* Shionogi soars after Roche's late-stage study shows new flu drug effective
* Takara, Tokyo Dome fall after brokerage takes guess to be excluded from Nikkei index in Oct
By Ayai Tomisawa
TOKYO, July 18 (Reuters) - Japan's Nikkei share average soared to a more than one-month high on Wednesday morning as exporters such as automakers and technology firms got a boost after the dollar hit a six-month high against the yen.
The Nikkei surged 1.0 percent to 22,919.59 in midmorning trade after rising to 22,949.32, its highest point since June 13.
The dollar was up 0.05 percent at 112.97 yen after going as high as 113.08, its strongest since Jan. 9 as U.S. Federal Reserve Chairman Jerome Powell gave an upbeat outlook for the economy and reinforced views that the Fed was on track to steadily hike interest rates.
Toyota Motor Corp advanced 1.5 percent, Mazda Motor Co surged 1.8 percent, TDK Corp soared 3.2 percent, Advantest Corp added 2.1 percent and Panasonic Corp rose 1.5 percent.
"In the mid-to-long term, a trade war risk will likely pressure global economic growth but investors are encouraged to take risks now on the back of the strong dollar," said Shogo Maekawa, global market strategist at JPMorgan Asset Management.
Drugmaker Shionogi & Co surged 1.9 percent after Swiss drugmaker Roche's late-stage study showed that its new flu drug worked for people at high risk for serious flu complications.
Roche has partnered with Shionogi to develop the single-dose drug, touting it as a more convenient alternative to Tamiflu's twice-daily, five-day regimen.
Meanwhile, the Nikkei benchmark index is set for an annual reshuffle in October and e-commerce business operator Start Today Co and Internet business operator CyberAgent Inc are seen as top picks to join, Daiwa Securities estimated. The stocks rose 2.1 percent and 1.7 percent, respectively.
Conversely, Daiwa said that brewer Takara Holdings and stadium and amusement park operator Tokyo Dome Corp are seen as likely candidates for removal, sending the stocks 2 percent and 2.7 percent lower, respectively.
Stocks added to the index benefit because managers of index-tracking funds must include them in their portfolios, while shares of companies that are dropped have to be sold.
The broader Topix gained 0.7 percent to 1,756.94. (Editing by Sam Holmes)