Asfotase alfa is an enzyme replacement therapy meant to directly address the cause of hypophosphatasia. While more research is necessary, it has been shown to decrease the mortality rate and help treat respiratory symptoms. It has been investigated by the German Institute for Quality and Efficiency in Health Care (IQWiG), but more research should be conducted in order to fully understand every aspect of this treatment.
About Hypophosphatasia (HPP)
Hypophosphatasia (HPP) is a rare genetic disorder that is characterized by skeletal abnormalities; bones and teeth experience problems during development. Mineralization, which is the process where bones take in calcium and other minerals, is defective in those with HPP. This defective process results in soft bones and teeth, which can result in fracturing and tooth loss. There are also different sub-types of HPP, depending on onset and other factors.
Symptoms include:
- Metaphyses abnormality
- Rib abnormality
- Teeth abnormality
- Bowing of the long bones
- Emphysema
- Large fontanelles in infants
- Narrow chest
- Anemia
- Hypercalcemia
- Muscular hypotonia
- Recurrent fractures
- Seizures
The ALPL gene is mutated in those with HPP, and this mutation may be inherited in an autosomal dominant or recessive pattern. The infantile form, which is treated by asfotase alfa, is passed down in the recessive pattern. The mutation causes a deficiency of the enzyme phosphatase, which results in the issues with mineralization.
Doctors will look for the characteristic symptoms during a clinical exam along with patterns in family history to obtain a diagnosis. They will confirm through blood tests, imaging tests, or genetic testing. After they are sure of the diagnosis, treatment consists of non-steroidal anti-inflammatory drugs for joint and bone pain, vitamin B6 for seizures, and orthopedic internal fixation. The FDA has also approved of asfotase alfa for treatment, but only for the perinatal, infantile, and juvenile-onset types of HPP.
About Asfotase Alfa
Asfotase alfa is an enzyme replacement therapy, and it is meant to directly treat the deficiency of phosphotase. IQWiG investigated this therapy in terms of its treatment for infantile HPP, which is an extremely severe form. The issue with this study is that it omitted other forms of HPP, making the full effects unknown.
The study conducted by IQWiG included two single-arm studies that only considered survival and respiratory function. It discovered that asfotase alfa increases the survival rate of infants with HPP. The trial enrolled 80 participants, with the requirement that the onset of HPP occurred within the first six months of life. They compared these 80 patients with previously recorded cases of 48 infants.
While the results of the study show that this therapy does increase the chance of survival, there were issues. The processing of data is nontransparent, making it difficult to see any potential bias. They also did not include other sub-types of the disorder, which leaves out many others affected by HPP.
Despite issues with this study, this treatment has received FDA approval and is being used for the treatment of HPP. Medical professionals hope to conduct more research into this therapy and that it continues to better the lives of those affected by HPP.
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