Calcitonin is a naturally occurring hormone involved in regulating calcium in the body. Pharmaceutical formulations of calcitonin are derived from salmon calcitonin, which is about 30 times more potent than human calcitonin. Calcitonin has demonstrated good efficacy and proven safety in the treatment of osteoporosis in postmenopausal women, as well as in the bone disorder Paget’s disease.
When calcitonin is released into the bloodstream, it binds to receptors located on bone cells known as osteoclasts, which are responsible for breaking down existing bone in an ongoing process of turnover that replaces old bone with newly synthesized bone. Once calcitonin binds to its receptor it causes the osteoclasts to stop breaking down (resorbing) bone. This action of calcitonin slows the rate of bone breakdown and resulting bone loss and is the basis for its use in the treatment of osteoporosis. Salmon calcitonin products have been on the market for over 35 years in the US and Europe and have a long history of safety.
Calcitonin is a peptide hormone that would be destroyed by the digestive system if taken orally; therefore the traditional route of administration has been via injection or a nasal spray. This is believed to have limited more widespread use of calcitonin, despite its long record of efficacy and safety. Tarsa Therapeutics in conjunction with Unigene Laboratories has developed a once-daily oral tablet version of calcitonin. This proprietary technology prevents the degradation of calcitonin in the gastrointestinal system and assists its transit across the cells lining the intestine and into the bloodstream. Tarsa’s oral calcitonin is expected to provide a more convenient dosage form for the many patients with osteoporosis or at risk of developing osteoporosis. Oral administration makes calcitonin a more feasible treatment option for some patients, and it may potentially result in better patient compliance.
Tarsa’s global Phase III ORACAL trial evaluating its oral calcitonin tablet for the treatment of postmenopausal osteoporosis yielded positive safety and efficacy results. The full data from the study were presented at the American Society for Bone and Mineral Research 2011 Annual Meeting and were published in the August 2012 edition of the Journal of Bone and Mineral Research*. The Phase III data showed that in postmenopausal women with osteoporosis, Tarsa’s oral calcitonin demonstrated superiority to both placebo and nasal calcitonin spray in increasing bone mineral density (BMD) at the lumbar spine after 48 weeks. In the trial, the safety profile of oral calcitonin did not differ substantially from nasal calcitonin or placebo. The majority of adverse events were mild or moderate, and Tarsa’s oral calcitonin was also significantly less immunogenic than nasal calcitonin spray.
Tarsa recently completed a Phase II study of its oral calcitonin in the prevention of postmenopausal osteoporosis. The Phase II trial evaluated the ability of Tarsa’s oral calcitonin to improve BMD at the lumbar spine in postmenopausal women with low bone mass (osteopenia) at increased risk of fracture. In this trial Tarsa’s oral calcitonin tablet produced statistically significant, clinically relevant improvements in bone mineral density at the lumbar spine and its safety profile did not differ substantially from placebo. These data were presented at the American Society for Bone and Mineral Research 2012 Annual Meeting.