Pharma's Biggest Flops

by Maureen Martino, Liz Jones Hollis and Erica Teichert

The cold, hard fact of drug R&D is that most projects fail. Of the thousands of candidates under development, only a handful get approved, and even fewer grow up to be blockbusters.

But on rare occasions, an experimental drug boasts such impressive data, or targets such an underserved market, that billions in sales seem almost guaranteed. Some of those drugs deliver. Others don't--and below are their stories. We've selected eight high-profile drugs that never lived up the the considerable hype surrounding them in development, including one drug that never made it to market. Click below to get the stories behind these famous flame-outs.

1. Acomplia - Sanofi-Aventis
2. Effient - Eli Lilly
3. Exubera - Pfizer
4. Fanapt - Vanda Pharmaceuticals, Novartis 
5. Relenza - GlaxoSmithKline
6. Rogaine - Upjohn
7. Torcetrapib - Pfizer
8. Xigris - Eli Lilly

Special thanks to Ira Loss of Washington Analysis for his contribution to this report.