NMR solution structure of salmon calcitonin in SDS micelles.

OSTORA™ ORAL CALCITONIN TABLET

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 an excellent safety profile and have been on the market for over 35 years in the US and Europe.

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 good efficacy and excellent safety. Tarsa Therapeutics in conjunction with Unigene Laboratories has developed OSTORA™, a once-daily oral tablet version of calcitonin.  This proprietary technology prevents the degradation of calcitonin in the GI system and assists its transit across the cells lining the intestine and into the bloodstream. OSTORA oral calcitonin is expected to be a more convenient dosage form for many patients with osteoporosis or at risk of developing osteoporosis, making it more feasible for them and their physicians to include calcitonin as one of their treatment options, and also potentially resulting in better patient compliance. 

Tarsa’s global Phase III ORACAL trial evaluating its OSTORA 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.  The Phase III data show that OSTORA achieved all of the efficacy endpoints in the trial and indicate that the safety profile of OSTORA did not substantially differ from nasal calcitonin or placebo.  The majority of adverse events were mild or moderate, and OSTORA was also significantly less immunogenic than nasal calcitonin spray.

Tarsa also has recently initiated a Phase II study of OSTORA in the prevention of postmenopausal osteoporosis, and patient enrollment and dosing are underway.