(Adds analyst comment, details, shares)
Jan 8 (Reuters) - An experimental drug being developed by AbbVie Inc and Neurocrine Biosciences Inc successfully reduced symptoms of endometriosis in pre-menopausal women in the first of two late-stage studies.
Neurocrine's stock soared 24 percent to $27.20 in premarket trading on Thursday, while AbbVie's shares were up 1.7 percent at $68.10.
Endometriosis occurs when the lining of the uterus grows outside of the womb, leading to chronic pelvic pain. It is the leading cause of infertility.
After six months of treatment, both a 150 mg once daily and 200 mg twice daily dose of the drug, elagolix, were found to significantly reduce menstrual and non-menstrual pain, compared with a placebo, AbbVie said.
The drug should represent a $3.5 billion peak sales opportunity, Deutsche Bank's Robyn Karnauskas said.
Endometriosis affects one in 10 women during their reproductive years, or about 176 million women worldwide, according to the World Endometriosis Research Foundation.
The late-stage study tested elagolix's safety and effectiveness in 872 women, aged 18 to 49, with moderate-to-severe endometriosis-associated pain.
Results of the second late-stage study are expected in late 2015, AbbVie said.
The drug, a peptide that stimulates secretion of the pituitary hormones responsible for sex steroid production and normal reproductive function, is also being tested for use in uterine fibroids.
(Reporting by Natalie Grover in Bengaluru; Editing by Ted Kerr and Simon Jennings)