My read of the article makes this sound more like a natural failure than a regulatory one. The anti-venoms are very expensive to make and very rarely needed.

I see no reason that these drugs should get a pass on FDA testing that other drugs are held to, so it doesn't seem like a regulatory failure. It seems like some body acting for the general good (ie, government or nonprofit, maybe some life/health insurance?) should pay for the FDA trials to help get the alternative drugs to market.