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Blue-chip biotech stocks Amgen (NASDAQ:AMGN) and Biogen (NASDAQ:BIIB) are two of the oldest and largest in their industry. Both are highly profitable, but they operate in different corners of the drug-making landscape.

Despite various challenges to overcome, and opportunities to seize, either stock would make a fine addition to most portfolios with a moderate tolerance for risk. Let's compare the two on a number of metrics to see which is the better buy today.

Products and patents

When Amgen reported second-quarter earnings last month, its top line grew 6% over the previous year period to $5.69 billion, mostly on the back of Enbrel. Sales of the anti-inflammatory injection grew 10% to $1.48 billion, which is impressive but deeply troubling. Enbrel first earned FDA approval in 1998, and its main patent expired long ago. Novartis brought U.S. competition several steps closer to market last month when an independent advisory panel voted unanimously to recommend the FDA license GP2015 as a biosimilar to Amgen's top product.

Amgen's second most important product is Neulasta, which boosts chemotherapy patients' white blood cell counts. Neulasta caught a break recently -- Novartis disclosed an FDA request for more info before ruling on Novartis' biosimilar version. These requests are confidential, and its significance is a mystery. We do know, however, that Neulasta finished the second quarter on pace to reach sales of $3.9 billion in the U.S. this year, which makes it a blinking red target for competition. Novartis isn't the only company working on a Neulasta biosimilar; Coherus BioSciences has a version nearly ready for an application.

Image source: Amgen Inc.

Amgen's other products are growing, but reliance on Neulasta and Enbrel hasn't waned. Combined, the pair still contributed 48.5% of total revenue in the first half of this year. Offsetting eventual losses to biosimilar pricing pressure for key products will be an enormous challenge in the years ahead.

Biogen reported a 12% expansion in second-quarter total revenue, compared to the same period last year, to $2.89 billion. Its top product, Tecfidera for treatment of multiple sclerosis (MS), made up about one-third of the top line, but that drug is just three years into its commercial stage.

Biogen's No. 2 product, Avonex, also a treatment for MS, is losing ground, but combined with sales of a longer-lasting version approved in 2014, Plegridy, the franchise is still growing. Combined, second-quarter sales of the pair grew 9% over the same period last year, to $728 million.

Biogen's pipeline: superlatives galore

While Biogen's product line is far younger than Amgen's, it's future is less than certain. Possibly the most important drug in its late-stage pipeline is licensed to longtime partner Roche. Ocrevus is the first candidate to significantly slow disease progression among about 15% of MS patients with the most aggressive form of the disease, and the FDA is widely expected to green light its use in this under-served population before the end of the year.

Months later, regulators could also approve Ocrevus for treatment of the same patients taking Biogen's entire line of MS therapies. This drug could revolutionize the way MS is treated, dealing a blow to Biogen's product revenue, but also delivering royalties as high as 24% on U.S. sales.

Also bounding toward commercialization is Nusinersen, a candidate that will probably become the first-ever treatment for the leading cause of infant mortality, spinal muscular atrophy. Biogen licensed the candidate from Ionis Pharmaceuticals after interim results from an ongoing phase 3 trial showed it significantly improved outcomes among infants receiving it. If approved, Nusinersen could reach peak annual sales of about $1.7 billion.

Much further out for Biogen is aducanumab, the most promising Alzheimer's candidate to enter phase 3 trials. The disease is quickly becoming the single largest weight on the backs of healthcare systems across the developed world, and the first drug to effectively slow its progression could become the top-selling medicine of its time. Unfortunately, we probably won't learn more about aducanumab's chances of success until Biogen tallies thousands of clinical dementia scores after a year and a half of monthly dosing -- probably in early 2020.

Amgen's pipeline: playing it safe

Compared to Biogen's strategy, Amgen's growth story isn't nearly as exciting. Next-generation cholesterol-busting injection Repatha is expected to generate peak annual sales north of $5 billion, but payer restrictions are currently holding it back. That might change if a long-term study, with results expected early next year, show it significantly reduces patients' risk of heart attack or stroke over a five-year period.

Possibly the most important drug in its pipeline is a potential biosimilar for the world's best-selling drug. AbbVie's Humira finished the first half of the year on pace to reach $9.8 billion in U.S. sales this year, and Amgen's contender, ABP 501, wooed an independent FDA advisory committee last month. Unfortunately, it's difficult to predict when, or if, the unanimous vote recommending approval of ABP 501 for seven of Humira's indications will begin shifting Humira's U.S. sales toward Amgen. Humira's main U.S. patent expires this December, but AbbVie insists additional patents protect domestic exclusivity through 2022.

Value and shareholder appreciation

Near the end of June, Biogen would have easily won this value contest, but the stock has recovered about 39% from that low point. At recent prices, the two are nearly even, with Amgen and Biogen shares trading at about 17.6, and 18.3 times trailing earnings, respectively. 

AMGN PE Ratio (TTM) Chart

AMGN PE Ratio (TTM) data by YCharts.

Looking forward, Amgen and Biogen shares are in a dead heat at about 15.4 and 15.5 times this year's estimates.

When it comes to returning profits to shareholders, though, Amgen has Biogen beaten by a mile. The Californian biotech has raised its dividend for six consecutive years. At recent prices, it's offering a yield of just 1.3%, but it's been raising payouts at a mind-blowing annual growth rate of 29.9% over the past three years.

Over the past couple of years, Biogen has repurchased enough of its own shares to lower the number outstanding by 7.2% (Amgen lowered its count by 1.6% over the same period), but it doesn't pay dividends. Biogen does, however, intend to spin off its growing hemophilia segment into a separate entity.

And the winner is...

I love BOGO deals, and Biogen's spin-off is an interesting one, but that's not the main reason I find Biogen more attractive right now. Incoming biosimilar competition for roughly half of Amgen's current revenue stream is impossible to ignore.

There's a chance the losses will be slow enough that Amgen can offset them, but if I'm going to take such risks, I'd rather have my chips on Biogen's side of the table. A potential Alzheimer's win down the road is far more exciting than just treading water.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.