(Adds CEO, analyst comments)
By Tamara Mathias
Jan 25 (Reuters) - AbbVie Inc said on Friday it expects a steeper decline in overseas sales of its top-selling drug, Humira, due to intense competition from cheaper versions in Europe, driving its shares down nearly 7 percent.
Humira is the world's best-selling prescription medicine and in the six years since AbbVie spun out from device maker Abbott Labs the rheumatoid arthritis drug has remained by far the company's top earner, accounting for about 60 percent of net revenue.
On Friday, AbbVie, which reported lower-than-expected quarterly earnings, said it expects 2019 Humira sales from outside the United States to be down about 30 percent on an operational basis.
In November, the company forecast a 26 to 27 percent decline in 2019 Humira sales outside the United States due to stiff competition in Europe from companies such as Mylan NV and Biogen Inc.
"What we're giving you is our best estimate of what will happen," Chief Executive Richard Gonzalez said on a conference call with analysts.
"Obviously, this is driven by not us, it's driven by competitors and their behavior and so ultimately it's not like we have a crystal ball that we can predict exactly what they do."
AbbVie said international sales of Humira fell 17.5 percent on a reported basis to $1.30 billion in the fourth quarter ended Dec.31.
Overall, the drug brought in sales of $4.92 billion in the quarter, falling short of the $5.02 billion forecast by six analysts polled by Refinitiv IBES.
"When they first started talking about outside U.S. biosimilar competition it was that it would be in the mid-teens over a two-year period," Piper Jaffray & Co analyst Christopher Raymond told Reuters.
"And now they've said they'll be down 30 percent so I think that's the issue. It's a concern that if they got it wrong once, how do we know that the current guidance is accurate?"
In the United States, AbbVie's largest market, Humira is not expected to face biosimilar competition until 2023.
The drugmaker has signed a series of deals with rivals, including Mylan NV and Amgen Inc, which prevent their biosimilars from entering the U.S. market before then.
The company forecast 2019 adjusted earnings of between $8.65 and $8.75 per share, largely below the average analyst forecast of $8.74 per share.
In the fourth quarter, AbbVie's adjusted earnings were $1.90 per share and revenue $8.31 billion, both missing Wall Street estimates.
Reporting by Tamara Mathias in Bengaluru; Editing by Maju Samuel and Sweta Singh