Well, autumn has descended on the East Coast, and the trees are orange and yellow and brown, and lately they've been wet. The days are flip-flopping between unseasonably warm and sunny to being cool, gray, and foggy near the nation's capital.

Tomorrow is Halloween. (The Fool offers a "Tricks and Treats" Halloween special.) Conjuring even more mystery than the costumed little fellas who'll trounce around the country's neighborhoods for treats (grant them good weather!) is the question of who will be the country's next president. We'll know next week!

Meanwhile, as leaves fall and days grow short, it's good to remember that the holidays are around the corner, and although fall inevitably leads to winter, spring will follow, renewing spirits. Sadly, though, it's difficult to enjoy anything when you're unhealthy.

Amgen (Nasdaq: AMGN) fights disease. The company's two blockbuster drugs, Epogen and Neupogen, are essential in the treatment and survival of tens of thousands of cancer patients annually. This alone makes the company a roaring success. In the year 2100, when historians look back to track our battle against cancer and AIDS, Amgen's role will be heralded as important and long.

Amgen is two decades old. Its drugs are aging. Epogen, its $2 billion per year bestseller, will begin to come off patent in 2004. We haven't heard much about the expiration, but we will.

Merck (NYSE: MRK) serves as a good example. Five of Merck's best-selling drugs begin to come off patent in 2003 and 2004. Like snow on pines, this began to weigh on Merck's stock in early 1999, a whole four years beforehand. Only in the past week did Merck finally surpass March 1999 prices, as sales beat estimates and, most importantly, as many of the sales were due to new drugs.

Amgen needs to do the same thing now: start to replace old blockbusters with new ones.

Expiring patents are not the only culprit. A saturated market is slowing Amgen's sales, too. The company reported results last Thursday (as covered by Fool News) that showed 12% growth in sales and 18% growth in earnings per share. However, management warned that sales would be slower than expected for the year, and sales of Neupogen would actually slip below the 1999 level. Some say that Amgen is a victim of its own success: Its two key drugs are already in all the key markets, leaving little room to grow.

Thankfully, Amgen has five products in late-stage trials, and one, Aranesp (or just NESP), is awaiting approval from the FDA. As the second-generation Epogen drug, NESP's sales could top $1.5 billion by 2003, replacing much of the sales lost by Epogen as its patents float away. (I recently learned in the Fool's biotech seminar that when a popular drug comes off patent, investors can expect generic drugs to grab around 70% of its market.)

NESP could be on the market in 2001. Another three or four drugs could roll onto the market between 2001 and 2004, helping to fill the rest of the gap and, hopefully, add more growth. At $60 per share, Amgen's stock trades at 55 times the latest 2000 earnings estimate of $1.06 per share. Growth prospects in 2001 are too sketchy to guess.

As its best two drugs age, investors can at least sleep easier knowing that Amgen has nearly half a dozen drugs near late-stage development, and at least one should be a blockbuster (NESP). However, until at least some of those drugs actually pass muster and become good-selling products, we won't be surprised if the stock lingers a while -- or dances morosely up and down, not really going anywhere -- like a skeleton in an old fright movie. At times, that comes with long-term investing.

Stock, here! Get yer stock here!
To close on Halloween Eve, Human Genome Sciences (Nasdaq: HGSI) priced 11 million secondary shares at $75 per share on Friday, raising $825 million before fees. This should put the company's cash balance around $1.5 billion, almost surely enough to fund expansion in research during the four years or so before its first drug might reach the market. By the way, if you haven't seen the Fool's new biotech sector page, check it out! And Fool on.

P.S. Human Genome Sciences had three business announcements today, including an agreement with Dow Chemical (NYSE: DOW). Also, eBay (Nasdaq: EBAY) announced that Half.com's CDs, DVDs, and movies will be listed on Buy.com (Nasdaq: BUYX). So, if you put your things for sale on Half.com, Buy.com shoppers can see them, too.