Abstract: The present invention relates to a mammalian FGF21 responsive reporter cell line and method of using the same for detecting and optionally quantitating FGF21 activity in a test sample. The invention further relates to a method for detecting and optionally quantitating neutralizing antibodies against FGF21 present in a test sample using the reporter cell line of the present invention.

Abstract: The present invention relates to small secreted reporter-peptides 15 to 150 amino-acids in length comprising a response element, activated by one or more transcription factors induced by the pharmacology active substance to be analyzed following its interaction with a specific intracellular or cell surface molecule, functionally linked to a response element, a TATA box, a signal peptide, anchor and detection sequences to which antibodies can be raised, and a poy-A tail. The anchor sequence may differ from one peptide to another or may be common to multiple secreted reporter-peptides such that all the peptides can be analyzed simultaneously by ELISA using a detection antibody labelled with for example HRP, or by the use of a commonly available immuno-detection platform such MSD, Gyros, AlphaLisa, or Biacore.