Shares of Adolor ( ADLR) plummeted after the company announced another regulatory delay for its bowel-disorders drug. Adolor, which has a development and marketing deal with GlaxoSmithKline ( GSK - Get Report), said the Food and Drug Administration wants more safety data about the drug Entereg.

The drug is targeted at post-operative ileus, or POI, a side effect sometimes seen among surgical patients who receive powerful painkillers like morphine. POI causes abdominal pain, nausea, vomiting and constipation. The companies say there are no other drugs approved by the FDA to treat the condition.

Adolor's stock fell $6.15, or 44%, to $7.79. GlaxoSmithKline was able to absorb the setback, and its stock was up 45 cents to $53.75.

CombinatoRx ( CRXX) soared after the biopharmaceutical company announced positive trial results on an experimental rheumatoid arthritis drug. Recently, the stock was up $1.33, or 18.9%, to $8.38.

The trial compared a treatment dubbed CRx-102, plus a disease-modifying antirheumatic drug, with the disease-modifying drug and a placebo. Patients getting CRx-102 had statistically significant improvements in their disease after 42 days of treatment.

Specialty drugmaker Kos Pharmaceuticals ( KOSP) rose sharply after Abbott Laboratories ( ABT - Get Report) said it would buy the company for $3.7 billion.

Through the acquisition, which amounts to $78 a share, Abbott gains a stronger presence in the $20 billion market for cholesterol treatments by taking over the Kos drugs Niaspan and Advicor.

Abbott's shares fell 0.5% to $47.42, while Kos' shares jumped 53.8% to $77.03.

McKesson ( MCK - Get Report) agreed to buy Per-Se Technologies ( PSTI - Get Report) for $1.09 billion in cash.

San Francisco-based McKesson, a big drug distributor, will pay $28 a share in cash for each share of Per-Se, which sells financial and administrative health care solutions for hospitals, physicians and retail pharmacies.

The deal offers a 15% premium to Friday's closing price in Atlanta-based Per-Se. Shares of Per-Se were up 12.5% to $27.50. McKesson rose 2.5% to $49.74.

Other movers included Celgene ( CELG - Get Report), up 1.7% to $52.53, Genzyme ( GENZ), 1% higher to $66.81, Pfizer ( PFE - Get Report), gaining 1.5% to $26.96, Gilead Sciences ( GILD), up 1.6% to $68.94, and Targacept ( TRGT), whose shares were boosted 11.6% to $8.35.

Moving lower were Hana Biosciences ( HNAB), down 3.5% to $7.69, Polydex Pharmaceuticals ( POLXF), whose shares sank 13.8% to $6.56, Vanda Pharmaceuticals ( VNDA), falling 7.8% to $11.75, Avanir Pharmaceuticals ( AVNR), off 5.5% to $2.93, and Cytogen ( CYTO), down 2.5% to $2.75.