Zelos Therapeutics, Inc. has reached agreements with the US Food and Drug Administration (FDA) and the European Medicines Agency (EMEA) for a phase 3 registration study of ZT-031 for the treatment of severe osteoporosis.

Following the special clinical protocol assessment (SPA) process with the FDA and a formal scientific advice meeting with the Committee for Human Medicinal Products of the EMEA, Zelos Therapeutics has received regulatory approval for the design, conduct and analysis of a pivotal phase 3 clinical study. The trial, if successful, would form the primary basis for an efficacy claim to support applications for marketing authorization of ZT-031 in the United States and Europe.

ZT-031, a parathyroid hormone analog, will be evaluated against alendronate (Fosamax) in the first active comparator osteoporosis registration study. The 24-month Phase 3 study is expected to enrol 3,255 post-menopausal women with severe osteoporosis. The primary efficacy endpoint is the incidence of new vertebral fractures in the ZT-031 study arm compared with the alendronate study arm.

In addition, the FDA and EMEA have agreed to an innovative weight-based dosing regimen in which different dose strengths of ZT-031 will be used in patients in different weight categories. Zelos Therapeutics believes that the safety and efficacy profile of ZT-031 that has been demonstrated to date, coupled with the anticipated improvements in clinical benefit that may result from weight-based dosing, could position ZT-031 favourably against Forteo (teriparatide), the only bone formation therapeutic currently approved for use in the United States.

ZT-031 (formerly Ostabolin-C) is a proprietary cyclic 31-amino acid parathyroid hormone (PTH) analog being developed for the treatment of osteoporosis. ZT-031 was recently studied in a 12-month double-blind, placebo-controlled Phase 2 study in 261 postmenopausal women with low bone mass (osteoporosis) at either the hip or the lumbar spine. In this study, ZT-031 was shown to be a bone formation agent with a rapid onset of effect leading to clinically relevant increases in bone mineral density (BMD) with no adverse events due to hypercalcemia observed.

Zelos Therapeutics specializes in the development of innovative treatments for bone disorders and related indications in large, underserved markets. Led by an experienced team of biopharmaceutical executives and funded by leading health care investors, Zelos Therapeutics is advancing a portfolio of product opportunities into late-stage clinical trials.