Vertex Pharmaceuticals reported a net loss for the third quarter on Thursday with results hurt by fast-declining sales of its Incivek hepatitis C drug, as the company turned its attention to developing a next generation of treatments for the serious liver disease.

Vertex posted a net loss of $57.5 million, or 27 cents per share, compared with a profit of $221.1 million, or $1.02 per share, a year ago. Analysts on average expected a profit of 20 cents per share, according to Thomson Reuters I/B/E/S.

Incivek sales fell nearly 23% from the previous quarter and 40% from a year ago to $254.3 million. The company maintained its full-year forecast for Incivek sales of $1.1 billion to $1.25 billion.

Results were also affected by a $57.6 million charge related to expected future payments under Vertex's collaboration with Alios BioPharma.

Earlier on Thursday, Vertex announced separate collaborations with GlaxoSmithKline and Johnson & Johnson to test various combinations of its own next-generation hepatitis C medicines with those being developed by GSK and J&J.

The Massachusetts-based biotechnology company reported $49 million in sales of its new cystic fibrosis drug Kalydeco and $20 million in royalty revenue from overseas sales of Incivek, known as Incivo in Europe.

Kalydeco currently helps only a small percentage of cystic fibrosis patients with a specific gene mutation. The company is testing other drugs and combinations with the hope of eventually reaching a larger portion of the CF population.

"We are advancing rapidly with our plans to evaluate multiple all-oral regimens of VX-135, both with medicines in our own pipeline and, as we announced earlier today, in collaboration with other companies," Chief Executive Jeffrey Leiden said in a statement. "We are also advancing toward our goal to help more people with cystic fibrosis."

Total revenue of $336 million for the quarter was shy of Wall Street estimates of $377.1 million.

Incivek, which was approved in May 2011 to great fanfare as it doubled cure rates and shortened treatment durations compared with older drugs, reached $1 billion in sales faster than any drug in pharmaceutical history. But it must still be taken with the older injected drug interferon that causes flu-like symptoms.

As excitement builds for interferon-free, all-oral regimens being pursued by several companies, including Vertex, more patients appear to be delaying treatment, hurting Incivek sales. In addition, hundreds of other potential Incivek patients have been recruited to take part of clinical trials of next-generation treatments.