After surveying 25 psychiatrists with experience managing patients with treatment-resistant depression, Piper Jaffray analyst David Amsellem believes Allergan's rapastinel is likely to be a niche product. A large number of oral options are available as generics, and there seems to be a lack of comfort with an intravenous treatment option, Amsellem tells investors in a research note. He's taking Allergan's opportunity in the treatment-resistant depression setting with a" "high degree of caution." Amsellem reiterates a Neutral rating on Botox maker with a $236 price target.