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DURHAM, N.C. -- Duke University has received a United States patent for a special formulation of drug-carrying microscopic fatty liposome spheres invented by Duke engineering professor David Needham.

The patent number is 6,200,598.

When injected into the bloodstream, this particular liposome type is designed to release anti-cancer drugs when triggered by small induced temperature elevations at a tumor site. Initial animal studies have shown it capable of cutting tumor growth in half and causing complete long-term remission in at least two thirds of cases.

Other kinds of liposomes, including varieties responding to temperature change, have been used or evaluated in the past as drug-carrying vesicles small enough to roam through the bloodstream. However, this type was shown in a recent Duke study to increase the concentration of the anti-cancer drug doxorubicin in animal-implanted tumors more than other treatments tested.

That study, reported in the Dec. 15, 2000 issue of Cancer Research, compared the results in mice injected with free doxorubicin alone, non-heat sensitive liposome types, a traditional temperature sensitive liposome and Needham's special low-heat liposome.

These drug delivery experiments were done both in tumors mildly heated to 42 degrees Celsius, levels easily reachable by heat focusing devices used in existing human cancer therapies, as well as in tumors kept at normal skin temperatures.

At 42 C, all the different liposomes performed better than drug or heat treatments alone. But the Duke-engineered liposome excelled.

Celsion Corp., headquartered in Columbia, Md., has exclusively licensed the rights to the newly patented formulation for use in cancer treatment that combines the temperature-sensitive liposome with focused heat Adaptive Phased Array technology separately licensed by the company from the Massachusetts Institute of Technology.

Celsion recently contracted with a Canadian liposome and drug formulation and manufacturing company to produce an initial batch of temperature-sensitive, drug-laden liposomes for use in several large animal toxicity studies as well as a Phase 1 clinical feasibility demonstration using up to 30 human patients.

The first of the large animal toxicity studies is expected to begin soon at Dartmouth University.

According to disclosure information in the patent application, Needham's special liposome is made up both of a two-layer membrane composed of phospholipids, the primary lipid source, and a smaller concentration of lysolipid, which can break the membrane apart. The drug is also entrapped within the bilayer membrane.

That special membrane chemistry allows the molecular structure to begin "melting" when slightly heated above normal body temperatures. Needham, of the Department of Mechanical Engineering and Materials Science at Duke's Pratt School of Engineering, has characterized his invention as resembling "a soccer ball with stitches. When its stitches become leaky, the drug that is trapped inside will come out, and in this invention it will come out rapidly."

In the recent Duke study, the Duke low-heat liposomes released 50 percent of their drug cargo in just 30 seconds.

Under Duke's patent policy, if the liposome is successful commercially, Needham will share some of the income from the license.