The invention provides a pharmaceutical composition comprising a macromolecular drug and an oligoguluronate or oligogalacturonate, e.g. having a number average degree of polymerization in the range 5 to 18, a guluronate (or galacturonate) fraction (FG)of at least 0.80, a mannuronate fraction (FM) of no more than 0.20, and having at least 95% mole with a degree of polymerization less than 20. The composition may be used in a method of treatment which comprises administering the composition to a mucosal surface in a human or non-human vertebrate subject.
