Compositions and methods for treatment of neoplastic disease

A method of delivering a therapeutic agent to a solid tumor characterized by hypoxia, acidosis and hypertonicity comprising loading the therapeutic agent into mature human sickle red blood cells or human nucleated sickle cell progenitor cells which express at least one hemoglobin S allele and administering said mature human sickle red blood cells or human nucleated sickle cell progenitor cells, into which said therapeutic agent is loaded, into the blood circulation of a human patient having said solid tumor wherein said mature sickle red blood cells or nucleated sickle cell progenitor cells accumulate in said solid tumor in order to treat said solid tumor.