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The drug: Lipitor
The companies: Pfizer/Astellas Pharma/Jeil Pharmaceutical
Estimated worldwide sales for 2012: $5.55 billion

If any drug is feeling the squeeze of generic competition, it's Pfizer's ($PFE) Lipitor. Just last year, the cholesterol med topped the list of highest earning drugs, bringing in $12.5 billion. After falling off patent in November, that number will drop by more than half, to $5.55 billion.

Generic Lipitor these days costs only $18 a month for insurers and $137 a month for the brand name. It's become so cheap that one retailer in Michigan is offering it to customers with no co-pay, just to help drive traffic to their stores.

As Lipitor falls victim to generics, Pfizer began pulling money out of advertising the drug. So it's no surprise that copycats brought in more money than the brand name drug in the first quarter; generics earned $950 million compared with Lipitor's $841 million.

As Lipitor loses its luster, Big Pharma is on the hunt for the next megablockbuster cholesterol fighter. Sanofi ($SNY) and Regeneron ($REGN) and Roche ($RHHBY) are working on PCSK9 inhibitors, heart drugs promising to lower cholesterol. And GlaxoSmithKline ($GSK) is researching darapladib, which regulates Lp-PLA2. We'll see how millions of dollars invested in these programs pans out.

For more:
Special report:
Darapladib - 15 top therapies in late-stage development
Big Pharma betting billions in high-stakes hunt for the next Lipitor
Pfizer adds healthy-eating app to Lipitor marketing arsenal
With generics horde advancing, Pfizer gives up Lipitor push
Sanofi and Roche race to PhIII with drugs aimed at hot PCSK9 gene