Century City’s Ritter Pharmaceuticals Inc. was the week’s biggest gainer, jumping 22.3 percent to close at $3.57. MGM Holdings Inc. of Beverly Hills, the parent company of Metro-Goldwyn-Mayer Studios Inc., also was up, gaining 13.3 percent to close at $96.75. The week’s biggest laggard was Nova Lifestyle Inc., which dropped 15.18 percent to close at $1.62.