The Experiment - Brotherly Bond, #1

After the mysterious death of his wife, FBI Agent Thomas Mason takes it upon himself to investigate when no one else will. He uncovers other suspicious deaths at the college she worked at, and he's sure they aren't accidents-it's murder. When all the killings seem linked to a top secret government drug, Mason will have to step carefully or he'll be next. Former special forces operative Jude Scott now handles security for a private pharmaceutical company, makers of the drug, Clarity, a high-performance mental enhancer.
At millions per dose, the wonder pill is by invitation only, but when the company's elite clientele start meeting violent ends, Jude might have to team up with his old friend Mason to put a stop to it.