Filmmaker John Landis and producer partners Robert K. Weiss and Leslie Belzberg have extended their exclusive relationship with MCA TV, inking a new two-year deal under which they’re developing two more series and three movies for Fox Broadcasting Co.On the series front, the trio, under their St. Clare Entertainment banner, are developing “Sliders,” a two-hour science-fiction series pilot for Fox that involves a small group traveling across parallel universes, and “Shock Treatment ,” an anthology suspense series for HBO. The telefilms are in the sci-fiand comedy genres, seeking to capture the slightly different tone preferred by Fox. “The mandate is to do non-traditional TV movies,” Weiss noted. The association between St. Clare and the studio encompasses both MCA Home Video and the MCA TV Group, through which Landis produces the long-running HBO comedy series “Dream On,” the upcoming USA network movie spinoff series “Weird Science,” and “Fast Lane,” a trio of two-hour movies that will air as part of Universal’s syndicated action movie wheel, which will launch in January. St. Clare initially linked up with Universal in January 1992. Weiss, Landis and Belzberg are exec producers on all projects.