Navicular Syndrome: Does FDA Approval of Tildren and Osphos Change Anything?

From bone to zone: Focus on navicular-type lameness has evolved from concentrating on identifying bone defects visible in radiography to a more dynamic approach to also detect possible soft tissue injury, deteriorating hoof condition and age- or sport-related stress factors. The navicular bone is circled in this distal limb bone model at the University of Nottingham Vet School.

The landscape of treatment options for equine navicular syndrome is set to change this year, as the U.S. Food and Drug Agency (FDA) recently approved two drugs for use in the treatment of this complex lameness problem in the horse's foot. "Tildren" and "Osphos" are two specific medications that cleared the difficult hurdles of the FDA approval process in May 2014.

Study Targets Gene in Bone Loss Similar to Pedal Osteitis, Navicular Degeneration Equine Lameness Conditions

A CT scan of the equine distal limb reveals the bony architecture. Image courtesy of Alex zur Linden, DVM, DACVR, Assistant Professor of Radiology at Ontario Veterinary College.

By now, most Hoof Blog readers know the mechanism behind degenerative bone loss that is so clearly illustrated by foot conditions like pedal osteitis and navicular degeneration. Tildren is the current great hope for treatment of those conditions, although only now it has only been studied in navicular disease and bone spavin. Still, there's hope!

Enter a new hope this week, thanks to a study from the University of Pennsylvania, as mentioned in the journal Nature Medicine. Senior author Yongwon Choi, PhD, professor of Pathology and Laboratory Medicine at the University of Pennsylvania and colleagues report their findings.

To quote from their press release:

"The basic principles behind bone metabolism are largely understood, hence a handful of drugs treating osteoporosis are available. Most drugs inhibit osteoclasts, which cause bone decay. But there is also at least one that stimulates osteoblasts, enhancing bone formation. A combined treatment will not only prevent the occurrence of osteoporosis, but also make the quality of bone even better.

"Our discovery proves that inhibiting osteoclasts while simultaneously stimulating new bone formation can be done.

"Bone health is maintained by the balanced activities of osteoblasts and osteoclasts. The study shows that the inactivation of gene Atp6v0d2 in mice results in dramatically increased bone mass due to defective osteoclasts as well as enhanced bone formation.

"These findings may provide some clarity into the regulation of bone metabolism and show that targeting the function of a single gene could possibly inhibit bone decay while stimulating bone formation."

(end quote)

Before you start lining up all those lame horses, please realize that it may be a while before this gene therapy becomes a reality and trickles down to equine medicine. Then again, the equine model may be a good one for experimentation. Let's hope!