New Data from a Natural History Study in Patients with Infantile- and Juvenile-Onset Hypophosphatasia Accepted as Late-Breaking Abstracts at the ENDO 2015 Annual Meeting

CHESHIRE, Conn.--(BUSINESS WIRE)--

Alexion Pharmaceuticals, Inc. ALXN announced today that researchers will present new data from a retrospective, multinational natural history study of children with hypophosphatasia (HPP) (symptom onset ≥6 months to <18 years) in two separate late-breaking presentations at the Endocrine Society's 97^th Annual Meeting and Expo (ENDO). Abstracts summarizing these presentations are published on the ENDO website and can be accessed using the links below. The ENDO annual meeting will be held March 5-8, 2015, in San Diego.

The following abstract will be presented in an oral session on Thursday, March 5, 2015, from 11:30 a.m. to 1:00 p.m., Pacific Standard Time (PST):

• Abstract LB-OR01-4: "A Retrospective, Multi-National, Non-Interventional, Natural History Study of the Childhood Form of Hypophosphatasia," Whyte, et al.

Accessible at: https://endo.confex.com/endo/2015endo/webprogram/Paper22822.html

The following abstract will be presented in a poster session on Saturday, March 7, 2015, from 1:00 to 3:00 p.m., Pacific Standard Time (PST):

• Abstract LBS-039: "Gait Assessment in Children with Childhood Hypophosphatasia: Impairments in Muscle Strength and Physical Function," Phillips, et al.

Accessible at: https://endo.confex.com/endo/2015endo/webprogram/Paper22842.html

In addition, as previously announced, Alexion will present new functional and quality-of-life data from clinical studies in children with HPP who were treated with asfotase alfa for at least three years, as well as data from two patient-reported surveys characterizing the burden of HPP in adults at the ENDO meeting.

About Hypophosphatasia (HPP)

HPP is a genetic, chronic and progressive ultra-rare metabolic disease characterized by defective bone mineralization that can lead to destruction and deformity of bones, profound muscle weakness, seizures, respiratory failure and premature death.^1-5

HPP is caused by mutations in the gene encoding an enzyme known as tissue non-specific alkaline phosphatase (TNSALP).^{1, 2} The genetic deficiency in HPP can affect people of all ages.¹ HPP is classified by the age of the patient at the onset of symptoms of the disease, with infantile- and juvenile-onset HPP defined as manifestation of the first symptom prior to 18 years of age.

HPP can have devastating consequences for patients at any stage of life.¹ In a natural history study, infants who had their first symptom of HPP within the first 6 months of life had high mortality, with an overall mortality rate of 73% at 5 years.⁶ In these patients, mortality is primarily due to respiratory failure.^1,5,7 In patients surviving to adolescence and adulthood, long-term clinical sequelae include recurrent and non-healing fractures, debilitating weakness, severe pain and the requirement for ambulatory assistive devices such as wheelchairs, wheeled walkers and canes.^1,4

About Alexion

Alexion is a biopharmaceutical company focused on serving patients with severe and rare disorders through the innovation, development and commercialization of life-transforming therapeutic products. Alexion is the global leader in complement inhibition and has developed and markets Soliris^® (eculizumab) as a treatment for patients with paroxysmal nocturnal hemoglobinuria (PNH) and atypical hemolytic uremic syndrome (aHUS), two debilitating, ultra-rare and life-threatening disorders caused by chronic uncontrolled complement activation. Soliris is currently approved in nearly 50 countries for the treatment of PNH and in nearly 40 countries for the treatment of aHUS. Alexion is evaluating other potential indications for Soliris in additional severe and ultra-rare disorders beyond PNH and aHUS, and is developing other highly innovative biotechnology product candidates, including asfotase alfa, across multiple therapeutic areas. This press release and further information about Alexion can be found at: www.alexion.com.

[ALXN-G]

Safe Harbor Statement

This news release contains forward-looking statements, including statements related to potential medical benefits of asfotase alfa for hypophosphatasia (HPP). Forward-looking statements are subject to factors that may cause Alexion's results and plans to differ from those expected, including, for example, decisions of regulatory authorities regarding marketing approval or material limitations on the marketing of asfotase alfa for HPP, delays in arranging satisfactory manufacturing capabilities and establishing commercial infrastructure for asfotase alfa for HPP, the possibility that results of clinical trials are not predictive of safety and efficacy results of asfotase alfa in broader or different patient populations, the risk that third party payors (including governmental agencies) will not reimburse for the use of asfotase alfa (if approved) at acceptable rates or at all, the risk that estimates regarding the number of patients with asfotase alfa and observations regarding the natural history of patients with asfotase alfa are inaccurate, and a variety of other risks set forth from time to time in Alexion's filings with the Securities and Exchange Commission, including but not limited to the risks discussed in Alexion's Quarterly Report on Form 10-Q for the period ended September 30, 2014. Alexion does not intend to update any of these forward-looking statements to reflect events or circumstances after the date hereof, except when a duty arises under law.

References

1. Rockman-Greenberg C. Hypophosphatasia. Pediatr Endocrinol Rev. 2013; 10(suppl 2):380-388.

2. Whyte MP. Hypophosphatasia: nature's window on alkaline phosphatase function in humans. In: Bilezikian JP, Raisz LG, Martin TJ, eds. Principles of Bone Biology. Vol 1. 3rd ed. San Diego, CA: Academic Press; 2008:1573-1598.

3. Whyte MP, Greenberg CR, Salman N, et al. Enzyme-replacement therapy in life-threatening hypophosphatasia. N Engl J Med. 2012; 366(10):904-913.

4. Seshia SS, Derbyshire G, Haworth JC, Hoogstraten J. Myopathy with hypophosphatasia. Arch Dis Child. 1990; 65(1):130-131.

5. Baumgartner-Sigl S, Haberlandt E, Mumm S, et al. Pyridoxine-responsive seizures as the first symptom of infantile hypophosphatasia caused by two novel missense mutations (c.677T>C, p.M226T; c.1112C>T, p.T371I) of the tissue-nonspecific alkaline phosphatase gene. Bone. 2007; 40(6):1655-1661.

6. Whyte MP, Leung E, Wilcox W, et al. Hypophosphatasia: a retrospective natural history study of the severe perinatal and infantile forms. Poster presented at the 2014 Pediatric Academic Societies and Asian Society for Pediatric Research Joint Meeting, Vancouver, B.C., Canada, May 5, 2014. Abstract 752416.

7. Whyte MP, Rockman-Greenberg C, Hofmann C, et al. Improved survival with asfotase alfa treatment in pediatric patients with hypophosphatasia at high risk of death. Poster presented at the American Society for Bone and Mineral Research (ASBMR) 2014 Annual Meeting, Houston, September 14, 2014. Abstract 1097.