A private blood-preservation company has added anotherarrow to its quiver of patents covering freezing and use ofblood cells with its eighth patent, issued Tuesday, which coversfreeze-drying of human platelets.
The process will have its main application in cancer patients, inwhom aggressive chemotherapy suppresses bone marrow thatcreates platelets essential to clotting and prevention of internalbleeding, said Roger Hackett, Cryopharm Corp.'s corporatedevelopment director.
The ability to prolong platelet storage might also allow patientsto stockpile their own platelets during periods of diseaseremission and to collect compatible platelets from relatives ona convenient basis.
Hackett said the company also plans to apply the preservativesolution used in the process to freezing of blood products atblood banks, which use expensive methods to keep bloodcomponents at extremely low temperatures.
Likewise, the solutions may allow companies working to purifystem cells from peripheral blood to safely store the cells beforeadministering them to patients. Stem cells are being exploredfor use in cancer patients whose bone marrow has beensuppressed by chemotherapy. The traditional storagepreservative, DMSO, may not be ideal for use in patientsbecause of toxicity concerns, Hackett said.
The FDA sets a five-day limit for the storage of platelets, whichare kept in a concentrated suspension in residual blood plasma.By the end of five days, the cells have lost roughly half theirfunction, Hackett said, and the need to store the cells at roomtemperature means that germs introduced at the puncture siteon a donor's arm could quickly colonize the cell suspension.
This limit on shelf life creates a problem for blood banks instocking adequate platelet supplies, especially over longweekends. The donated platelets are segregated by A-B-Oblood type, but the option of longer shelf life might also allowconvenient storage of more specific subtypes of donatedplatelets.
"This could allow physicians and blood banks to providepatients with platelets from more compatible donors tominimize reactions against foreign platelets," said Carl Brooks,president and chief executive officer of the 6-year-oldPasadena, Calif., company.
Total platelet transfusions in the U.S. exceeded 7.2 million in1989 and have increased since that time as their use in cancertreatment has become more widely accepted.
"It's an interesting technology," said Thomas Schmitz, generalmanager of Baxter International Inc.'s blood substitutesdivision. "They probably have a pretty strong patent position."
Cryopharm's patents cover fundamental freezing solutions, thefreeze-drying process, rehydration solutions, lyophilized redblood cells and platelets.
The current patent, No. 5,213,814, is the first issued by the U.S.Patent and Trademark Office to cover lyophilized platelets fortherapeutic use. It covers a new method of freeze-drying thatallows storage from three to six months or more, as well as thelyophilized platelets as a composition of matter.
Competitor PRP Inc. of Watertown, Mass., has developedplatelet fragments, which Hackett said may be less effectivethan the whole cells. PRP obtained a patent in March forproducing its platelet derivative from fresh or outdatedplatelets for use in transfusion to control bleeding.
-- Nancy Garcia Associate Editor
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