Extended use of levonorgestrel-releasing intrauterine system (LNG-IUS) 52 mg: A population pharmacokinetic approach to estimate in vivo levonorgestrel release rates and systemic exposure including comparison with two other LNG-IUSs

OBJECTIVE

To characterize performance of levonorgestrel-releasing intrauterine system (LNG-IUS) 52mg (Mirena) over 8 years of use and facilitate comparisons with LNG-IUS 19.5mg and LNG-IUS 13.5mg.

STUDY DESIGN

We estimated in vivo levonorgestrel (LNG) release rates and LNG plasma/serum concentrations for LNG-IUS 52mg up to 8 years of use with a population pharmacokinetic (popPK) approach using data from the Mirena Extension Trial (MET) and earlier clinical trials. We compared these with previously published release rates and exposure data for LNG-IUS 19.5mg and 13.5mg. Our 8-year popPK and release models were developed based on measured plasma/serum LNG and sex hormone-binding globulin concentrations and residual LNG content from removed LNG-IUS 52mg devices.

RESULTS

Model-based estimated LNG release rates for LNG-IUS 52mg decreased from ∼21 µg/d after insertion to ∼7.0 µg/d after 8 years, similar to LNG-IUS 19.5mg after 5 years (7.6 µg/d) and higher than LNG-IUS 13.5mg after 3 years (5.5 µg/d). Model-based estimated and measured plasma/serum LNG concentrations showed satisfactory agreement. Average model-based estimated LNG concentrations after 8 years of LNG-IUS 52mg use (100 ng/L [coefficient of variance 39.9%]) were similar to LNG-IUS 19.5mg after 5 years (84.8 ng/L [39.9%]) and higher than LNG-IUS 13.5mg after 3 years (58.1 ng/L [40.8%]).

CONCLUSIONS

The 8-year release and popPK models provide reliable in vivo LNG release rates and concentration estimates, respectively, facilitating direct comparisons between the 3 studied LNG-IUSs. LNG release rates from LNG-IUS 52mg at 8 years are similar to LNG-IUS 19.5mg at 5 years and higher than LNG-IUS 13.5mg at 3 years.

IMPLICATIONS

Levonorgestrel release from intrauterine system reservoirs declines with duration of use in a predictable way, and in relation to the initial load. As release rates and plasma concentrations of levonorgestrel may influence endometrial and systemic side effects, these data may assist clinical decision-making.

The effect of a combined indomethacin and levonorgestrel-releasing intrauterine system on short-term postplacement bleeding profile: a randomized proof-of-concept trial

BACKGROUND

Long-acting reversible contraceptives, including hormonal levonorgestrel-releasing intrauterine systems, are the most effective methods of reversible contraception. However, unfavorable bleeding, particularly during the first months of use, is one of the most important reasons for discontinuation or avoidance. Minimizing this as early as possible would be highly beneficial. Nonsteroidal anti-inflammatory drugs inhibiting prostaglandin synthesis are known to reduce bleeding and pain at time of menses. A levonorgestrel-releasing intrauterine system has been developed with an additional reservoir containing indomethacin, designed to be released during the initial postplacement period.

OBJECTIVE

This proof-of-concept study aimed to establish whether the addition of indomethacin to the currently available levonorgestrel-releasing intrauterine system (average in vivo levonorgestrel release rate of 8 μg/24 h during the first year of use) reduces the number of bleeding and spotting days during the first 90 days of use compared with the unmodified system. The dose-finding analysis included 3 doses of indomethacin-low (6.5 mg), middle (12.5 mg), and high (15.4 mg)-to determine the ideal dose of indomethacin to reduce bleeding and spotting days with minimal side-effects.

STUDY DESIGN

This was a multicenter, single-blinded, randomized, controlled phase II trial conducted between June 2018 and June 2019 at 6 centers in Europe. Three indomethacin dose-ranging treatment groups (low-, middle-, and high-dose indomethacin/levonorgestrel-releasing intrauterine system) were compared with the unmodified levonorgestrel-releasing intrauterine system group, with participants randomized in a 1:1:1:1 ratio. The primary outcome was the number of uterine bleeding and spotting days over a 90-day reference (treatment) period. Secondary outcomes were the number of women showing endometrial histology expected for intrauterine levonorgestrel application and the frequency of treatment-emergent adverse events. Point estimates and 2-sided 90% credible intervals were calculated for mean and median differences between treatment groups and the levonorgestrel-releasing intrauterine system without indomethacin. Point and interval estimates were determined using a Bayesian analysis.

RESULTS

A total of 174 healthy, premenopausal women, aged 18 to 45 years, were randomized, with 160 women eligible for the per-protocol analysis set. Fewer bleeding and spotting days were observed in the 90-day reference period for the 3 indomethacin/levonorgestrel-releasing intrauterine system dose groups than for the levonorgestrel-releasing intrauterine system without indomethacin group. The largest reduction in bleeding and spotting days was achieved with low-dose indomethacin/levonorgestrel-releasing intrauterine system, which demonstrated a point estimate difference of -32% (90% credible interval, -45% to -19%) compared with levonorgestrel-releasing intrauterine system without indomethacin. Differences for high- and middle-dose indomethacin/levonorgestrel-releasing intrauterine system groups relative to levonorgestrel-releasing intrauterine system without indomethacin were -19% and -16%, respectively. Overall, 97 women (58.1%) experienced a treatment-emergent adverse event considered related to the study drug, with similar incidence across all treatment groups including the unmodified levonorgestrel-releasing intrauterine system. These were all mild or moderate in intensity, with 6 leading to discontinuation. Endometrial biopsy findings were consistent with effects expected for the levonorgestrel-releasing intrauterine system.

CONCLUSION

All 3 doses of indomethacin substantially reduced the number of bleeding and spotting days in the first 90 days after placement of the levonorgestrel-releasing intrauterine system, thus providing proof of concept. Adding indomethacin to the levonorgestrel-releasing intrauterine system can reduce the number of bleeding and spotting days in the initial 90 days postplacement, without affecting the safety profile, and potentially improving patient acceptability and satisfaction.

Associations between model-predicted rivaroxaban exposure and patient characteristics and efficacy and safety outcomes in the prevention of venous thromboembolism

Anticoagulant plasma concentrations and patient characteristics might affect the benefit–risk balance of therapy. The study objective was to assess the impact of model-predicted rivaroxaban exposure and patient characteristics on outcomes in patients receiving rivaroxaban for venous thromboembolism (VTE) prophylaxis (VTE-P) after hip/knee replacement surgery. Post hoc exposure–response analyses were conducted using data from the phase 3 RECORD1–4 studies, in which 12,729 patients were randomized to rivaroxaban 10 mg once daily or enoxaparin for ≤ 39 days. Multivariate regression approaches were used to correlate model-predicted individual rivaroxaban exposures and patient characteristics with outcomes. In the absence of measured rivaroxaban exposure, exposure estimates were predicted based on individual increases in prothrombin time (PT) and by making use of the known correlation between rivaroxaban plasma concentration and dynamics of PT. No significant associations between rivaroxaban exposure and total VTE or major bleeding were identified. A significant association between exposure and a composite of major or non-major clinically relevant (NMCR) bleeding from day 4 after surgery was observed. The relationship was shallow, with an approximate predicted absolute increase in a composite of major or NMCR bleeding from 1.08 [95% confidence interval (CI) 0.76–1.54] to 2.18% (95% CI 1.51–3.17) at the 5th and 95th percentiles of trough plasma concentration, respectively. In conclusion, based on the underlying data and analysis, no reliable target window for exposure with improved benefit–risk could be identified within the investigated exposure range. Hence, monitoring rivaroxaban levels is unlikely to be beneficial in VTE-P.

Exposure-response relationship of regorafenib efficacy in patients with hepatocellular carcinoma

PURPOSE

To explore the relationship between regorafenib exposure and efficacy in patients with hepatocellular carcinoma (HCC) who had disease progression during sorafenib treatment (RESORCE).

METHODS

Exposure-response (ER) analyses for regorafenib were performed using data from a phase 3, randomized, placebo-controlled trial (RESORCE). Patients received 160mg regorafenib or placebo once daily (3weeks on/1week off in a 4-week cycle) with best supportive care until disease progression, death, or unacceptable toxicity. Kaplan-Meier analyses for overall survival (OS) and time-to-progression (TTP) were performed in which regorafenib-treated patients were grouped into four categories according to their estimated average exposure over 4weeks in cycle 1. While this analysis primarily focused on efficacy, a potential correlation between exposure and treatment-emergent adverse events (TEAEs) was also evaluated. If any differences were observed between Kaplan-Meier plots, the ER analysis continued with a multivariate Cox regression analysis to evaluate the correlation between exposure quartile categories and the efficacy and safety parameters while taking into consideration the effect of the predefined clinically relevant demographic and baseline covariates. The functional form of the ER relationship within the regorafenib treatment group was subsequently evaluated.

RESULTS

Based on visual assessment of the Kaplan-Meier plots, no meaningful relationship between the exposure categories and TEAEs were observed, although median OS and TTP tended to be longer in the higher exposure categories. Further ER analyses, which considered the effects of predefined covariates and the different shapes of the ER relationship, focused on efficacy. The baseline risk factors Eastern Cooperative Oncology Group (ECOG) performance status ≥1, alpha-fetoprotein levels ≥400ng/ml, and aspartate transaminase or alanine transaminase levels >3×upper limit of normal were significantly associated with OS (P<0.01) and age was associated with TTP. A statistically significant difference was found for OS and TTP between patients receiving regorafenib compared with those receiving placebo in the multivariate ER analysis (P<0.01) in favor of regorafenib. However, within the group of regorafenib-treated patients, the effect of regorafenib exposure on efficacy, either by estimating four effect sizes for each quartile, or by including a continuous linear or nonlinear relationship between individual exposure and efficacy, was not significant (P>0.01) and relatively flat. This suggests that increasing regorafenib exposure would not result in a meaningful increase in OS or TTP.

CONCLUSION

After considering the baseline risk factors: ECOG performance status, alpha-fetoprotein levels, and hepatic function for OS and age for TTP, the ER analysis in regorafenib-treated patients showed similar efficacy over the entire predicted exposure range in RESORCE. This supports the selected regorafenib dose of 160mg once daily (3weeks on/1week off in a 4-week cycle) in patients with intermediate or advanced HCC who have experienced disease progression on sorafenib.

Exposure-response (ER) relationship of regorafenib (REG) in patients with hepatocellular carcinoma (HCC)

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Background: In the phase 3 RESORCE trial (N = 573), REG (160 mg QD, 3 weeks on/1 week off) significantly (P < 0.001) improved overall survival (OS) versus placebo in patients with HCC who progressed during sorafenib treatment (HR 0.63; 95% CI 0.50‒0.79). This exploratory analysis evaluated the ER relationship between REG and both OS and time-to-progression (TTP). Methods: Exposure estimates were available for 327 and 315 patients for the OS and TTP analysis, respectively. A multivariate Cox proportional hazard analysis was used to evaluate differences between exposure quartiles and efficacy, taking into consideration all preselected baseline covariates. Subsequently, the functional form of the ER relationship within the REG group was evaluated. Results: The baseline risk factors ECOG status, AFP category, and AST/ALT baseline levels were significantly associated with OS (P < 0.01), with higher HRs for ECOG category ≥ 1, AFP levels ≥ 400 ng/mL, and AST/ALT levels > 3 x ULN. For TTP, a significant correlation (P < 0.01) with age was observed, with a higher HR for patients < 65 years of age. After adjusting for these baseline risk factors, the average exposure over the first 28 days grouped in exposure quartiles for REG was significantly associated with OS and TTP (P < 0.01), i.e. the HR in all exposure quartiles was < 1 versus placebo. By contrast, the difference in HR between exposure quartiles was found to be small and not significant. While no statistically significant ER relationship could be identified between (continuous) individual exposure and efficacy in the REG group, the analysis of the functional form of the ER relationship indicates that OS and TTP improved with an increase in exposure, under the assumption of a linear and a non-linear ER relationship. Conclusions: In addition to a significant difference in OS and TTP between REG and placebo, a trend towards improved efficacy was observed with an increase in REG exposure in HCC patients, which was not statistically significant when taking into consideration ECOG status, AFP level, and AST/ALT risk factors (OS) or age (TTP). Therefore, similar efficacy was observed in patients with HCC who started on REG 160 mg QD 3 weeks on/1 week off over the entire exposure range. Clinical trial information: NCT01774344.

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.

Impact of body mass index on suppression of follicular development and ovulation using a transdermal patch containing 0.55-mg ethinyl estradiol/2.1-mg gestodene: a multicenter, open-label, uncontrolled study over three treatment cycles

BACKGROUND

Body mass index (BMI) may influence ovulation inhibition resulting from transdermal hormone delivery. Investigation of this effect is important given the high prevalence of obesity in the US.

STUDY DESIGN

This open-label, uncontrolled, Phase 2b trial stratified 173 women (18-35 years) according to three BMI groups (Group 1, n = 56, ≤ 30 kg/m²; Group 2, n = 55, > 30 kg/m² and ≤ 35 kg/m²; and Group 3, n = 47, > 35 kg/m²). Women used a contraceptive patch containing 0.55-mg ethinyl estradiol (EE) and 2.1-mg gestodene (GSD). The EE/GSD patch was used weekly for three 28-day cycles (one patch per week for 3 consecutive weeks followed by a 7-day, patch-free interval), and its effect on ovulation was assessed by the Hoogland score, a composite score that comprises transvaginal ultrasound and estradiol (E₂) and progesterone levels every 3 days in Cycles 2 and 3. Evaluation of pharmacokinetic parameters was a secondary aim of the study, and blood samples for analytic determination of EE, GSD and sex hormone-binding globulin were taken during the pretreatment cycle, Cycle 2 and Cycle 3. Compliance was assessed using diary information and serum drug levels.

RESULTS

In the per-protocol set, there were only six ovulations during the study, and no participant ovulated in both study cycles. One ovulation occurred in Group 1, three in Group 2 and two in Group 3. Ovulation inhibition was unaffected by BMI; in all groups, most participants had Hoogland scores of 1 or 2 (i.e., follicle-like structures < 13 mm: Group 1, ≤ 30 kg/m², 80.0% in Cycle 2, 85.7% in Cycle 3; Group 2, > 30 kg/m² and ≤ 35 kg/m², 61.4% in Cycle 2, 75.0% in Cycle 3; Group 3, > 35 kg/m², 78.0% in Cycle 2, 72.5% in Cycle 3). Serum levels of follicle-stimulating hormone, luteinizing hormone, E2 and progesterone were similar between groups. Body weight had a limited effect on EE clearance that was unlikely to be clinically relevant.

CONCLUSION

The EE/GSD patch provided effective ovulation inhibition, even in women with higher BMI.

IMPLICATIONS

This is the largest-to-date study of physiologic endpoints and found no clinically important differences in ovarian suppression among obese and normal-weight users of the EE/GSD contraceptive patch, thus providing reassurance that obese women can achieve the same high level of contraceptive protection as normal-weight users.

Current trends in hormone replacement therapy: perceptions and usage

OBJECTIVE

To determine whether physicians' confidence in the use of hormone replacement therapy (HRT) for climacteric symptoms has been affected by the negative media interpretation of data from landmark studies investigating HRT usage such as the Women's Health Initiative (WHI) study.

METHODS

A structured questionnaire was completed via the internet by European and US gynecologists, obstetrician/gynecologists and general practitioners - all experienced in treating women with climacteric symptoms.

RESULTS

Six hundred physicians completed the survey in six countries. Overall, 98% agreed that the menopause significantly affects quality of life and 97% considered that the majority/all of their patients experienced positive benefits from HRT. Most physicians (90%) believed the benefits of HRT outweigh the risks in suitable patients, and 92% would prescribe HRT for themselves/spouse/family. For treatment of atrophic vaginitis, 86% agreed that local estrogen was the most effective course of action. While 82% of participants were aware of the latest recommendations on low-dose HRT, and estrogen dose in particular, 67% cited lowering the progestogen dose as important. With regard to the recent negative media coverage on HRT, 78% of physicians felt this was unjustified.

CONCLUSIONS

These results provide reassurance that health-care professionals in Europe and the US, experienced in treating women with climacteric symptoms, have not lost confidence in HRT. Despite a consensus on the importance of lowering the dose of HRT and a focus on estrogen, there remains a need to heighten prescribers' awareness on the pivotal role that a lower progestogen dose plays in optimizing the risk-benefit profile.

A complex mathematical model of the human menstrual cycle

Despite the fact that more than 100 million women worldwide use birth control pills and that half of the world's population is concerned, the menstrual cycle has so far received comparatively little attention in the field of mathematical modeling. The term menstrual cycle comprises the processes of the control system in the female body that, under healthy circumstances, lead to ovulation at regular intervals, thus making reproduction possible. If this is not the case or ovulation is not desired, the question arises how this control system can be influenced, for example, by hormonal treatments. In order to be able to cover a vast range of external manipulations, the mathematical model must comprise the main components where the processes belonging to the menstrual cycle occur, as well as their interrelations. A system of differential equations serves as the mathematical model, describing the dynamics of hormones, enzymes, receptors, and follicular phases. Since the processes take place in different parts of the body and influence each other with a certain delay, passing over to delay differential equations is deemed a reasonable step. The pulsatile release of the gonadotropin-releasing hormone (GnRH) is controlled by a complex neural network. We choose to model the pulse time points of this GnRH pulse generator by a stochastic process. Focus in this paper is on the model development. This rather elaborate mathematical model is the basis for a detailed analysis and could be helpful for possible drug design.