This trial is a Phase 2, multicenter, double-blind, randomized (ratio 2:1 TransCon CNP vs. placebo), placebo-controlled trial, designed to evaluate the safety, tolerability, and efficacy of 100 μg CNP/kg of Navepegritide (TransCon CNP) administered SC once-weekly for 52 weeks in infants with genetically verified heterozygous ACH, aged 0 to \< 2 years at the time of randomization.