TOKYO, Oct 23 (Reuters) - Japan's key benchmark stock index edged up to a one year-high, supported by gains for the phrama sector thanks to drugmaker Eisai rallying hard, though weak chip-related stocks capped the gains after disappointing results from Texas Instruments.
The benchmark Nikkei average added 0.3% to 22,625.38, its highest finish since October last year, while the broader Topix advanced 0.6% to a 10-1/2-month closing peak at 1,638.14.
Tokyo-listed semiconductor-related shares were hit hard, with Rohm, Renesas Electronics and Tokyo Electron sliding 4.1%, 5.3% and 4.1%, respectively, as Texas Instruments slumped nearly 10% in after-hour trading overnight.
The leading American chip designer on Tuesday forecast current-quarter revenue well below estimates, in a fresh sign that the global microchip industry is being squeezed by a downturn in demand as well as a prolonged U.S.-China trade dispute.
The Nikkei heavyweight Softbank Group shed 2.5% as the tech conglomerate agreed to spend $10 billion to take over U.S. office-space sharing startup WeWork on Tuesday, doubling down on an ill-fated investment and paying off its co-founder Adam Neumann to relinquish control.
Drugmaker Eisai soared 18.1% to its daily-limit high after its partner Biogen revived plans on Tuesday to seek U.S. approval for Alzheimer's treatment aducanumab, which surprised investors and sent the U.S. pharma firm's share up 27% overnight.
The pharmaceutical sector jumped 2.4%, helped by Eisai's big gains, to become the second best performers among the Tokyo bourse's 33 sector subindexes.
Sumitomo Chemical dropped 3.2% after the company slashed its operating profit forecast for the year through March by 10.5% to 170 billion yen ($1.6 billion).
Japan's mid-year earnings season kicks off this week, with electric-motor maker NIDEC's results coming after the market close on Wednesday.
($1 = 108.3800 yen) (Editing by Simon Cameron-Moore & Shri Navaratnam)