Source: Celgene Corporation.

Gilead Sciences (NASDAQ:GILD) fast-growing hepatitis C drugs Sovaldi and Harvoni may have made it one of the stock market's best performers this past year, but it's Celgene (NASDAQ:CELG) that industry watchers think will post the best earnings growth among big cap biotech companies in 2015.

Rapidly rising
Gilead Sciences is the leading maker of HIV and hepatitis C drugs, and those drugs have catapulted Gilead Science's revenue and profit significantly higher this year. Revenue from Gilead Science's HIV therapies is up 12% to more than $7.4 billion through the first nine months and, thanks to $8.5 billion in sales for Sovaldi, Gilead's top line has soared from less than $3 billion last year to more than $17 billion this year.

Those are indisputably impressive results, so it may be surprising to learn that analysts believe it's Celgene, not Gilead Sciences, that will post the biggest jump in year-over-year earnings growth next year. Analysts believe that Gilead's EPS will expand by 24.6%, from $7.96 this year to $9.92 next year; but they expect Celgene's earnings will jump 31.98%, from $3.69 this year to $4.87 next year.

Source: Celgene Corp

Analysts' optimism over Celgene's earnings growth stems from Celgene's own impressive drug franchise. For example, Celgene's top seller Revlimid is the market share leader as a second-line treatment in multiple myeloma patients.

Sales of Revlimid, which is also approved to treat mantle cell lymphoma, climbed 19% from a year ago to $1.3 billion in the third quarter, putting it on pace to achieve sales of nearly $5 billion this year. Revlimid's revenue could head even higher next year given that Celgene filed for U.S. and EU approval of it as a first-line therapy earlier this year. The FDA is expected to make its decision for use in that indication on February 22nd; if they give Celgene the go-ahead, Celgene could see Revlimid prescription volume increase.

In addition to Revlimid, Celgene also markets Abraxane, a cancer therapy that won approval for use in pancreatic cancer patients in 2013. In the third quarter, Abraxane revenue increased 25% from a year ago to $212 million, but growth overseas, where the product has more recently launched, improved by 62%. As launch success in Europe builds momentum, Abraxane could see its sales eclipse the billion dollar sales mark in 2015.

Abraxane's overseas sales may also benefit if EU regulators approve its use in non-small cell lung cancer patients. A decision from EU regulators for use in that indication should come in the first half of 2015.

Celgene's earnings are also heading higher thanks to Pomalyst, another multiple myeloma therapy that is used in patients who have been treated with other drugs like Revlimid, but have seen their disease return. Since winning approval in February 2013, Pomalyst's sales have grown markedly. In the third quarter, Pomalyst revenue reached $181 million, up 102% from the year before.

In addition to those therapies, Celgene's newly launched psoriasis drug Otezla should begin contributing to the bottom line next year, too. The FDA approved Otezla this past summer, and the drug's sales totaled $18 million during its first full quarter on the market.

Otezla revenue should continue to improve now that the FDA has expanded the drug's label to include both psoriatic arthritis and psoriasis patients. During Celgene's third-quarter conference call, the company reported that Otezla "had captured the highest share of new patients of any brand in the U.S. psoriatic arthritis category."

A great year ahead?
Analysts need Gilead Sciences' newly launched second-generation hepatitis C drug Harvoni to be as successful as Sovaldi next year if they hope to see Gilead Sciences hit their EPS guidance. So far, that appears likely, but investors might be more attracted to Celgene given that Celgene has multiple catalysts that could drive its earnings higher next year. Regardless, both of these companies are biotech blockbusters worthy of investor portfolios.