If Spectrum had real visibility into Fusilev's performance, especially vs. cheaper, generic leucovorin, it would give sales guidance. The company still chooses not to do so.

Zevalin sales totaled $8.4 million in the June quarter, up 42% sequentially. That's a nice turnaround, but I would also mention that Zevalin sales are now only just back to fourth-quarter levels. Spectrum continues to forecast "modest" Zevalin growth.

I'm a stubborn Spectrum bear and I see no reason yet to change my stance, particularly around the Fusilev vs. leucovorin issues. The main risk to the bear thesis is if Spectrum is successful in signing up enough physician practices to long-term Fusilev supply agreements to ensure the drug's continued growth even if or when generic leucovorin supplies are more fully replenished.

Spectrum mentioned these customer agreements on the call, so it's definitely worth noting if you're short the stock, and it's a reason to be optimistic if you're long.

One buy-side source whom I respect recently took a long position in Spectrum based on his belief that Fusilev sales will grow even with increased competition from cheaper leucovorin. I'll let him explain:

"We believe this business Fusilev will last and grow from accounts we have spoken to. Economic reasons play a part and also dosing error phenomenon is now playing a role in why doctors are fed up with switching back and forth from generic leucovorin… This is something doctors are telling us is a sticky issue in their practice," this buy-side investor tells me. He's long Spectrum but is not allowed to speak on the record to the media.

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.

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