Biohaven falls after RBC downgrades on regulatory uncertainty

Brokerage RBC Capital Markets downgrades Biohaven Pharmaceuticals BHVN.N to "sector perform" from "outperform", trims PT to $21 from $54

New PT still implies a 23.7% upside to the stock's last close

Shares of BHVN fall 3.8% to $15.4 premarket

Brokerage says the drugmaker has many promising projects, but also many risks with regard to its pipeline

Brokerage believes the two projects, troriluzole and Kv7, are crucial for the company's success and flags concerns about troriluzole's chances of getting approved by the FDA

Co's financial constraints might limit its potential upside, says RBC

"We are not confident enough in any single one to be able to recommend shares" - RBC

As of last close, BHVN stock down 57.1% YTD