The drug: Tofacitinib
The disease: Rheumatoid arthritis
The developer: Pfizer
Peak projections: $2.6 billion (Credit Suisse)

Pfizer ($PFE) has an acute need for new blockbuster drugs as the world's largest drugmaker stares down the end of its exclusivity on Lipitor next year. While not expected to come close to replacing future declines in Lipitor revenues, the company's tofacitinib for rheumatoid arthritis has been one of the brightest prospects in its late-stage pipeline.

An oral med like Pfizer's rheumatoid arthritis pill could quickly seize a chunk of the more than $20 billion RA annual market, which is now dominated by injectable treatments such as Humira. Pfizer delivered data on multiple late-stage studies in September that showed the benefits of its oral JAK inhibitor, and officials pointed out the similar efficacy of the pill to the injected TNF drugs on the market.

Pfizer aims to file for regulatory approvals of tofacitinib by the end of the year in major markets including the U.S., Europe and Japan. Regulators will be probing safety data on the drug. In tofacitinib's case, some data show a rise in infection rates among patients on the drug, and there's evidence suggesting that there could be an uptick in side effects.

Still, the RA pill could gain key approvals despite safety risks, paving the way for the drug to achieve blockbuster status within a small number of years.

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