(Corrects issue dates of economic indicators in the fifth paragraph)
* Stocks going ex-dividend, weighing some 110 points on Nikkei
* Thin trading expected before key data - analysts
* Drug makers underperform on Clinton's comments to put cap on prices - analyst
By Ayai Tomisawa
TOKYO, Sept 28 (Reuters) - Japan's Nikkei share average fell on Monday morning as investors took profits from Friday's gains, and they remained risk-averse before a run of key economic indicators scheduled this week.
Also denting the market was stocks going ex-dividend. For companies that close their books for their first half on Sept 30, Friday was the final day that an investor could buy their stock and qualify for mid-year dividends.
Stocks usually fall after going ex-dividend, and the Nikkei index was expected to drop about 110 points Monday for this reason alone, but ended up falling further.
The Nikkei dropped 1.0 percent, or 173.87 points, to 17,706.64 in mid-morning trade after jumping 1.8 percent on Friday.
Analysts said that investors will stay cautious with economic indicators in Japan and overseas scheduled to come out this week. They include Wednesday's Japan industrial production data, Thursday's Bank of Japan's corporate sentiment survey and China's Caixin manufacturing survey and Friday's U.S. jobs data.
"Investors would not take large positions until they digest the outcomes of these key data, so directionless trading is expected this week and volume is likely to be thin," said Takuya Takahashi, a strategist at Daiwa Securities. "If these data are better than expected, the market will likely start recovering next week."
Steelmakers and brokerages underperformed. Nippon Steel & Sumitomo Metal Corp dropped 2.5 percent and JFE Holdings shed 2.7 percent. Nomura Holdings dropped 2.0 percent.
Pharmaceutical stocks lost ground. Takeda Pharmaceutical Co declined 1.8 percent and Eisai Co tumbled 3.2 percent. Traders attributed the drops to weakness in U.S. healthcare stocks after U.S. Democratic presidential candidate Hillary Clinton last week said she would announce a plan to stop "price gouging" for speciality drugs.
"Both Takeda and Eisai have large exposures to the U.S. market, so investors think this news is negative to these companies," said Norihiro Fujito, senior investment strategist at Mitsubishi UFJ Morgan Stanley Securities.
Since the news came out last week, Takeda has dropped 3.8 percent and Eisai has slid 6.7 percent.
Nippon Paper Industries shed 3.2 percent after the Nikkei reported that its April-Sept operating profit has likely dipped about 30 percent on the year to around 9 billion yen.
The broader Topix shed 0.2 percent to 1,450.67 and the JPX-Nikkei Index 400 shed 0.3 percent to 13,002.93. (Reporting by Ayai Tomisawa; Editing by Eric Meijer)