It's obvious that AbbVie's (NYSE:ABBV) fourth-quarter earnings update didn't please Wall Street. Shares of the big drugmaker fell nearly 7% in early trading on Friday morning following AbbVie's earnings release.

But what was AbbVie's bad news? Did the market overreact? What's next for AbbVie? Here are the three key things you need to know from the company's Q4 update.

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1. Misses on revenue and earnings

Investors have become accustomed to AbbVie beating Wall Street estimates. It didn't happen this time around.

AbbVie reported Q4 revenue of $8.3 billion, up 7.3% year over year. Analysts were expecting revenue of $8.38 billion. The company posted adjusted earnings per share (EPS) of $1.90. This reflected strong year-over-year growth of 28.4%. However, the consensus Wall Street adjusted EPS estimate was $1.94.

The big pharma company's GAAP earnings numbers especially looked bad. AbbVie reported a loss of $1.23 per share. This loss resulted from a big write-off related to its Stemcentrx acquisition following clinical failures for experimental cancer drug Rova-T.

2. Challenging times for Humira

Going into AbbVie's Q4 update, all eyes were focused on how Humira would fare in its first quarter facing biosimilar competition in Europe. AbbVie CEO Rick Gonzalez had warned in the company's Q3 conference call that competitors were discounting their biosimilars more than expected.

AbbVie reported Q4 sales of Humira of $4.9 billion. This included U.S. sales of $3.6 billion and international sales of $1.3 billion. Although international sales fell nearly 15% year over year, the decline was pretty much in line with what I expected

U.S. sales, though, were a little lower than what I thought they'd be. My view was that AbbVie would report U.S. sales of Humira of around $3.7 billion.

3. Relatively weak 2019 guidance

Another key story from AbbVie's Q4 update was the company's guidance for 2019. AbbVie projected adjusted diluted earnings per share (EPS) this year between $8.65 and $8.75. This reflects growth of 10% at the midpoint.

Achieving that level of growth might not sound too bad. But AbbVie has delivered adjusted EPS growth at a compound annual growth rate (CAGR) of 20% over the last five years. Falling to 10% growth is definitely a step backward for the drugmaker.

The big culprit for the relatively weak guidance is Humira. AbbVie expects international sales for its top-selling drug will plunge 30% in 2019. The company thinks that U.S. sales will continue to grow, but AbbVie will feel the impact of taking lower price increases than in the past.

Looking ahead

There's no question that AbbVie is at a turning point. The company has been planning for the day that it would face a serious threat to Humira. That day has arrived.

However, AbbVie's hematologic oncology drugs Imbruvica and Venclexta are going strong, with more growth likely on the way. New drug Orilissa should have blockbuster potential. The company is also on the cusp of potentially winning approvals for two other drugs that could be major blockbusters -- risankizumab and upadacitinib. 

AbbVie disappointed Wall Street in the fourth quarter. But with its strong dividend and sustained growth potential despite the challenges for Humira, the pharma stock still looks like a smart pick for long-term investors.

Check out the latest AbbVie earnings call transcript.