Many large health care companies experienced a challenging fourth quarter and are reporting profits down versus the prior year, but biotechnology companies Vertex Pharmaceuticals (VRTX 1.36%), Alexion Pharmaceuticals (ALXN), and Amgen (AMGN -0.21%) bucked the trend. All three have opportunities to expand their business in 2014.

Vertex swung to a fourth quarter profit from a loss in the fourth quarter of 2012 after receiving a royalty payout from former partner Johnson & Johnson for the overseas rights to its hepatitis C drug, Incivek. Incivek is one of only two approved drugs that Vertex currently has and came at an opportune moment, since U.S. domestic sales of the drug fell by more than 90% to $19 million. So, the royalty payment for overseas sales of the drug -- sold under the brand name Incivo by Johnson & Johnson outside of the U.S. -- made a huge impact on the results.

Overall, net income in the fourth quarter was $0.19 per share, which is a vast improvement on a loss of $0.35 per share in the fourth quarter of 2012. However, excluding the royalty payment and other one-time items, Vertex would have made a loss of more than $0.50 per share. So, while the earnings news is encouraging, it may be more difficult to duplicate since it was based on one-time items.

Still, shares in Vertex responded positively to the news and posted gains of more than 6% in the aftermath of the release. This week has seen shares lose much of that gain, but they remain more than 70% higher over the last year as the market responds relatively favorably to the measures introduced by Vertex to counter the challenges brought on by increased competition for Incivek, which included the loss of around 15% of its workforce.

Indeed, shares in Vertex have performed better than Alexion Pharmaceuticals, despite the latter posting gains of around 20% this week due to upbeat sales forecasts for Soliris. This is a treatment for a life-threatening condition called paroxysmal nocturnal hemoglobinuria, which causes a breakdown of red blood cells and leads to anemia.

Since its approval in 2007, Alexion has sought further marketing approvals to boost sales, and last month regulators deemed Soliris an orphan treatment for the prevention of delayed graft function, which is a complication for kidney-transplant patients. This, and other marketing approvals, have meant that the company's guidance for 2014 sales of the drugs are ahead of market forecasts, with shares reacting positively as a result.

Meanwhile, Amgenalso delivered impressive fourth quarter results, with total revenues increasing by 13% to $5 billion and product sales growing at 11%. Adjusted earnings per share increased by 30% to $1.82, with higher revenues, the end of the Enbrel profit share and a lower tax rate being offset (to an extent) by increased research and development spending.

Amgen appears to be well placed to deliver long-term growth, and shares are up 35% over the last year, surpassing gains on the Nasdaq, which is up around 27% over the same period. So, while many large health care stocks have disappointed recently, with fourth quarter results showing a decline in sales, the likes of Vertex, Amgen, and Alexion seem to have bucked the trend. Indeed, all three stocks have had a great 12 months and could be worth paying closer attention to over the course of 2014.