Sage Therapeutics Inc. shares dropped 3.3% in Thursday morning trade after the company announced a $90 million deal with Shionogi & Co. Ltd. for the clinical development and commercialization of its drug SAGE-217 in Japan, Taiwan and South Korea. In addition to $90 million upfront, the deal makes Sage eligible for additional milestone payments of up to $485 million, as well as tiered royalties on sales in the three countries. Shionogi will also handle clinical development, regulatory filings and commercialization of SAGE-217 for major depressive disorder and any other indications in those countries. Sage is developing SAGE-217 for major depressive disorder, postpartum depression, bipolar depression and insomnia; just this week the company announced plans to expedite U.S. development of the drug in major depressive disorder and postpartum depression, sending the company’s shares up. Why, precisely, shares declined on Thursday is unclear; it’s possible investors expected a more lucrative deal, or hoped for the company to be acquired entirely. Because of how far along its drug pipeline is, Sage has been viewed by some as a promising acquisition target. Sage shares have dropped 5.2% over the last three months, compared with a 1.4% rise in the S&P 500 and a 2.3% rise in the Dow Jones Industrial Average .