"Not a whole lot. My healing might actually be faster than yours," he admitted frankly. "Silver's the biggest one, but other than that, dismemberment or fire or...similar things are just about the only things that can take me out."

Sam wasn't sure how it would react with the serum, either - it could kill Steve, but he imagined that the more likely worst case scenario would be that the serum would just boost his immune system to reject the lycanthropy. However that worked; he didn't really know a damn thing about magic, or if this even was magic, or just really advanced science. Maybe he should've let Stark do some analysis before making the offer.