In a similar vain to the Bacteriophage Launcher, a weapon that uses another non-cellular infectious agent as a weapon: The Prion!
Prions are infectious particles that lack DNA or RNA, being merely a tangled mass of proteins that cause normal proteins to degenerate and cause cellular death.
The weapon would launch a prion that wraps around the enemy like a net dealing damage over time and/or maybe another effect? (edit: maybe it makes the enemies more vulnerable to damage?)
Im not sure what kind of projectile, maybe set as some sort of barbed wire-esque trap, possibly using the tether system that already exists for the harpoon-type weapons, or just some kind of net-like projectile.
At first I was thinking about a Prion character and how it would work, like maybe they would have no health and instead rely entirely on armor or something (like the robot from Enter the Gungeon)... and realized it would probably work better as a weapon since they don't have any conventional structure to attach organelles to in the first place so i went with a weapon
could probably use tweaking