The goal of this clinical trial is to assess the safety and tolerability of a single oral dose of BMN 349 in participants with PiZZ or PiMZ/MASH. Primary outcome measures include incidence of any adverse events (including serious adverse events, dose limit toxicities, and adverse events of special interest), incidence of any laboratory test abnormalities, incidence of lung function test abnormalities and 12-lead ECG parameters. Participants will receive a single dose of either BMN 349 or placebo and then monitored for safety and tolerability.