearl Index (pregnancies per 100-woman-years) for drospirenone alone is 4.0 in the United States and 0.93 in the European Union and for the estetrol-drospirenone combination it is 2.65 and 0.44, respectively. Drospirenone alone demonstrates high rates of unscheduled bleeding and low rates of scheduled bleeding, whereas the estetrol-drospirenone combination demonstrates a predictable and regular bleeding profile for most users with a high stable rate of scheduled bleeding and a low rate of unscheduled bleeding, reported primarily as spotting only. The adverse event profiles and discontinuation rates owing to adverse events are comparable, and no clinically significant effects were observed on metabolic parameters with either product. Hemostatic assays for drospirenone do not fully evaluate all parameters although the testing that is available suggests negligible effects, whereas validated hemostatic assays demonstrate that the estetrol-drospirenone combination has limited impact on hemostasis. The introduction of 4 mg drospirenone and 15 mg estetrol with 3 mg drospirenone are valuable additions to the contraceptive market. Adding estetrol to 3 mg drospirenone provides advantages of contraceptive efficacy and a regular, predictable bleeding profile with minimal impact on hemostasis parameters.

Comparison of Estetrol Exposure between Women and Mice to Model Preclinical Experiments and Anticipate Human Treatment.

Estetrol (E4) is a natural estrogen with promising therapeutic applications in humans. The European Medicines Agency and the Food and Drug Administration have approved the use of 15 mg E4/3 mg drospirenone for contraceptive indication. Phase III clinical trials with 15-20 mg E4 for the relief of climacteric complaints are currently running. Relevant data from preclinical animal models are needed to characterize the molecular mechanisms and the pharmacological effects of E4 and possibly to reveal new therapeutic applications and to anticipate potential adverse effects. Therefore, it is important to design experimental procedures in rodents that closely mimic or anticipate human E4 exposure. In this study, we compared the effects of E4 exposure after acute or chronic administration in women and mice. Women who received chronic E4 treatment per os at a dose of 15 mg once daily reached a steady state within 6 to 8 days, with a mean plasma concentration of 3.20 ng/mL. Importantly, with subcutaneous, intraperitoneal or oral administration of E4 in mice, a stable concentration over time that would mimic human pharmacokinetics could not be achieved. The use of osmotic minipumps continuously releasing E4 for several weeks provided an exposure profile mimicking chronic oral administration in women. Measurements of the circulating concentration of E4 in mice revealed that the mouse equivalent dose necessary to mimic human treatment does not fit with the allometric prediction. In conclusion, this study highlights the importance of precise definition of the most appropriate dose and route of administration to utilize when developing predictive preclinical animal models to mimic or anticipate specific human treatment.

Estetrol: From Preclinical to Clinical Pharmacology and Advances in the Understanding of the Molecular Mechanism of Action.

Estetrol (E4) is the most recently described natural estrogen. It is produced by the human fetal liver during pregnancy and its physiological function remains unclear. E4 is the estrogenic component of a recently approved combined oral contraceptive. It is also in development for use as menopausal hormone therapy. In the context of these developments, the pharmacological activity of E4, alone or in combination with a progestin, has been extensively characterized in preclinical models as well as in clinical studies in women of reproductive age and postmenopausal women. Despite the clinical benefits, the use of oral estrogens for contraception or menopause is also associated with unwanted effects, such as an increased risk of breast cancer and thromboembolic events, due to their impact on non-target tissues. Preclinical and clinical data for E4 point to a tissue-specific activity and a more selective pharmacological profile compared with other estrogens, including a low impact on the liver and hemostasis balance. This review summarizes the characterization of the pharmacological properties of E4 as well as recent advances made in the understanding of the molecular mechanisms of action driving its activity. How the unique mode of action and the different metabolism of E4 might support its favorable benefit-risk ratio is also discussed.

Use of liposome-encapsulated estetrol for treatment of neonatal hypoxic-ischemic encephalopathy.

Estetrol (E4) is a natural estrogen synthesized only during pregnancy. It has strong neuroprotective and antioxidative activities. The aim of the present study was to define the neuroprotective potency of E4 encapsulated either in liposome (Lipo-E4) or in drug-in cyclodextrin (HP-ß-CD) in liposome (DCL) system, and compare them with a single use of E4. In vitro studies were performed in an oxidative stress model of primary hippocampal neuronal cell cultures, followed by the lactate dehydrogenase activity and cell proliferation assays. In vivo studies were conducted by using a model of neonatal hypoxic-ischemic encephalopathy in immature rat pups. Brain samples were studied by (immuno)histochemistry for the detection of survived cells, expression of microtubule-associated protein-2, myelin basic protein, doublecortin and vascular-endothelial growth factor. Concentrations of glial fibrillary acidic protein in blood serum were studied by ELISA. In vitro, cell proliferation was significantly up-regulated in cultures treated either by DCL-E4 or E4 compared to the control cells, whereas DCL-E4 treated cells had significantly higher survival rate than the cells treated by E4 alone. Evaluation of brain samples showed that DCL-E4 and a high dose of E4 alone significantly preserve the grey and the white matter loses, and diminish GFAP expression in blood. Although DCL-E4 and E4 have similar effect on neurogenesis in the hippocampus and the cortex, DCL-E4 treatment significantly up-regulates angiogenesis in the hippocampus compared to a single use of E4. Present work reveals for the first time that liposome-encapsulated E4 might be a better alternative to a single use of E4.

The different natural estrogens promote endothelial healing through distinct cell targets.

The main estrogen, 17ß-estradiol (E2), exerts several beneficial vascular actions through estrogen receptor α (ERα) in endothelial cells. However, the impact of other natural estrogens such as estriol (E3) and estetrol (E4) on arteries remains poorly described. In the present study, we report the effects of E3 and E4 on endothelial healing after carotid artery injuries in vivo. After endovascular injury, which preserves smooth muscle cells (SMCs), E2, E3, and E4 equally stimulated reendothelialization. By contrast, only E2 and E3 accelerated endothelial healing after perivascular injury that destroys both endothelial cells and SMCs, suggesting an important role of this latter cell type in E4's action, which was confirmed using Cre/lox mice inactivating ERα in SMCs. In addition, E4 mediated its effects independently of ERα membrane-initiated signaling, in contrast with E2. Consistently, RNA sequencing analysis revealed that transcriptomic and cellular signatures in response to E4 profoundly differed from those of E2. Thus, whereas acceleration of endothelial healing by estrogens had been viewed as entirely dependent on endothelial ERα, these results highlight the very specific pharmacological profile of the natural estrogen E4, revealing the importance of dialogue between SMCs and endothelial cells in its arterial protection.

Tolerability and safety of the estetrol/drospirenone combined oral contraceptive: Pooled analysis of two multicenter, open-label phase 3 trials.

OBJECTIVES: To evaluate tolerability and safety of estetrol (E4) 15 mg/drospirenone (DRSP) 3 mg oral contraceptive using pooled data from two, multicenter, phase 3 trials. STUDY DESIGN: The two trials enrolled participants aged 16-50 years with a body mass index ≤35.0 kg/m2 to use E4/DRSP in a 24/4-day regimen for up to 13 cycles. We pooled data from participants who used at least one E4/DRSP dose and had a follow-up assessment to analyze adverse events (AEs), vital signs, and laboratory parameters, including serum lipids, glucose, glycated hemoglobin, and potassium. We consolidated similar Medical Dictionary for Regulatory Activities preferred terms into groupings. RESULTS: Of 3725 participants enrolled, we included 3417 in the analyses of whom 1786 (52.3%) reported ≥1 AE. Most participants with reported AEs had AEs that investigators rated as mild or moderate (n = 1665, 93.2%); of participants reporting AEs, 1105 (61.9%) did so during cycles 1 to 3. In total, 981 (28.7%) participants experienced ≥1 treatment-related AE, most frequently related to bleeding complaints (n = 323, 9.5%), breast pain or tenderness (n = 136, 4.0%), acne (n = 113, 3.3%), and mood disturbance (n = 111, 3.2%). Discontinuation due to treatment-related AEs occurred in 272 participants (8.0%), with only bleeding complaints (n = 97, 2.8%) and mood disturbance (n = 38, 1.1%) at rates exceeding 1%. Three participants experienced serious AEs, which the site investigators considered treatment-related: one venous thromboembolism, one worsening of depression, and one ectopic pregnancy. We found no clinically relevant changes in weight, blood pressure, heart rate, or laboratory parameters during treatment. CONCLUSIONS: E4/DRSP is associated with a favorable tolerability and safety profile. IMPLICATIONS STATEMENT: Pooling data allowed for a robust assessment of tolerability and safety, including relatively infrequent events. Other than bleeding complaints and mood disturbance, no adverse event resulted in E4/DRSP discontinuation at rates >1%. Post-marketing surveillance studies are needed to evaluate long-term safety of the E4/DRSP COC and population-based venous thromboembolism risks.

Pooled efficacy results of estetrol/drospirenone combined oral contraception phase 3 trials.

OBJECTIVE: To evaluate overall and subgroup efficacy of an estetrol (E4) 15 mg drospirenone (DRSP) 3 mg oral contraceptive in a 24/4-day regimen. STUDY DESIGN: We pooled efficacy outcomes from 2 pivotal phase 3 contraceptive trials with E4/DRSP conducted in the United States/Canada and Europe/Russia. We assessed Pearl Index (PI; pregnancies per 100 participant-years) and 13-cycle life-table pregnancy rates in at-risk cycles (confirmed intercourse and no other contraceptive use) among participants 16 to 35 years. We calculated PI by age and further subcategorization (contraceptive history and body mass index [BMI]). We performed multivariable analysis using Cox regression to assess impact of potential confounding factors. RESULTS: Analyses included 3027 participants, of whom 451 (14.9%) had a BMI ≥30 kg/m2. The pooled PI was 1.52 (95% confidence interval 1.04-2.16) and the 13-cycle life-table pregnancy rate was 1.28% (0.83%-1.73%). We calculated unadjusted pooled PI in participants 16 to 25 years and 26 to 35 years of 1.61 (0.94-2.57) and 1.43 (0.78-2.40), respectively; in new starters and switchers of 1.88 (1.09-3.00) and 1.24 (0.68-2.08), respectively; and by BMI <25 kg/m2, 25 to 29.9 kg/m2, and ≥30 kg/m2 of 1.14 (0.64-1.88), 2.19 (1.05-4.03), and 2.27 (0.83-4.94), respectively. In multivariable analysis, we found associations of prior pregnancy (hazard ratio [HR] 3.61[1.56-8.38]), Black race (HR 4.61[1.97-10.80]), age 16 to 25 years (HR 2.37[1.09-5.15]) and compliance <99% of expected pills (HR 4.21[2.04-8.66]) with conception. CONCLUSION: E4/DRSP is an effective oral contraceptive overall and across subgroups stratified by age, contraceptive history, and BMI. Other than compliance, predictors of contraceptive failure are nonmodifiable. IMPLICATIONS STATEMENT: Pooled results from two phase 3 trials demonstrate high contraceptive efficacy of the novel estetrol-drospirenone oral contraceptive. Several non-modifiable risk factors, including prior pregnancy, race, and age, are associated with higher pregnancy risk. Additional research is needed to better understand predictors of combined oral contraceptive failure.

Pooled analysis of two phase 3 trials evaluating the effects of a novel combined oral contraceptive containing estetrol/drospirenone on bleeding patterns in healthy women.

OBJECTIVE: To evaluate the bleeding patterns of a new combined oral contraceptive containing estetrol (E4) 15 mg/drospirenone (DRSP) 3 mg in a 24/4-day regimen. STUDY DESIGN: We pooled bleeding data from two parallel, open-label, 13-cycle phase 3 trials that enrolled participants 16 to 50 years old with body mass index (BMI) ≤35 kg/m2. Participants reported vaginal bleeding/spotting in daily diaries. For this bleeding analysis, we included participants with at least one evaluable cycle. We calculated mean frequencies of scheduled and unscheduled bleeding/spotting episodes and median duration of bleeding/spotting episodes, and assessed associations between treatment compliance, BMI and recent hormonal contraceptive use on bleeding/spotting outcomes. RESULTS: We included 3409 participants with 33,815 cycles. Scheduled bleeding/spotting occurred in 87.2% to 90.4% of participants/cycle, with a median duration of 4 to 5 days. Unscheduled bleeding/spotting decreased from 27.1% in Cycle 1 to 20.6% in Cycle 2 to ≤17.5% from Cycle 5 onwards. Most (66.5%) unscheduled bleeding/spotting episodes were spotting-only. Between 5.8% and 7.8% of users/cycle experienced absence of any scheduled or unscheduled bleeding/spotting. Missing one or more active pills resulted in a higher occurrence of unscheduled bleeding/spotting (adjusted odds ratio [aOR] 2.13 [95% confidence interval 1.68-2.70]) and absence of scheduled bleeding/spotting (aOR 2.36 [1.82-3.07]). Participants with a BMI ≥30 kg/m2 reported more absence of scheduled bleeding/spotting (aOR 1.68 [1.37-2.05]). Switchers and starters reported similar frequencies of unscheduled bleeding/spotting (aOR 0.94 [0.83-1.07]) and absence of scheduled bleeding/spotting (aOR 1.00 [0.85-1.19]). Three percent of participants discontinued for a bleeding-related adverse event. CONCLUSION: E4/DRSP use results in a predictable bleeding pattern with limited unscheduled bleeding/spotting. Noncompliance and BMI affect bleeding patterns. IMPLICATIONS STATEMENT: Most estetrol/drospirenone users experience a predictable and regular bleeding pattern. Providers can educate patients about the expected bleeding patterns and should advise users that they may infrequently experience no scheduled bleeding/spotting. This information may improve user acceptability and continuation of this new oral contraceptive.

A novel estetrol-containing combined oral contraceptive: European expert panel review.

PURPOSE: Despite considerable advances in recently developed combined oral contraceptives (COCs), resulting in lower rates of adverse events while maintaining contraceptive efficacy, there is interest in further innovation. MATERIALS AND METHODS: Estetrol (E4), a native oestrogen, and progestin drospirenone (DRSP) were combined in a new COC. A European expert panel reviewed the pharmacology, efficacy, and safety and tolerability of this combination. Their findings are presented as a narrative review. RESULTS: E4 15 mg/DRSP 3 mg in a 24/4 regimen provided effective contraception with good cycle control, characterised by a predictable regular bleeding pattern and minimal unscheduled bleeding, together with a good safety profile. The combination was associated with high user satisfaction, well-being, and minimal changes in body weight. The effects on endocrine and metabolic parameters were limited, and the combination was found to have a limited impact on liver function and lipid and carbohydrate metabolism. Moreover, its effect on several haemostatic parameters was lower than that of comparators containing ethinyl oestradiol (EE) 20 µg/DRSP 3 mg and EE 30 µg/levonorgestrel 150 µg. CONCLUSION: E4 15 mg/DRSP 3 mg provides safe and effective contraception, with high user satisfaction and predictable bleeding. Further research will evaluate the long-term safety of the COC.

Profile of estetrol, a promising native estrogen for oral contraception and the relief of climacteric symptoms of menopause.

INTRODUCTION: Estrogens used in women's healthcare have been associated with increased risks of venous thromboembolism (VTE) and breast cancer. Estetrol (E4), an estrogen produced by the human fetal liver, has recently been approved for the first time as a new estrogenic component of a novel combined oral contraceptive (E4/drospirenone [DRSP]) for over a decade. In phase 3 studies, E4/DRSP showed good contraceptive efficacy, a predictable bleeding pattern, and a favorable safety and tolerability profile. AREAS COVERED: This narrative review discusses E4's pharmacological characteristics, mode of action, and the results of preclinical and clinical studies for contraception, as well as for menopause and oncology. EXPERT OPINION: Extensive studies have elucidated the properties of E4 that underlie its favorable safety profile. While classical estrogens (such as estradiol) exert their actions via both activation of nuclear and membrane estrogen receptor α (ERα), E4 presents a specific profile of ERα activation: E4 binds and activates nuclear ERα but does not induce the activation of membrane ERα signaling pathways in specific tissues. E4 has a small effect on normal breast tissue proliferation and minimally affects hepatic parameters. This distinct profile of ERα activation, uncoupling nuclear and membrane activation, is unique.

Membrane estrogen receptor alpha (ERα) participates in flow-mediated dilation in a ligand-independent manner.

Estrogen receptor alpha (ERα) activation by estrogens prevents atheroma through its nuclear action, whereas plasma membrane-located ERα accelerates endothelial healing. The genetic deficiency of ERα was associated with a reduction in flow-mediated dilation (FMD) in one man. Here, we evaluated ex vivo the role of ERα on FMD of resistance arteries. FMD, but not agonist (acetylcholine, insulin)-mediated dilation, was reduced in male and female mice lacking ERα (Esr1-/- mice) compared to wild-type mice and was not dependent on the presence of estrogens. In C451A-ERα mice lacking membrane ERα, not in mice lacking AF2-dependent nuclear ERα actions, FMD was reduced, and restored by antioxidant treatments. Compared to wild-type mice, isolated perfused kidneys of C451A-ERα mice revealed a decreased flow-mediated nitrate production and an increased H2O2 production. Thus, endothelial membrane ERα promotes NO bioavailability through inhibition of oxidative stress and thereby participates in FMD in a ligand-independent manner.

Estetrol and Mammary Gland: Friends or Foes?

Estrogens have pleiotropic effects on many reproductive and non-reproductive tissues and organs including the mammary gland, uterus, ovaries, vagina, and endothelium. Estrogen receptor α functions as the principal mediator of estrogenic action in most of these tissues. Estetrol (E4) is a native fetal estrogen with selective tissue actions that is currently approved for use as the estrogen component in a combined oral contraceptive and is being developed as a menopause hormone therapy (MHT, also known as hormone replacement therapy). However, exogenous hormonal treatments, in particular MHTs, have been shown to promote the growth of preexisting breast cancers and are associated with a variable risk of breast cancer depending on the treatment modality. Therefore, evaluating the safety of E4-based formulations on the breast forms a crucial part of the clinical development process. This review highlights preclinical and clinical studies that have assessed the effects of E4 and E4-progestogen combinations on the mammary gland and breast cancer, focusing in particular on the estrogenic and anti-estrogenic properties of E4. We discuss the potential advantages of E4 over current available estrogen-formulations as a contraceptive and for the treatment of symptoms due to menopause. We also consider the potential of E4 for the treatment of endocrine-resistant breast cancer.

Estetrol Combined to Progestogen for Menopause or Contraception Indication Is Neutral on Breast Cancer.

Given the unequivocal benefits of menopause hormone therapies (MHT) and combined oral contraceptives (COC), there is a clinical need for new formulations devoid of any risk of breast cancer promotion. Accumulating data from preclinical and clinical studies support that estetrol (E4) is a promising natural estrogen for MHT and COC. Nevertheless, we report here that E4 remains active on the endometrium, even under a dose that is neutral on breast cancer growth and lung metastasis dissemination. This implies that a progestogen should be combined with E4 to protect the endometrium of non-hysterectomized women from hyperplasia and cancer. Through in vivo observations and transcriptomic analyses, our work provides evidence that combining a progestogen to E4 is neutral on breast cancer growth and dissemination, with very limited transcriptional impact. The assessment of breast cancer risk in patients during the development of new MHT or COC is not possible given the requirement of long-term studies in large populations. This translational preclinical research provides new evidence that a therapeutic dose of E4 for MHT or COC, combined with progesterone or drospirenone, may provide a better benefit/risk profile towards breast cancer risk compared to hormonal treatments currently available for patients.

Estetrol-drospirenone combination oral contraceptive: North American phase 3 efficacy and safety results.

OBJECTIVE: To assess efficacy, cycle control, and safety of an oral contraceptive containing estetrol (E4) 15 mg and drospirenone (DRSP) 3 mg. STUDY DESIGN: Women aged 16 to 50 years with a body mass index ≤35 kg/m2 enrolled in this multicenter, open-label, 13-cycle, phase 3 trial evaluating E4/DRSP in a 24-active/4-placebo regimen. Follow-up was scheduled at Cycles 2, 4, 7, and 10 and within 3 weeks of completing Cycle 13. Participants used daily diaries to record pill use and vaginal bleeding. We evaluated efficacy outcomes in women 16 to 35 years and bleeding patterns and safety (adverse events [AEs]) in all participants. We assessed overall and method-failure pregnancy rates using the Pearl index (PI) and life-table analysis. Scheduled bleeding included spotting or bleeding starting during the 4-day placebo period or first 3 days of the next cycle. RESULTS: We enrolled 1864 women of whom 1674 were 16 to 35 years. Women 16 to 35 years had a PI of 2.65 (95% CI 1.73-3.88), method-failure PI of 1.43 (95% CI 0.7-2.39) and 13-cycle life-table pregnancy rate of 2.1%. Scheduled bleeding occurred in 82.9% to 87.0% of women per cycle; median duration was 4.5 days. Unscheduled bleeding decreased from 30.3% in Cycle 1 to 21.3% to 22.1% during Cycles 2 to 4 and remained stable (15.5% to 19.2%) thereafter. The most frequently reported AEs were headache (5.0%) and metrorrhagia (4.6%). One-hundred thirty-two (7.1%) women discontinued the study early for an AE, most commonly for metrorrhagia (0.9%) and menorrhagia (0.8%). No thromboembolic events occurred. CONCLUSION: E4/DRSP is an effective oral contraceptive with a predictable bleeding pattern for most women and low AE rates. IMPLICATIONS STATEMENT: A new oral contraceptive with a novel estrogen, estetrol, combined with drospirenone has efficacy and safety within the range of other available oral contraceptives. Large phase 4 studies will be needed to confirm if this combination is associated with an improved adverse event profile or lower thrombosis risk.