Phase I study of onapristone, a type I antiprogestin, in female patients with previously treated recurrent or metastatic progesterone receptor-expressing cancers

Antiprogestins for breast cancer treatment: We are almost ready

The development of antiprogestins was initially a gynecological purpose. However, since mifepristone was developed, its application for breast cancer treatment was immediately proposed. Later, new compounds with lower antiglucocorticoid and antiandrogenic effects were developed to be applied to different pathologies, including breast cancer. We describe herein the studies performed in the breast cancer field with special focus on those reported in recent years, ranging from preclinical biological models to those carried out in patients. We highlight the potential use of antiprogestins in breast cancer prevention in women with BRCA1 mutations, and their use for breast cancer treatment, emphasizing the need to elucidate which patients will respond. In this sense, the PR isoform ratio has emerged as a possible tool to predict antiprogestin responsiveness. The effects of combined treatments of antiprogestins together with other drugs currently used in the clinic, such as tamoxifen, CDK4/CDK6 inhibitors or pembrolizumab in preclinical models is discussed since it is in this scenario that antiprogestins will be probably introduced. Finally, we explain how transcriptomic or proteomic studies, that were carried out in different luminal breast cancer models and in breast cancer samples that responded or were predicted to respond to the antiprogestin therapy, show a decrease in proliferative pathways. Deregulated pathways intrinsic of each model are discussed, as well as how these analyses may contribute to a better understanding of the mechanisms involved.

Steroid profile in patients with breast cancer and in mice treated with mifepristone

Progesterone receptors (PRs) are biomarkers used as prognostic and predictive factors in breast cancer, but they are still not used as therapeutic targets. We have proposed that the ratio between PR isoforms A and B (PRA and PRB) predicts antiprogestin responsiveness. The MIPRA trial confirmed the benefit of 200 mg mifepristone, administered to patients with tumors with a high PRA/PRB ratio, but dose-ranging has not been conducted. The aim of this study was to establish the plasma mifepristone levels of patients from the MIPRA trial, along with the resultant steroid profiles, and compare these with those observed in mifepristone-treated mice using therapeutic schemes able to induce the regression of experimental mammary carcinomas with high PRA/PRB ratios: 6 mg pellets implanted subcutaneously, or daily doses of 12 mg/kg body weight. The plasma levels of mifepristone and other 19 plasma steroids were measured by liquid chromatography-tandem mass spectometry. In mifepristone-treated mice, plasma levels were lower than those registered in mifepristone-treated patients (i.e. day 7 after treatment initiation, pellet-treated mice: 8.4 ± 3.9 ng/mL; mifepristone-treated patients: 300.3 ± 31.7 ng/mL (mean ± s.d.; P < 0.001)). The increase in corticoid related steroids observed in patients was not observed in mifepristone-treated mice. The increase in progesterone levels was the most significant side effect detected in mifepristone-treated mice after 14 or 21 days of treatment, probably due to an ovarian compensatory effect not observed in postmenopausal patients. We conclude that in future clinical trials using mifepristone, the possibility of lowering the standard daily dose of 200 mg should be considered.

Reevaluating the Role of Progesterone in Ovarian Cancer: Is Progesterone Always Protective?

Ovarian cancer (OC) represents a collection of rare but lethal gynecologic cancers where the difficulty of early detection due to an often-subtle range of abdominal symptoms contributes to high fatality rates. With the exception of BRCA1/2 mutation carriers, OC most often manifests as a post-menopausal disease, a time in which the ovaries regress and circulating reproductive hormones diminish. Progesterone is thought to be a "protective" hormone that counters the proliferative actions of estrogen, as can be observed in the uterus or breast. Like other steroid hormone receptor family members, the transcriptional activity of the nuclear progesterone receptor (nPR) may be ligand dependent or independent and is fully integrated with other ubiquitous cell signaling pathways often altered in cancers. Emerging evidence in OC models challenges the singular protective role of progesterone/nPR. Herein, we integrate the historical perspective of progesterone on OC development and progression with exciting new research findings and critical interpretations to help paint a broader picture of the role of progesterone and nPR signaling in OC. We hope to alleviate some of the controversy around the role of progesterone and give insight into the importance of nPR actions in disease progression. A new perspective on the role of progesterone and nPR signaling integration will raise awareness to the complexity of nPRs and nPR-driven gene regulation in OC, help to reveal novel biomarkers, and lend critical knowledge for the development of better therapeutic strategies.

Therapeutic resistance to anti-oestrogen therapy in breast cancer

The hormone receptor oestrogen receptor-α (ER) orchestrates physiological mammary gland development, breast carcinogenesis and the progression of breast tumours into lethal, treatment-refractory systemic disease. Selective antagonism of ER signalling has been one of the most successful therapeutic approaches in oncology, benefiting patients as both a cancer preventative measure and a cancer treatment strategy. However, resistance to anti-oestrogen therapy is a major clinical challenge. Over the past decade, we have gained an understanding of how breast cancers evolve under the pressure of anti-oestrogen therapy. This is best depicted by the case of oestrogen-independent mutations in the gene encoding ER (ESR1), which are virtually absent in primary breast cancer but highly prevalent (20-40%) in anti-oestrogen-treated metastatic disease. These and other findings highlight the 'evolvability' of ER+ breast cancer and the need to understand molecular processes by which this evolution occurs. Recent development and approval of next-generation ER antagonists to target ESR1-mutant breast cancer underscores the clinical importance of this evolvability and sets a new paradigm for the treatment of ER+ breast cancers.

The role of progesterone and the progesterone receptor in cancer: progress in the last 5 years

INTRODUCTION

Patients with various advanced cancers devoid of nuclear progesterone receptors (nPR) have demonstrated increased quality and length of life when treated with the PR modulator mifepristone, which likely works by interacting with membrane PRs (mPR).

AREAS COVERED

Two immunomodulatory proteins are discussed that seem to play a role in cancers that proliferate whether the malignant tumor is positive or negative for the nPR. These two proteins are the progesterone receptor membrane component-1 (PGRMC-1) and the progesterone-induced blocking factor (PIBF). Both PGRMC-1 and the parent form of PIBF foster increased tumor aggressiveness, whereas splice variants of the 90 kDa form of PIBF inhibit immune response against cancer cells.

EXPERT OPINION

The marked clinical improvement following 200-300 mg of mifepristone is likely related to blocking PIBF. In the low dosage used, mifepristone likely acts as an agonist for PGRMC-1 protein. Mifepristone may be less effective for cancers positive for the nPR because the nPR may be protective and blocking it may have detrimental effects. Based on this hypothetical model, the development of other potential treatment options to provide even greater efficacy for treating cancer are discussed.

Nuclear Receptor Imaging In Vivo-Clinical and Research Advances

Nuclear receptors are transcription factors that function in normal physiology and play important roles in diseases such as cancer, inflammation, and diabetes. Noninvasive imaging of nuclear receptors can be achieved using radiolabeled ligands and positron emission tomography (PET). This quantitative imaging approach can be viewed as an in vivo equivalent of the classic radioligand binding assay. A main clinical application of nuclear receptor imaging in oncology is to identify metastatic sites expressing nuclear receptors that are targets for approved drug therapies and are capable of binding ligands to improve treatment decision-making. Research applications of nuclear receptor imaging include novel synthetic ligand and drug development by quantifying target drug engagement with the receptor for optimal therapeutic drug dosing and for fundamental research into nuclear receptor function in cells and animal models. This mini-review provides an overview of PET imaging of nuclear receptors with a focus on radioligands for estrogen receptor, progesterone receptor, and androgen receptor and their use in breast and prostate cancer.

Progesterone Receptor-Mediated Regulation of Cellular Glucose and 18F-Fluorodeoxyglucose Uptake in Breast Cancer

Context

Positron emission tomography imaging with 2-deoxy-2-[¹⁸F]-fluoro-D-glucose (FDG) is used clinically for initial staging, restaging, and assessing therapy response in breast cancer. Tumor FDG uptake in steroid hormone receptor-positive breast cancer and physiologic FDG uptake in normal breast tissue can be affected by hormonal factors such as menstrual cycle phase, menopausal status, and hormone replacement therapy.

Objective

The purpose of this study was to determine the role of the progesterone receptor (PR) in regulating glucose and FDG uptake in breast cancer cells.

Methods and Results

PR-positive T47D breast cancer cells treated with PR agonists had increased FDG uptake compared with ethanol control. There was no significant change in FDG uptake in response to PR agonists in PR-negative MDA-MB-231 cells, MDA-MB-468 cells, or T47D PR knockout cells. Treatment of T47D cells with PR antagonists inhibited the effect of R5020 on FDG uptake. Using T47D cell lines that only express either the PR-A or the PR-B isoform, PR agonists increased FDG uptake in both cell types. Experiments using actinomycin D and cycloheximide demonstrated the requirement for both transcription and translation in PR regulation of FDG uptake. GLUT1 and PFKFB3 mRNA expression and the enzymatic activity of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were increased after progestin treatment of T47D cells.

Conclusion

Thus, progesterone and progestins increase FDG uptake in T47D breast cancer cells through the classical action of PR as a ligand-activated transcription factor. Ligand-activated PR ultimately increases expression and activity of proteins involved in glucose uptake, glycolysis, and the pentose phosphate pathway.

Lost but Not Least-Novel Insights into Progesterone Receptor Loss in Estrogen Receptor-Positive Breast Cancer

Estrogen receptor α (ERα) and progesterone receptor (PgR) are crucial prognostic and predictive biomarkers that are usually co-expressed in breast cancer (BC). However, 12-24% of BCs present ERα(+)/PgR(-) phenotype at immunohistochemical evaluation. In fact, BC may either show primary PgR(-) status (in chemonaïve tumor sample), lose PgR expression during neoadjuvant treatment, or acquire PgR(-) phenotype in local relapse or metastasis. The loss of PgR expression in ERα(+) breast cancer may signify resistance to endocrine therapy and poorer outcomes. On the other hand, ERα(+)/PgR(-) BCs may have a better response to neoadjuvant chemotherapy than double-positive tumors. Loss of PgR expression may be a result of pre-transcriptional alterations (copy number loss, mutation, epigenetic modifications), decreased transcription of the PGR gene (e.g., by microRNAs), and post-translational modifications (e.g., phosphorylation, sumoylation). Various processes involved in the down-regulation of PgR have distinct consequences on the biology of cancer cells. Occasionally, negative PgR status detected by immunohistochemical analysis is paradoxically associated with enhanced transcriptional activity of PgR that might be inhibited by antiprogestin treatment. Identification of the mechanism of PgR loss in each patient seems challenging, yet it may provide important information on the biology of the tumor and predict its responsiveness to the therapy.

Onapristone Extended Release: Safety Evaluation from Phase I-II Studies with an Emphasis on Hepatotoxicity

Introduction

Antiprogestins have demonstrated promising activity against breast and gynecological cancers, but liver-related safety concerns limited the advancement of this therapeutic class. Onapristone is a full progesterone receptor antagonist originally developed as an oral contraceptive and later evaluated in phase II studies for metastatic breast cancer. Because of liver enzyme elevations identified during clinical studies, further development was halted. Evaluation of antiprogestin pharmacology and pharmacokinetic data suggested that liver enzyme elevations might be related to off-target or metabolic effects associated with clinical drug exposure.

Objective

We explored whether the use of a pharmaceutic strategy targeting efficacious systemic dose concentrations, but with diminished peak serum concentrations and/or total drug exposure would mitigate hepatotoxicity. Twice-daily dosing of an extended-release formulation of onapristone was developed and clinically evaluated in light of renewed interest in antiprogestin therapy for treating progesterone receptor-positive breast and gynecologic cancers. The hepatotoxic potential of extended-release onapristone was assessed from two phase I–II studies involving patients with breast, ovarian, endometrial, and prostate cancer.

Results

Among the 88 patients in two phase I–II studies in progesterone receptor-positive malignancies treated with extended-release onapristone, elevated alanine aminotransferase/aspartate aminotransferase levels were found in 20% of patients with liver metastases compared with 6.3% without metastases. Of five patients with grade 3 or higher alanine aminotransferase elevations with or without bilirubin elevations (four with breast cancer and one with endometrial cancer), four were assessed as unrelated to extended-release onapristone by the safety data review committee. Furthermore, while the fifth patient’s liver enzyme elevations were considered possibly drug related by the study investigator, they were adjudicated as unlikely to be related (< 25% likelihood) by a subsequent independent hepatologist.

Conclusions

These results suggest that the extended-release formulation by reducing drug exposure may be associated with a reduced risk of hepatotoxicity, and supports the continued clinical evaluation of extended-release onapristone for treating progesterone receptor-positive cancers.

Leveraging Antiprogestins in the Treatment of Metastatic Breast Cancer

Although incurable, the prognosis for patients with metastatic breast cancer (MBC) has considerably improved with the approvals of multiple targeted and cytotoxic therapies. For hormone receptor-positive (HR+), ie, estrogen receptor and progesterone receptor positive (ER+/PgR+) and human epidermal growth factor receptor-2 negative (ie, ERBB2 gene nonamplified or HER2-) MBC, current approved treatment options include palliative endocrine therapy (ET), cyclin-dependent kinase (CDK 4/6) inhibitors, mTOR inhibitors, and PI3 kinase inhibitors. Most treatments target ER+ disease regardless of PgR status. Although the presence of PgR is crucial for ER+ cell proliferation in both normal and malignant mammary tissue, currently, there are no approved treatments that specifically target PgR. Recent literature has demonstrated the potential of antiprogestins in the treatment of MBC both in preclinical and clinical studies. Antiprogestins, including selective PgR modulators (SPRMs) that act as PgR antagonists, are a promising class of therapeutics for overcoming endocrine resistance in patients who develop activating estrogen receptor 1 (ESR1) and phosphatidylinositol 3-kinase (PI3K) gene mutations after prior endocrine therapy. Herein, we summarize the role of PgR and antiprogestins in the treatment of MBC. Other aspects on the use of functional imaging, clinical trials incorporating novel antiprogestins, and potential treatment combinations to overcome endocrine resistance will be briefly discussed.

Progesterone receptors in normal breast development and breast cancer

Progesterone receptors (PR) play a pivotal role in many female reproductive tissues such as the uterus, the ovary, and the mammary gland (MG). Moreover, PR play a key role in breast cancer growth and progression. This has led to the development and study of different progestins and antiprogestins, many of which are currently being tested in clinical trials for cancer treatment. Recent reviews have addressed the role of PR in MG development, carcinogenesis, and breast cancer growth. Thus, in this review, in addition to making an overview on PR action in normal and tumor breast, the focus has been put on highlighting the still unresolved topics on hormone treatment involving PR isoforms and breast cancer prognosis.

Anti-CEA tagged iron nanoparticles for targeting triple-negative breast cancer

Systemic therapy is generally required for breast cancer. However, treatment toxicity and side effects are a concern, especially for triple-negative breast cancer (TNBC), a subtype that usually develops resistance to chemotherapy. To overcome this issue, new nanoformulations capable of targeting cancer cells have been developed and alternative biomarkers have been explored as target molecules for TNBC management. In this study, we performed an in vivo assay in a murine orthotopic TNBC model to evaluate the targeting ability of anti-carcinoembryonic antigen (anti-CEA) loaded nanoparticles (labelled MFCEA), which had been previously synthetized by our research group. 4T1 cells were injected in the mammary gland of balb-c mice, and tumors were evaluated for CEA expression by immunohistochemistry. Tumor-bearing mice received targeted (MFCEA) and non-targeted (MF) nanoparticles intraperitoneally. Tumors were removed 1, 4, 15 and 24h after treatment, and Prussian blue iron staining was performed. Our results showed, as far as we know for the first time, that 4T1 induced tumors are CEA positive, and this opens up new prospects for treating TNBC. Furthermore, MFCEA nanoparticles were able to target malignant tissue and were retained in the tumor for longer than MF nanoparticles. The retention property of MFCEA, together with the absence of toxicity observed in the MTT assay, make these nanoparticles a promising device for management of CEA positive tumors and perhaps for TNBC. Nevertheless, further studies must be carried out to improve their performance and ensure safety for clinical studies.

Treating PMP22 gene duplication-related Charcot-Marie-Tooth disease: the past, the present and the future

Charcot-Marie-Tooth (CMT) disease is the most frequent inherited neuropathy, affecting 1/1500 to 1/10000. CMT1A represents 60%-70% of all CMT and is caused by a duplication on chromosome 17p11.2 leading to an overexpression of the Peripheral Myelin Protein 22 (PMP22). PMP22 gene is under tight regulation and small changes in its expression influences myelination and affect motor and sensory functions. To date, CMT1A treatment is symptomatic and classic pharmacological options have been disappointing. Here, we review the past, present, and future treatment options for CMT1A, with a special emphasis on the highly promising potential of PMP22-targeted small interfering RNA and antisense oligonucleotides.

90 YEARS OF PROGESTERONE: Steroid receptors as MAPK signaling sensors in breast cancer: let the fates decide

Steroid hormone receptors (SRs) are classically defined as ligand-activated transcription factors that function as master regulators of gene programs important for a wide range of processes governing adult physiology, development, and cell or tissue homeostasis. A second function of SRs includes the ability to activate cytoplasmic signaling pathways. Estrogen (ER), androgen (AR), and progesterone (PR) receptors bind directly to membrane-associated signaling molecules including mitogenic protein kinases (i.e. c-SRC and AKT), G-proteins, and ion channels to mediate context-dependent actions via rapid activation of downstream signaling pathways. In addition to making direct contact with diverse signaling molecules, SRs are further fully integrated with signaling pathways by virtue of their N-terminal phosphorylation sites that act as regulatory hot-spots capable of sensing the signaling milieu. In particular, ER, AR, PR, and closely related glucocorticoid receptors (GR) share the property of accepting (i.e. sensing) ligand-independent phosphorylation events by proline-directed kinases in the MAPK and CDK families. These signaling inputs act as a 'second ligand' that dramatically impacts cell fate. In the face of drugs that reliably target SR ligand-binding domains to block uncontrolled cancer growth, ligand-independent post-translational modifications guide changes in cell fate that confer increased survival, EMT, migration/invasion, stemness properties, and therapy resistance of non-proliferating SR+ cancer cell subpopulations. The focus of this review is on MAPK pathways in the regulation of SR+ cancer cell fate. MAPK-dependent phosphorylation of PR (Ser294) and GR (Ser134) will primarily be discussed in light of the need to target changes in breast cancer cell fate as part of modernized combination therapies.

Improving response to progestin treatment of low-grade endometrial cancer

OBJECTIVES

This review examines how response rates to progestin treatment of low-grade endometrial cancer can be improved. In addition to providing a brief overview of the pathogenesis of low-grade endometrial cancer, we discuss limitations in the current classification of endometrial cancer and how stratification may be refined using molecular markers to reproducibly identify 'low-risk' cancers which may represent the best candidates for progestin therapy. We also discuss constraints in current approaches to progestin treatment of low-grade endometrial cancer and perform a systematic review of predictive biomarkers.

METHODS

PubMed, ClinicalTrials.gov, and Cochrane Library were searched for studies reporting pre-treatment biomarkers associated with outcome in women with low-grade endometrial cancer or endometrial hyperplasia with an intact uterus who received progestin treatment. Studies of fewer than 50 women were excluded. The study protocol was registered in PROSPERO (ID 152374). A descriptive synthesis of pre-treatment predictive biomarkers reported in the included studies was conducted.

RESULTS

Of 1908 records reviewed, 19 studies were included. Clinical features such as age or body mass index cannot predict progestin response. Lesions defined as 'low-risk' by FIGO criteria (stage 1A, grade 1) can respond well; however, the reproducibility and prognostic ability of the current histopathological classification system is suboptimal. Molecular markers can be reproducibly assessed, have been validated as prognostic biomarkers, and may inform patient selection for progestin treatment. DNA polymerase epsilon (POLE)-ultramutated tumors and a subset of p53 wild-type or DNA mismatch repair (MMR)-deficient tumors with 'low-risk' features (eg, progesterone and estrogen receptor-positive) may have improved response rates, though this needs to be validated.

DISCUSSION

Molecular markers can identify cases which may be candidates for progestin treatment. More work is needed to validate these biomarkers and potentially identify new ones. Predictive biomarkers are anticipated to inform future research into progestin treatment of low-grade endometrial cancer and ultimately improve patient outcomes.

Progesterone receptor promotes degradation of STAT2 to inhibit the interferon response in breast cancer

Type I (IFNα/β) interferon signaling represents a critical transduction pathway involved in recognition and destruction of nascent tumor cells. Downregulation of this pathway to promote a more immunosuppressed microenvironment contributes to the ability of tumor cells to evade the immune system, a known Hallmark of Cancer. The present study investigates the progesterone receptor (PR), which is expressed in the vast majority of breast cancers, and its ability to inhibit efficient interferon signaling in tumor cells. We have shown that PR can block the interferon signaling cascade by promoting ubiquitination and degradation of STAT2. Targeting STAT2 is critical, as we show that it is an essential protein in inducing transcription of interferon-stimulated genes (ISG); shRNA-mediated knockdown of STAT2 severely abrogates the interferon response in vitro. Importantly, we were able to reverse this inhibition by treating with onapristone, an anti-progestin currently being investigated in breast cancer clinical trials. Additionally, we have found that an interferon-related gene signature (composed of ISGs) is inversely correlated with PR expression in human tumors. We speculate that PR inhibition of interferon signaling may contribute to creating an immunosuppressed microenvironment and reversal of this through anti-progestins may present a novel therapeutic target to promote immune activity within the tumor.

A 12-month extension study to evaluate the safety and efficacy of asoprisnil in women with heavy menstrual bleeding and uterine fibroids

STUDY QUESTION

What is the safety and efficacy profile during long-term (12–24 months) uninterrupted treatment with the selective progesterone receptor modulator asoprisnil, 10 and 25 mg in women with heavy menstrual bleeding (HMB) associated with uterine fibroids?

SUMMARY ANSWER

Uninterrupted treatment with asoprisnil should be avoided due to endometrial safety concerns and unknown potential long-term consequences.

WHAT IS KNOWN ALREADY

Asoprisnil was well tolerated in shorter-term studies and effectively suppressed HMB and reduced fibroid volume.

STUDY DESIGN, SIZE, DURATION

Women with uterine fibroids who had previously received placebo (n = 87) or asoprisnil 10 mg (n = 221) or 25 mg (n = 215) for 12 months in two double-blind studies entered this randomized uncontrolled extension study and received up to 12 additional months of treatment followed by 6 months of post-treatment follow-up. Women who previously received placebo were re-randomized to either asoprisnil 10 or 25 mg for the extension study. This report focuses on the 436 women who received asoprisnil in the double-blind studies and this extension study. Results for women who previously received placebo in the double-blind studies are not described.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Women ≥18 years of age who completed a 12-month, double-blind, placebo-controlled study, had estradiol levels indicating that they were not menopausal and had no endometrial hyperplasia or other significant endometrial pathology were eligible. The safety endpoints were focused on endometrial assessments. The composite primary efficacy endpoint was the proportion of women who demonstrated a response to treatment by meeting all three of the following criteria at the final month for participants who prematurely discontinued or at month 12 for those who completed the study: a reduction from initial baseline to final visit of ≥50% in the menstrual pictogram score, hemoglobin concentration ≥11 g/dl or an increase of ≥1 g/dl from initial baseline at the final visit, and no surgical or invasive intervention for uterine fibroids. Other efficacy endpoints included rates for amenorrhea and suppression of bleeding, changes in fibroid and uterine volume and changes in hematologic parameters. No statistical tests were planned or performed for this uncontrolled study.

MAIN RESULTS AND ROLE OF CHANCE

Imaging studies revealed a progressive increase in endometrial thickness and cystic changes that frequently prompted invasive diagnostic procedures. Endometrial biopsy results were consistent with antiproliferative effects of asoprisnil. Two cases of endometrial cancer were diagnosed. At the final month of this extension study (total duration of uninterrupted treatment up to 24 months), the primary efficacy endpoint was achieved in 86 and 92% of women in the asoprisnil 10- and 25-mg groups, respectively. During each month of treatment, amenorrhea was observed in the majority of women (up to 77 and 94% at 10 and 25 mg, respectively). There was a progressive, dose-dependent decrease in the volume of the primary fibroid with asoprisnil 10 and 25 mg (−55.7 and −75.2% median decrease, respectively, from baseline [i.e. the beginning of the placebo-controlled study] to month 12 [cumulative months 12–24] of this extension study). These effects were associated with improvements in quality of life measures.

LIMITATIONS, REASONS FOR CAUTION

This study was uncontrolled, which limits the interpretation of safety and efficacy findings. The study also had multiple protocol amendments with the addition of diagnostic procedures and, because no active comparator was included, the potential place of asoprisnil in comparison to therapies such as GnRH agonists and surgery cannot be determined.

WIDER IMPLICATIONS OF THE FINDINGS

Long-term, uninterrupted treatment with asoprisnil leads to prominent cystic endometrial changes that are consistent with the ‘late progesterone receptor modulator’ effects, which prompted invasive diagnostic procedures, although treatment efficacy is maintained. Although endometrial cancers were uncommon during both treatment and follow-up, these findings raise concerns regarding endometrial safety during uninterrupted long-term treatment with asoprisnil. This study shows that uninterrupted treatment with asoprisnil should be avoided due to safety concerns and unknown potential long-term consequences.

STUDY FUNDING/COMPETING INTEREST(S)

AbbVie Inc. (prior sponsor, TAP Pharmaceutical Products Inc.) sponsored the study and contributed to the design and conduct of the study, data management, data analysis, interpretation of the data and the preparation and approval of the manuscript. Financial support for medical writing and editorial assistance was provided by AbbVie Inc. M. P. Diamond received research funding for the conduct of the study paid to the institution and is a consultant to AbbVie. He is a stockholder and board and director member of Advanced Reproductive Care. He has also received funding for study conduct paid to the institution for Bayer and ObsEva. E. A. Stewart participated as a site investigator in the phase 2 study of asoprisnil and served as a consultant to TAP Pharmaceuticals during the time of design and conduct of the studies while on the faculty of Harvard Medical School and Brigham and Women’s Hospital, Boston, MA. In the last 3 years, she has received support from National Institutes of Health grants HD063312, HS023418 and HD074711. She has served as a consultant for AbbVie Inc., Allergan, Bayer HealthCare AG and Myovant for consulting related to uterine leiomyoma and to Welltwigs for consulting related to infertility. She has received royalties from UpToDate and the Med Learning Group. A.R.W. Williams has acted as a consultant for TAP Pharmaceutical Products Inc. and Repros Therapeutics Inc. He has current consultancies with PregLem SA, Gedeon Richter, HRA Pharma and Bayer. B.R. Carr has served as consultant and received research funding from AbbVie Inc. and Synteract (Medicines360). E.R. Myers has served as consultant for AbbVie Inc., Allergan and Bayer. R.A. Feldman received compensation for serving as a principal investigator and participating in the conduct of the trial. W. Elger was a co-inventor of several patents related to asoprisnil.

C. Mattia-Goldberg is a former employee of AbbVie Inc. and owns AbbVie stock or stock options. B.M. Schwefel and K. Chwalisz are employees of AbbVie Inc. and own AbbVie stock or stock options.

TRIAL REGISTRATION NUMBER

NCT00156195 at clinicaltrials.gov.