Eiger BioPharmaceuticals Inc. and Merck & Co. Inc. expanded their agreement to include the development of lonafarnib, a potential treatment for Hutchinson-Gilford progeria syndrome.

Hutchinson-Gilford progeria syndrome, or progeria, is a rare and fatal genetic condition characterized by rapid aging in children.

Under the expanded deal, Eiger will be in charge of regulatory execution, commercialization and distribution of the drug. The company said it will ask the U.S. Food and Drug Administration's guidance for a potential regulatory approval of the drug in the progeria indication.

In addition, Eiger will have the commercial and distribution rights to lonafarnib across the licensed and approved indications in the future.

Meanwhile, Eiger has completed its partnership with the Progeria Research Foundation, an organization dedicated to discovering the cause, treatments and cure for progeria, under which it will provide lonafarnib at its sole cost and expense to ongoing clinical trials as well as expanded access. The company will also consult the FDA regarding a potential filing of a new drug application for lonafarnib to treat progeria using data from the multiple clinical studies completed by the foundation.

Eiger will also examine lonafarnib to treat hepatitis delta virus infection in a phase 3 study.

Palo Alto, Calif.-based Eiger BioPharmaceuticals is engaged in the development of treatments for orphan diseases in the U.S.