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From bench to bottle: Toward precision medicine in endometriosis

From bench to bottle: Toward precision medicine in endometriosis

Endometriosis researchers are coming closer to “stratified medicine,” but truly targeted treatments are lacking.

BY KARI OAKES

By the time an endometriosis patient is diagnosed, she’s ready for the treatment that will work for her. The arc of endometriosis can span decades, with diagnosis alone often taking years. Additionally, it’s possible that multiple, potentially overlapping etiologies underpin the heterogeneous manifestations of the disease, which still needs a surgical procedure for diagnostic certitude.


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Perspectives on Endometriosis Management


These are some of the characteristics of endometriosis that make it an especially tough target for the pharmaceutical holy grail of precision medicine, which seeks to achieve effective, safe, targeted therapy on an individual level. At the 13th World Conference on Endometriosis, Patrick Groothuis, PhD, took the stage during a plenary session to talk about what’s needed to find better and more targeted treatments for endometriosis.

Dr. Groothuis, principal scientist at Synthon Biopharmaceuticals, Nijmegen, the Netherlands, contrasted the precision approach with empirical medicine, in which therapies achieve approval through large clinical trials that show efficacy and safety on a population scale.

Although it’s known that profound interindividual variations exist for the effectiveness of a host of medications – from antibiotics to cytotoxic agents to analgesics – clinical trials are not ordinarily designed or powered to detect individual patient characteristics that may lie behind these variations. In endometriosis therapy, combined oral contraceptives (COC), nonsteroidal anti-inflammatory drugs, and progestins all have a solid empiric foundation for use. However, it’s not always known who may benefit from which treatment.

Lying somewhere between the empiric and the precision realm, said Dr. Groothuis, is stratified medicine, where particulars of an individual’s diagnosis can be used to target treatment. Researchers in endometriosis, he said, are coming closer to this intermediate level of precision in delivering the right therapy to the right patient, but truly targeted treatments are lacking.

Patrick Groothuis, PhD

Room for more therapies

Since 1998, said Dr. Groothuis, a very short list of endometriosis drugs have been approved. These include the depot formulation of medroxyprogesterone (Provera), approved in 2005; the progestin dienogest (Visanne), approved in 2007, and the drospirenone-ethinyl estradiol COC (Yasmin), approved in Japan only for the endometriosis indication in 2016.

And endometriosis was not the target for these therapies when they were initially developed, Dr. Groothuis pointed out; depot medroxyprogesterone acetate was first introduced in the 1950s, dienogest was part of a COC introduced in the 1990s, and drospirenone, with its additional mineralocorticoid receptor antagonist properties, came to the market in 2000.

Additionally, he said, there’s significant off-label use of medications to treat endometriosis. “Why invest in a labeled indication?” when physicians and patients are using off-label prescribing as a work-around, he asked.

Currently, said Dr. Groothuis, there are about two dozen endometriosis drugs in development. “This might sound like a lot until you realize that there are over 3,000 oncology drugs in the pipeline,”

out of the 12,000 drugs that were in development during the 2011-2013 window, he said. Of the oncology candidate drugs, and the nearly 3,000 drugs in the infections disease and neurology pipelines, “70% are first in class.”

Over the past 20 years, about 60% of drugs that eventually achieved Food and Drug Administration approval were brought forward by large pharmaceutical companies, while just under 10% began as a university-developed drug that was later transferred to a pharmaceutical company. The remaining drugs that reached approval came from smaller biotechnology companies, working alone or with a university. “Involvement of industry in the development of innovative drugs is vital,” said Dr. Groothuis.

Know the hurdles, identify the drivers

The herculean task of bringing a drug to market can get derailed at many stages, and the vast majority of candidate drugs never make it to the patient, so what’s the way forward for endometriosis researchers? “Learn from other indications,” said Dr. Groothuis. “Understand the hurdles in drug development. … Most drugs that fail in phase 1 fail for safety; most drugs that fail in phase 2 fail for efficacy,” said Dr. Groothuis.

If a new endometriosis drug – and certainly one that is first in class – is going to make it to market, Dr. Groothuis said that many “critical project drivers” will have to fall in place. Though these might number in the dozens, he said to the room of endometriosis researchers, “there are a few you can have an impact on.”

Some of these drivers, he said, come under the general rubric of scientific opportunity, where it’s not enough to have identifiable targets and good candidate chemicals. It’s unlikely that a successful development pathway will occur, said Dr. Groothuis, without well-developed animal models that are predictive of performance in human studies, and the identification of biomarkers and other surrogate endpoints that can help mark the way to clinically meaningful outcomes.

Other drivers, he said, include meeting a genuinely unmet medical need, and although the need certainly exists for better endometriosis therapies, there are still some market forces working against a robust endometriosis pipeline.

Overall, said Dr. Groothuis, endometriosis is a small market with a “low disease profile,” meaning that though morbidity is high for those with endometriosis, the condition isn’t associated with mortality. Public awareness is relatively low compared with, for example, breast cancer. Also, he said, endometriosis currently requires laparoscopy – an invasive procedure – for definitive diagnosis, and clear biomarkers are lacking.

Researchers can help the chances of new successful – and targeted – treatments for endometriosis, he said, by “upscaling biomarker discovery activities.” Moving toward the use of phenotypic and functional genetic screens would be a first step, he said. “Study the exosome – the mirror of the cells,” to search for measurable, unique endometriosis biomarkers. Along the way, said Dr. Groothuis, “make sure to generate robust and verifiable data.”

The subjective nature of pain, one of endometriosis’ cardinal symptoms, can mean problems in constructing a replicable clinical trial with measurable endpoints.

One key to successful drug discovery programs, he said, will be to register with and utilize the resources of the World Endometriosis Research Foundation’s Endometriosis Phenome and Biobanking Harmonisation Project. Through this effort, said Dr. Groothuis, “researchers can create a platform for biomarker validation, and access to diseased tissue,” with the goal of creating a global consortium that includes academic and industry partners.

The pathway to true precision medicine for endometriosis will involve a deeper understanding of pathophysiology, closer attention to candidate molecules for biomarkers, and better parsing of individual risks and protective factors. Tantalizing clues from bench science and early clinical work may broaden investigators’ options for potential therapeutic targets; some of this work was presented during the scientific sessions of the World Congress on Endometriosis.

Are microRNAs the key to a biomarker?

In the search for biomarkers, researchers in China are working to identify deregulated microRNA transcription factors. By integrating messenger RNA sequencing with microRNA data from ovarian-derived endometriosis cells, and then comparing the data to that from eutopic endometrium, Luyang Zhao, MD, and his colleagues were able to trace a regulatory network of transcription factors governing endometriosis formation.

They validated their results using quantitative reverse transcriptase–polymerase chain reaction methods, finding that overall, six selected microRNAs and five transcription factors “were differentially expressed with the same trend (up- or down-regulated)” in ectopic versus eutopic endometrium, said Dr. Zhao; the results were statistically significant.

“The network included some well-studied candidate molecules, but also identified novel subjects,” said Dr. Zhao, of the department of gynecology and obstetrics, Peking University People’s Hospital (Beijing). Among the microRNA and gene clusters identified, Dr. Zhao said that the FOX family genes were lower in endometriosis; the microRNA 183/182 cluster “inhibits apoptosis and enhances the invasive ability of endometrial stromal cells,” he said. The microRNA 449/34 cluster is implicated in cell proliferation, migration, and invasion but may also serve as a tumor suppressor, he said.

Though the results are preliminary, said Dr. Zhao, “[Our] integration analysis presents unique insight into the pathogenesis of this enigmatic disorder and provides clues for further research.”

Neurotrophic crosstalk contributes to fibrogenesis

“Ovarian endometriosis, deep endometriosis, and peritoneal endometriosis have long been viewed as three separate disease entities,” said Sun-Wei Guo, PhD, professor of obstetrics and gynecology at Fudan University, Shanghai, China. It’s even possible, he said, that the three variants differ in pathogenesis and pathophysiology.

Both ovarian and deep endometriosis lesions, though, share the characteristic of cyclic bleeding, said Dr. Guo. This means, he said, that

“endometriotic lesions are fundamentally wounds undergoing repeated tissue injury and repair.”

This injury-repair cycle is associated with transdifferentiation of fibroblasts to myofibroblasts, with smooth muscle metaplasia, and eventually fibrosis, said Dr. Guo, all changes he and his research team have seen with both ovarian and deep endometriotic (OE and DE) lesions.

However, there were histologic differences between the two variants, with DE lesions showing more fibrosis, less vascularity, and higher hormone receptor expression. Deep lesions are often sited in intimate association with the nerve plexuses of the pelvis; could nerves and these deep lesions be “partners in crime”?

Some previously known clues said yes: endometriotic lesions, especially DE, can be hyperinnervated; the lesions are themselves secretors of neurotrophic factors; and sensory and sympathetic nerve fibers are overrepresented in endometriotic tissue, said Dr. Guo.

What wasn’t known was whether communication from the endometriosis lesion to the CNS was “just a one-way street of pain signals,” though. More work suggested that traffic runs both ways; “sensory neurons secrete multiple bioactive neuropeptides,” said Dr. Guo. These include calcitonin gene-related peptide, which interacts with substance P and neurokinin-1 receptor in the milieu of the endometriotic lesion to promote fibrogenesis in a mouse model.

In another mouse model, sensory and sympathetic denervation reduced fibrosis in endometriosis lesions and dampened proliferation, suggesting that “sensory nerve fibers may play important roles in the fibrogenesis of lesions,” he said.

“The proximity to nerve plexuses is responsible for the development of deep endometriosis,” said Dr. Guo, suggesting that though OE and DE share many traits, different targets and treatment modalities may be needed for precise treatment of DE.

Is there a male factor?

Mohammed Ibrahim, MD, is an endometriosis researcher who’s also investigating the metaplastic processes of endometriosis. The pathway from eutrophic endometrial tissue to endometriosis, he said, is thought to involve persistent survival of shed endometrial tissue that lodges, attaches, and invades after retrograde menstruation.

A known player in this process, and a significant contributor to metaplasia, is transforming growth factor–beta 1 (TGF-beta 1), normally present at a concentration of about 2 mcg/mL in peritoneal fluid. However, in human seminal plasma, the concentration of TGF-beta 1 is about 85 mcg/ml, said Dr. Ibrahim, of the clinic for gynecology and obstetrics at the University Hospital of Muenster (Germany).

Dr. Ibrahim and his research team set out to determine whether seminal plasma actually did induce metaplasia in endometrial tissue. They used seminal plasma taken as a supernatant from centrifuged human semen, which, as expected, yielded a TGF-beta 1 concentration of 88.17 mcg/mL. Control peritoneal fluid had a concentration of just 6.79 pg/mL.

Then, the seminal plasma was incubated with endometrial epithelial and endometrial stromal cell lines and the researchers looked for mRNA expression of markers and mediators of metaplasia using reverse transcriptase–polymerase chain reaction. For both cell lines, they found upregulation of one metaplasia marker, alpha–smooth muscle antigen, becoming more pronounced over time. One metaplasia mediator, SNAIL 1/2, was rapidly and markedly upregulated, while another mediator, ZEB2, saw delayed upregulation. “In contrast, TWIST [a third mediator] expression was down-regulated in both lines,” said Dr. Ibrahim.

When TGF-beta 1 effects were nullified by the addition of anti–TGF-beta 1 antibody to the samples, alpha–smooth muscle antigen levels plummeted to the levels seen in the control samples, confirming the role TGF-beta 1 played in the seminal plasma–induced metaplasia, said Dr. Ibrahim.

There’s much more to the endometriosis story than just exposure to seminal plasma, he said, but the intriguing results merit more inquiry, to see whether there’s the potential to influence the course of endometriosis in a given patient by controlling her exposure. He and his colleagues are conducting ongoing work, with early results showing an influence of seminal plasma on cell migration and apoptosis of endometrial cells as well.