Investors will have to wait until later this year for detailed data on such matters as bone mineral density (BMD) – as well as phase IIb results from a separate, earlier-stage study in uterine fibroids – but the six-month top-line results from the first of two phase III trials with oral elagolix for endometriosis put a spark in shares of Neurocrine Biosciences Inc.

The elagolix program "in the good hands of Abbvie," as Neurocrine's chief medical officer Chris O'Brien said during the November conference call on earnings, is slated to yield full results in both indications later this year. Meanwhile, Abbvie, of North Chicago, disclosed that the gonadatropin-releasing hormone (GnRH) receptor inhibitor met the study's co-primary endpoints (p <0.001) of reducing scores of nonmenstrual pelvic pain and menstrual pain at the third and sixth month.

A spokesperson for Abbvie told BioWorld Today that no information beyond what was contained in a press release would be disclosed.

It was enough for Neurocrine, shares of which (NASDAQ:NBIX) closed Thursday at $27.48, up $5.60, or 25.6 percent. Abbvie's stock (NYSE:ABBV) closed at $67.63 up 70 cents.

The second, larger phase III trial, SOLSTICE, is expected to yield data later this year, too.

The safety profile of elagolix turned up consistent with previous experiments, with the most common adverse events (AEs) hot flush, headache, nausea and fatigue. While most AEs were similar across treatment groups, some, such as hot flush and BMD loss, were dose-dependent.

Dropout rates, too, were similar across treatment groups, and those due to AEs were 5.9 percent, 6.4 percent and 9.7 percent for placebo, at doses of 150 mg once daily and 200 mg twice daily, respectively.

Patients in the trial will continue on in either post-treatment follow-up or a blind six-month extension study, Abbvie said.

Called M12-665, the 24-week, randomized, double-blind, placebo-controlled study enrolled 872 women,ages 18 to 49, with moderate to severe endometriosis-associated pain, and is ongoing at about 160 sites in the U.S., Puerto Rico and Canada.

The World Endometriosis Research Foundation estimated that the disease affects one in 10 women during their reproductive years, about 176 million women worldwide. Cowen and Co. analyst Phil Nadeau pegged the potential market for elagolix at more than $1 billion, of which San Diego-based Neurocrine would get about a 19 percent royalty, though he said the drug's "potential to be bone-sparing is a key attribute" and the fine points about that result in the phase III trials are still unknown. Evercore ISI analyst Mark Schoenebaum had a different take on Abbvie's news, pointing to a sentence in the press release about the consistent safety profile, which he said in an email alert to investors "would seem to apply to bone loss as well."

Piper Jaffray analyst Charles Duncan also weighed in, deeming the top-line results "at least an incremental risk-reducer" and upped the price target for Neurocrine from $29 to $33. "As expected, both efficacy and safety details are sparse," Duncan wrote in a research report.

"The high dose (details previously not disclosed) was higher than we expected (200 mg twice daily), which may bode well for Abbvie's comfort with elagolix's mechanism and likely safety profile, we think," he added.

Current therapy for endometriosis patients who fail oral contraceptives is generally limited to either injectables and/or drugs that result in bone loss and side effects bad enough that treatment often stops after six months to a year.

Neurocrine and Abbvie entered their potential $575 million deal in 2010, when the latter paid $75 million up front to develop elagolix as a candidate to join the leading approved, injectable endometriosis therapy Lupron (leuprolide acetate), also a GnRH inhibitor, in Abbott's arsenal. (See BioWorld Today, June 17, 2010.)

Neurocrine has a separate program with NBI-98854, a vesicular monoamine transporter 2 inhibitor in tardive dyskinesia, Cowen's Nadeau noted, saying in his report that he "expect[s] both to succeed in their phase III programs by the end of 2015," and they will "drive outperformance" of Neurocrine, which he dubbed a top small-cap pick.

During the earnings call, Nadeau asked about "the quality and quantity of data that [will be] released from the phase IIb" study in fibroids. Tim Coughlin, chief financial officer, said the companies were "working through those" but Abbvie had other, more immediate projects. "And so what we've decided do is just table that discussion until early [in 2015], and then we'll just start talking about that."