Even with debt levels at Eli Lilly and Co. at paltry lows, the bad news finally forced Standard & Poor’s to lower its rating on the company’s senior unsecured debt. But the New York-based agency said it believes the Indianapolis-based drugmaker will eventually break its string of bad luck on developing products.

S&P dropped its rating on Lilly debt to AA- from AA on Aug. 19, citing the company’s string of late-stage clinical-trial failures, a couple of court losses over patents on existing drugs, the disappointing sales of its newest product, Effient, and, of course, looming patent expirations on its two top-selling drugs.

"The rating action considers the disappointments and delays for both new and existing products experienced by this top-tier drug company, which we believe weaken its ability to offset the lost revenues for products facing generic competition over the next three years," credit analyst David Lugg said in a statement.

Lugg noted that Lilly’s debt represents just 60 percent of the company’s cash flow, as measured by earnings before interest, taxes, depreciation and amortization. That’s well below S&P’s desired maximum of 150 percent.

Lugg and his colleagues retained their rating on Lilly’s bonds and their stable outlook for the company, saying that they hold the "expectation that Lilly will continue to pursue conservative financial policies while improving its new-product-development success rate.”

S&P’s downgrade decision was made before Lilly received a federal committee's recommendation to market its drug Cymbalta to treat chronic pain. The antidepressant is already Lilly’s No. 2 drug, behind the antipsychotic Zyprexa. Some analysts expect the new use to add $500 million to Cymbalta’s more than $3 billion in annual sales.

On Friday, Lilly won a delay of a court decision that invalidated its U.S. patent on Strattera, an attention-deficit hyperactivity disorder medicine with about $600 million in worldwide sales. Lilly is moving to appeal that decision.

Lilly also said last week it would push ahead with its second experimental Alzheimer’s drug after its first candidate actually worsened patients' condition during a large, late-stage clinical trial.