This study comprises 2 stages; a Dose Optimization Stage followed by an optional Dose Expansion Stage. The study is designed to evaluate multiple doses and dosing intervals of mRNA-3705.~In both stages, after confirmation of eligibility, participants will enter an Observation Period (48 to 72 hours pre-dose), which includes 24 hours inpatient hospital stay, followed by a Treatment Period (up to 40 weeks). Participants who complete the Treatment Period, including the End of Treatment (EOT) Visit, are offered participation in the mRNA-3705 extension study. If the participant chooses to participate and meets eligibility criteria, they will be enrolled in the extension study; otherwise, they will transition to the 2-year follow-up part of this study.
This is a study of mRNA-3705 in participants with isolated elevated methylmalonic acid (MMA) due to methylmalonyl-coenzyme A (CoA) mutase (MUT) deficiency. The main goal of the study is to assess safety, pharmacokinetics, and pharmacodynamics of mRNA-3705.