Osteoporosis drugs may prevent future bone growth

Nov 13 2008

Patients who start and eventually stop regimens of a common class of osteoporosis drugs called bisphosphonates may be unable to benefit from parathyroid hormone (PTH), which can rebuild bone mass lost due to advanced stage osteoporosis. PTH has been proven to increase the volume and strength of the honeycomb-like bone infrastructure, the inner mesh that begins to diminish in old age.

Bisphosphonates, the active ingredient in widely prescribed osteoporosis medications such as Fosamax, Actonel, and Boniva are currently taken by more than thirty million Americans.

"These medicines work by preventing further bone loss," explains Dr. Warren Levy, president and CEO of Unigene Laboratories, Inc. "However, recent reports suggest that some patients using bisphosphonates may be unable to repair or replace older or damaged bone. Furthermore, it has been reported that the prior use of certain bisphosphonates may blunt the effects of PTH, which could render the only currently available bone growth drug ineffective. Since bisphosphonates typically deposit in the bones for years, the use of a bisphosphonate could compromise the ability to grow new bone later in life when it is most needed."

Estrogen alternatives have grown in recent years, including calcitonin, a naturally occurring hormone involved in calcium regulation and bone metabolism. In third-party clinical trials, calcitonin demonstrated a 62% reduction in the incidence of new vertebral fractures for a subgroup of women over seventy-five years of age, one of the most significant reductions demonstrated by any current osteoporosis therapy.

"Calcitonin has a proven, thirty-five-year record of safe human use with virtually no significant side effects and can be taken simultaneously with other medications," said Dr. Levy. "Since it is rapidly cleared by the body, it does not build up in the bone and may allow the patient to effectively employ PTH therapy in subsequent years if necessary."

Although, PTH injections have been shown to reduce the incidence of fractures by restoring bone, the treatment can be very costly and requires daily injections. Unigene and GlaxoSmithKline are jointly developing a low-cost, orally administered PTH treatment, and Unigene is currently performing a Phase I clinical study in the U.S. Twenty-four healthy postmenopausal women are enrolled in the study, which is designed to assess product safety and measure PTH blood levels.

The tablets being tested utilize the improved Enteripep® oral delivery technology. "One pill a day to treat bone fractures would be ideal for patients who need to take this medicine for life," adds Dr. Levy.