TransCon CNP, a sustained-release C-Type Natriuretic Peptide prodrug, a potentially safe and efficacious new therapeutic modality for the treatment of comorbidities associated with FGFR3-related skeletal dysplasias.

TransCon CNP is a C-type natriuretic peptide (CNP-38) conjugated via a cleavable linker to a polyethylene glycol carrier molecule, designed to provide sustained systemic CNP levels upon weekly subcutaneous administration. TransCon CNP is in clinical development for the treatment of comorbidities associated with achondroplasia. In both mice and cynomolgus monkeys sustained exposure to CNP via TransCon CNP, was more efficacious in stimulating bone growth than intermittent CNP exposure. TransCon CNP was well tolerated with no adverse cardiovascular effects observed at exposure levels exceeding the expected clinical therapeutic exposure. At equivalent dose levels, reductions in blood pressure and/or an increase in heart rate, were seen following single s.c. injections of the unconjugated CNP-38 molecule or a daily CNP-39 molecule (same amino acid sequence as Vosoritide, USAN:INN). The half-life of the daily CNP-39 molecule in cynomolgus monkey was estimated to be 20 minutes, compared to 90 h for CNP-38, released from TransCon CNP. Cmax for the CNP-39 molecule (20μg/kg) was approximately 100-fold higher, compared to the peak CNP level associated with administration of 100μg/kg CNP as TransCon CNP. Furthermore, CNP exposure for the daily CNP-39 molecule, was only evident for up to 2 h post dose (LLOQ 37 pmol/L), whereas TransCon CNP gave rise to systemic exposure to CNP-38 for at least 7 days post-dose. The prolonged CNP exposure and associated hemodynamically safe peak serum concentrations associated with TransCon CNP administration are suggested to improve efficacy, compared to short-lived CNP molecules, due to better therapeutic drug coverage and decreased risk of hypotension. SIGNIFICANCE STATEMENT: The hormone C-type Natriuretic Peptide (CNP) is in clinical development for the treatment of comorbidities associated with achondroplasia (ACH), the most common form of human dwarfism. The TransCon Technology was used to design TransCon CNP, a prodrug that slowly releases active CNP in the body over several days. Pre-clinical data show great promise for TransCon CNP to be an effective and well-tolerated drug that provides sustained levels of CNP in a convenient once weekly dose, while avoiding high systemic CNP bolus concentrations that can induce cardiovascular side effects.