As of 12 January, the likelihood of approval (LoA) for ObsEva’s Yselty (linzagolix) in the US for endometriosis pain dropped 24 points, according to GlobalData’s LoA data.

The score change was based on the company’s 11 January broad update on Yselty’s clinical development, which noted that the US-based Phase III EDELWEISS 2 study had been discontinued due to recruitment hurdles.

ObsEva, which has a $206.85m market cap, has also stated that it is planning to conduct a new Phase III endometriosis-associated pain study and is aiming to maintain the original filing timelines in the US as well as in Europe, where Phase III EDELWEISS 3 is ongoing.

The new Phase III will include protocol and operational changes to improve enrollment, the company noted, explaining that screening and recruitment for EDELWEISS 2 had become increasingly challenging, particularly due to the COVID-19 pandemic.

Convenience could be a benefit for Yselty

While the LoA prior to this company update was 36%, GlobalData’s analysis using a combination of machine learning and a proprietary algorithm has bumped down the LoA to 12%. In November 2019, this news service reported that based on available trial data experts said Yselty’s efficacy is largely comparable to AbbVie’s approved drug for endometriosis pain, Orilissa (elagolix), and Myovant Sciences’ Phase III relugolix.

All three are gonadotropin-releasing hormone (GnRH) antagonist therapies. If Yselty and relugolix both hit the market for endometriosis, interviewed experts noted that the latter may suffer from a lack of dosing options. The convenience that comes from being able to choose a dose and consequently use add-back therapy will likely be an important factor for uptake.

While a once-daily schedule is a significant advantage for relugolix compared to  twice-daily Orilissa, it is a benefit that Yselty  also possesses. Furthermore, relugolix is being evaluated at one high dose with add-back therapy, but Orilissa is available in two dosage strengths and Yselty was being trialed at two doses with or without add-back therapy.