Source: Celgene.

Gilead Sciences (NASDAQ:GILD) has captured investors' attention this year thanks to wildly impressive sales of its hepatitis C drug Sovaldi, but the company is by no means the only fast-growing big biotech out there. Gilead's bottom line might jump in the coming year thanks to billions of dollars in expected sales for Harvoni, its next-generation hepatitis C drug, but three big-cap biotechs could grow profit even more quickly.

Source: Medivation

Innovating treatment for millions
Prostate cancer is the most common cancer in men, with more than 233,000 new cases diagnosed every year in the United States. One in seven American men will be diagnosed with the disease during his lifetime.

Fortunately, new drug therapies approved in recent years, such as Xtandi from Medivation (NASDAQ:MDVN) and Astellas (OTC:ALPMY), are having a significant impact on survival.

In 2012, the FDA approved Xtandi for use in post-chemotherapy prostate cancer patients after trials showed that overall survival in patients taking the drug totaled 18.4 months o average, far better than the 13.6 months reported for patients taking a placebo. Xtandi has since displaced Johnson & Johnson's (NYSE:JNJ) Zytiga as the leading therapy in post-chemotherapy patients.

As a result, Medivation's second-quarter revenue jumped from $70 million in 2013 to $148 million this year, driving earnings per share up from a $0.07 loss to a $0.63 profit in.  

That's an impressive improvement, but even better results might be coming. In September, the FDA cleared Xtandi for use in pre-chemotherapy patients, significantly expanding the drug's addressable patient population. That has analysts thinking that Medivation's EPS will climb 42%, from $2.43 this year to $3.45 next year. If so, Medivation's earnings growth would more than double the 20% EPS growth expected for Gilead next year.

Expanding product line
 (NASDAQ:CELG) has built a large and growing drug business on the back of Revlimid, its highly successful therapy for multiple myeloma. Revlimid is a $4 billion a year blockbuster treatment that has allowed Celgene to usher a slate of fast-growing drugs through clinical trials, including Abraxane.

Abraxane, a cancer treatment that won a label expansion last year to include use as a treatment of pancreatic cancer, posted sales of $212 million in the third quarter, up 25% from a year ago. In addition to Abraxane, Celgene has also launched Pomalyst, another multiple myeloma drug, which has seen sales jump 102% year over year to $181 million in the third quarter, and Otezla, an autoimmune drug that last month won label expansion to include psoriasis patients. Although Otezla's sales totaled a small $18 million in the third quarter, Celgene thinks it could eventually deliver revenue of more than $1 billion per year.

Thanks to ongoing growth for Revlimid (sales were up 19% year over year last quarter), and growing sales for Abraxane, Pomalyst, and Otezla, Celgene expects it will deliver EPS of between $3.65 and $3.70 this year, above its previous $3.60-$3.65 guidance. Analysts think Celgene's EPS will hit $4.88 next year, which would be 33% earnings growth, also outpacing Gilead.

Source: Biogen

Overcoming worries
Biogen Idec (NASDAQ:BIIB) shares have been a bit of a roller-coaster ride following its third-quarter earnings results this week.

The results were impressive, but speculators took shares lower after Biogen reported that an MS patient taking its fast-growing oral drug Tecfidera died after being diagnosed with PML, a rare brain disease.

Shares are recovering some ground as investors recognize that while PML is a deadly disease, it's also uncommon. Also, Tecfidera isn't the only MS drug that has been tied to PML. In 2005, sales of Biogen's blockbuster drug Tysabri were temporarily halted following reports that three patients had been diagnosed with PML, and Novartis (NYSE:NVS)last fall reported a case of PML in a patient taking its blockbuster MS drug Gilenya.

Assuming this latest case is an isolated incidence, Tecfidera's sales should support Biogen's bottom line next year. In the third quarter, Tecfidera sales advanced from $286 million last year to $787 million. That helped Biogen's total sales climb from $1.45 billion a year ago to $2.1 billion last quarter.

As a result, Biogen reported EPS of $3.80, up 61% year over year, and boosted its full-year 2014 EPS guidance to between $13.45 and $13.55. If Tecfidera sales remain unchecked and sales pick up for Biogen's new hemophilia drugs Eloctate and Alprolix, Biogen should deliver solid earnings growth next year, too -- especially if sales of Plegridy, which won FDA approval in August for MS relapses, take off. Analysts covering Biogen remain a bit below the company's guidance for the current year, with EPS expectation of $13.23, but think that EPS will reach $16.20 next year. If so, that would also works out to earnings growth slightly better than Gilead's.

Looking ahead
There's little doubt that Harvoni will prove to be a multibillion-dollar blockbuster next year for Gilead that will prop up the company's 
bottom line. But Gilead isn't the only biotech company that is firing on all cylinders. Medivation, Celgene, and Biogen might outpace Gilead's earnings growth in the coming year, and that means that investors may want to have them in their portfolios, too. 

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.