Osteologix, Inc (SAN FRANCISCO, California), a specialty biopharmaceutical company targeting musculoskeletal diseases, announced positive top-line results of an international, randomized, double-blind, active-controlled phase II dose-response of its lead investigational drug, strontium malonate (NB S101) for osteoporosis. The 12-week trial met its primary endpoint by significantly decreasing CTX-1 (C-terminal telopeptide of type 1 collagen), a well-validated biomarker for measuring bone resorption activity, at all dose levels compared with the control group.

Known as the STRONG study, the trial enrolled 289 postmenopausal women with low bone mineral density (BMD) and evaluated three doses of NB S101 and one dose level of Protelos® (strontium ranelate, Les Laboratoires Servier), which was approved in Europe in 2004 for the treatment and prevention of postmenopausal osteoporosis. The reductions in serum CTX-1 were 13.5% in the group receiving 0.75 g of NB S101, 15.5% in the group receiving 1 g, and 22.2% in the group receiving 2 g, compared with the controls (P <.001 for all doses versus control). Protelos demonstrated a statistically significant reduction in CTX-1 of 8.5% (P = .03) at the EMEA-approved 2 g dose. When compared with Protelos, both the 1 g and 2 g doses of the agent achieved significantly greater reductions of CTX-1 with equivalent results (P <.001). NB S101 has been formulated as a once-daily tablet for which Osteologix has full worldwide commercial rights.

The trial investigated as secondary endpoints the effects of NB S101 on BMD at specific sites including lumbar spine, total hip, and femoral neck. At 3 months, the agent significantly increased lumbar spine BMD at all doses tested, with the most significant increase of 2.66% (P <.01) for the 2 g dose; Protelos 2 g increased lumber spine BMD by 1.96% (P <.05). Strontium therapy was well-tolerated and side effects were generally mild in all dose groups. There were no significant differences in the side effect profiles among the four treatment groups.

In preclinical studies, the agent demonstrated significant beneficial effects by reducing bone resorption and increasing strong bone formation and bone mineralization.

NB S101 is administered in a once-daily 1 g tablet whereas Protelos is administered as a sachet to be dissolved in water. The labeled dose of Protelos is 2 g, although total weight of one dose of Protelos is 2.44 g. 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 in NB S101 compared with Protelos.