Abstract: The invention provides composition comprising, 1) polyprenol monophosphates of the formula H—[—CH2-C(CH3)═CH—CH2]n-O—P(═O)(OH)2 wherein n is an integer from 6-19 inclusive or a salt thereof, and 2) polyprenol pyrophosphates of the formula H—[—CH2-C(CH3)═CH—CH2]m—O—P(═O)(OH)—O—P(═O)(OH)2 wherein m is an integer from 6-19 inclusive or a salt thereof, which is useful as an antiviral agent, as an immunomodulatory agent, and for treating cancer. The invention also provides pharmaceutical compositions comprising the compositions of the invention as well as therapeutic methods for using the the compositions.