Eli Lilly and Co has withdrawn its supplemental New Drug Application, for FDA's approval, to market its anti-depressant - Cymbalta - for use as chronic-pain medicine for low back pain. The decision to pull out comes after US health regulators raised questions about the drug's effectiveness.

In August, Lilly released data on its efforts, saying a study showed the drug "significantly" reduced chronic lower-back pain. The application, submitted in the second quarter, was based primarily on three clinical trials: one positive study on chronic osteoarthritis pain of the knee and two studies - one positive and one that is supportive, but did not meet its primary goal - on chronic low back pain.

About FDA's objection, Lilly said: "In discussions between Lilly and the FDA, agency reviewers raised questions about efficacy and dosing that revolved primarily around statistical methodology and study design."

However, the decision does not affect Cymbalta's existing FDA-approved indications for major depressive disorder, generalized anxiety disorder, management of diabetic peripheral neuropathic pain and management of fibromyalgia.

In fact, Lilly posted third-quarter sales of $716.4 million for Cymbalta - its second-largest revenue-generating drug after Zyprexa. Cymbalta sales in the first three quarters of the year were $1.97 billion.

Lilly plans to resubmit the application to the FDA in the first half of 2009, after adding data from a recently completed study in chronic osteoarthritis pain of the knee.

John Hayes, vice president of Lilly Research Laboratories, said: "We believe the updated data package will give the FDA a broader basis for reviewing our application."