The present disclosure relates to antibodies and antibody conjugates having one or more site-specific mutations in the CH2 domain of the heavy chain. The antibody variants disclosed herein can have improved characteristics (e.g., thermal stability, antibody yields, antibody titers, cell-killing) relative to a parent or wild type antibody, including aglycosylated parent or wild type antibodies. Pharmaceutical compositions, diagnostic compositions and kits comprising the same, as well as methods of using these compositions and kits for therapeutic and diagnostic purposes, are also described.