By Sara Sjolin, MarketWatch
LONDON (MarketWatch) -- Shire PLC led U.K. shares lower on Monday after a rival was cleared to market a generic version of one of Shire's drugs, while banks and miners declined ahead of euro-zone events later in the week.
The FTSE 100 index fell 0.6% to 5,481.55, after closing out last week with a 0.6% gain.
Pharma firm Shire tumbled the most in the index, down more than 10%, after the U.S. Food and Drug Administration approved a rival's generic version of its hyperactivity drug Adderall XR.
Analysts at Goldman Sachs said that the approval is a "negative relative to our expectations" and that they had not expected a generic approval before 2014.
"We assume Shire loses 50% of its market share," they said.
Among other stocks driving losses in the U.K., mining firms headed south while metals prices were mixed.
Heavyweight Rio Tinto PLC (RIO) lost 1%, Evraz PLC shed 0.8% and Vedanta Resources PLC gave up 0.9%.
Banks were lower as investors looked toward a much anticipated European Union summit at the end of the week for any announcements on closer fiscal integration in the region and the creation of a banking union.
Standard Chartered PLC ticked 0.9% lower, Lloyds Banking Group PLC (LYG) shed 0.7% and Barclays PLC gave up 0.6%.
Food retailer Wm Morrison Supermarkets PLC dropped 2.3% after announcing that group Finance Director Richard Pennycook plans to step down from the board and leave the firm at the end of June 2013.