Phosphatase inhibition by LB-100 enhances BMN-111 stimulation of bone growth.

The study suggests that combining a phosphatase inhibitor with an NPR2 agonist may enhance bone growth in a mouse model of achondroplasia, but further research is needed to confirm these effects in humans.

Summary and findings

This study evaluated the effects of a phosphatase inhibitor (LB-100) in combination with the NPR2 agonist BMN-111 (vosoritide) on bone growth in a mouse model of achondroplasia. The combination treatment was shown to enhance bone length and cartilage area compared to BMN-111 alone. Notably, the study focused on cGMP production and chondrocyte activity.

Abstract

Activating mutations in fibroblast growth factor receptor 3 (FGFR3) and inactivating mutations in the natriuretic peptide receptor 2 (NPR2) guanylyl cyclase both result in decreased production of cyclic GMP in chondrocytes and severe short stature, causing achondroplasia (ACH) and acromesomelic dysplasia, type Maroteaux, respectively. Previously, we showed that an NPR2 agonist BMN-111 (vosoritide) increases bone growth in mice mimicking ACH (Fgfr3Y367C/+). Here, because FGFR3 signaling decreases NPR2 activity by dephosphorylating the NPR2 protein, we tested whether a phosphatase inhibitor (LB-100) could enhance BMN-111-stimulated bone growth in ACH. Measurements of cGMP production in chondrocytes of living tibias, and of NPR2 phosphorylation in primary chondrocytes, showed that LB-100 counteracted FGF-induced dephosphorylation and inactivation of NPR2. In ex vivo experiments with Fgfr3Y367C/+ mice, the combination of BMN-111 and LB-100 increased bone length and cartilage area, restored chondrocyte terminal differentiation, and increased the proliferative growth plate area, more than BMN-111 alone. The combination treatment also reduced the abnormal elevation of MAP kinase activity in the growth plate of Fgfr3Y367C/+ mice and improved the skull base anomalies. Our results provide a proof of concept that a phosphatase inhibitor could be used together with an NPR2 agonist to enhance cGMP production as a therapy for ACH.

Limitations

Not reported in abstract.

Elsewhere in the Vosoritide corpus