Bone Healing


Currently, no pharmacological treatments are available. There is therefore an unmet need for medications that can stimulate bone healing. Parathyroid hormone (PTH) is the first bone anabolic drug approved for the treatment of osteoporosis, and intriguingly a number of animal studies suggest that PTH could be beneficial in the treatment of fractures and could thus be a potentially new treatment option for induction of bone healing.

Non-union of fractures occur when the normal process of bone healing is interrupted and the fracture does not heal properly or does not heal at all. Nonunion of bones is a serious complication of a fracture and may occur when the fracture moves too much, has a poor blood supply or gets infected. The most common reported risk factor is an open fracture. A non-union will not heal if left alone. Therefore the patient's symptoms will not improve and the function of the limb will remain impaired. It will be painful to bear weight on the affected area and it may be deformed or unstable. Another population that could use assistance with bone healing is someone who needs dental implants. The bone takes 2-4 months to properly heal in order to be ready for the dental implants.

Current treatment for non-union is only operative and there are no medications available to accelerate bone healing. The idea of offering PTH 1-34 which is a bone building hormone, will help to reduce the amount of non-unions occurring each year and can help in the bone healing process for people who suffer from non-union. This will lead to less secondary surgeries and possibly help decrease the amount of sick time due to the faster healing time.
There have been a number of animal studies conducted that suggest that PTH could be beneficial in the treatment of fractures.

Stress fractures are overuse injuries to bones caused by repetitive stresses. Stress fractures may be the result of a small number of repetitions with a relatively large load (eg, a military recruit marching for several miles with a heavy backpack), a large number of repetitions with a usual load (eg, an athlete training for a long-distance race), or a combination of increased load and increased repetitions.


In the UK there are approximately 850,000 new fractures seen each year, while it has been suggested that approximately 5-10% of such fractures are fractures in which the fractured bone fails to heal, medically referred to as nonunion fractures. The cost to the National Health Service of treating non-union fractures has been reported to range between £18,000 and £79,000 per person. The estimated addressable market for nonunion and enhanced healing of fractures for the EU is approximately 0.7 to 2 billion Euros per year, assuming an expense of approximately 2,000 to 2,500 Euro per treatment regimen. In the U.S there are approximately seven million new fractures/broken bones each year, with approximately 300,000 developing slowly (delayed union) or nonunion fractures. Estimates for the average non-union treatment cost vary from nearly $25,000 to $45,000. Nonunions are estimated to cost the health care system in the US $9.2 billion/ year. This excludes losses in productivity to the economy.

Retrospective studies have found that 8.3% to 52% of runners have had a history of stress fracture, whereas the incidence in a 12-month prospective study of track and field athletes was 21.1%. When expressed as a percentage of all injuries, stress fractures have been reported to represent between 0.5% and 20.0% of all injuries sustained by athletic populations. Prospective data in recruits undergoing basic training indicate a stress fracture incidence of 3.3% to 8.5% in the US military and 3.6% to 28.9% in the Israeli military.

Current Status

Entera is currently working to advance the bone healing application through collaborations.

Entera is preparing for a phase 2 clinical trial in an academic institution abroad in collaboration with its local military. This trial is expected to address the clinical potential of oral PTH as a treatment for stress fractures and possibly prevention.

Bone HealingFotolia