Osteologix Inc (SAN FRANCISCO, California), a developer of proprietary therapeutics for the treatment of bone disease and women's health, announced that it has initiated a randomized, double-blind, placebo-controlled, phase II dose-response study in healthy postmenopausal women of its lead investigational drug, strontium malonate (NB S101) for osteoporosis. The primary endpoint of the study is the change in patients' bone resorption. Osteologix plans to enroll approximately 275 postmenopausal women with low bone mineral density and treat them for 12 weeks. The study is being conducted at sites in the UK and Denmark.

The clinical trial is designed with five randomized arms. Osteologix plans to enroll approximately 55 patients in each arm. Four arms of the trial will be double-blind, including three different doses of NB S101 (750 mg, 1000 mg and 2000 mg) and placebo. The primary endpoint will be the effect of NB S101 on CTX-1 (C-terminal telopeptide of type 1 collagen), a biochemical marker of bone resorption. In addition to the four double-blind arms, there will be an open-label arm containing Protelos® (strontium ranelate, Les Laboratoires Servier, approved in Europe in 2004 for the treatment of postmenopausal osteoporosis to reduce the risk of vertebral and hip fractures). The Protelos arm is open-label because this drug is only available in a sachet and must be mixed with water prior to ingestion.

In addition to the primary endpoint of quantifying bone resorption, Osteologix plans to evaluate the effect of NB S101 on bone formation by measuring markers specific for this process. Other secondary endpoints being evaluated include the effects of NB S101 on bone mineral density, strontium levels, and markers of cartilage degradation; side effects will also be assessed.

The advantage of NB S101 over Protelos is that it can be administered in a once-daily tablet while Protelos is administered as a sachet dissolved in water. The labeled dose of PROTELOS is 2 g (although the total weight of one dose of Protelos is 2.44 g) whereas NB S101 in a 1 g tablet dose resulted in the same blood levels of free strontium. The amount of free strontium in the Protelos product is 680 mg whereas the amount of free strontium in NB S101 is 465 mg. Therefore, the bioavailability of free strontium has been increased by NB S101 when compared to Protelos.

Osteologix believes that NB S101 may have the ability to both increase bone formation and decrease bone resorption in addition to providing patients with greater convenience and fewer side effects than drugs currently approved for osteoporosis.

—A. Techman

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