Voxzogo specifically activates the CNP/NPR-B signaling pathway in chondrocytes, directly stimulating the proliferation and differentiation of growth plate chondrocytes, thereby improving linear growth in children with achondroplasia (ACH). Its mechanism of action is similar to that of natural CNP, but with a longer half-life, which can overcome growth inhibition caused by FGFR3 mutations.

Molecular mechanism of action

Fossoli peptide, as a C-type natriuretic peptide (CNP) analogue, binds with high affinity to the NPR-B receptor. This receptor is highly expressed in growth plate chondrocytes and, upon activation, downregulates MAPK signaling downstream of FGFR3 through the cGMP pathway, antagonizing chondrocyte proliferation inhibition caused by FGFR3 mutations.

1.1 Signal pathway regulation

By increasing intracellular cGMP levels, upregulate the expression of key cartilage differentiation genes such as SOX9 and COL2A1. Simultaneously inhibiting the activity of degradation enzymes such as MMP13, maintaining the extracellular matrix homeostasis of growth plates, and prolonging the proliferation cycle of chondrocytes.

2 Clinical growth promoting effects

Phase III clinical trials have shown that daily subcutaneous injection can increase the annualized growth rate of ACH patients by 1.57cm/year (2.3 times higher than baseline). After 52 weeks of treatment, the height Z-score improved by 0.3-0.5, and the continuous treatment effect accumulated over time.

2.1 Morphological changes in growth plates

MRI confirmed that the thickness of the growth plate increased by 15% -20%, and the columnar arrangement of chondrocytes became more regular. Histology shows that the ratio of proliferative and hypertrophic areas has been optimized, and the rate of ossification front has been re matched with the rate of cartilage formation.

3 Pharmacodynamic characteristics

The serum peak concentration is reached 2-4 hours after administration, with a bioavailability of approximately 80%. At steady state, the local concentration of the drug in the growth plate is 5-8 times that of the serum, achieving targeted action. Continuous administration can maintain cGMP levels in growth plates 3-5 times higher than baseline.

3.1 Dose effect relationship

There is a linear growth response within the range of 15-30 μ g/kg/day, and the effect plateau appears when it exceeds 40 μ g/kg/day. The recommended dose of 20 μ g/kg/day can achieve a maximum growth stimulating effect of 90%.