NEW YORK (Reuters Health)—Romosozumab shows smaller benefits for increasing bone mineral density (BMD) in the second year of treatment compared to the first, new research suggests.
The extension of a phase 2 study in postmenopausal women with low bone mass also found BMD decreased sharply when patients on romosozumab were switched to placebo after two years, while those switched to denosumab maintained BMD and showed additional increases.
“There appears to be no advantage to using romosozumab for more than 12 months,” Dr. Michael R. McClung of Oregon Osteoporosis Center in Portland, the study’s first author, told Reuters Health by email. “Like all other osteoporosis drugs except bisphosphonates, the advantages and benefits of therapy disappear quickly when treatment is stopped.”
Romosozumab is a humanized monoclonal antibody that targets sclerostin, a protein produced by osteocytes that reduces bone formation while increasing bone resorption.
The U.S. Food and Drug Administration rejected Amgen’s application for approval of romosozumab as an osteoporosis treatment in 2017, after it was linked to an increase in adverse cardiovascular events in a phase 3 trial. The FDA asked the drug company to put in another application incorporating data from two additional phase 3 trials.
The new study, online April 25 in the Journal of Bone and Mineral Research, is a follow-on to a phase 2 trial that evaluated three different doses of romosozumab for 12 months. At one year, those who agreed to participate in the continuation trial were randomly assigned to romosozumab or alendronate/romosozumab for 12 months, followed by 12 months on denosumab or placebo.
Of the 364 original trial participants, 315 finished two years of treatment, and 248 completed three years. There were additional increases in BMD measurements through month 24, but the gains were smaller than those seen in the first year of treatment. Study participants who were randomly assigned to denosumab had additional increases in BMD, but BMD in the placebo group fell, with some measurements close to baseline levels.
“Following romosozumab with denosumab results in very impressive gains in bone mineral density at hip and spine – confirming the findings from the FRAME study published in 2016,” Dr. McClung said. “The consistent results of our study along with FRAME and ARCH studies demonstrate clearly that the sequence of romo followed by denosumab or a bisphosphonate should become the treatment of choice for patients at high or imminent risk of fracture if/when romosozumab receives regulatory approval.”