Source: AbbVie.

AbbVie Inc.'s (ABBV 0.54%) investments to offset the impact of lost sales tied to expiring patent protection on Humira in 2017 include a big push into hepatitis C and its $21 billion acquisition of the cancer drugmaker Pharmacyclics earlier this year. 

Because AbbVie's first hep C drug -- Viekira Pak -- won approval in December, and its Pharmacyclics acquisition closed in May, the company's second-quarter results offer investors an important glimpse into whether the company's spending is starting to pay off.

New kids on the block
Although Viekira Pak's $231 million in first-quarter sales fell far short of the billions of dollars in sales put up by Gilead Sciences' hepatitis C drugs Sovaldi and Harvoni during their first quarters on the market,  AbbVie investors still expect Viekira Pak to become a blockbuster drug -- something that should happen this year given that AbbVie sold $385 million worth of Viekira Pak in the second quarter.

In addition to delivering 67% quarter-over-quarter sales growth for Viekira Pak, AbbVie also recorded solid sales from Imbruvica, the blood cancer drug it acquired when it bought Pharmacyclics. AbbVie and Imbruvica co-developer Johnson & Johnson split global profit on Imbruvica evenly, and in the second quarter, AbbVie's share of Imbruvica's profits totaled $107 million, including $97 million from U.S. sales and $10 million from international sales. That was well above the $56 million in pre-tax profit reported by Pharmacyclics in the first quarter.

That's pretty impressive, but expectations for greater use and label expansion have industry watchers thinking Imbruvica's peak sales opportunity could be as high as $3.6 billion. If so, then AbbVie could be in a position to deliver much larger profit from Imbruvica in the future.

Source: AbbVie.

Filling the gap
In Q2, Humira's $3.5 billion in sales represented 64% of AbbVie's total revenue, and that means Humira sales won't be easily replaced. 

Viekira Pak and Imbruvica will likely take some of the sting out of losing patent protection on Humira in 2016, but AbbVie still needs sales growth from its other drugs, too.

That means AbbVie's other fast-growing drugs will need to keep putting up solid results, including Creon, which, aside from Viekira Pak, was AbbVie's fastest-growing drug last quarter.

Sales of Creon, a pancreatic enzyme replacement therapy, increased 44.6% year over year to $159 million last quarter. AbbVie also reported that Lupron's $198 million in sales and Synthroid's $187 million in sales grew by 9.9% and 11.9% versus last year, respectively.

It also means AbbVie's R&D team needs to deliver more top sellers, including venetoclax, a treatment for CLL patients that have a specific gene mutation. AbbVie and its development partners expect to file for approval of venetoclax by the end of this year. AbbVie also plans to file for the approval of its multiple myeloma drug elotuzumab as an adjunct therapy to chemotherapy in both first-line and relapsing patients this year. The company could also get a FDA green light for Zinbryta, a multiple sclerosis drug, and a go-ahead for its next-generation hepatitis C drugs soon.

If all of this pipeline activity pans out, these drugs could begin contributing to sales before Humira's patent expires.

Looking ahead
AbbVie estimates Viekira Pak will close out 2015 at an annualized sales run rate of roughly $3 billion, and that its various oncology programs could yield drugs with peak annual sales of $15 billion. Toss in sales from other drugs in its pipeline, such as Zinbryta, and AbbVie could be in a position to offset the generic threat to Humira.

However, research shows that peak sales projections are often massively incorrect and that promising drugs -- even those in late-stage trials -- often fail and for that reason. AbbVie is still risky relative to other large-cap biopharma stocks, and that means investors should approach it cautiously.