TOKYO, Dec 22 (Reuters) - Japan's Nikkei share average eked out small gains on Friday as gains in banks and commodities trading houses offset weakness in pharmaceuticals, while Kobe Steel stumbled after it said senior executives were aware of its data tampering.
The Nikkei ended 0.2 percent higher at 22,902.76. For the week, it gained 1.6 percent, the biggest weekly percentage gain in more than a month.
Outperforming the market were banks and trading houses, with Mitsubishi UFJ Financial Group soaring 1.9 percent and Itochu Corp rising 2.4 percent.
The pharmaceutical sector tumbled 1.4 percent and was the worst performer on the board, after Eisai Co dived 15 percent on news a drug it is jointly developing to treat Alzheimer's disease failed to achieve mid-stage trial goals.
Santen Pharmaceutical stumbled 8 percent after it said on Thursday that the U.S. regulator had declined to authorise its medication to treat eye disease.
Kobe Steel Ltd dropped 2.4 percent after the company admitted for the first time that executives were aware of falsified data, and said it had reassigned three senior staff.
The broader Topix rose 0.4 percent to 1,829.08.
(Reporting by Ayai Tomisawa; Editing by Eric Meijer)