Pasadena-based biotechnology company Arrowhead Pharmaceuticals was this week’s biggest mover, gaining 26 percent to end at $7.50. Hawthorne-based OSI Systems, Inc. was also among the week’s movers. The specialized electronics manufacturer gained 11 percent to end at $68.46. Santa Monica toy company Jakks Pacific Inc. was the week’s biggest loser, dropping 6 percent to end at $8.93.