{"paper_id":"ab1451f5-0688-43df-9b0f-e77e1f98217b","body_text":"ENDOMETRIOSIS (P STRA TTON, SECTION EDITOR)\nMethodological Issues in Preclinical Mouse Efficacy Studies\nof Adenomyosis\nSun-Wei Guo\nPublished online: 30 June 2012\n# Springer Science+Business Media, LLC 2012\nAbstract Adenomyosis is a benign, non-neoplastic gyne-\ncologic disorder with a poorly understood pathogenesis. Its\ntreatment has been a challenge, with hysterectomy being\nconsidered the definitive therapy for severe adenomyosis.\nMore efficacious drugs with better side-effect and cost pro-\nfiles are sorely needed. Unfortunately, there is a dearth of\nregistered clinical trials on adenomyosis, and the registered\ntrials are not testing new compounds. This appears to sug-\ngest a loss in translating discoveries made in preclinical\nstudies to clinical practice. This article presents a systematic\nreview of all published mouse efficacy studies of adeno-\nmyosis aimed at the evaluatio n of potential therapeutic\ncompounds, focusing on methodological quality and de-\nscribing the limitations of the published studies. The com-\nplex issues involved in transl ating preclinical studies to\nclinical practice will be summarized. Lastly, some method-\nological issues in mouse efficacy studies of adenomyosis\nwill be highlighted, with the aim to improve such studies in\nthe future.\nKeywords Adenomyosis . Animal studies . Drug\ndevelopment . Efficacy . Methodological quality . Mouse .\nOutcome measures\nIntroduction\nAdenomyosis is a benign, non-neoplastic gynecologic disor-\nder characterized by the ectopic proliferation of endometrial\ntissue into the myometrium with smooth muscle hypertro-\nphy. A common disorder with a prevalence in hysterecto-\nmy specimens ranging from 14 % to 66 % [ 1], its\ncommon presenting symptoms include abnormal uterine\nbleeding, dysmenorrhea, and subfertility [ 2], although a\nsizeable portion of patients are asymptomatic [ 3]. Dysmen-\norrhea is the most debilitating symptom [ 4]. Treatment of\nadenomyosis has been a challenge, with hysterectomy\nbeing considered the definitive therapy for severe adeno-\nmyosis [ 5]. Uterine artery embolization (UAE) also has\nshown promise, but a recent review noted that the recur-\nrence risk after UAE is high [ 6].\nAlthough adenomyosis is hormone-sensitive, progesto-\ngenic agents are not very effective, and gonadotrophin-\nreleasing hormone (GnRH) agonists induce suppression of\nadenomyosis, yet their use is restricted by short duration [ 7].\nIn addition, the symptoms quickly reappear after discontin-\nuation of GnRH agonist therapy [ 8]. While the insertion of a\nlevonorgestrel-releasing intrauterine system (LNG-IUS) has\nbeen reported to result in a reduction in adenomyosis-\nassociated pain and abnormal bleeding [ 9], side effects such\nas spotting are reported in one third of the women, with\nmany women experiencing oligomenorrhea [ 9]. Conse-\nquently, more efficacious drugs with better side-effect and\ncost profiles are sorely needed.\nDespite this unmet medical need, a search of clinical trial\nregistries suggests few new agents are being investigated.\nCompared with 1,679 trials on ovarian cancer, 146 on\nuterine fibroids, and 132 on endometriosis, only 15 trials\non adenomyosis were registered ( www.ClinicalTrials.gov,\naccessed on June 5, 2012). Among the 15 trials, 1 was not\nyet recruiting, 1 was active but not recruiting, 3 were com-\npleted, 4 were recruiting, and 6 had an “unknown” status,\nmeaning that “the trial status has not been verified in more\nt h a n2y e a r s .” Of the 15 trials, only 4 trials evaluated\nS.-W. Guo (*)\nShanghai Obstetrics and Gynecology Hospital, Fudan University,\n419 Fangxie Road,\nShanghai 200011, China\ne-mail: hoxa10@gmail.com\nCurr Obstet Gynecol Rep (2012) 1:138 –145\nDOI 10.1007/s13669-012-0018-3\n\nnonsurgical treatment: one on progestin, one on acupunc-\nture, one on LUS-IUD, and one on letrozole, an aromatase\ninhibitor. There are no novel compounds currently under\ntrial evaluation. The completed trial on letrozole indicated\nthat its efficacy, evaluated 12 weeks after treatment, was\ncomparable with the GnRH agonist [ 10]. Thus, the research\nand development (R&D) for medical treatment of adeno-\nmyosis seem to be limited.\nOne indispensable component of preclinical research in\ndrug R&D is animal efficacy studies. This review will focus\non the methodology of mouse efficacy studies through a\nsystematic review of all published mouse efficacy studies of\nadenomyosis evaluating potential therapeutic compounds\nand will describe the limitations in these studies. With the\nexception of danazol and danazol-containing intrauterine\ndevices (IUDs) that were tested clinically before mouse\nstudies, no compound evaluated preclinically has been test-\ned clinically or in clinical trials, at least not within the public\ndomain. The completed trial on letrozole was conducted\nwithout an animal study demonstrating its therapeutic po-\ntential. Many complex issues are involved in translating\npreclinical studies to clinical practice. Some methodological\naspects of preclinical animal studies of adenomyosis will be\nreviewed, with the aim to improve mouse efficacy studies of\nadenomyosis.\nMethods\nA systematic and comprehensive search of PubMed was per-\nformed for all studies published up to June 5, 2012, using the\nfollowing search terms: “adenomyosis” or “endometriosis”in\ncombination with“mouse,”“ mice,”“ rat,”“ rodent,” or “animal\nmodel.” Included studies used rodent models of adenomyosis,\nnot endometriosis and evaluated the therapeutic potential of a\ncompound or compounds. The search was limited to publica-\ntions written in English. Thus, articles on endometriosis, but\nnot adenomyosis per se, were excluded. The focus on mouse\nstudies is of necessity because no other animal models of\nadenomyosis have been used for efficacy studies.\nThe search resulted in 14 studies of mouse models of\nadenomyosis [ 11–20, 21, 22, 23, 24]. Of the 14 studies,\nfour were excluded because one study started the interven-\ntion from the day of birth [ 24], one reported an intervention\nthat was not effective [ 13], one actually focused on mam-\nmary tumors and mentioned adenomyosis as a secondary\nend point [ 15], one that tested the same compound that was\nevaluated previously [ 16], and one study to test feasibility,\nbut not efficacy, of an intervention [ 20]. The characteristics\nof the remaining ten studies, along with the major treatment\noutcome measures in the control group and the group re-\nceiving the highest dose, representing the best treatment\neffect, are listed in Table 1.\nMethods of Inducing Adenomyosis in Mouse Studies\nGreaves and White [ 26] recently reviewed animal models of\nadenomyosis, including mouse models. Briefly, adenomyo-\nsis can be induced in mice through various forms of hor-\nmonal imbalance, such as hyperprolactinemia [27, 28],\nprolonged\ntreatment with or prenatal exposure to estrogenic\ncompounds [ 27, 29], and prolonged treatment with proges-\nterone [30, 31]. For efficacy studies, however, none of these\ninduction methods have been used. One reason is the long\ninduction period. The other reason is their nonspecific ef-\nfect, such that in addition to inducing adenomyosis, other\npathological changes in the reproductive tract are also in-\nduced. For example, prenatal exposure to diethylstilbestrol\nalso results in cervix enlargement with extensive mucoid\nalterations within the muscularis [ 27].\nFor efficacy studies, some publ ished studies used the\nSHN mouse strain, which has spontaneous adenomyosis\n[32]. Others have used one of two adenomyosis induction\nmethods, ectopic grafting of pituitary glands (EGPG) or\nneonatal feeding with tamoxifen (NFT). In EGPG, adeno-\nmyosis is induced by intrauterine implantation of isographs\nof anterior pituitary glands [ 33–35]. This induction method\nhas the advantage of a high success rate, reported to be\ngreater than 90 % 50 days after induction [ 16], and the\nultrastructural changes in myometrium from mice with in-\nduced adenomyosis have been documented [ 36]. The limi-\ntations of this approach include that the induction procedure\nrequires a certain level of surgical skill such that surgical\nchanges might be a confounding effect in efficacy studies. A\nsecond limitation is that the success rate is strain dependent,\nwith high rates in SHN and SLN mouse strains but lower\nrates in other strains [ 34, 35]. A third limitation is the long\ninduction period of 4 months in an strain of ICR mice to\nreach a success rate of 95 % [ 21] and a 6-month induction\nperiod in C3H and F1 hybrids with a variable success rate\n[35]. Lastly, the induction method appears to be sensitive to\ntreatment with dimethyl sulfoxide (DMSO), often used as a\nvehicle for many compounds. In Dr. Mori ’s lab, the success\nrate of adenomyosis induction after EGPG followed by\nDMSO treatment was reduced to 80 % in one study [ 18]\nand 40 % in another [ 19]. The anti-inflammatory effect of\nDMSO may be related to its use to treat intractable intersti-\ntial cystitis, radiation cystitis, chronic prostatitis, and chron-\nic female trigonitis [ 37]. DMSO also is used most as a\ntopical analgesic [ 38]. Thus, if the induction is truly sensi-\ntive to DMSO, an underestimation of the efficacy of studied\ncompounds may occur when DMSO is used as a solvent.\nNeonatal feeding with tamoxifen was first reported by\nParrott et al. [ 39, 40] in CD-1 mouse. A previous study of\nneonatal exposure to tamoxifen, delivered through subcuta-\nneous injection, in the CD-1 mouse resulted in atypical\nhyperplasia in the endometrium, uterine adenocarcinoma,\nCurr Obstet Gynecol Rep (2012) 1:138 –145 139\n\nTable 1 Characteristics of published preclinical mouse efficacy studies\nID* Study Compound(s)\ntested\nMouse\nstrain\nMethod of\ninduction\nLength of\ninduction, d\nTreatment\nduration, d\nMajor outcome\nmeasure\nRandomization\nmentioned?\nDose–\nresponse?\nTotal\nsample\nsize\n**\nTrt*** Ctl COI\nstatement?\nD1, Singtripop et al.\n[11]\nDanazol SHN S NA 35 (+35 d no Tx) P Y es No 8+13 0.375 0.846 No\nD2a EGPG 0 35 (+35 d no Tx) Y es No 9+11 0.222 1.00\nK Mori et al. [ 12] KBG (Chinese\nherb medicine)\nSHN S NA 95 P , H Y es No 11+13 0.182 No\nM Zhou et al. [ 14] Mifepristone (SPRM) SHN EGPG 21 28 P . UWW Y es No 10+9 0.200 0.778 No\nO1 Mori et al. [ 16] ONO-4817 SHN EGPG 7 42 P , FI, GLCI No Yes 12+12 0.083 0.917 No\nO2a (MMP inhibitor) EGPG 42 28 No No 10+10 1.00 1.00\nC1 Mori et al. [ 17] CP8816 SHN EGPG 0 41 P No No 10+10 0.10 0.80 No\nC2a CP8863 7 35 No No 12+10 0.083 0.90\n(SPRM)\nT Zhou et al. [ 18] TNP-470 (anti-\nantiogenic\nagent)\nSHN EGPG 1 41 P ,BW,OW,EC Y es No 15+15 0.00 0.80 No\nP Zhou et al. [ 19] Probucol (hypo-\ncholesterolemic\nagent)\nSHN EGPG 1 41 P ,BW,OW,SL Y es No 10+10 0.00 0.40 No\nU Zhang et al. [ 21] Danazol-IUD ICR EGPG 120 60 UWW/BW ratio,\nN, HE\nY es Yes 5+5 2.2 (5.6) 2.5 (11.5) No\nVL i u a n d G u o [ 22] VPA (HDACI) ICR NFT 84 28 UWW/BW ratio,\nD, HP , TF\nY es Yes 12+12 0.0030 0.0047\nb Yes\n12.1 10.3\nH Mao et al. [ 23] l-THP , Andro, VPA ICR NFT 107 21 D, HP , UT, UWW Y es Yes 10+8 1.0 c 2.5 Yes\nCOI conflict of interest, S spontaneous, EGPG ectopic graft of pituitary gland, Tx treatment, P prevalence, KBG Keishi-Bukuryo-Gan, H histology, SPRM selective progesterone receptor modulator,\nUWW uterine wet weight, MMP matrix metalloproteinase, FI food intake, GLCI graded levels of cell invasiveness, BW body weight, OW organ weight, EC estrous cycle, SL serum levels of lipids,\nIUD intrauterine device, UWW/BW ratio uterine wet weight vs body weight ratio, N number of nodules, HE hematoxylin eosin staining, VP Avalproic acid, HDACI histone deacetylase inhibitor, NFT\nneonatal feeding of tamoxifen, D depth of myometrial infiltration, HP hotplate test, TF tail-flick test, l-THP levo-tetrahydropalmatine, Andro andrographolide, UT uterine contractility\n* Identification of study on graph in Fig. 1. ** Sample size of the treatment and the control groups combined. *** The treatment with the best effect, typically the group receiving the highest dose or\njoint treatment.\na Two experiments were conducted and were thus labeled differently\nb The first row was the UWW/BW ratio, and the second was the hotplate response latency (in seconds)\nc The depth of myometrial infiltration\n140 Curr Obstet Gynecol Rep (2012) 1:138– 145\n\nand uterine hypoplasia with focal areas of basal cell hyper-\nplasia in the endometrium, but not adenomyosis [ 41]. Be-\ncause the ICR mouse is genetically related with the CD-1\nmouse, NFT with the ICR mouse yielded identical results in\ninducing adenomyosis [ 22]. Compared with the EGPG\nmethod, NFT is much simpler, requiring no surgical skill.\nIn addition, it also has a high success rate in induction:\n3 months after the induction procedure, all mice have adeno-\nmyosis [22, 40]. In fact, by day 42 or 37 days after the NFT,\nthe success rate is 100 % [ 42]. Like the EGPG method, the\nNFT also has the limitation that the success of the induction\nis highly strain dependent [ 43].\nFeatures of Published Mouse Efficacy Studies\nFrom Table 1, several notable features can be seen. First, the\nearlier (up to 2004) mouse efficacy studies were conducted\nexclusively in Japan, specifically, in Dr. Mori ’s lab in the\nUniversity of Tokyo, which first reported that EGPG\nresulted in a high rate of development of adenomyosis\n[44]. In SHN mouse strain, which has a high incidence of\nmammary tumors, an unusually high incidence of spontane-\nous adenomyosis also was reported [ 45]. In this model, an\nincrease in plasma levels of prolactin is noted [ 28].\nDiverse compounds have been evaluated for their thera-\npeutic potential. These included danazol, a Chinese herb\nconcoction, a matrix metalloproteinase (MMP) inhibitor\n(ONO-4817), several selective progesterone receptor mod-\nulators (SPRMs [mifepristone, CP-8816, and CP-8863]), a\ndanazol-containing IUD, a histone deacetylase inhibitor\n(valproic acid [VPA]), an anti-angiogenic agent (TNP-\n470); a hypocholesterolemic agent (probucol), an analgesic\n(levo-tetrahydropalmatine [l -THP]), and a nuclear factor\n(NF)-κB inhibitor (andrographolide). Of these, only danazol\n[46], VPA [ 47, 48], and andrographolide [ 49], have been\nevaluated in in vitro or clinical studies for endometriosis or\nadenomyosis. Despite promising results, only danazol has\nbeen tested in clinical trials or is in use clinically today.\nHowever, adenomyosis usually fails to respond to oral\ndanazol therapy [ 50].\nEarlier studies were focused on biological plausibility.\nFor example, because adenomyosis involves cell migration\nor invasion, which is associated with the degradation and\nreconstruction of the extracellular matrix in which MMPs\nare involved, MMP inhibitors were studied. In contrast,\nmore recent, studies have been designed based on previous\nmolecular studies. For example, because adenomyosis may\nbe an epigenetic disease [ 51], it may be treatable by histone\ndeacetylase inhibitors similar to endometriosis [ 52]. Conse-\nquently, VPA recently has been tested in animal models of\nadenomyosis [ 22]. Interestingly, clinical studies of oral ad-\nministration of VPA in treating symptomatic adenomyosis\nhave yielded promising results [ 48, 53]. Andrographolide is\nan NF- κB inhibitor that causes covalent modification of\nreduced cysteine 62 of the p50 subunit of NF- κB[ 54] and\nmay also be therapeutic given the constitutive NF- κB acti-\nvation in adenomyosis [ 55]. Tetrahydropalmatine (THP) is\nan alkaloid compound and a main active ingredient of\nCorydalis\nyanhusuo W. T. Wang [56], a well-known analge-\nsic in traditional Chinese medicine (TCM) often used as a\nconstituent herb for treating endometriosis [ 57]. Its levo-\nenantiomer (l-THP) is an analgesic with remarkable sedative\ntranquilizing but nonaddictive effects [58]. Listed in the\nChinese Pharmacopoeia since 1977, l-THP has been used\nas a sedative or analgesic for chronic pains in China. The\ndanazol-containing IUD and vaginal ring were tested clini-\ncally for adenomyosis [ 50, 59, 60] and endometriosis [ 61].\nOn a molecular level, danazol treatment results in reduced\nexpression of estrogen receptor and bcl-2 in adenomyotic\nendometrium with concomitant increased apoptosis [ 62].\nOver time, the clinical outcome in animal models has\nevolved from using only the prevalence of adenomyosis to\nincluding details such as the ratio of uterine wet weight\nversus total body weight [ 21], number of nodules [ 21],\nor depth of myometrial infiltration of endometrial cells [ 22,\n23] as outcome measures. Additionally, two recent studies\nused latency response to noxious thermal stimuli as outcome\nmeasures [ 22, 23]. Using adenomyosis prevalence as an\noutcome measure is useful in determining suppression or\nslowed development of adenomyosis. However, because\nwomen with endometriosis and a prolong history of dys-\nmenorrhea often have adenomyosis [ 63], ideal compounds\nwill reverse adenomyosis and treat associated symptoms.\nAnalysis of Earlier Mouse Studies\nAs seen in Table 1, the seven mouse efficacy studies pub-\nlished up to 2004 were conducted by one research group\nusing the SHN mouse strain and evaluated different com-\npounds. The induction methods and major outcomes were\nnearly identical. The three later studies from 2008 ( n01) and\n2011 ( n02), used different strains of mice or different in-\nduction methods. The outcome measures also differed from\nearlier studies.\nAn analysis was conducted to determine whether the\nmagnitude of treatment effect, defined as the difference in\nprevalence of adenomyosis between the treatment and con-\ntrol groups, was associated with features of the experiment.\nComparison of the distributions among two or more groups\nof continuous variables was made using the Wilcoxon and\nKruskal-Wallis tests, respectively. Pearson ’s or Spearman ’s\nrank correlation coefficient was used when evaluating cor-\nrelations between two variables when both variables were\ncontinuous or when at least one variable was ordinal. To see\nCurr Obstet Gynecol Rep (2012) 1:138 –145 141\n\nwhether the age of mice used in the experiment, the length\nof adenomyosis-induction period, duration of treatment, and\nt o t a ls a m p l es i z ew e r er e s p o n s i b l ef o rt h er e d u c t i o ni n\nprevalence of adenomyosis between treatment and control\ngroups, a multiple linear regression model was used. P\nvalues of less than 0.05 were considered statistically signif-\nicant. All computations were made with R statistics software\nsystem version 2.15.0 [ 25].\nAs illustrated in Fig. 1, the treatment effect was inversely\ncorrelated with the length of induction period (ie, the time\nbetween performing the pituitary graft and the start of treat-\nment [ r00.79, P00.02; Fig. 1A]). In other words, better\nefficacy was reported from experiments using a shorter\ninduction period, or earlier intervention.\nI m p r o v e de f f i c a c ya l s os e e m e dt ob ea s s o c i a t e dw i t h\nlonger duration of treatment, although the correlation did\nnot reach statistical significance ( r 0−0.38, P 00.38\n[Fig. 1B]). Greater reduction in prevalence tended to be\nreported from experiments that did not mention randomiza-\ntion in allocating animals, but no statistical significance was\nreached ( P00.61 [Fig. 1C]).\nA multiple linear regression analysis using the difference\nin prevalence of adenomyosis between the treatment and\ncontrol groups as the independent variable and the age of\nmice used in the experiment, year of publication, length of\ninduction period, duration of treatment, total sample size,\nand the mention of randomization as dependent variables\nrevealed that the length of induction period was the only\ncovariate that was significantly associated with the reduc-\ntion in prevalence ( P00.035, R\n2 00.78) indicating that great-\ner efficacy is associated with earlier intervention.\nMethodological Qualities of Published Mouse Efficacy\nStudies\nThe recently proposed Animals in Research: Reporting In\nVivo Experiments (ARRIVE) guidelines [ 64]c o m p r i s e\nseven core categories that indicate methodological qualities\nof animal efficacy studies. These categories for the ten\nreviewed studies are summarized in Table 2. In considering\nthese core elements, none of the reviewed studies provide\nany justification for number of mice studied or how the\nsample size was determined. Eight of ten studies mentioned\nthat the animal allocation was carried out randomly, but\nnone described how it was done. None of the reviewed\nstudies reported allocation concealment. None of the ten\nstudies explicitly stated that the outcome measures were\nevaluated blinded to treatment allocation. Of the ten studies,\nfour used two or more dosages to establish the minimally\neffective or maximally tolerated doses. Because the two\nmajor complaints from women with adenomyosis are pain\nand heavy menstrual bleeding, one needs to evaluate not\nFig. 1 a Scatter plot of the difference in incidence of adenomyosis\nbetween treatment and control groups versus length of induction. The\nalphabets were identifications of experiments listed in Table 1. b\nScatter plot of the difference in prevalence of adenomyosis between\ntreatment and control groups versus duration of treatment (in days).\nThe alphabets were identifications of experiments listed in Table 1. The\nexperiments with blue alphabets were done with spontaneous adeno-\nmyosis in SHN mice, while those with red were performed with\nectopic graft of pituitary glands. c Box plot of the difference in\nincidence of adenomyosis between treatment and control groups by\nthe statement of randomization in allocating mice in experiment\n142 Curr Obstet Gynecol Rep (2012) 1:138– 145\n\nonly the histological outcome of an intervention (ie, number\nof nodules, depth of myometrial infiltration, with or without\nproliferation index measurement or immunostaining analysis)\nbut also functional outcome (ie, severity of pain or fertility).\nWhile eight of ten studies evaluated at least two disease-\nrelated outcomes, only two of those eight studies evaluated\nfunctional outcomes (ie, pain behavior). Of the ten studies,\nonly two recently published studies addressed possible con-\nflict of interest (COI). The lack of a statement regarding COI\nin the earlier studies may reflect their publication at an earlier\ntime when disclosure regarding COI was not required.\nThe importance of the methodological quality in animal\nstudies has been appreciated in other clinical settings, such as\nstroke, after some failed clinical trials [ 66–68]. Rigorous,\nrobust, and detailed preclinical evaluation has been recog-\nnized as a critical step in the development of effective novel\ntherapies [66]. The less than desirable methodological quality\nof mouse efficacy studies of adenomyosis illustrated in Table2\ncould have contributes to the lack of progress in developing\nnovel treatments for adenomyosis. The scarcity of registered\nclinical trials on adenomyosis may be attributable, at least in\npart, to various deficiencies in mouse efficacy studies.\nThe tendency to alter animal numbers based on scientifi-\ncally irrelevant issues such as availability or cost has been\nnoted before [ 69]. Inadequate sample sizes would result in\nunderpowered studies, bringing into question the statistical\nvalidity of study conclusions. For continuous outcome meas-\nures, the rule of thumb for calculating the desired sample size\nn to achieve the significance level of 0.05 and 80 % power in\nthe treatment and the control group is n – 1016 s\n2/d2,w h e r es\nis the standard deviation, andd is the difference to be detected\n[70]. In other words, n−1 is proportional to the squared\nstandard deviation, but inversely proportional to the squared\ndifference to be detected. Without knowings and/or d,s a m p l e\nsize determination is impossible. Ideally, pilot experiments\nwould aid in determining s and/or d. In some cases, this\napproach would result in doing the entire experiment. There-\nfore, this quandary may explain why in many mouse efficacy\nstudies, sample size justification is not done or is carried out\npost hoc.\nRandomization and allocation concealment can be done\nin mouse efficacy studies. Blinding also can be done, but\nwhen there is a shortage of hands, as in experiments for a\nstudent’s PhD dissertation, extra care should be taken to\nmeet this requirement. Declaration of potential COI is now\nmandatory for publication in many biomedical journals.\nWhen a preclinical study is sponsored or even conducted\nby a drug company testing a compound developed by the\ncompany itself, there is obvio usly vested interest in the\nresults of the tested compound and, as such, potential COI\nshould disclosed and declared.\nConclusions\nPreclinical mouse efficacy studies of adenomyosis appar-\nently have deficiencies in methodology. Critical evalua-\ntion of published data before embarking on animal\nstudies, the use of mouse models that adequately mimic\nhuman adenomyosis, the use of at least one functional\noutcome, and higher methodological quality could greatly\nincrease the chance of a successful translation of mouse\nexperiments into clinical success. Fortunately, the impor-\ntance of methodological quality of animal efficacy studies\nis now well recognized, and, as a result, the ARRIVE\nguidelines for experimental design, execution, and report-\ning have been established [65 ]. The use of these guide-\nlines in future mouse efficacy studies of adenomyosis\nwould strengthen preclinical research.\nAdenomyosis is a difficult disease to manage [ 65], espe-\ncially by nonsurgical means. Developing novel, more effi-\ncacious therapeutics with better safety and cost profiles is a\npressing but unmet medical need. On www.ClinicalTrials.\ngov, the number of registered clinical trials studying adeno-\nmyosis is currently only 15, about one tenth of the number\nof trials on endometriosis; none are testing novel drugs. The\namount of research on adenomyosis indicated by PubMed\nusing the phrase “adenomyosis not endometriosis ” yielded\n389 publications, as compared with 18,593 when the search\nused the word “endometriosis” alone (PubMed, accessed on\nMay 14, 2012). Insufficient breadth of research regarding\nadenomyosis may hamper compiling information relevant to\ndrug development.\nBesides the methodological quality as discussed above,\nproceeding from preclinical studies to clinical trials requires\nthat efficacy is reproduced in two laboratories, one of which\nis independent of any sponsoring company [ 66]. In addition,\nthe use of second larger species such as cats, dogs, or\nprimates would be highly valuable, but, unfortunately, no\nsuch animal model is available now. Only when the preclin-\nical mouse efficacy study is carried out with methodological\nTable 2 Summary of core quality features of ten published mouse\nefficacy studies of adenomyosis\nCategory Fulfilled, %\nSample size justification 0\nRandomization 80\nAllocation concealment 0\nBlinding 0\nDoes-response relationship 40\nAssessment of at least one functional outcome 20\nStatement regarding possible conflicting interest 20\nCurr Obstet Gynecol Rep (2012) 1:138 –145 143\n\nrigor and careful consideration will there be a better chance\nto develop a successful drug to treat adenomyosis.\nAcknowledgment This research was supported in part by grants\n09PJD015 and 10410700200 from the Shanghai Science and Technol-\nogy Commission, and support from Shanghai Key Laboratory of\nFemale Reproductive Endocrine-Related Diseases and from the Key\nSpecialty Project of the Ministry of Health, People’ s Republic of\nChina. 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