Genetic and Congenital

Continued use of burosumab in X-linked hypophosphatemia needed to sustain clinical benefit

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To sustain clinical benefit from treatment with burosumab in X-linked hypophosphatemia (LH), long-term, continued use appears to be needed, according to results from a Phase 3 open-label extension trial.

In this study, 31 patients from a 96-week phase 3 study continue treatment on a burosumab regimen for a further 48 weeks. Between the period of 6-18 months between the 2 studies, some patients received compassionate use of burosumab. The primary efficacy outcome was fasting serum phosphate concentration; secondary outcomes were serum 1,25 dihydroxyvitamin D concentration, renal phosphate reabsorption, PROs and ambulatory function.

Improvements at 96 weeks in these outcomes were maintained through the 48-week extension, as well as improvements in stiffness and physical function, pain and fatigue endpoints, and in ambulatory function (6-Minute Walk Test).

A post-hoc exploratory analysis compared outcomes between 7 participants in the a 96-week phase 3 study who discontinued treatment with burosumab between the studies and 23 participants receiving at least 1 dose.

“The benefits of burosumab on clinical laboratory tests of efficacy, PROs and ambulatory function may be lost when treatment is interrupted but recover over time when treatment is reinstated,” the authors concluded.

Kamenicky P, Briot K, Brandi ML, et al. Benefit of burosumab in adults with X-linked hypophosphataemia (XLH) is maintained with long-term treatment. RMD Open. 2023;9(1):e002676. doi: 10.1136/rmdopen-2022-002676. PMID: 36854566; PMCID: PMC9980374.