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

The weighted LABJ Stock Index rose less than 1 percent to $154.63 for the trading week ending April 5. Decliners outpaced gainers 108 to 50, with 13 companies unchanged.

The biggest gainer was Obagi Medical Products Inc., jumping 25 percent to $25.42. The Long Beach company maker of physician-dispensed skin care products said its initial suitor, Valeant Pharmaceuticals International Inc., increased its bid for the company to more than $418 million in order to top a rival offer from Merz Pharma Group.

Virtual Piggy Inc. rose 15 percent to $1.75. The Hermosa Beach online payment firm signed a deal with a British payment processor.

MannKind Corp. gained 12 percent to $3.76. The Valencia biotech benefited from positive coverage on investor blogs.

The biggest decliner was Ixia, falling 16 percent to $17.79. The Calabasas network company disclosed in its 10-K annual financial report that it would have to restate financial results for 2010, 2011 and the first three quarters of last year.

Kythera Biopharmaceuticals Inc. fell 14 percent to $20.35. The Calabasas biotech disclosed in a regulatory filing that its chief medical officer had been replaced.