Benzinga's Top Pre-Market Gainers

Horizon Pharma

moved up 16.63% to $2.80 in the pre-market session. Horizon Pharma will receive approval of DUEXIS from the United Kingdom (UK) Medicines and Healthcare products Regulatory Agency (MHRA). Ameristar Casinos

added 16.31% to $25.67 in the pre-market session. Pinnacle Entertainment

announced its plans to buy Ameristar Casinos for around $869 million. Halozyme Therapeutics

surged 14.86% to $6.34 in the pre-market session. Halozyme Therapeutics and Pfizer

entered into a worldwide Collaboration for the purpose of developing and commercializing subcutaneous biologics using recombinant human hyaluronidase. Red Hat

soared 5.49% to $55.50 in the pre-market trading. Red Hat posted better-than-expected third-quarter revenue and announced its plans to buy privately held ManageIQ for $104 million in cash.