Myovant socks it to Orilissa

Two years after Abbvie’s disappointing launch of Orilissa Myovant hails the development of something much better.

Trial Results

Yesterday’s clinical trial success for relugolix gives Myovant's lead project its second knockout hit in endometriosis, and a third possible indication, albeit in combination with hormone replacement. In a battle between three GnRH antagonists relugolix now has chance to catch up with Abbvie’s Orilissa, which was launched first but which has disappointed as monotherapy.

Investors might be wondering how to trade the news. Myovant stock closed up 14% yesterday, giving a $1.8bn market cap, but the position of Sumitomo Dainippon Pharma is intriguing. The Japanese group last September paid Roivant $3bn for various subsidiaries, including a 46% Myovant stake, and is currently valued at $5.7bn.

This suggests that Myovant still accounts for a relatively small part of the valuation of Sumitomo, which is struggling with patent expiries and clinical failures. One solution for Sumitomo could be to buy out Myovant and gain the full benefit of relugolix, and no doubt this takeout thesis underpins much of the smaller company’s valuation.

At $1.8bn it is not clear how much of relugolix’s value the market factors in, however. Sellside consensus amounts to a product NPV of $1.3bn, as computed by EvaluatePharma, but analysts assign most of 2026 forecast revenues to uterine fibroids and endometriosis, despite the project scoring in prostate cancer too (Relugolix gets a Hero’s welcome in prostate cancer, November 19, 2019).

The three-way GnRH product battle
Project Company Indication  Status 2026e sales ($m)
Orilissa Abbvie Endometriosis Marketed  561
    Uterine fibroids Filed 500
         
Relugolix Myovant Uterine fibroids Filed 656
    Prostate cancer Filed 168
    Endometriosis Phase III 329
         
Linzagolix Obseva Uterine fibroids Phase III 466
    Endometriosis Phase III 151
Source: EvaluatePharma.

Myovant filed relugolix monotherapy for prostate cancer on the back of the Hero programme in April, while a differently dosed combo with hormone-replacement therapy (HRT) was submitted for uterine fibroids in May.

Data in endometriosis, therefore, give the asset its third leg. Here, two near-identical pivotal studies were run, Spirit-1 and Spirit-2, testing relugolix plus HRT. The latter read out positively two months ago, while the former was the success Myovant celebrated yesterday.

Spirit-1 confirmed the earlier positive data: a knockout result in pain reduction for relugolix plus HRT versus placebo in terms of responders according to a patient daily assessment, among those with period pain and non-menstrual pelvic pain, amounting to the two co-primary endpoints. There was also a clean sweep of seven key secondary measures.

While in uterine fibroids relugolix failed to meet expectations relative to Abbvie’s similarly acting and already approved Orilissa, in endometriosis it could have an advantage. On a cross-trial basis efficacy is in line with a high Orilissa dose, but without the same association with hot flushes and bone density loss.

Cross-trial comparison, adapted from Myovant presentation. Elagolix = Orilissa.

The latter has resulted in Orilissa’s high dose being limited to six months’ use – suboptimal for what is a chronic condition. It has been suggested that this side-effect profile has contributed to Orilissa’s poor uptake; EvaluatePharma archives show that 2024 sellside forecasts have fallen from $1.7bn to $860m in two years.

Still, one difference is that Orilissa is prescribed as monotherapy, without HRT. Abbvie will imminently report data from a 681-subject study comparing Orilissa monotherapy versus Orilissa plus HRT, and versus placebo; if HRT is shown to reduce bone loss Orilissa’s label could be expanded, neutralising the relugolix threat.

The third horse in this GnRH antagonist race is Obseva’s linzagolix. However, not only is this a laggard, it has been associated with bone loss, whether given with or without HRT; Obseva’s $267m valuation reflects this fact.

Linzagolix’s most advanced indication is uterine fibroids, where six-month data from the Primrose-1 trial, and a 12-month update from Primrose-2, are expected imminently. The safety figures just put up by Myovant could prove hard to match.

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