Pharmacokinetic and Dose Response Study of Asfotase Alfa in Adult Patients With Pediatric-Onset Hypophosphatasia (HPP)

Inclusion Criteria:

1. Participants or their legal representative(s) provided written informed consent prior
to undergoing any study-related procedures.

2. Participants were ≥18 years of age at Screening.

3. Participant had pediatric-onset hypophosphatasia (HPP), defined as onset of first
sign(s)/symptom (s) of HPP prior to 18 years of age.

4. Participants had a documented diagnosis of HPP as indicated by a documented history of
HPP-related skeletal abnormalities and 1 or more of the following:

- Documented tissue-nonspecific alkaline phosphatase (TNSALP) gene mutation(s) from
a certified laboratory.

- Serum alkaline phosphatase (ALP) level below the age-adjusted normal range AND
plasma pyridoxal-5'-phosphate (PLP) above the upper limit of normal at Screening.

5. Participants had a plasma inorganic pyrophosphate (PPi) level of ≥3.9 micromolar (µM)
at Screening.

6. Female participants of childbearing potential had a negative pregnancy test at the
time of enrollment.

7. Sexually active male and female participants of childbearing potential agreed to use a
highly effective method of birth control during the study.

8. Female participants not of child-bearing potential due to sterilization (at least 6
weeks after surgical bilateral oophorectomy with or without hysterectomy or at least 6
weeks after tubal ligation) confirmed by medical history, or menopause.

9. Participants were willing to comply with study procedures and the visit schedule.

Exclusion Criteria:

1. Investigational site personnel directly affiliated with this study and/or their
immediate families. Immediate family was defined as a spouse, parent, child, or
sibling, whether biological or legally adopted.

2. Employees of Alexion Pharmaceuticals.

3. Currently enrolled in a clinical study involving another study drug or non-approved
use of a drug or device.

4. Participated, within the last 30 days, in a clinical study involving a study drug
(other than the study drug used in this study).

5. Completed or withdrawn from this study or any other study investigating asfotase alfa
in the previous 3 years.

6. Women who were pregnant, planning to become pregnant, or breastfeeding.

7. Serum 25-hydroxy Vitamin D levels below 20 nanogram (ng) per milliliter (mL) at
Screening.

8. Screening serum creatinine or parathyroid hormone (PTH) levels ≥1.5 times the upper
limit of normal.

9. Any medical condition, serious concurrent illness and/or injury, recent orthopedic
surgery, or other extenuating circumstance that, in the opinion of the Investigator,
may have significantly interfered with study compliance or study endpoints.

10. Prior treatment with bisphosphonates within 2 years of study entry for any length of
time or for more than 2 consecutive years at any prior timepoint.

11. Treatment with PTH, strontium, or sclerostin inhibitors within 6 months prior to the
first dose of study drug.

12. Unwilling or unable to comply with the use of a data collection device on which study
participants directly recorded data.