WASHINGTON (Reuters) - The U.S. Supreme Court on Monday gave Merck & Co a new opportunity to avoid lawsuits accusing the company of failing to properly warn patients of debilitating thigh-bone fractures from taking its osteoporosis drug Fosamax, throwing out a lower court decision that had revived the litigation.

FILE PHOTO: The Merck logo is seen at a gate to the Merck & Co campus in Linden, New Jersey, U.S., July 12, 2018. REUTERS/Brendan McDermid/File Photo

The nine justices unanimously directed the Philadelphia-based 3rd U.S. Circuit Court of Appeals to reconsider its decision to let the lawsuits proceed even though the Food and Drug Administration had rebuffed Merck when the company sought to add a warning to Fosamax’s label about fracture risk.

Monday’s ruling added clarity to a powerful defense employed by drug makers that product liability claims brought under state law are preempted by the actions of a federal agency, because federal law generally trumps state law under the U.S. Constitution. Merck argued that it cannot be penalized for failing to issue a warning that the FDA had blocked.

Merck in 2008 submitted data to the FDA suggesting Fosamax might be linked to certain bone fractures, but the FDA denied its warning label proposal. After a task force further studied the issue, the FDA in 2010 ordered manufacturers to revise labels to include a warning, which Merck did.

The plaintiffs contend that the FDA rejected only Merck’s proposed language for the warning that focused on relatively minor stress fractures rather than the more serious fractures they suffered.

In a decision written by Justice Stephen Breyer, the Supreme Court said a drug manufacturer must show it “fully informed” the FDA of the need for a warning before it was rebuffed and that judges, not juries, must decide whether such lawsuits are preempted, as Merck has claimed. Lower courts now must revisit the case reflecting the Supreme Court’s guidance.

Merck’s shares were flat on Monday.

Fosamax helps prevent and treat osteoporosis, a condition that can lead to bone fractures, in women who have gone through menopause. But it may increase the risk of fractures in the thigh bone or just below the hip joint, often requiring surgical intervention.

‘FULLY COMMITTED’

In a statement, Merck said it was pleased with the decision and “remains fully committed to defending these cases going forward and will continue to present evidence that it acted appropriately at all times in regard to the potential risk of atypical femur fractures.”

David Frederick, an attorney for the Fosamax users who sued Merck, said Monday’s decision reaffirms patients’ ability to hold drug companies accountable. “This opinion protects access to justice for injured patients,” Frederick said.

Sales of Fosamax, also available as a generic drug, totaled $209 million in 2018, according to New Jersey-based Merck.

Fosamax users sued Merck, alleging the drug caused them to sustain serious thigh bone fractures and that the company failed to warn of the risk. The number of cases has swelled to more than 1,000.

A federal trial court in New Jersey threw out the cases, but in 2017 the 3rd Circuit allowed the claims to proceed to trial, ruling that a jury could find that the FDA had objected only to Merck’s phrasing of the proposed warning label.

On Monday, three justices - John Roberts, Samuel Alito and Brett Kavanaugh - agreed with the outcome of the case but did not join Breyer’s decision. In a separate opinion, Alito signaled sympathy for Merck, noting the FDA had long been aware of the issue and was communicating with drug manufacturers, and noted that President Donald Trump’s administration also backs Merck’s position.