Two months ago, we wrote that Pfizer was scrambling to boost Lipitor by signing a deal to have its cholesterol pill placed on the Express Scripts preferred formulary. This was an important move for the drugmaker, of course, because Express Scripts is a big pharmacy benefits manager, and Lipitor hadn’t been on its formulary since 2005.

But so far, “definitive proof of its success is lacking,” writes Joe Tooley, an analyst at AG Edwards, in an investor note today. There’s hasn’t been a “significant bump in scripts as absolute total prescription numbers are up only 1 percent since the deal” began. Meanwhile, he notes that the statin cholesterol market is up 4.5 percent over the same period.

This is also evident in Lipitor’s share of total prescriptions, which is down 1.1 percent since June 1, he adds. Three years ago, Lipitor commanded nearly 50 percent of the market, but today has about 32 percent, reflecting the inroads made by generic Zocor over the past year.

Tooley expects Pfizer to details plans for Lipitor’s resurgence at its July 18 earnings call, but forecasts worldwide sales of $13.0B for Lipitor this year, which represents slightly less than 1 percent growth. Not so great for the world’s best-selling drug.