ObsEva’s second uterine fibroids PhIII comes through, sending some investors to the hills
In the three-company race to develop a new uterine fibroid treatment, ObsEva long lagged behind AbbVie and Myovant. Still, they hoped that better efficacy — including a 93.9% response rate in one Phase III trial — could ultimately deliver better sales.
Now, though, the second of those Phase III studies is out, and it has brought the Swedish biotech back to earth.
In the second of their Phase III trials, 75.5% of patients who took ObsEva’s experimental tablet linzagolix plus a hormone saw their bleeding reduced by at least 50% and at least 80 ml after 24 weeks. Pooling those results with new data from their first Phase III trial — which showed a 93.9% response rate at 24 weeks and a 91.6% response rate at 52 weeks — ObsEva calculated a collective 84.7% responder rate for patients taking their therapy and said the data “confirm potential best-in-class” status.
“These excellent data move us closer to the potential commercialization of Yselty and our immediate priority is to progress our regulatory filings,” Ernest Loumaye, ObsEva CEO and co-founder said in a statement, using the branded name for his drug.
Yet some investors and analysts were disappointed, noting that these new results erase the edge that the first trial seemed to give ObsEva. 75.5% falls right in line with the results from AbbVie and Myovant. Abbvie had a 68.5% response rate in one Phase III trial and a 76.2% response rate in the second. Myovant saw response rates of 71.2% and 73.4%.
In fact, SVB Leerink’s Ami Fadia wrote in a note to investors that because ObsEva had high placebo response in both trials. the company now has the worst placebo-adjusted response of any of the three.
“We believe the placebo-adjusted response rate will be a key metric that investors pay attention to, and the PRIMROSE1 results on that measure likely fell short of expectations,” Fadia wrote, noting their own ObsEva model is now under review.
The market agreed, cutting ObsEva’s stock $OBSV by 40%, or $2.75, Monday morning.
Even before the new trial, analysts had expressed reservations about ObsEva’s apparent efficacy. In December, Baird’s Brian Skorney chalked up their high score to a 29.4% placebo response rate, far higher than those seen in their two competitors’ trials. “We think the resounding takeaway here is that the efficacy profiles of these 3 … inhibitors are essentially the same,” he wrote in a note to investors.
If these drugs are effectively the same, Skorney bet that the first ones out of the gate will establish a beach-head and garner the most sales. That would spell bad news for ObsEva. Timing-wise, they now sit in third place. AbbVie’s drug has already been approved and Myovant submitted an NDA in June, while ObsEva has yet to file an application. Known as GnRH inhibitors, these drugs block a hormone receptor in the body.
Some analysts, though, bet that despite some initial concerns, safety could ultimately be ObsEva’s advantage. When the FDA approved AbbVie’s drug, Oriahnn, they also put strict limits on its use after multiple patients in their trial had thrombotic events, including a pulmonary embolism. These likely came from extra hormone treatments, known as add-back therapy, patients take to stop the menopause-like symptoms GnRH inhibitors can cause.
That’s partly why ObsEva included an arm on both trials where patients took a smaller dose of the drug and didn’t receive the add-back therapy. In the company’s first trial, a little over half of those patients saw their bleeding cut in half. That could make it a good candidate for patients with other co-morbidities, Fadia and other analysts wrote. The new study showed a 56.6% rate of patients on the no-add-back treatment arm, but it also had a 35% rate in placebo, cutting the placebo-adjusted rate to just 21.4%. With new 52-week data out, there were also questions about how long the therapy would last.
“We still view the profile of both the low dose and the high dose as approvable,” Fadia wrote, “although we see potential questions coming up regarding the treatment duration on the label and the commercial viability for the low dose.”