And the total number of Americans living with a rare disease is estimated at between 25-30 million. Several Pharma companies are working to advance the therapy methodologies of rare disease. Moreover, several government organizations are supporting the research by providing funds and favourable policies. Amgen plans to buy Celgene's Psoriasis drug Otezla Amgen has entered into a definitive agreement with Celgene Corporation for the possession of its psoriasis and arthritis drug Otezla (apremilast) for USD 13.4 billion. Otezla is the only oral, non-biologic treatment for psoriasis and psoriatic arthritis.