The purpose of this study is to find out whether 4-PBA will increase the level of AAT in persons with AAT deficiency whether or not they have liver disease.

The purpose of this study is to determine whether 4-PBA will significantly increase serum Z AAT levels in AAT-deficient individuals with and without evidence of hepatocellular injury and to assess its effects on liver injury.

Inclusion Criteria:

• Age 18-65
• Serum A1-PI levels <11uM an appropriate genetic phenotype/genotype
• 5 of 10 subjects must have documented laboratory evidence of liver disease
• Willingness to withhold Prolastin therapy for 6 weeks prior to screening and throughout the 4-PBA dosing period (up to 3 months)

Exclusion Criteria:

• Any cause of liver disease other than Alpha-1 Antitrypsin deficiency
• Evidence of advanced liver disease
• HIV positive
• Use of systemic steroids, ursodeoxycholic acid (Actigall, Urso), or herbs in the prior 6 months