Glaxo bets big on drug for clogged arteries

* 15,000-patient Phase III darapladib trial launched

* Second 12,000-patient trial planned for late 2009

* Shares in partner Human Genome Sciences up 10 pct

(Adds Human Genome Science share price, detail on royalty deal)

By Ben Hirschler

LONDON (Reuters) - GlaxoSmithKline Plc (GSK.L) placed a big bet on a new type of medicine for clogged arteries on Thursday by launching a costly three-year clinical trial involving more than 15,000 patients worldwide.

The world's second biggest drugmaker said it expected the Phase III study of darapladib to last about three years, with a second large trial involving around 12,000 subjects due to start in late 2009.

Glaxo wants to find out if patients live longer and have fewer heart attacks and strokes when given the drug.

The move comes at a time when some other large drugmakers are cutting back on developing new cardiovascular treatments.