AbbVie (ABBV 1.15%) shares have been one of the bright spots in the stock market this year. They're outperforming the S&P 500 index. But the stock has lost a bit of ground since AbbVie's third-quarter earnings report in late October.

The pharmaceutical company noted a slowdown in one of its key businesses -- aesthetics. And its blockbuster immunology drug Humira continued to see sales drop internationally due to biosimilar competition -- and biosimilars will hit the market in the U.S. next year.

All of this may sound grim, but there are positive elements to AbbVie's story that outweigh the negative news, and they're why I still view the stock as a buy.

The No. 1 dermal filler

First, we'll talk about the aesthetics business. AbbVie makes Juvederm, the dermal filler collection patients in the U.S. choose most. The problem is, these days, economic woes are weighing on consumers' discretionary spending, and they're spending less on filler treatments.

These treatments are more costly than AbbVie's other leading aesthetics product -- the anti-wrinkle treatment Botox. So Juvederm has felt more of an impact. In the third quarter, net revenue from Juvederm slipped by 0.6%. And AbbVie expects this pressure to continue into next year.

This is difficult right now. But it's important to remember this is a temporary situation. And AbbVie's aesthetics portfolio has what it takes to grow once consumers return to their usual spending habits. The company has maintained its U.S. market share in the toxins and fillers spaces. AbbVie still expects to reach its goal of total aesthetics sales topping $9 billion by the end of the decade.

All of this means we shouldn't be overly worried about the slowdown in the aesthetics business today.

Now, let's turn to Humira. The blockbuster's revenue fell 25% internationally in the quarter as biosimilars won market share. As mentioned above, those treatments are set to hit the U.S. market next year.

With that in mind, AbbVie hasn't yet shared Humira sales forecasts for 2023 or 2024. The company says it will offer guidance in the fourth-quarter earnings call. But Morningstar predicts Humira's U.S. sales may drop nearly 50% next year. Last year, Humira generated more than $20 billion in sales -- about 35% of AbbVie's total revenue.

A gain to compensate for a loss

It's clear a decline in Humira sales will be a big loss for AbbVie. But the company is heading for a big gain that may compensate for that over time thanks to its newer immunology drugs, Skyrizi and Rinvoq. AbbVie is commercializing them across all of Humira's indications. And so far, things are looking good.

Skyrizi has won U.S. regulatory approval in three indications so far. Rinvoq has gained six U.S. approvals. The drugs have been developed for a broad range of conditions -- from skin problems such as atopic dermatitis to inflammatory bowel disorders like Crohn's disease.

Skyrizi and Rinvoq sales together represented 15% of AbbVie's total third-quarter revenue. Combined, the drugs are set to bring in more than $7.5 billion in sales this year. This is more than AbbVie originally expected. And the two drugs are on track to eventually meet a major goal. Together, they should surpass the peak revenue of Humira.

So, AbbVie's progress with Skyrizi and Rinvoq means we should be optimistic about the future of the immunology portfolio -- even considering the inevitable decline in Humira sales.

A reasonable price

AbbVie trades for about 10 times forward earnings estimates -- down from its level of more than 12 earlier this year. That's also much lower than the average forward price-to-earnings ratio of 24 for the pharmaceutical industry, according to New York University's Stern Business School. 

Yes, AbbVie is facing challenges today. But in the case of its aesthetics business, the problems are transient. And a potential slowdown in immunology sales may be temporary too. Skyrizi and Rinvoq are already spurring a new phase of growth.

AbbVie's long-term picture remains bright, and the stock price is reasonable right now. Together, these two elements suggest this stock is a great buying opportunity.