Diketopiperazine salts for drug delivery

摘要

A pharmaceutically-acceptable salt of a heterocyclic compound according to Formula 1:
wherein R 1 or R 2 comprise at least one carboxylate functional group;
E 1 and E 2 are either N or O;
said salt further comprises at least one cation; and
wherein said salt is not a lithium salt of 2,5-diaspartyl-3,6-diketopiperazine or 2,5-diglutamyl-3,6-diketopiperazine and said salt is in a solid form.