Treating endometriosis: what lies ahead? 

Endometriosis, an under-researched condition, has been rather difficult to treat with no cures to date. It is caused by the growth of tissue – similar to those in the uterine lining – outside the uterus, leading to debilitating pelvic pain during sex and heavy periods. 

Around 190 million women and girls have been diagnosed with endometriosis across the world, according to the World Health Organization (WHO), and although the disease affects one in 10 women and people who menstruate, therapeutic research has often been ignored. 

Endometriosis research: an underfunded area

As 50% of endometriosis patients deal with fertility issues, the economic cost that the condition has on the U.S. alone – both in terms of medical care and lost productivity – is estimated to be around $78-120 billion annually, according to Bruce Nicholson, co-founder of Hera Biotech, a U.S.-based women’s health company that is developing endometriosis diagnosis tests. 

Nicholson explained that despite this pervasive challenge to women’s health, patients suffer an average delay of eight years for diagnosis, which can only be done reliably with surgery.  

While hormonal therapy can help alleviate symptoms, it fails to address infertility. Moreover, the surgical removal of lesions is often temporary as the lesions return 50% of the time, according to Nicholson. 

And clinical failures like Organon’s “disappointing” phase 2 trial of OG-6219 this year has been crushing for the endometriosis community. The small molecule was meant to inhibit an enzyme called HSD17B1, which plays a role in regulating the growth of tissues that form the layers of the uterus, to treat pelvic pain in endometriosis. However, the study did not meet its primary endpoint, and the New Jersey-based company gave up on OG-6219 development. 

Still, lately, therapeutic progress has not stalled. 

“Despite these limitations, we have seen some significant progress in the study of endometriosis over the last five to 10 years,” said Nicholson. 

Kissei’s linzagolix for endometriosis approved in Taiwan after UK win 

And in 2025, a few advances in endometriosis care have pushed through in the face of a challenging treatment space. The medicine linzagolix’s approval in Taiwan for uterine fibroids two weeks ago paves the way for global access. Developed by Japanese pharmaceutical Kissei, the once-daily pill was already given the go-ahead by the National Health Service (NHS) in England in May.  

It is a gonadotropin releasing hormone (GnRH) receptor antagonist that binds to the receptor, blocking it from producing hormones, whose overproduction is implicated in the manifestation of endometriosis.  

An endometriosis pill is a step forward in easing the treatment burden. Most treatments that manage pain are given as injections, which means that patients have to regularly go into clinics to get their shots. Linzagolix, however, will be given alongside an add-back therapy, which is a low dosage of low-dose hormone replacement therapy to prevent menopause-like symptoms and bone loss. 

The drug significantly reduced painful periods as well as pelvic pain in clinical trials, which led to the NHS stamp of approval. 

“This is welcome news for women with endometriosis who haven’t found relief from previous therapies or surgery – it’s another treatment option which will help women take control of their health and better manage the symptoms of this often painful and debilitating condition,” Sue Mann, National Clinical Director in Women’s Health for NHS England, had said earlier this year. 

Linzagolix is only the second take-at-home pill to be authorized by U.K. regulators for endometriosis following the approval of the combination therapy relugolix in March. Relugolix, sold under the brand name Ryeqo for endometriosis in the U.K. and the European Union (EU) – the latter having approved it two years ago – is also a GnRH receptor antagonist but unlike linzagolix, it is specifically designed to include add-back therapy and combines the two into one pill. 

Can Hope Medicine’s HMI-115 reduce endometriosis-related pelvic pain? 

Now, with the Taiwan Food and Drug Administration’s (TFDA’s) clearance of the inhibitor drug, the global push towards endometriosis therapies – which has been a long time coming – is apparent. And with different medicines homed in on different drug targets, the goal is to broaden treatment options. That’s what Hope Medicine wants to do with its monoclonal antibody HMI-115, which has just reaped positive results in a phase 2 trial. 

The Shanghai-based drug developer’s clinical candidate relieved pain by 42%, according to the dysmenorrhea pain score. Dysmenorrhea, also known as menstrual cramps, are the throbbing pains in the lower abdomen that many women and people with endometriosis experience. Non-menstrual pelvic pain, which is another major symptom of endometriosis, was measured, and it was found that pelvic pain declined by 52% in patients. 

As new drug targets are being discovered to better tackle endometriosis, the prolactin receptor was what Hope Medicines set its sights on, and HMI-115 targets. The antibody is designed to block the receptor which produces the hormone prolactin – responsible for milk production – as the overexpression of this receptor is linked to endometriosis.  

Previous studies have even found that prolactin has a direct effect on pain. Researchers at the University of Arizona saw that higher the levels of prolactin in female animal models, lower the threshold for triggering pain, specifically migraine pain. But in male animal models, there was no such link between prolactin and pain. 

This could explain why hindering the receptors from generating prolactin could reduce pain in patients. And HMI-115 managed to demonstrate that in the clinic. 

As Hope plans to conduct phase 3 trials worldwide, Lan Zhu, director of Gynecology at Peking Union Medical College Hospital and lead investigator of the phase 2 study, said: “Endometriosis is a common and debilitating disease. The findings from this proof-of-concept study are exciting. HMI-115 relieved endometriosis pain in women without disturbing their sex hormones. It can potentially shift the treatment paradigm. We will be able to treat women without menopausal side effects or even infertility.” 

Small molecule vipoglanstat gets UK go-ahead for clinical trial 

While Hope Medicines’ phase 2 trial ended with promising outcomes, Gesynta pharma is just about to kickstart its phase 2 trial of vipoglanstat, a small molecule that inhibits an enzyme that promotes production of a proinflammatory molecule called prostaglandin E2 (PGE2). This molecule can drive both pain and lesion progression in endometriosis and blocking it has shown that downregulation reduces endometriotic lesions in preclinical studies.  

The UK Medicines and Healthcare products Regulatory Agency’s (MHRA’s) greenlit the drug for a phase 2 trial following a $27 million series B funding round that took place in February for the study. 

A heavily underfunded field of therapeutic research, investments such as Gesynta’s funding round and U.K.-based Cyclana Bio’s £5 million ($6.7 million) fundraising last month to expedite endometriosis drug discovery, point towards changing tides in women’s healthcare. Pekka Simula, a partner at Innovestor, had said in an interview with Forbes earlier this year that “big pharma is waking up to the fact that half of the world’s population are women,” and that attitudes towards discussing women’s health are shifting. 

Repurposed cancer drug dichloroacetate shows promise in endometriosis study 

Meanwhile, there is buzz around a cancer drug that is being repurposed to address endometriosis. As people with the condition tend to produce excessive amounts of a harmful chemical called lactate – a byproduct of metabolic reactions in the body – which leads to the development of endometriosis cells, dichloroacetate has been found to reduce lactate levels and control the spread of abnormal cells.  

The researchers at the University of Edinburgh in Scotland had also tested the drug on a mouse model, which exhibited lower levels of lactate and lesions that had shrunk after seven days.  

With hopes to see the drug perform well in the clinic, dichloroacetate is now being tested in people with endometriosis after recruitment began in spring. 

 Moreover, contenders to linzagolix like merigolix, owned by South Korean biopharma TiumBio, which is collaborating with Daewon Pharmaceutical for the therapy’s development in South Korea and Hansoh Pharma for Greater China, are in the early stages of the clinic. It was also successful in treating uterine fibroids in a phase 2 study recently. 

Pain relief: can cannabis help with managing endometriosis symptoms? 

As for relieving pelvic pain, cannabis has been studied to address neuropathic pain in general.  A clinical trial by the Western Sydney University in Australia is ongoing to investigate its potential benefits for the treatment of endometriosis. 

It is looking into the effect of cannabis on the cell-signaling endocannabinoid system (ECS), as well as inflammatory markers. The double-blind randomized controlled trial will evaluate whether medicinal cannabis – in the form of cannabidiol (CBD) isolate or a balanced oil containing both CBD and delta-9-tetrahydrocannabinol (THC) – can counter symptoms like pain caused by endometriosis against a placebo.  

As 59% of people who used cannabis for endometriosis-related pain relief reported that they do not rely on painkillers anymore, the trial is based on evidence from an earlier study that revealed that cannabis can regulate inflammation and immune function, through interaction with the ECS.   

And while there is still a lot we don’t know about how or why cannabis may affect endometriosis symptoms and possibly slow lesion progression, cannabis candidates like Ananda Pharma’s MRX1 CBD aim to shed light on its effects in the clinic. It will test the candidate in 100 women with pelvic pain caused by endometriosis to evaluate to what extent the drug helps mitigate the pain. 

Diagnosing endometriosis: the earlier the better 

With these therapies in the clinic, diagnostic research is as important, as it allows for early intervention. The longer endometriosis goes undiagnosed, the increased tissue growth, which can further cause severe complications, such as the formation of scar tissue, adhesions, and cysts. These can lead to more intense pain and complications down the road, according to the Endometriosis Treatment Center of America. 

That’s where diagnostic tool developers like French company Ziwig and Texas-based Hera Biotech, co-founded by Nicholson, to name a few, come in. Ziwig has come up with its approach, the Endotest, which is the first diagnostic medical device for endometriosis where people spit in a tube and the sample is sent to lab, where they look at people’s microRNA – dysregulated in endometriosis. And then, more recently, Paris-based Endogene Bio debuted its new method to diagnose endometriosis from period blood in weeks. The tool was validated in study results revealed last month. 

As various therapies climb up the ranks in the clinic, news of OG-6219 flunking trials still hit hard for the endometriosis community, especially since there wasn’t much research going on in the field for a long time. Now, while that looks like it’s shifting with greater awareness, how these therapies and tools to address the debilitating condition will be perceived by regulators, we will have to watch for.