Which class of drugs is designed to stop replication in specific DNA cells?

Alkylating agents are specifically designed to stop the replication of DNA within cells, making them a vital part of cancer treatment. These drugs work by attaching an alkyl group to the DNA molecule, leading to cross-linking of DNA strands. This cross-linking inhibits the cells' ability to divide and replicate, which is particularly effective against rapidly dividing cancer cells.

On the other hand, anti-androgens work by interfering with the action of male hormones in certain cancers, antibiotics target bacterial infections rather than manipulating DNA, and antidepressants are designed to help manage depression and mental health conditions rather than affecting cellular replication processes. Thus, the unique mechanism of alkylating agents in disrupting DNA replication clearly positions them as the correct choice for this question.