High-molecular-weight fucan compositions comprising a therapeutically effective, medically acceptable fucan in a composition comprising wherein the fucan, for example, has a molecular weight distribution in which more than 60 % w/w of the composition has a molecular weight above 100 kDa.高分子量聚海藻糖組成物,其包含含治療學上有效、醫療上可接受之聚海藻糖之組成物,其中該聚海藻糖例如具有一分子量分佈,其中該組成物之超過60% w/w具有高於100 kDa之分子量。