By Maggie Fick and Ludwig Burger

LONDON Eli Lilly on Thursday said it has not yet gained approval in Britain for the injection pen it plans to use for its Mounjaro drug against obesity and diabetes, adding to uncertainty over timing of the product's launch.

The drug itself was cleared for weight loss by the British regulator on Wednesday.

"We have submitted an alternative device presentation of tirzepatide for regulatory approval. We are continuing to work closely with relevant government agencies and are focusing on ensuring a sustainable supply," a spokesperson for the U.S. company told Reuters in a statement.

Tirzepatide is the name of the active pharmaceutical ingredient in Mounjaro.

The spokesperson added that the injection device in question would be different from the pen that Lilly plans to use for the weight-loss drug in the United States, where it was rebranded as Zepbound. Within the UK, Lilly will use one pen type for both uses against type 2 diabetes and obesity.

"We would be unable to confirm the status or time lines of any potential or ongoing applications due to commercial confidentiality," Britain's drug regulator, the Medicines and Healthcare products Regulatory Agency (MHRA), said in a response to a request for comment.

(Reporting by Maggie Fick in London and Ludwig Burger in Frankfurt; Editing by David Goodman)