Ken Griffin acquired 3.78 Million Merck & Co shares worth $415 Million. That's 0.49% of their equity portfolio (17th largest holding). The first Merck & Co trade was made in Q2 2013. Since then Ken Griffin bought shares 45 more times and sold shares on 39 occasions. The stake costed the investor $280 Million, netting the investor a gain of 48% so far.