• An experimental drug from Myovant Sciences met its main goal in a Phase 3 trial of women with uterine fibroids, results which keep the biotech on track to file the drug for U.S. approval later this year if a second late-stage study is similarly positive.
• Investors, though, were apparently not impressed, sending shares in Myovant down by nearly a third at one point Tuesday. Myovant’s treatment, called relugolix, is in the same class of drugs as AbbVie’s elagolix, which posted positive data from two Phase 3 uterine fibroid trials last fall.
• In unveiling its data on relugolix, Myovant pushed back against comparisons to elagolix, noting its drug’s once-daily dosing and benefit over placebo in reducing pain and uterine volume.

In typical biotech fashion, Myovant secured the positive results it needed from the first of two Phase 3 studies testing relugolix, but found itself on the wrong end of a stock slide after Wall Street took its measure of the data.

Both relugolix and AbbVie’s elagolix work by blocking signaling across hormone receptors that reside in the pituitary gland, a mechanism of action that suits the drugs to treating conditions spurred by ovarian sex hormones.

Elagolix, marketed as Orilissa, is already approved to treat endometriosis, a painful condition that involves uterine tissue growing outside the uterus. With positive Phase 3 data in uterine fibroids, AbbVie plans to file for an expanded approval in the coming months — a goal Myovant is also chasing.

Uterine fibroids, or non-cancerous growths inside the walls of the uterus, affect most women, but in many cases the growths don’t cause any symptoms. For one in four, though, the fibroids lead to heavy menstrual bleeding, pain and pregnancy-related complications, according to Myovant.

In Myovant’s study, which enrolled 388 women with uterine fibroids and heavy menstrual bleeding, nearly three quarters of participants who received a combination of relugolix and two other drugs responded, compared to just under 19% of those on placebo.

A response was defined as menstrual blood loss volume of less than 80 mL and a 50% reduction from baseline during the last 35 days of the six-month treatment period.

That rate stacks up to what AbbVie showed with elagolix, though the higher placebo response in Myovant’s study yields a slightly lower placebo-adjusted figure.

Recent study results for GnRH receptor antagonists elagolix, relugolix

SOURCE: Companies

Cross-trial comparisons can be fraught, but AbbVie’s and Myovant’s measured responses by the same criteria over a similar time period give some degree of comparability.

On a conference call with analysts Tuesday, Myovant CEO Lynn Seely acknowledged the studies enrolled patient populations with similar baseline characteristics as well.

Still, Seely and Myovant argue relugolix can hold its own against elagolix. Myovant also detailed secondary study results which showed significant reductions in pain from its drug over placebo, a data point it says it alone has reported.

“We believe our emerging product profile could position us to compete effectively in a multi-billion dollar marketplace with few competitors,” said Seely.

Data from LIBERTY-1 did not show, however, a significant reduction in uterine fibroid volume from relugolix over placebo from baseline to Week 24.

AbbVie and Myovant aren’t alone in seeking approval for a uterine fibroid treatment. ObsEva is also testing a GnRH antagonist called linzagolix, with late-stage results expected by the end of this year or early next. Allergan, by contrast, saw its experimental uterine fibroid drug ulipristal acetate rejected by the Food and Drug Administration last year.

According to a recent survey by investment bank SVB Leerink, the three GnRH antagonists are viewed as roughly similar by specialists, who anticipated cycling through treatments to find the most effective for each patient.

Correction: A previous version of the table above transposed the placebo response rates for the three studies.