Shares of drug makers were getting a nice boost in premarket trading Tuesday, after AbbVie Inc.'s deal to buy Allergan PLC for a 45% premium. The SPDR S&P Pharmaceuticals ETF rallied 2.2% ahead of the open. Besides the 31% jump in Allergan's stock, among other shares seeing nice gains in the premarket, Mylan N.V. rose 2.7%, Endo International PLC climbed 4.5%, Theravance Biopharma Inc. hiked up 4.2%, Mallinckrodt PLC tacked on 2.7% and Perrigo Co. PLC gained 2.2%. Meanwhile, Medicines Co.'s stock shed 4.6%, after the company announced late Monday the public offering of $150 million worth of common stock. The pharmaceuticals ETF has lost 7.7% over the past three months through Monday, while the S&P 500 has gained 5.3%.