Image source: Gilead Sciences.

If the year ended on Groundhog Day, 2016 would be the worst year for Gilead Sciences (GILD -0.01%) since 2009. But the year doesn't end on Feb. 2. And Gilead's announcement of its fourth-quarter results after the market closed on Tuesday could help make 2016 seem at least a little less scary for investors. Here are the highlights from the big biotech's quarterly results. 

By the numbers
Gilead reported fourth-quarter GAAP earnings of $4.683 billion, or $3.18 per diluted share. This figure reflected an impressive 34% jump over GAAP earnings posted in the fourth quarter of 2014. On a non-GAAP basis, Gilead's earnings came in at $4.889 billion, or $3.32 per diluted share -- a 26% year-over-year increase.

Revenue for fourth quarter totaled $8.506 billion. This represented a 16% gain from the $7.314 billion in revenue reported in the same quarter of 2014. As usual, the lion's share of Gilead's revenue stemmed from product sales, with $97 million generated from royalty, contract, and other sources.

Gilead announced full-year 2015 GAAP earnings of $18.108 billion, or $11.91 per diluted share. Non-GAAP earnings for the year were $19.174 billion, or $12.61 per diluted share. Gilead posted full-year revenue of $32.639 billion.

One other big number stood out from the biotech's earnings announcement: the amount of cash on hand. Gilead reported $26.2 billion of cash, cash equivalents, and marketable securities as of Dec. 31. That's a huge leap from the $11.7 billion on hand at the end of 2014.

Behind the numbers
Anyone expecting a letdown in sales of Gilead's hepatitis C virus (HCV) drugs was surely disappointed. Harvoni generated revenue of $3.345 billion in the fourth quarter -- up nearly 59% compared with the same quarter of 2014. Sovaldi's sales did drop around 11% year over year to $1.547 billion, but that dip was easily made up by Harvoni's success.

The striking thing from Gilead's HCV results in the fourth quarter was where the sales are coming from. U.S. sales for both Harvoni and Sovaldi fell significantly. Sovaldi also saw slower sales in Europe. However, other international sales soared for both drugs, and Harvoni performed well in Europe.

Revenue from Gilead's HIV franchise grew, but momentum appears to be slowing. Truvada notched sales of $936 million in the fourth quarter, up 4% year over year. Stribild's sales jumped nearly 33% to $511 million. However, those gains were almost matched by declining sales for Atripla.

Gilead also continued to experience somewhat sluggish overall growth from its other products. Sales for Letairis, which treats pulmonary arterial hypertension, increased 6% from the fourth quarter of 2014 to $192 million. Angina drug Ranexa generated fourth-quarter sales of $169 million, a respectable 17% year-over-year increase. Sales for blood cancer drug Zydelig jumped to $40 million in the fourth quarter -- a 135% increase. On the other hand, anti-fungal drug AmBisome's sales fell enough to more than wipe out the good news for Zydelig. 

Looking ahead
How will Gilead fare in 2016? The company anticipates revenue of $30 billion to $31 billion -- less than generated last year. There's a simple reason for this: the launch of Merck's (MRK -0.94%) rival HCV drug, Zepatier.

Merck recently won FDA approval for Zepatier. The bad news for Gilead is two-fold. First, Merck has priced its drug at $54,600 for a 12-week regimen. While Gilead has heavily discounted Harvoni, its starting point is a much-higher $84,000 per treatment. Second, Zepatier seems to offer comparable convenience and effectiveness as Harvoni.

Things could improve for Gilead not too far down the road, though. An HCV regimen that covers all genotypes of the virus is waiting on regulatory approval. The biotech has a promising hepatitis B virus drug in late-stage clinical trials. Gilead's oncology program also claims several late-stage studies underway that could bear fruit.

Don't forget that large stack of cash that Gilead's sitting on, either. While some of that $26.2 billion will be paid back to shareholders in the form of increasing dividends, the biotech will have plenty left over to make more strategic investments. Gilead's history includes some smart acquisitions that paid off in a big way. 

Competition, pipeline, and cash will all factor into how well 2016 turns out for Gilead Sciences. And there are a lot of days remaining on the calendar.