Provided herein are in vitro methods of comparing effectiveness of an antitumor compound against a plurality of primary tumor cells, comprising introducing a plurality of primary tumor cells to a mammalian placenta or portion thereof, contacting said plurality of primary tumor cells for a period of time with said antitumor compound, determining the effectiveness of said antitumor compound against said primary tumor cells, and comparing the effectiveness of said antitumor compound against said primary tumor cells with primary tumor cells not contacted with said antitumor compound.
