Which of the following could lead to termination during lead optimization related to DNA risk?

• A. Evidence that the molecule may damage DNA.
• B. Evidence that the molecule enhances DNA repair.
• C. Evidence that DNA remains unaffected.
• D. DNA sequencing results.

Answer: (A)

Genotoxicity risk is a key safety concern in lead optimization. If there is evidence that the molecule may damage DNA, it signals a real risk of mutations and cancer with long-term use, which is typically unacceptable for a development candidate and leads to termination or major redesign. This is the strongest reason to halt progress—the potential for heritable or persistent DNA damage drives safety decisions.

Other options don’t imply a DNA-damage risk in the same way. Evidence that a molecule enhances DNA repair would generally be favorable or at least not a safety red flag. If DNA remains unaffected, that argues against genotoxic risk. DNA sequencing results alone don’t automatically trigger termination unless they demonstrate actual harmful mutations or a causal link to DNA damage; the key trigger is demonstrated DNA damage risk.