Oestrogens in oral contraception: considerations for tailoring prescription to women's needs.

BACKGROUND: The oestrogenic component of combined oral contraceptives (COCs) has changed over years with the aim of reducing oestrogen-related side effects and risks, whilst maintaining oestrogen beneficial effects, particularly on cycle control. PURPOSE: To describe the pharmacological profiles of different oestrogens commonly used in COCs to provide insights on contraceptive prescription tailored to women's needs. RESULTS: All COCs ensure a high contraceptive efficacy. COCs containing the natural oestrogens oestradiol (E2), oestradiol valerate (E2V) and estetrol (E4) have limited impact on liver metabolism, lipid and carbohydrate metabolism, haemostasis and sex hormone binding globulin levels, compared with ethinylestradiol (EE). COCs with E2 and E2V appear also to entail a lower elevation of the risk of venous thromboembolism vs. EE-containing pills. No epidemiological data are available for E4-COC. E2- and E2V-containing COCs seem to exert a less stabilising oestrogenic effect on the endometrium compared with EE-COCs. The E4-COC results in a predictable bleeding pattern with a high rate of scheduled bleeding and minimal unscheduled bleeding per cycle. Based on in vitro and in vivo animal data, E4 seems to be associated with a lower effect on cell breast proliferation. CONCLUSION: Today various COCs contain different oestrogens. Prescribers must be familiar with the different properties of each oestrogen for a tailored contraceptive recommendation, considering their safety and contraceptive efficacy, as well as women's needs and preferences.

For contraceptive pills physicians can choose among different oestrogens, besides many progestins. Natural oestrogens have less metabolic impact vs EE, while EE and E4 seem to provide a better cycle control. Knowing the different oestrogen characteristics is crucial for adjusting pill prescription to women's needs and desires.

Is the multinational, surveillance PRO-E2 study informative for all countries? The Italian data on VTE and contraceptive effectiveness.

PURPOSE: To evaluate whether the thromboembolic risk and contraceptive effectiveness of NOMAC-E2 observed in the PRO-E2 study can be extended to each participating country, as lifestyle, cardiovascular risk factors and prescribing habits may differ geographically. This analysis was performed on the PRO-E2 Italian subpopulation, where smoking habit and women over 35 years were more prevalent compared with the overall study population. MATERIALS AND METHODS: Data from NOMAC-E2 or levonorgestrel-containing COCs (COCLNG) new users were descriptively analysed. Incidence rates of thrombosis (events/10,000 women-years [WY]) and the Pearl Index (pregnancies/100 WY) were calculated. RESULTS: Overall, 11,179 NOMAC-E2 and 8,504 COCLNG users were followed up to 2 years (34,869 WY). The NOMAC-E2 cohort included more women over 35 vs. COCLNG (37.7% vs. 31.8%; p = 0.001). A comparable low risk of combined deep venous thrombosis of lower extremities (DVT) and pulmonary embolism (PE) was observed in NOMAC-E2 (1.7/10,000 WY; 95% CI: 0.21-6.2) and COCLNG users (6.6/10,000 WY; 95% CI: 2.4-14.4). Similar results were obtained by considering all thromboembolic events (VTE). Unintended pregnancies did not differ between NOMAC-E2 (0.12/100 WY; 95% CI: 0.06-0.21) and COCLNG (0.15/100 WY; 95% CI: 0.08-0.26) cohorts. CONCLUSION: Despite the higher age and tobacco use, findings from the Italian subpopulation were broadly consistent with overall PRO-E2 results, confirming a similar low thromboembolic risk and high contraceptive effectiveness of NOMAC-E2 and COCLNG. SHORT CONDENSATION: This subgroup analysis of the PRO-E2 study provides comprehensive epidemiological data on the use of combined oral contraceptives in a large Italian cohort, with a higher prevalence of women over 35 years and smokers. The study confirms the low thromboembolic risk and high contraceptive effectiveness of NOMAC-E2 pill.

NOMAC-E2 shows a better contraceptive effectiveness than LNG combined oral contraceptives in women under 25: real-world PRO-E2 study.

Objective: To investigate unintended pregnancy and changes in mood, acne, and weight in NOMAC-E2 vs levonorgestrel-containing COC (COCLNG) users under 25 years.Methods: In this large, observational study, new users (first-ever users of an eligible COC or restarting with the same or a new eligible COC after a break of at least 2 months) of NOMAC-E2 and COCLNG were recruited in 12 countries in Europe, Australia, and Latin America and followed up via questionnaires for up to 2 years. Unintended pregnancy was expressed by the Pearl Index (PI; contraceptive failures/100 women-years). Crude (HRcrude) and adjusted hazard ratios (HRadj) were calculated. Mood and acne changes were defined as change of score from baseline. Weight change was defined as percent change of body weight.Results: Overall, 12,829 NOMAC-E2 users and 17,095 COCLNG users under 25 were followed-up. The risk of unintended pregnancy was statistically significantly lower in the NOMAC-E2 cohort; confirmed events: 30 NOMAC-E2 (PI 0.24; 95% CI, 0.16-0.35) vs 94 COCLNG (PI 0.51; 95% CI, 0.41-0.62). The HRcrude for unintended pregnancy comparing NOMAC-E2 to COCLNG was 0.47 (95% CI, 0.31-0.71) and the HRadj was 0.52 (95% CI, 0.34-0.78). No differential effect on acne, mood, and weight was observed between cohorts.Conclusions: NOMAC-E2 shows a significantly better contraceptive effectiveness in young women and has no differential effect on acne, mood, and weight compared to COCLNG.

NOMAC-E2 compares to LNG combined oral contraceptives in women over forty: real-world PRO-E2 study.

OBJECTIVE: To investigate safety and effectiveness of NOMAC-E2 and levonorgestrel-containing COCs (COCLNG) in users over 40. METHODS: In this large, observational study, new users1 of NOMAC-E2 and COCLNG were recruited in Europe, Australia, and Latin America and followed-up via questionnaires. Incidence of venous thromboembolism (VTE) was expressed as incidence rate (IR; events/104 women-years [WY]). Unintended pregnancy was expressed by the Pearl Index (PI; contraceptive failures/100 WY). Mood and weight changes were defined as mean changes in mood score and percentage of body weight. RESULTS: Overall, 7,762 NOMAC-E2 and 6,059 COCLNG users over 40 were followed-up. NOMAC-E2 showed no increased VTE risk compared to COCLNG; confirmed events: 5 NOMAC-E2 (IR 5.9; 95% CI, 1.9-13.7) vs 4 COCLNG (IR 5.9; 95% CI, 1.6-15.1). Unintended pregnancy did not differ substantially between cohorts; confirmed events: 4 NOMAC-E2 (PI 0.05; 95% CI, 0.01-0.13) vs 5 COCLNG (PI 0.08; 95% CI, 0.03-0.18). No differential effect on mood and weight was observed between cohorts. CONCLUSIONS: NOMAC-E2 can be considered a valid alternative to COCLNG in perimenopausal women.

COVID-19, gender and estroprogestins, what do we know?

The new coronavirus disease-19 (COVID-19) pandemic has rapidly spread all around the world, eliciting many questions and doubts about the pathogenesis of the disease and treatment. Mortality has been related to a prothrombotic state. Risk factors for the infection and for severe forms of COVID-19 have still to be defined. According to data collected, women appear to be less prone to severe forms of the disease and their mortality was lower than for men. The role of female hormones in the modulation of inflammation may be the reason behind this gender gap.Considering the prothrombotic state activated by the virus, hormone therapies have been placed under investigation as possible increasing risk factors for severe forms. Moreover, new vaccines and their rare thrombotic side effects have increased the concern about this issue.The goal of this review is to go over the mechanisms that lead up to thrombosis during COVID-19, trying to explain the possible reasons why women seem to be naturally protected. The expert opinions about whether to continue/discontinue hormonal therapies are reviewed. Moreover, available data about the so-called 'vaccine induced immune thrombotic thrombocytopaenia' caused by vaccines against COVID-19 are discussed.

Long-term treatment with α-lipoic acid and myo-inositol positively affects clinical and metabolic features of polycystic ovary syndrome.

The aim of this retrospective study was to evaluate the effects of a long-term treatment with α-lipoic acid (ALA) combined with myo-inositol (MI) on clinical and metabolic features of women with polycystic ovary syndrome (PCOS). Fifty-seven women with PCOS and a history of oligoamenorrhea were treated with MI and ALA (800 mg + 2000 mg per day). Forty-four of them had complete clinical charts and were considered eligible for the study. Information about cycle length and body mass index (BMI) was checked after 6, 12, and 24 months. After 12 months ovarian volume, total testosterone plasma levels and changes in hirsutism were also evaluated. The metabolic parameters were evaluated in 16 women after 6 and 18 months of the treatment. Cycle length was significantly reduced at 6 (p < .001), 12, and 24 months of treatment (p < .01). BMI showed a reduction only at 6 months (p < .05), thereafter returning similar to the basal values. No changes of testosterone and ovarian volume were observed. HOMA-IR and fasting insulin were unchanged, but the insulin response to a 3 h OGTT was improved after 6 (p < .01) and 18 months (p < .05) of treatment. No individual suffered from any adverse event. In conclusion, the combination of ALA and MI showed to be useful as long-term therapy in PCOS women, providing a normalization of the menstrual cycle and an amelioration of insulin levels with a high tolerability.

Treatment with d-chiro-inositol and alpha lipoic acid in the management of polycystic ovary syndrome.

To evaluate the effects of the combination of d-chiro inositol and alpha lipoic acid on menstrual cycles and insulin sensitivity in women with polycystic ovary syndrome (PCOS). Forty-one women with PCOS and 31 controls have been enrolled in the study. The menstrual cycle, BMI, homeostasis model assessment index (HOMA-I), and insulin secretion in response to an OGTT were evaluated before and after 6 months of treatment. During the observation period, the patients have been asked to not modify their diet and physical activity. The menstrual cycle length improved in 76.7% of the women. Ovulation was restored in 40%. During treatment, BMI significantly decreased (p<.002). The HOMA-I and insulin secretion were unchanged by treatment. However, when women were divided according to the presence of insulin resistance (IR; HOMA-I > 2.5), in those with IR the HOMA-I and the insulin secretion significantly decreased (p<.05 and p<.006). The association of d-chiro-inositol and alpha lipoic acid improves menstrual cycle length, restoring ovulation in the majority of women. Insulin sensitivity improved in women with IR only, confirming that in presence of IR the d-chiro-inositol has a role in restoring the insulin action overcoming the inactivity of epimerase in transforming myo-inositol to d-chiro inositol.

Features of polycystic ovary syndrome (PCOS) in women with functional hypothalamic amenorrhea (FHA) may be reversible with recovery of menstrual function.

OBJECTIVE: Since features of polycystic ovary syndrome (PCOS) have been found to be prevalent in women with functional hypothalamic amenorrhea (FHA), we wished to determine what happens to these features after recovery of menstrual function in FHA Design: Prospective cohort study. Twenty-eight women with FHA and 30 age-matched ovulatory controls were studied. METHODS: Twenty-eight women with FHA and 30 age-matched ovulatory controls were studied. We measured serum estradiol, LH, FSH, testosterone, DHEAS, anti-Mullerian hormone (AMH), body mass index, and ovarian morphology on transvaginal ultrasound. RESULTS: At baseline, 12 of the 28 women (43%) had increased AMH (>4.7 ng/mL), and higher testosterone and larger ovaries compared to the other 16 women with normal AMH. One year after recovery of menstrual function, in the 12 women with increased AMH, serum AMH, testosterone and ovarian size decreased, while LH and estradiol increased. At one year, only one of the 12 women in the high AMH group developed clinical features of PCOS. CONCLUSIONS: In the majority of women with FHA who have PCOS-like features, these features may be due to the hypothalamic state and appear to be reversible. Few women may develop clinical PCOS after recovery.

Observational prospective study on Lactobacillus plantarum P 17630 in the prevention of vaginal infections, during and after systemic antibiotic therapy or in women with recurrent vaginal or genitourinary infections.

We performed a prospective cohort parallel observational study on the use of Lactobacillus plantarum P 17630 in the prevention of vaginal infections. Eligible were women with a diagnosis of bacterial vaginosis (<15 days) and documented history of recurrent vaginal infections; and/or cystitis (<15 days); and/or treatment with antibiotics for bacterial respiratory tract infections during the week before the study entry. Study subjects were prescribed Lactobacillus plantarum P 17630 > 100.000.000 UFC one vaginal capsule per day for 6 days, then a capsule per week for 16 weeks. Eligible subjects were enrolled in two parallel cohorts: 85 women using (group A) and 39 not using (group B) Lactobacillus plantarum P 17630. The risk of recurrent infection within 4 months from the study entry, was higher among untreated women: multivariate OR 2.6 (95%CI 0.7-9.4). The modification of presence/intensity or symptoms was significant in both the study groups (p < .001). Impact statement What is already known on this subject? The Lactobacillus plantarum P 17630 has been shown to be active in the treatment of bacterial vaginosis and vaginal candidiasis. No data are available on its efficacy in the prevention of recurrent vaginal or urological infection or as a prevention strategy during systemic treatment with antibiotics. What do the results of this study add? This observational study suggests that Lactobacillus plantarum given for 4 months may lower the risk of recurrent infection in women with recurrent vaginal or genitourinary infection or after antibiotic systemic treatment for bacterial respiratory tract infection. The finding, however, is not statistically significant, possibly due to the lower than expected rate of infection observed in our population and consequently the limited power of the study. What are the implications of these findings for clinical practice and/or further research? New studies are needed in order to evaluate in different populations the role of Lactobacillus plantarum in lowering the risk of recurrent infection in a high-risk populations.

Comparison of two insulin sensitizers, metformin and myo-inositol, in women with polycystic ovary syndrome (PCOS).

Insulin resistance (IR) plays a pivotal role in PCOS. Insulin-sensitizer agents such as metformin and inositols have been shown to improve the endocrine and metabolic aspects of PCOS. The purpose of this study is to compare their effects on the clinical and metabolic features of the women with PCOS. Fifty PCOS women with IR and/or hyperinsulinemia were randomized to treatment with metformin (1500 mg/day) or myo-inositol (4 g/day). IR was defined as HOMA-IR >2.5, while hyperinsulinemia was defined as a value of AUC for insulin after a glucose load over the cutoff of our laboratory obtained in normal women. The Matsusa Index has been calculated. The women have been evaluated for insulin secretion, BMI, menstrual cycle length, acne and hirsutism, at baseline and after 6 months of therapy. The results obtained in both groups were similar. The insulin sensitivity improved in both treatment groups. The BMI significantly decreased and the menstrual cycle was normalized in about 50% of the women. No significant changes in acne and hirsutism were observed. The two insulin-sensitizers, metformin and myo-inositol, show to be useful in PCOS women in lowering BMI and ameliorating insulin sensitivity, and improving menstrual cycle without significant differences between the two treatments.

Increased anti-Mullerian hormone levels and ovarian size in a subgroup of women with functional hypothalamic amenorrhea: further identification of the link between polycystic ovary syndrome and functional hypothalamic amenorrhea.

BACKGROUND: Functional hypothalamic amenorrhea is a disorder characterized by cessation of menstrual cycles in the absence of organic disease. In most patients, it occurs in adult life after a stressful event and may be related to a condition of mild chronic energy deprivation. The endocrine pattern is characterized by low estrogen levels with an absent response to a progestogen challenge test and low-normal gonadotropin levels. A few studies have shown that some of these women may have some features of polycystic ovary syndrome; these features include an increased androgen response to gonadotropins, increased anti-Mullerian hormone levels, and altered ovarian morphology or increased ovarian size. These findings suggest a link between these 2 completely different disorders: functional hypothalamic amenorrhea and polycystic ovary syndrome. The importance of the possible coexistence of these disorders in some women is important for follow-up of these women and in their treatment if they desire to become pregnant. OBJECTIVE: To determine whether a subgroup of well-characterized women with functional hypothalamic amenorrhea may have the coexistence of polycystic ovary syndrome. STUDY DESIGN: Retrospective analysis of women with functional hypothalamic amenorrhea. Forty consecutive patients and 28 normal age-matched control patients were studied. Blood was obtained for serum anti-Mullerian hormone, androgens, and other hormone levels and all women had ovarian ultrasonographic measurements. RESULTS: In the entire group of women with functional hypothalamic amenorrhea, anti-Mullerian hormone and ovarian volume were greater than in control patients. In 13 patients (32.5%), anti-Mullerian hormone was elevated (>4.7 ng/mL, levels consistent with polycystic ovary syndrome) and in this group, ovarian volume was significantly greater than in the remaining patients with functional hypothalamic amenorrhea. Four of the 13 women with functional hypothalamic amenorrhea who had elevated anti-Mullerian hormone levels (10%), also had ovarian volume ≥10 cc (consistent with polycystic ovarian syndrome). In these patients all studied androgens were in the upper normal range or slightly elevated despite low-normal gonadotropins; mean total testosterone was significantly greater than in the other patients with increased anti-Mullerian hormone values with normal ovarian size (P<.05.) Six other women with functional hypothalamic amenorrhea who had increased anti-Mullerian hormone also had isolated elevations of some androgen levels, but mean testosterone and ovarian size were normal. CONCLUSIONS: As many as 10% of women with functional hypothalamic amenorrhea may have the coexistence of polycystic ovary syndrome. Because no signs or symptoms of this disorder were reported by these women before the appearance of the amenorrhea, it does not seem to be a coincidental relationship. The possibility that functional hypothalamic amenorrhea favors the appearance of polycystic ovary syndrome or more likely, that a mild (ovulatory) phenotype of polycystic ovary syndrome predisposes to the development of functional hypothalamic amenorrhea should be considered. Possible mechanisms are unclear and need to be investigated but may involve common vulnerabilities such as psychologic and mood disturbances.

AMH MEASUREMENT VERSUS OVARIAN ULTRASOUND IN THE DIAGNOSIS OF POLYCYSTIC OVARY SYNDROME IN DIFFERENT PHENOTYPES.

OBJECTIVE: This study was designed to assess the value of serum anti-Müllerian hormone (AMH) in the diagnosis of polycystic ovary syndrome (PCOS) in various phenotypes and to assess ovarian ultrasound parameters. METHODS: We performed a retrospective matched controlled study of 113 females with various PCOS phenotypes and 47 matched controls. The diagnostic utility of AMH measurement and ovarian ultrasound were compared. Using receiver operating characteristic (ROC) curve analyses, the threshold for AMH (>4.7 ng/mL) and ultrasound parameters (follicle number per ovary [FNPO] >22 and ovarian volume [OV] >8 cc) were established. RESULTS: In the entire cohort, AMH had a low sensitivity of 79%; while FNPO and OV were 93% and 68%, respectively. Specificities ranged from 85 to 96%. In classic anovulatory PCOS, AMH exhibited a sensitivity of 91%, and for FNPO and OV the corresponding sensitivities were 92% and 72%. In the ovulatory phenotype, AMH sensitivity was only 50%, while FNPO and OV were 95% and 50%, respectively. In the nonhyperandrogenic phenotype, the sensitivity of AMH was 53% while those for FNPO and OV were 93% and 67%. CONCLUSION: AMH does not appear to be helpful for all subjects with PCOS but may be of some value in those who are anovulatory. However, FNPO was highly sensitive in all phenotypes, and was the single best criterion assessed for all subjects, suggesting the important role of ultrasound.

Discontinuation of modern hormonal contraceptives: an Italian survey.

OBJECTIVES: The aim of the study was to examine, in a sample of Italian women, the rate of discontinuation of use of hormonal contraception. METHODS: In a retrospective cross-sectional study, data were collected from a chart review of 1809 women using or stopping the hormonal contraceptive prescribed by their physician. The name of the contraceptive and the reason for discontinuation were taken from the charts. The differences between the methods regarding reasons for discontinuation were analysed. RESULTS: Of the 1809 women examined, 34.9% had discontinued their hormonal contraception: 6.9% did so for non-method-related reasons, 20.5% due to minor side effects, 4.4% due to major side effects and 3.8% due to difficulties with compliance. Irregular bleeding, weight gain and headache were the main reasons reported for discontinuation. Pills containing 30 µg or 20 µg ethinylestradiol (EE) and the vaginal ring were the most used contraceptive methods. Women using the vaginal ring discontinued less frequently compared with pill users (p < .005). Pills containing 20 µg and 30 µg EE had the same discontinuation rate. Venous thrombosis was the most frequently reported major side effect leading to discontinuation. CONCLUSION: About one-third of women who used modern hormonal contraceptives discontinued the method. Although the percentage of women who gave up as a result of minor side effects was lower than it used to be, and the use of low doses of EE by the vaginal route has decreased the rate of discontinuation, physicians should counsel women about the possibility of side effects and encourage them to seek advice before stopping.

Unilateral adnexal agenesis and dermoid cyst: fertility implications.

We report the loss of potential fertility in a 23-year-old nulliparous woman who attended the outpatient gynaecological endocrinology clinic for amenorrhea and hot flushes started after a laparoscopic surgery for dermoid cyst. During surgery an unilateral ovarian and fallopian tube agenesis were found. The hormonal evaluation was performed. The results evidenced high plasma levels of LH and FSH. Their values were 56.6 and 121.3 mUI/ml, respectively. The concentrations of plasma E2 were < 20 pg/ml and of AMH were <0.08 ng/ml. Genetic analysis showed normal karyotype (46, XX). We think that if an embryological defect is suspected, an appropriate counselling about fertility preservation along with the assessment of hormonal levels before ovarian surgery should be recommended to all women in the reproductive age in order to offer future reproductive chances.

A review of the pharmacology, clinical outcomes, and real-world effectiveness, safety, and non-contraceptive effects of NOMAC/E2.

Selecting an appropriate oral contraceptive can be challenging for healthcare professionals due to the abundance of marketed contraceptive options with different clinical and real-world effectiveness and safety profiles. Nomegestrol acetate + 17ß-estradiol (NOMAC/E2) is a combined oral contraceptive (COC) that inhibits ovulation by suppressing ovarian function by a 17-hydroxy-progesterone derivative and an estrogen identical to that endogenously produced by the ovaries. This narrative review examines clinical and real-world studies of NOMAC/E2 based on a background literature search using PubMed and Google Scholar. The review outlines the pharmacology of NOMAC/E2, including its progestational activity, pharmacokinetics, and effects on carbohydrate metabolism, lipid metabolism, and coagulation parameters, and summarizes key clinical efficacy and safety data that led to the approval of NOMAC/E2 in Europe, Brazil, and Australia. To help elucidate how NOMAC/E2 clinical trial data translate into a real-world setting, this review describes the effectiveness and safety of NOMAC/E2 in prospective studies that include over 90,000 users (half of whom received NOMAC/E2), outlining its effects on risk of thrombosis, menstrual bleeding patterns, weight, mood, acne, bone health, and patient quality of life. Non-contraceptive benefits of NOMAC/E2 for women with endometriosis, dysmenorrhea, or pre-menstrual dysphoric disorder are also discussed. These data demonstrate that NOMAC/E2 has a long half-life and rapid absorption, is effective at preventing unwanted pregnancies, and exhibits a favorable safety profile in both clinical trials and real-world settings. Importantly, NOMAC/E2 is not associated with increased risk of venous thromboembolism, a major safety concern of healthcare professionals for women receiving hormonal contraceptives. This review highlights NOMAC/E2 as a differentiated option among COCs and could help inform oral contraceptive choice to ultimately improve patient management and outcomes in real-world settings.

Multidisciplinary care of peripartum heart failure: A scientific statement of the Heart Failure Association of the ESC.

Heart failure is the most common cardiovascular complication during pregnancy and the postpartum period. It is associated with increased risk of maternal morbidity and mortality as well as potentially life-threatening foetal pathology. Management of heart failure in pregnancy requires expert knowledge of cardiovascular disease as well as obstetrics which underscores the importance of multidisciplinary cardio-obstetrics teams in order to optimize diagnosis, treatment and outcome. This includes counselling of women at risk before and during the course of pregnancy in order to strengthen the relationship between medical specialists and patients, as well as to allow patient-centred delivery of care and improve quality of life.

An overview of the development of combined oral contraceptives containing estradiol: focus on estradiol valerate/dienogest.

Natural estrogens such as estradiol (E(2)) or its valerate ester (E(2)V) offer an alternative to ethinyl estradiol (EE). E(2)-containing combined oral contraceptives (COCs) have demonstrated sufficient ovulation inhibition and acceptable contraceptive efficacy. However, earlier formulations were generally associated with unacceptable bleeding profiles. Two E(2)V-containing preparations have been approved to date for contraceptive use: E(2)V/cyproterone acetate (CPA) (Femilar(®); only approved in Finland and only in women >40 years or women aged 35-40 years in whom a COC containing EE is not appropriate) and E(2)V/dienogest (DNG; Qlaira(®)/Natazia(®)). The objective of the current review is to provide an overview of the development of COCs containing natural estrogen, highlighting past issues and challenges faced by earlier formulations, as well as the current status and future directions. The majority of information to date pertains to the development of E(2)V/DNG.