A Study to Evaluate the Safety and Efficacy of BEAM-302 in Adult Patients With Alpha-1 Antitrypsin Deficiency (AATD)

Part A: Inclusion Criteria: * Males or females 18 – 70 years of age inclusive at the time of consent. * Diagnosis of AATD and homozygous for the PiZZ mutation (confirmed by genetic testing). * Blood total AAT level 4x/year]). * Liver disease with any of the following: * FibroScan liver stiffness measurement ≥7.5 kilopascals (kPa). (For sites without access to FibroScan, APRI >0.5 can be used as a surrogate exclusion criterion [Yilmaz, 2011]. * Known history of liver cirrhosis or complications of cirrhosis (eg, varices, ascites, hepatic encephalopathy). * Presence of ≥F2 liver fibrosis if a patient has previously had a liver biopsy. * Have ALT or AST > upper limit of normal (ULN). * Total bilirubin levels > ULN; if documented Gilbert's Syndrome, total bilirubin >2 × ULN. * INR ≥1.2 at screening. If deemed appropriate by the investigator and/or prescribing physician, the patient may stop taking anticoagulants for an appropriate washout period or reversal with vitamin K and if indicated, a repeat INR within 4x/year]) * Previous diagnosis of liver cirrhosis or complications of cirrhosis (eg, varices, ascites, hepatic encephalopathy).