Mansoor Amiji, Ph.D., of Northeastern University, and Robert Langer, Ph.D., at MIT, led the team of investigators that tested the ability of biodegradable, pH-sensitive nanoparticles to safely and effectively deliver paclitaxel to rapidly growing tumors. These nanoparticles are made of several polymers, each of which contributes useful characteristics to the nanoparticle, such as water-solubility, water-insoluble drug packaging, and ability to repel proteins in blood and avoid elimination by immune system cells. The nanoparticles are stable in blood and normal tissues, but fall apart under the acidic, or low pH conditions, characteristic of virtually all solid tumors.
To test the utility and safety of these polymer nanoparticles, the researchers loaded them with anticancer agent paclitaxel and administered them to mice with human ovarian tumors. The researchers assessed therapeutic efficacy by measuring the volume of the tumors over the course of four weeks after receiving a single dose of either the paclitaxel-loaded nanoparticle or paclitaxel alone. After four weeks, tumors in the mice treated with the nanoparticle formulation were about half the size of those treated with paclitaxel alone. In addition, tumors removed from the animals treated with the nanoparticle formulation weighed 80 percent less than those treated with paclitaxel alone.
The investigators also measured changes in the animals’ weight and blood cell counts over the course of the four-week experiment. These data indicated that neither the nanoparticle formulation nor paclitaxel alone triggered therapy-limiting side effects after a single dose of drug.