Spectrum Pharmaceuticals (Nasdaq: SPPI) is a biopharmaceutical company focused on developing treatments with an oncological or hematological focus.

Today, let's look at three things investors should be watching regarding Spectrum Pharmaceuticals, as they will provide us better insight into the company.

1. Fusilev sales and pricing
 Without question, the near-term catalyst for Spectrum Pharmaceuticals is the growth of its lead drug, Fusilev. Fusilev is approved as a combination therapy in patients being treated for advanced colorectal cancer, and is administered to treat the nasty side effects of methotrexate.

In Spectrum's most recent quarter, Fusilev sales shot up 67% to $56.6 million from its year-earlier total of $33.9 million. Sales of the drug have consistently increased since its debut, and it remains the primary growth driver, accounting for 82.4% of total revenue.

However, things aren't always what they appear on the surface. It's clear from regulatory filings -- despite Spectrum's unwillingness to breakdown its gross Fusilev sales -- that it's doling out big discounts to physicians in order to encourage them to keep prescribing Fusilev instead of switching to the cheaper generic, leucovorin, which is made by generic giant Teva Pharmaceuticals (NYSE: TEVA), among others. According to monthly data compiled by research firm Wolters Kluwer, Fusilev sales could have been as high as $97 million this past quarter, but came in at a discount of 41% to that figure. If Spectrum is going to protect its brand name, keep shareholders happy, and grow sales volume, it's going to need to walk on water with the pricing of its combination therapy Fusilev.

2. Zevalin sales and the Allos acquisition
 On the other side of the coin, Zevalin sales have been stagnant for years. The drug, which is approved to treat follicular lymphoma, has suffered from a competitive sales environment and an unpleasant amount of steps that needed to be undertaken to prescribe the drug. One of those steps fell by the wayside late last year when the Food and Drug Administration lifted the requirement that a bioscan be done on patients prior to prescribing Zevalin. This could be the impetus that finally moves sales higher.

Also working in Spectrum's favor could be its purchase of Allos Therapeutics (Nasdaq: ALTH) for $1.82 per share (plus an additional $0.11 if its key drug is approved in the European Union), which is set to close this week. Allos' lead drug, Folotyn, treats patients with relapsed or refractory peripheral T-cell lymphoma (PCTL) and is a drug that would be prescribed by the same doctors prescribing Zevalin. The two drugs aren't competitors to each other, and Spectrum is forecasting significant synergies from the combination.

As usual, investors should also be keeping their eyes on Folotyn's sales and the sizable amount of competition that threatens to eat into its existing sales. As my Foolish colleague Keith Speights noted last week, Folotyn volume actually decreased 10% in the first half of 2012 and was aided only by a 5% increase in price. On top of that, there are three notable PCTL drugs already carving into Folotyn's piece of the pie, including Baxter International's generic drug Cytoxan, Celgene's Istodax, and Teva's generic drug, Vincristine.

3. Spectrum's remaining pipeline
 According to Spectrum's product pipeline, it's currently advancing 14 drug candidates. Even if many of these drugs fail, with the company profitable from just Fusilev, Zevalin, and with the addition of Folotyn, there's a good chance that at least a few of these experimental drugs could become winners.

Belinostat is one such drug that investors should be keeping an eye on. The drug, which is targeted at treating PCTL and non-small cell lung cancer (NSCLC), has shown efficacy and tolerability in reducing cancer cell proliferation in various phase 1 and 2 clinical trials with minimal side effects and marrow toxicity. Lucanthone, which is still in early clinical trials, is also worth keeping an eye on. It's being targeted at treating brain metastasis tied to NSCLC by crossing the blood brain barrier.

Of course, there will be losers as well. Just prior to announcing the buyout of Allos Therapeutics, Spectrum noted unfavorable results in two phase 3 clinical trials for its bladder cancer drug apaziquone, which is developed with its marketing partner, Allergan (NYSE: AGN). It's unlikely apaziquone will be shelved, but an FDA-approval appears unlikely as of now.

Foolish roundup
 Now that you know what to watch for, it should be easier to analyze Spectrum Pharmaceuticals' successes and pitfalls in the future, and hopefully you'll gain a competitive investing edge.

If you're still craving even more info on Spectrum Pharmaceuticals, I would recommend adding the stock to your free and personalized watchlist so you can keep up on all of the latest news with the company.

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