Why might it be impossible to use cone snails to treat cancer patients? Give two reasons

Because all cone snails are venomous and capable of "stinging" humans, live ones should never be handled, as their venomous sting will occur without warning and can be fatal.Cone snail venoms are mainly peptides. The venoms contain many different toxins that vary in their effects; some are extremely toxic. 

Because cone snails are slow-moving, they use a venomous harpoon (called a toxoglossan radula) to capture faster-moving prey, such as fish. And the venom of a few larger species, especially the piscivorous ones, is powerful enough to kill a human being.