slid 14% in late trading Tuesday after the company warned of less stringent government recommendations for establishing the bioequivalence of a generic version of its top-selling pain patch, Lidoderm.
The company said that the Office of Generic Drugs has recommended, in response to an inquiry, that a bioequivalence study for a potential generic version of Lidoderm should characterize the pharmacokinetic profile of the drug. The OGD also recommends a skin irritation/sensitivity study.
Endo, however, said it believes that generics should be required to demonstrate bioequivalence through a comparative clinical efficacy study, which the company maintains is consistent with the OGD's past practices for a topical product.
Endo said it has already expressed this view to the OGD, and the discussions are ongoing.
Lidoderm, or lidocaine in its generic form, is a topical patch to treat the pain associated with post-herpetic neuralgia, a condition resulting from nerve damage caused by shingles. The company said earlier this month that it expects Lidoderm sales to total $540 million to $540 million this year.
Endo noted that it holds five patents related to Lidoderm, the last of which is scheduled to expire in 2015.
"These patents form the basis of what the company believes is a strong intellectual property estate around Lidoderm and cover not only the product's method of use in neuropathic pain, including post-herpetic neuralgia pain, but also its formulation," the company said, noting it will vigorously assert these patents against any generic challenge.
Endo shares recently were down $4.91 to $29 in after-hours trading.