Amgen, Inc. (NASDAQ:AMGN) treated investors to another year of double-digit bottom-line growth in 2017, and plans to do it again in 2018. That's a tall order for a company that's been reporting sinking sales for many of its best-selling products.

Here's what we can expect to see from the big biotech's development pipeline this year as it attempts the seemingly impossible, again.

Scientist examining a vial.

Image source: Getty Images.

The five horsemen will keep riding downhill

In 2016, Enbrel, Neulasta, Aranesp, Epogen, and Neupogen generated a combined $14.75 billion in sales. By the third quarter of 2017, annualized top-line contributions from the same five drugs were $1.14 billion lower.

Declining sales of the company's aging blockbusters was a stiff headwind for more recently launched drugs to overcome, which is why total sales of $16.23 billion recorded during the first nine months of 2017 was a few million less than the company reported during the previous year's period.

Aging blockbusters will continue to pressure Amgen's top line in 2018. The FDA approved a lower-cost biosimilar version of Enbrel called Erelzi in 2016, but a court challenge from Amgen still prevents its launch. Novartis (NYSE:NVS) expects the challenge in question to reach a conclusion this year, which could allow it to finally launch Erelzi in 2018.

On the way up

Since earning approval in 2010, Amgen's bone-density drug, Prolia, has been firing on all cylinders. Third-quarter Prolia sales surged 22% over the previous-year period to an annualized $1.9 billion run rate.

Although I don't think Prolia will overtake Enbrel and Neulasta in 2018, this could be the company's best selling drug in a few years. Osteoporosis leads to broken bones for one in three women over the age of 50, and older adults are America's fastest-growing demographic.

Amgen has another drug aimed at a large patient population that's slowly gaining steam, Repatha. A lot of people can't control their cholesterol with cheap generic statins. Repatha did a fine job for this underserved group during trials that led to its approval, but insurers are extremely reluctant to pay for the drug without proof it lowers risk of heart attacks and other cardiovascular events.  

Amgen provided the proof and the FDA adjusted the drug's prescription label to reflect it late last year. Now physicians can prescribe Repatha to reduce risk of heart attack and stroke for any adult with established cardiovascular disease.

In the third quarter last year, Repatha sales more than doubled to an annualized $356 million. Now that physicians have a much wider hoop to jump through to prescribe Repatha, we could see sales of the drug surge in 2018.

Three Scientists in a lab.

Image source: Getty Images.

Keeping it bi-specific

New CAR-T therapies are all the rage lately, but Amgen contends it built a better mousetrap years ago that nobody's noticed yet. In a nutshell, CAR-T therapies involve removing each patient's immune cells, then modifying them to recognize cancer cells before reintroducing them to each patient a few weeks later.

In 2014, Amgen earned approval for Blincyto, the first bispecific antibody approved to treat cancer. As the name implies, bispecific antibodies employ two pockets that immune cells and cancer cells in place long enough for one to recognize the other in the bloodstream. The concept is interesting, but Blincyto sales have been dull since the drug earned FDA approval to treat a rare form of leukemia in late 2014.

Blincyto sales totaled just $129 million in 2017, but Amgen thinks it could go much further as a treatment for an aggressive form of lymphoma that's also treatable with Yescarta, a recently approved CAR-T therapy from Gilead Sciences (NASDAQ:GILD). Blincyto lessened disease activity for six of 11 patients treated, while 51% of patients treated with Yescarta displayed no disease activity at all.

There haven't been any head-to-head studies between Yescarta and Blincyto, so it's still hard to make direct comparisons. That said, Blincyto doesn't appear nearly as effective as Yescarta in this population. That doesn't bode well for this cornerstone of Amgen's oncology strategy, but it probably won't stop the company from from carrying out expensive plans to advance a dozen bispecific antibody programs in 2018.

Headache medicine

Investors will want to keep an eye open for Amgen's first neuroscience drug, Aimovig, for the treatment of migraine headaches. Amgen submitted an application for this first-in-class drug last summer, and the FDA is expected to issue an approval decision on or before May 17. 

Amgen thinks around 3.5 million underserved Americans that suffer chronic migraines could become Aimovig customers if the FDA gives its blessing. In a big trial supporting the drug's application, 50% of those treated experienced 50% fewer migraines. That appears competitive with similar therapies in development by Amgen's peers, which means we can probably look forward to a successful launch in the back half of the year, if approved.

Cory Renauer owns shares of Gilead Sciences. The Motley Fool owns shares of and recommends Gilead Sciences. The Motley Fool has a disclosure policy.