As if any of us needed a reminder of how times have changed, Regeneron Pharmaceuticals Inc.'s stock price history serves as a benchmark of the way things were and the way they are.

Considered pricey even in the halcyon days of April 1991, REGN went public at $22, selling 4.5 million shares and raising $99 million. That works out to a $239 million pre-money valuation and $338 million post-money. It was the biggest IPO of its time and the second-largest, after Cetus'.