Krystal Biotech Inc. has received IND clearance from the FDA for KB-408 for the treatment of α1-antitrypsin deficiency (AATD). KB-408 is a modified, replication-defective, nonintegrating HSV-1-derived vector carrying two full-length copies of the serpin family A member 1 gene (SERPINA1) to enable expression of α1-antitrypsin (AAT).