Geron (NASDAQ:GERN) had a rough go of it over the last two years, as shares have lost over 70% of their value. The company controversially sold off its stem-cell business to focus on hot cancer drug candidate imetelstat. If imetelstat were a success, management would look brilliant for backing the right horse while avoiding the stem cell R&D black hole. Unfortunately, that proved to be a big if. Imetelstat's Phase 2 trial for breast cancer was cancelled, and Geron decided not to advance it to Phase 3 in NSCLC.

As Geron presses ahead with imetelstat, it is losing support from Wall Street. A Stifel Nicolaus analyst ripped the company's plans apart, calling them "flawed and sluggish," while dropping its rating all the way to sell.

Watch and find out what Motley Fool health-care analyst David Williamson thinks about Geron's downgrade, and what it means for investors.