Jan 8 (Reuters) - Johnson & Johnson said on Monday it had agreed to buy drug developer Ambrx Biopharma for $2 billion to gain access to its portfolio of targeted cancer therapies.

J&J will pay $28 per share of Ambrx, which represents a premium of about 105% to the stock's last close.

Ambrx is developing therapies that belong to the class of drugs called antibody drug conjugates (ADC), which are described by researchers as "guided missiles" to target cancer cells and minimize damage to healthy tissue.

J&J's acquisition is the latest deal announced in the space. In November, AbbVie said it would buy ADC-developer ImmunoGen for $10.1 billion in cash.

(Reporting by Manas Mishra in Bengaluru; Editing by Krishna Chandra Eluri)