The last week of July was a busy one for investors, with several big-name companies releasing their quarterly updates for the period ending on June 30. One of those was pharma giant AbbVie (ABBV 0.45%), and the drugmaker's results were impressive.

AbbVie recorded total revenue of roughly $14 billion, 19.3% higher than the year-ago period on an operational basis. On the bottom line, the company reported earnings per share of $0.42, which was much better than the loss per share of $0.46 recorded during the second quarter of 2020. What was behind this performance? Here are three key aspects of AbbVie's success during the second quarter.

1. Humira's U.S. revenue is still growing

International sales of AbbVie's blockbuster rheumatoid arthritis medicine Humira have been declining since it lost patent exclusivity in Europe in 2018. Things were no different during the second quarter. International revenue from this drug came in at $811 million, a 6% year-over-year decline.

Doctor giving a thumbs-up.

Image source: Getty Images.

However, Humira is still going strong in the U.S., its most important market. And at least for this quarter, U.S. sales of Humira were enough to pull the drug's total revenue in the right direction. Domestic sales of the RA treatment were $4.3 billion, 7% higher than the comparable period of the previous fiscal year. Its total revenue for the quarter was $5.1 billion, a 4.8% year-over-year increase.

Still, AbbVie expects biosimilars for Humira to enter the U.S. market in 2023, and with that date fast approaching, the company needs to find other avenues for growth. Fortunately, the pharma giant seems to have done that already.

2. Passing of the torch 

AbbVie's reliance on Humira would be a major problem if it weren't for the fact that the company devised a careful plan to decrease its top-line dependence on this drug. The pharma giant now has several other medicines whose sales are growing rapidly, and these are expected to take the mantle away from Humira eventually.

Arguably the two most important are Skyrizi and Rinvoq, which treat a range of autoimmune disorders. During the second quarter, sales of both drugs more than doubled; revenue from Skyrizi came in at $674 million, and Rinvoq's sales were $378 million.

Regarding these two drugs, AbbVie's CEO Richard Gonzalez said the following during the company's second-quarter earnings conference call: "The focus for us going forward is the next-generation assets, Skyrizi and Rinvoq. And you can see those two assets this year will do $4.6 billion, so call it $5 billion. They're rapidly growing, and they're doing exactly what we had hoped they would do."

Another important growth driver for AbbVie is cancer medicine Venclexta, whose sales during the second quarter jumped by 43.2% year over year to $435 million. These assets will undoubtedly help AbbVie keep its revenue afloat once biosimilars for Humira enter the U.S. market. 

3. Allergan's acquisition is having an impact 

AbbVie closed its $63 billion acquisition of Allergan in May 2020. One of the reasons behind the move was to expand and diversify its revenue base. And by the looks of it, AbbVie is benefiting a great deal from this transaction already.

To quote Gonzalez again: "I'm particularly pleased with the robust revenue performance that we've been able to drive since acquiring Allergan, with 2021 sales tracking to grow significantly faster than legacy Allergan's historical performance."

Two former Allergan products that are performing especially well are Botox therapeutics and schizophrenia treatment Vraylar. During the second quarter, sales of the former jumped by more than 38% year over year to $603 million, while Vraylar's revenue came in at $432 million, more than 25% higher than the year-ago period.

As these products continue to contribute meaningfully to AbbVie's financial results, the pharma company will become even less dependent on Humira. 

Still worth buying

The bears' doomsday scenario for AbbVie had the company not surviving the loss of patent exclusivity for its top-selling medicine. But the way things look, the drugmaker is capable of doing that -- and then some. And with growing revenue and earnings, as well as one of the safest dividends around, AbbVie's stock still looks like a buy, especially considering it has underperformed the broader market in the past year.