Pharmaceutical firm Celgene has passed on an option to acquire portfolio company Acetylon Pharmaceuticals, according to a regulatory filing flagged by Xconomy.
US-based Acetylon is developing small molecule drug treatments for diseases including neurodegeneration, autoimmune disease and cancer.
Celgene invested $15m in Acetylon, which had previously received $40m in funding from backers including Leukemia & Lymphoma Society, in 2012 and paid the company $100m in 2013 for an option to acquire it for an additional $500m.
The option expired in May this year, though Celgene will retain its equity stake in Acetylon.