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

The weighted LABJ Stock Index closed down 0.78 percent to 187.81 for the trading week ended March 28. Decliners outpaced gainers 106 to 47, with seven companies unchanged.

The biggest decliner was American Apparel Inc., dropping 36 percent to 48 cents. The downtown L.A. apparel company priced a dilutive sale of common shares at a discount.

Arrowhead Research Corp. fell 34 percent to $15.62. Investors took profits in shares of the Pasadena biotech after the stock made a huge run-up in recent months. The company also announced that its lead drug candidate was advancing to the next stage of clinical trials.

MannKind Corp. fell 18 percent to $4.83, ahead of a Tuesday meeting of Food and Drug Administration advisory panel on the Valencia biotech’s Afrezza inhalable insulin device. An FDA staff report recommended a warning label that could limit the product’s use by smokers, asthma patients and those with kidney or liver impairment.

Among the biggest gainers was Herbalife, rising more than 9 percent to $55.65. The downtown Los Angeles nutritional supplement company launched an informational web site in an effort to improve its image.