Methodological Issues in Preclinical Mouse Efficacy Studies of Adenomyosis

Preclinical models of endometriosis and interstitial cystitis/bladder pain syndrome: an Innovative Medicines Initiative-PainCare initiative to improve their value for translational research in pelvic pain

ABSTRACT

Endometriosis (ENDO) and interstitial cystitis/bladder pain syndrome (IC/BPS) are chronic pain conditions for which better treatments are urgently needed. Development of new therapies with proven clinical benefit has been slow. We have conducted a review of existing preclinical in vivo models for ENDO and IC/BPS in rodents, discussed to what extent they replicate the phenotype and pain experience of patients, as well as their relevance for translational research. In 1009 publications detailing ENDO models, 41% used autologous, 26% syngeneic, 18% xenograft, and 11% allogeneic tissue in transplantation models. Intraperitoneal injection of endometrial tissue was the subcategory with the highest construct validity score for translational research. From 1055 IC/BPS publications, most interventions were bladder centric (85%), followed by complex mechanisms (8%) and stress-induced models (7%). Within these categories, the most frequently used models were instillation of irritants (92%), autoimmune (43%), and water avoidance stress (39%), respectively. Notably, although pelvic pain is a hallmark of both conditions and a key endpoint for development of novel therapies, only a small proportion of the studies (models of ENDO: 0.5%-12% and models of IC/BPS: 20%-44%) examined endpoints associated with pain. Moreover, only 2% and 3% of publications using models of ENDO and IC/BPS investigated nonevoked pain endpoints. This analysis highlights the wide variety of models used, limiting reproducibility and translation of results. We recommend refining models so that they better reflect clinical reality, sharing protocols, and using standardized endpoints to improve reproducibility. We are addressing this in our project Innovative Medicines Initiative-PainCare/Translational Research in Pelvic Pain.

An overview of the current status of clinical trials on endometriosis: issues and concerns

OBJECTIVE

To examine and compare differences, if any, between industry- and nonindustry-sponsored clinical trials on endometriosis and to evaluate the effect of prior published positive preclinical results, or lack thereof, on trial status.

DESIGN

Cross-sectional study of clinical trials on endometriosis that evaluate drugs/biologicals registered at ClinicalTrials.gov as of July 3, 2013.

SETTING

University-affiliated hospital.

PATIENT(S)

None.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Trial status, size, phase, and duration; use of comparator groups; drug classes, number of arms, targeting conditions; and presence or absence of prior positive preclinical results before the launch of the trial.

RESULT(S)

Eighty trials were identified. The trials sponsored by industry and non-industry have distinct features, differing in trial status, phase, comparator, drug classes, number of arms, trial size, and duration. The phase II/III trials are predominantly industry supported, but these trials frequently use placebo as the comparator. Trials launched without prior published preclinical results do not seem to fare well, although the presence of such studies is no guarantee for success.

CONCLUSION(S)

Questions as to whether the drug on trial is truly superior to the best available drug or of its cost-benefit profile are overlooked in most cases. There seems to be a deluge of "me-too" drugs with equivocal superiority over existing drugs and cost-benefit profiles. Because clinical trials are time-consuming, no blockbuster drug for endometriosis seems to be on the horizon yet.

Epigallocatechin-3-gallate reduces myometrial infiltration, uterine hyperactivity, and stress levels and alleviates generalized hyperalgesia in mice induced with adenomyosis

In an effort to search for novel therapeutics for adenomyosis, we sought to determine whether treatment with epigallocatechin-3-gallate (EGCG) would suppress the myometrial infiltration, improve pain behavior, lower stress level, and reduce uterine contractility in a mice model of adenomyosis. Adenomyosis was induced in 28 female ICR mice neonatally dosed with tamoxifen, while another 12 (group C) were dosed with solvent only, which served as a blank control. Starting from 4 weeks after birth, hot plate test was administrated to all mice every 4 weeks. At the 16th week, all mice induced with adenomyosis were randomly divided into 3 groups: low-dose EGCG (5 mg/kg), high-dose EGCG (50 mg/kg), and untreated. Group C received no treatment. After 3 weeks of treatment, the hot plate test was administered again, a blood sample was taken to measure the plasma corticosterone level by enzyme-linked immunosorbent assay, and then all mice were sacrificed. The depth of myometrial infiltration and uterine contractility were also evaluated. We found that the induction of adenomyosis resulted in progressive generalized hyperalgesia, along with elevated amplitude and frequency of uterine contractions as well as elevated plasma corticosterone levels. The EGCG treatment dose dependently suppressed myometrial infiltration, improved generalized hyperalgesia, reduced uterine contractility, and lowered plasma corticosterone levels. These results suggest that induced adenomyosis causes pain and elevates stress levels in mice. Uterine hyperactivity may contribute to dysmenorrhea in women with adenomyosis who might also have elevated stress level due to pain. The EGCG appears to be a promising compound for treating adenomyosis.