Healthcare stocks were falling premarket Monday, with the State Street Health Care Select Sector SPDR ETF (XLV) 0.5% lower and the iShares Biotechnology ETF (IBB) down 0.6%.

Arrowhead Pharmaceuticals' (ARWR) plozasiran met its primary and secondary endpoints in two phase 3 studies as a potential treatment for adults with severe hypertriglyceridemia, the company said. Shares of Arrowhead Pharmaceuticals were down more than 2% pre-bell.