The document discusses the inevitability of interchangeable follow-on biologics gaining FDA approval and becoming a lucrative market reality. It provides several reasons why: 1) FDA has historically approved interchangeable versions of complex protein drugs and biological products made by different processes if analytical data shows similar safety and efficacy. 2) Distinct biological products are already being used interchangeably to treat diseases like Gaucher's disease. 3) Advances in protein analytics may allow demonstration of similar safety and efficacy for biologics made by different processes.