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Ultra-Rare Diseases

Alexion, one of the world's leading rare disease companies, is focused on providing life-transforming treatments to patients with severe and life-threatening rare diseases for which there are few, if any, effective treatment options.

The impact of these diseases on patients, their families, and society is profound as many are severe, chronic and progressive, with high mortality rates. Ultra-rare diseases often present unique public health challenges. Typically, few researchers or companies explore such diseases. It is also highly likely that very few physicians are familiar with diagnosing and treating these conditions, leading to missed, delayed or inaccurate diagnosis and thereby delaying treatment, even when an approved, effective therapy is available.

When developing treatments for patients with rare and ultra-rare diseases, often there are no pre-existing regulatory pathways or prior controlled studies. Alexion is one of the few companies in this field with a proven track record in drug discovery, regulatory affairs, clinical trial design and recruitment, and manufacturing. This expertise has allowed Alexion to emerge as a leading rare disease company in the biotech industry. 

Our approach to serving patients is driven by education and a passion for understanding and meeting the unique needs of patients and families around the world suffering from rare and ultra-rare diseases.

What is an Ultra-Rare Disease?

In a population of one million people,  fewer than 20 have an ultra-rare disease


  1. World Health Organization’s Diabetes Fact Sheet, accessed at:
  2. US and World Population Clock, accessed at:
  3. US Food and Drug Administration’s Definition of Disease Prevalence for Therapies Qualifying Under Orphan Drug Act, accessed at:
  4. REGULATION (EU) No 536/2014 OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 16 April 2014 on clinical trials on medicinal products for human use, and repealing Directive 2001/20/EC.