The Los Angeles Business Journal’s index of largest local public companies closed up for the week.

The weighted LABJ Stock Index closed at 177.35, up 3 percent to for the trading week ended Dec. 20. Gainers outpaced decliners 121 to 34, with 6 companies unchanged.

Among the biggest movers was Arrowhead Research Corp., jumping 25 percent to $9.93. The Pasadena biotech firm benefitted from investor optimism that its experimental drugs could become blockbusters.

Puma Biotechnology Inc. was among top gainers for a third week, rising another 18 percent to $101.39. The rise of the West L.A. cancer drug developer was related to positive preliminary clinical trial results for its experimental cancer therapies.

Herbalife Ltd. rose more than 17 percent to close the week at $80.61. The Los Angeles nutritional supplement company said a re-audit of more than three years of financial results resulted in no material changes to its earlier statements.

Among the biggest decliners was CytRx Corp. which was last week’s biggest gainer after announcing positive clinical trial result. Shares of the West L.A. biotech fell 24 percent to $4.66 as some investors took profits.

Semtech Corp. fell more than 13 percent to $24.20. The Camarillo semiconductor maker reported a better-than-expected fiscal second quarter profit, but gave cautious guidance for future quarters.