Health care stocks were mixed pre-bell Tuesday, with the State Street Health Care Select Sector SPDR ETF (XLV) down 0.2% and the iShares Biotechnology ETF (IBB) slightly higher.

Galapagos (GLPG) said it is in advanced discussions for a strategic collaboration with Gilead (GILD) following the partner's agreement to purchase private biotechnology firm Ouro Medicines. Galapagos shares were down more than 1% premarket.

Karyopharm Therapeutics (KPTI) shares were down more than 9% after the company said it agreed with RA Capital Management to raise about $30 million through a private placement, with potential additional proceeds of $44 million if accompanying warrants are exercised.

Ocugen (OCGN) said its experimental gene therapy showed a 31% reduction in lesion growth compared with a control group in a phase 2 clinical trial for a dry age-related macular degeneration treatment. Shares of Ocugen were down more than 5% pre-bell.