June 21 (Reuters) - Amylyx Pharmaceuticals has agreed to buy the rights to bankrupt drugmaker Eiger BioPharmaceuticals' experimental drug for low blood sugar in a $35.1 million deal, Eiger said in a filing on Friday.

Amylyx's acquisition of avexitide would mean a foray into drug development for metabolic diseases. The company had so far been a developer of drugs to treat neurodegenerative diseases.

Avexitide is a GLP-1 antagonist drug that help treat low blood sugar, the opposite of what diabetes and weight-loss medicines such as Novo Nordisk's Ozempic and Wegovy, and Eli Lilly's Mounjaro and Zepbound do.

In April, Amylyx announced its plans to remove Relyvrio - its approved drug for amyotrophic lateral sclerosis (ALS) - from the market after failing in a key late-stage trial.

Amylyx did not immediately respond to Reuters' request for comment.

Eiger has tested avexitide in mid-stage studies as a potential treatment for low blood sugar caused by bariatric surgery and also a metabolic disorder called congenital hyperinsulinism.

Congenital hyperinsulinism occurs in newborns and causes permanent brain damage and life-long insulin-dependent diabetes.

Separately, Eiger had filed for Chapter 11 bankruptcy in April. (Reporting by Puyaan Singh in Bengaluru; Editing by Alan Barona)