ESPE2024 Poster Category 1 Bone, Growth Plate and Mineral Metabolism 2 (9 abstracts)
1Department of Health Sciences, University of Florence, Florence, Italy. 2Diabetology and Endocrinology Unit, Meyer Children's Hospital IRCCS, Florence, Italy
Background: Achondroplasia is the most common form of skeletal dysplasia, caused by activating mutations of FGFR3 gene. In the previous years the management of achondroplasia was focused on prevention and treatment of complications related to the altered cartilage maturation. Therapeutic spectrum of achondroplasia was broadened by approval of Vosoritide (VOXOZOGO®), a synthetic recombinant analogue of C-natriuretic peptide (CNP). The interaction between activation of natriuretic peptide receptor B (NPR-B) by Vosoritide and effects of growth hormone on growth plates is crucial to assess potential combination of Vosoritide with other therapeutic agents, as recombinant human GH analogue(rhGH). In the current issue we describe two patients who were affected by both Achondroplasia and GH deficiency (GHD) and therefore underwent both treatment with Vosoritide and daily rhGH.
Case descriptions: Two female patients in periodic follow up in our hospital for achondroplasia underwent stimulation tests to assess GHD because of deflection in syndrome-related growth curves for height. In both patients causes of growth restriction unrelated to idiopathic GHD and achondroplasia were excluded. Stimulated GH secretion with GHRH+ arginine and then levo-DOPA in Patient 1 and with clonidine and then arginine in Patient 2 was deficient. Therefore, Patient 1 and Patient 2 started daily rhGH (initial dose of 0.21 mg/kg per week) at the age of 7 years and 3 years and 3 months respectively with significant response of height and increase in growth velocity. As treatment with Vosoritide was approved in Italy in 2022, both girls have been treated with this drug too for 12 months. After 1 year of treatment with Vosoritide and rhGH Patient 1 showed a persistent response to therapy with constant increase of height above +3 SDS in syndrome-related growth charts. On the other hand, after a rapid increase in growth velocity with rhGH alone leading to increase in height from 0 SDS to +2 SDS, Patient 2 had steady decline in growth velocity even with addition of Vosoritide and her growth in height stabilized between +1 and +2 SDS.
Conclusions: Currently Vosoritide is the only approved pharmacological option for achondroplasia but its effects in case of association with rhGH are not clear. Our patients showed a contrasting response to Vosoritide and rhGH treatment but the reason for these differences are still to be clarified. Further investigations about this topic are needed to overcome the current pitfalls in treatment of skeletal dysplasias.