Eli Lilly (NYSE:LLY) will release its quarterly report on Wednesday, and investors remain concerned about the pharmaceutical company's share-price weakness. Even as rivals Merck (NYSE:MRK) and Pfizer (NYSE:PFE) have overcome fears about their ability to sustain their lucrative drug pipelines, Lilly has seen its stock drop considerably in recent months as its struggles continue.

Eli Lilly has a number of successful drugs in its stable, including antidepressant Cymbalta, lung-cancer treatment Alimta, and its Humalog insulin product. But Lilly faces a huge patent cliff in the near future. Obviously, Lilly isn't alone in its fight, as Pfizer had to deal with the loss of its cholesterol treatment Lipitor, and Merck has been dealing with the loss of Singulair as a blockbuster product. The big question Lilly faces is whether it can do as good a job as Pfizer and Merck have of sustaining its sales with new products. Let's take an early look at what's been happening with Eli Lilly over the past quarter and what we're likely to see in its report.

Stats on Eli Lilly

Analyst EPS Estimate

$1.04

Change From Year-Ago EPS

32%

Revenue Estimate

$5.76 billion

Change From Year-Ago Revenue

5.9%

Earnings Beats in Past 4 Quarters

3

Source: Yahoo! Finance.

Can Eli Lilly earnings keep growing?
In recent months, analysts have gotten more optimistic about Eli Lilly earnings prospects, raising their third-quarter estimates by $0.07 per share and their full-year 2013 projections by more than triple that amount. The stock, though, hasn't responded favorably to those moves, remaining flat since mid-July.

Eli Lilly's second-quarter results actually came in quite strong, apparently giving the stock some momentum. Both revenue and net income came in well above what investors had expected, with positive contributions from its animal-health unit and a 22% jump in Cymbalta sales helping the company. But in one way, Cymbalta's success only heightens what's at stake for Eli Lilly as it goes off-patent in December, and other key drugs will lose their patent protection in the near future as well.

Yet Lilly has had difficulty getting new drugs through the pipeline to replace sales from its blockbusters. Alzheimer's drug solanezumab had a huge amount of potential to change the face of Alzheimer's disease research, but it failed two phase 3 trials last year and has investors questioning whether it has any chance of eventually gaining approval. Lilly said in July that it will do a new phase 3 study focusing on milder forms of the disease, but the company had hoped that solanezumab would already be producing profits by now.

Still, Lilly is doing its best to bolster its other promising pipeline products. Despite a setback for its ramucirumab cancer treatment from the failure of a breast-cancer trial, Lilly still might be able to use the drug to fight stomach cancer. Diabetes treatments like dulaglutide, which helps increase insulin release rates after meals to help diabetes sufferers, have huge potential to move the needle for Lilly even though many competing companies have already successful diabetes-related products on the market.

Lilly also has to decide how it will streamline its business. Pfizer's spinoff strategy involved the IPO of its animal-health assets into a separate company, Zoetis, leaving Pfizer to focus solely on pharmaceuticals. Merck, on the other hand, has aimed at a more-extensive internal restructuring that it hopes will boost the success of its research and development program and cut costs. Whichever path Lilly picks, it'll be important to the company's success in the years to come.

In the Eli Lilly earnings report, watch to see how the company responds to the imminent loss of patent protection on Cymbalta. In order to keep up with Pfizer and Merck, Lilly needs to demonstrate ongoing work with its pipeline to give investors something to look forward to in the future.

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Fool contributor Dan Caplinger has no position in any stocks mentioned. You can follow him on Twitter @DanCaplinger. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.