This document summarizes the results of a clinical trial testing the efficacy of asfotase alfa (ENB-0040), an investigational enzyme replacement therapy, for treating life-threatening hypophosphatasia in infants and young children. In the open-label trial, 10 patients received subcutaneous injections of ENB-0040 and showed significant improvements in skeletal mineralization and development over 48 weeks according to radiographic and developmental assessments. Treatment also improved respiratory function in most patients. The therapy was generally well-tolerated with few serious adverse events reported. The results provide evidence that ENB-0040 is an effective treatment for severe hypophosphatasia in young patients.

1. JOURNAL CLUB
Dr.Yassin Alsaleh

4. Introduction
• Hypophosphatasia is a rare, and
sometimes fatal metabolic bone disease.
• characterized by low serum alkaline-
phosphatase activity.
• tissue non-specific alkaline phosphatase
(TNSALP) deficiency in osteoblast and
chondrocytes impairs bone
mineralization, leading to rickets or
osteomalacia.

5. • Condition result from loss-of-function
mutations, typically missense within the
gene (TNSALP).
• patterns of inheritance :
• autosomal recessive and autosomal
dominant.
Introduction

6. • Natural substrates that accumulate in
hypophosphatasia include :
• 1- inorganic pyrophosphate (an inhibitor of
mineralization)
• 2- Pyridoxal 5′-phosphate (PLP), the
circulating form of vitamin B6.
Introduction

7. • High extracellular levels of inorganic
pyrophosphate block hydroxyapatite
crystal growth and cause rickets or
osteomalacia.
• Hypercalcemia and hyperphosphatemia
can develop in severely affected patients.
Introduction

8. • The manifestations of hypophosphatasia
are heterogeneous range from :
• rapidly fatal perinatal variant with almost
no skeletal mineralization.
• to mild disease with dental problems in
adults without any bone symptoms.
Introduction

9. • Perinatal hypophosphatasia:
is characterized by extreme skeletal
hypomineralization, and survival is rare.
• Infantile hypophosphatasia:
• develops before 6 months of age with rickets,
failure to thrive, hypotonia, and myopathy
• is often complicated by hypercalcemia,
nephrocalcinosis, epilepsy, and
craniosynostosis.
Introduction

10. • Skeletal deterioration typically results in
death from respiratory insufficiency.
Introduction

11. • Treatment trials:
• 1- administering intravenous infusions of
plasma enriched in soluble alkaline
phosphatase from patients with Paget’s
disease.
• 2-alkaline phosphatase purified from human
placentas .
Introduction

12. • There is no approved medical treatment
for hypophosphatasia
Introduction

13. • To conducted a clinical trial of treatment
with ENB- 0040 for at least 1 year in infants
and young children with life-threatening
hypophosphatasia.
• To evaluated the safety, tolerability,
bioavailability, pharmacokinetics,
pharmacodynamics, and efficacy of
treatment with ENB-0040
METHODS

14. • ENB-0040 (asfotase alfa; Enobia
Pharma) is an investigational,
recombinant, fusion protein comprising
the TNSALP ectodomain.
METHODS

15. • In an open-label study.
• Efficacy assessments included skeletal
changes, as evaluated by means of
radiography, and gross motor, fine
motor, and cognitive development.
METHODS

16. • Inclusion criteria :
• an age of 3 years or less.
• symptoms of hypophosphatasia
occurring before the age of 6 months,
• an elevated plasma PLP level,
• hypophosphatasia related skeletal
disease as assessed radiographically.
METHODS

17. • Inclusion criteria (cont):
• failure to thrive, rachitic chest deformity or
pyridoxine-responsive seizures, and
nontraumatic
• poorly healing fractures, hypercalcemia,
craniosynostosis, nephrocalcinosis, or
respiratory compromise from
hypophosphatasia0
METHODS

18. • Exclusion criteria
• a treatable form of rickets,
• previous exposure to bisphosphonates,
• hypocalcemia or hypophosphatemia,
• a serum 25-hydroxyvitamin D level of less
than 20 ng /ml(50 nM) .
• if they had received another experimental
treatment for hypophosphatasia (e.g., bone
marrow transplantation).
METHODS

19. • The study design was developed through a
collaboration between the sponsor, Enobia
Pharma, and the authors.
• The protocol was approved by the local
institutional review boards
• written informed consent was obtained from
the patients’ parents.
METHODS

20. • Patients received ENB-0040 as a single
intravenous infusion at a dose of 2 mg/kg.
• followed by subcutaneous injections three
times per week at a dose of 1 mg/kg
• dose could be increased up to 3 mg/kg if
there was worsening failure to thrive,
deteriorating pulmonary function, or no
evidence of skeletal improvement.
METHODS

21. • The primary end point :
• A change in the skeletal manifestations
of hypophosphatasia, as assessed on
radiography.
METHODS

22. • First, three radiologists rated changes
from baseline to week 48 using a 7-
point scale (radiographic global
impression of change [RGI-C]).
METHODS

23. • Points:
• irregularity of the provisional zone of
calcification.
• ephyseal widening. metaphyseal flaring,
fraying,
• radiolucencies.patchy osteosclerosis.
• altered ratio of mid-diaphyseal cortex to bone
thickness.
• gracile bones, absence of some or all bones;
and recent fractures.
METHODS

24. • severe worsening:
• A reduction of 3 points .
• complete healing:
• an increase of 3 points .
• substantial healing:
• a response to treatment defined as a
mean increase of 2 or more points
METHODS

25. • Second, a single reader rated the growth-
plate abnormalities at the wrists and
knees, using a 10-point rickets-severity
scale (RSS).
• The proportion of patients with a response,
was calculated at weeks 24 and 48.
METHODS

26. • Additional efficacy studies included
evaluations of respiratory status and
motor and cognitive function.
METHODS

27. • A total of 11 patients, 7 girls and 4 boys,
were enrolled.
• between October 2008 and December
2009;
• they ranged in age at baseline from 2
weeks to 3 years
RESULTS

28. RESULTS

29. RESULTS

30. • Consent for treatment was withdrawn for 1
of the 11 patients because of irritability,
oxygen desaturation, rigors, and low-grade
fever during receipt of the intravenous
dose.
• The other 10 patients completed 6 months
of treatment and entered the extension
study.
RESULTS

31. • One patient died from sepsis after 7.5
months of therapy.
• Nine patients are currently participating in
the extension study, with an average
treatment duration of 18 months
RESULTS

32. • Skeletal healing :
• Baseline radiographs in all patients showed
hypophosphatasia associated skeletal
disease.
• Skeletal healing became apparent as early
as week 3 in Patient 2 and was striking at
week 24 in all patients except Patient 3.
RESULTS

33. • No skeletal deterioration was
observed, except in Patient 4, whose
consent for treatment was withdrawn
during the intravenous infusion and
who subsequently had marked
skeletal demineralization
RESULTS

35. • RGI-C scores improved from baseline
to week 24 with 9 of 10
• from baseline to week 48, in 8 of 9
patients , meeting the criterion for a
treatment for response.
RESULTS

37. • SECONDARY END POINTS:
• Respiratory function :
• At baseline, all (except one)
accompanied by respiratory
compromise ranging from progressive
insufficiency to frank ventilatory failure
requiring full mechanical ventilation
RESULTS

39. • Respiratory function tended to decline
initially during ENB-0040 therapy in the
infants who were not receiving ventilatory
support .
• but then improved in all patients, along with
better mineralization of the rib cage
RESULTS

40. • At week 48, 6 of the 9 patients were
breathing ambient air without ventilatory
support (as compared with 1 of 11 at
baseline),
• 1 on nasal cannula,
• 1 on mechanical ventilation only at night.
• 1 remained on full mechanical ventilation
RESULTS

41. • Developmental assessment :
• Performance on the Bayley-III instrument
was assessed at baseline in all but two
patients and at weeks 24 and 48.
• At baseline, all the patients had gross
motor delays.
• None could bear weight through the legs
owing to skeletal abnormalities and muscle
weakness
RESULTS

42. • Improvements in age-
equivalent scores for
gross motor, fine motor,
and cognitive development
were noted in 7/8 patients
with complete evaluations.
RESULTS

43. • Of the nine patients who were treated
for 48 weeks,
• all but two were bearing weight through
the legs.
• four were walking or taking early steps.
• one was standing.
• two were crawling.
• and one was sitting.
RESULTS

45. • Patient 3, who at baseline had no
radiographically visible bone, had a
tracheostomy,and had no spontaneous
movement.
• at 48 weeks became able to move all limbs
against gravity.
RESULTS

46. • The most common adverse event was a
reaction at the subcutaneous-injection site.
consisting of mild, transient erythema.
• There was no evidence of ectopic
calcification from the treatment.
• nephrocalcinosis did not progress after the
initial 6 months of treatment and it even
improved in some patients.
ADVERSE EVENTS

47. • Three serious adverse events (one case
each of respiratory respiratory distress,
craniosynostosis, and conductive hearing
loss) were considered by the investigators
to be possibly related to the study
treatment.
ADVERSE EVENTS

48. • bone-targeted enzyme replacement with
ENB-0040 ( a recombinant human
TNSALP coupled to a deca-aspartate) was
effective in infants and young children with
life-threatening or severely debilitating
hypophosphatasia (perinatal or infantile ).
CONCLUSION

50. • Sep 13: Results from an ongoing multinational PII study in
15 infants and young children (<5 years) with
hypophosphatasia (HPP). The study met its primary
endpoint: asfotase alfa led to significant improvement in
skeletal mineralization as assessed radiographically after 24
weeks of treatment, with a mean (SD) increase in RGI-C
score of 1.74 (1.107) and a median increase of 2.00
(p=0.001). This response was observed as early as 12
weeks and improvement continued at 48 weeks. 93% of
patients survived the first 48 weeks of treatment with 80%
having improved respiratory status or requiring no
respiratory support at the final analysis. Asfotase alfa was
well-tolerated with no deaths, serious AEs or
discontinuations deemed treatment-related. The most
common AEs were mild to moderate injection site
reactions,(66.7% of patients). The trial is continuing to enrol
patients

51. • NCT01176266 is an open-label, multicentre,
multinational 2-year PII/III study of the safety,
efficacy and pharmacokinetics of asfotase alfa in
30 infants and children ≤ 5 years of age with
hypophosphatasia.
• Patients will receive a total of 6 mg/kg/week of
asfotase alfa by SC injection, either as 1mg/kg 6
times per week or 2mg/kg 3 times per week. The
primary outcomes are the effect of asfotase alfa
on skeletal manifestations of HPP using a
qualitative Radiographic Global Impression of
Change (RGI-C) scale and tolerability.
• The study started Jul 10 and is due to complete
Dec 14 .