There's no stopping bioweapons. Bioweapons are easy. The reason bioweapons aren't built is because very few biology nerds with sufficient lab skills are evil; and just having an LLM won't give you the lab skills to do it.

Anyone who can publish a gene technology/biomedicine paper can make a bioweapon. If you wrote a paper about how to make a bioweapon easily, it would be unpublishable not because of any danger, but because there wasn't enough novelty.