Investigation of the activity of extracts of the clam Spisula polynyma has led to antitumor long-chain, straight-chain alkane or alkene compounds which have a 2-amino group and a 3-hydroxy group. The present invention is directed to compositions and methods comprising an isolated and purified long-chain, straight-chain 2-amino-3-hydroxyalkane, or prodrug thereof, and a pharmaceutically acceptable carrier, wherein the carbon chain in the long-chain, straight-chain 2-amino-3-hydroxyalkane is C.sub.16 C.sub.24.