Benzinga's Top Pre-Market Gainers

F5 Networks FFIV moved up 2.57% to $92.19 in the pre-market session after analysts at Barclays upgraded the stock from “equal-weight” to “overweight.” Merrimack Pharmaceuticals MACK soared 2.52% to $4.47 in the pre-market trading. Merrimack shares have dropped 42.93% over the past 52 weeks, while the S&P 500 index has gained 20.46% in the same period. Laboratory Corp. of America Holdings LH surged 1.26% to $99.00 in the pre-market session. Laboratory Corp's PEG ratio is 1.30. NetApp NTAP shares gained 1.53% to $43.17 in the pre-market session. NetApp is expected to post its FQ1 results on August 14, 2013.