One drop-dead rule for biotech investing (any investing, actually) is to read closely a company's regulatory filings. What a company discloses to the Securities and Exchange Commission in an 8-K, 10-Q or 10-K is much more important than what's trumpeted in a press release. Don't ignore press releases. Instead, compare the language and details scripted in the press release to what's disclosed in the SEC filings. If the two documents differ, i.e., if the press release leaves out salient yet less-than-positive details, you can infer that management may be more interested in spin than transparency.