NEW YORK (AP) — GlaxoSmithKline PLC said Friday that it sold approximately 5.7 million shares of Quest Diagnostics Inc. for more than $250 million, reducing its stake to about 16.5 percent. The British drugmaker sold about 1.2 million shares on the open market for $45.37 apiece, or about $56.1 million. It also sold approximately 4.5 million shares back to Quest for $44.33 per share, or about $200 million. GlaxoSmithKline said it sold the stock as part of a plan to gradually lower its Quest stake, as well as to capitalize on the medical lab operator's expanded buyback program. GlaxoSmithKline will have an approximately 16.5 percent stake in Quest, valued at about $1.36 billion, once the transaction is completed. GlaxoSmithKline initially acquired the Quest stock in 1999. Qwest is based in Madison, N.J. Last month GlaxoSmithKline said it would increase its restructuring efforts and look to cut costs, which would probably mean job cuts. The company would not say how many job cuts would be likely be necessary.