Denver, Oct. 20, 1997 -- Researchers at Washington University School ofMedicine in St. Louis announced today that a new drug may dramatically increasethe nation's supply of platelets, a chronically scarce blood product needed bymany cancer patients.
A single injection of the drug, a synthetic human hormone calledPEG-rHuMGDF, can triple the number of platelets received from each donor, saysLawrence T. Goodnough, M.D., professor of medicine and of pathology at theSchool of Medicine. "Platelets are precious, and this drug could help ease theshortage," he says. Goodnough, a lead researcher in a multicenter study of thedrug, announced the findings today at the annual American Association of BloodBanks meeting in Denver.
Platelets are blood cells that strengthen blood vessel walls and helpseal cuts. Healthy people have hundreds of thousands of platelets in each cubicmillimeter of blood. But chemotherapy and radiation therapy can quickly destroythe cells, leaving many cancer patients in dangerously short supply. Whenplatelets are low, microscopic vessels become weak and rupture easily. Patientscan have spontaneous nosebleeds, and merely brushing one's teeth can lead tosignificant bleeding.
Today, platelet transfusions go hand-in-hand with chemotherapy. Thetransfusions are particularly critical for patients undergoing bone marrowtransplants, a procedure that usually involves heavy doses of chemotherapy. Itusually takes between four and 10 donations to collect enough platelets for asingle bone marrow transplant patient. Because Washington University School ofMedicine has one of the largest bone marrow transplant programs in the country,there's constant pressure on the stockpile of cells. "We have barely enoughplatelet donors to meet the current demand," Goodnough says. "Even people whodonate blood regularly don't realize the critical need for platelet donations."
Platelet donors spend about 90 minutes hooked up to a special machinethat draws blood, spins it to separate platelets from other cells and thenreturns the rest of the blood back into the body. The machine processes aboutfour liters of blood, roughly the amount that most people have in their bodies.The procedure, called pheresis, is expensive. According to Goodnough, it costsabout $400 to harvest enough platelets for a single transfusion. Some patientsneed as many as 10 transfusions.
Realizing that increasing the platelet payload from each donation wouldbe a boon to cancer patients, researchers began a multicenter trial ofPEG-rHuMGDF on volunteer donors. "Previous studies had shown that the drughelped improve the recovery of platelets in patients undergoing chemotherapy,"Goodnough says. "We wanted to see if we could boost platelets in healthy peoplebefore they donated."
The drug was developed by Amgen, Inc. of Thousand Oaks, Calif., abiotechnology company that also funded the study. Researchers at the Universityof Minnesota in Minneapolis and Massachusetts General Hospital in Boston alsoparticipated in the study.
The researchers found that, on average, a small dose of the drug giventwo weeks before donation tripled the number of platelets collected. In somecases, volunteers were able to donate six times the normal level of platelets.None of the donors showed side-effects from the drug, and their platelet levelsreturned to normal soon after donation.
Goodnough had surprisingly little trouble finding platelet donors whowere willing to try the new drug. "Blood donors in general and platelet donorsin particular are very generous people," he says. "Many donors were excitedabout the prospect of making larger donations."
An increased supply of platelets would give physicians more options fortreating chemotherapy patients, Goodnough says. Instead of receiving normalplatelet transfusions, many patients would benefit from transfusions that aresuper-enriched with cells. At the School of Medicine, all of the plateletscollected in the study went to patients in the school's bone marrow transplantprogram. One patient recently received a single platelet transfusion containingsix times the normal level of cells. Within one hour, her dangerously lowplatelet count had risen to healthy levels, and she did not need anothertransfusion, Goodnough says.
Use of the drug could also make transfusions more affordable. Triplingthe number of platelets in each donation should lead to a three-fold decrease inthe cost of harvesting platelets, Goodnough says. The calculation does notinclude the cost of the drug, which is unknown at this point.
Goodnough and colleagues now intend to conduct a follow-up trial withmore donors and more patients. "We're very pleased that this drug works, and webelieve that it's safe," Goodnough says. "Now we need to collect more data toprove the point." He anticipates FDA approval of the drug in one or two years.
Editor's note: People in the St. Louis area who want more information aboutdonating platelets can call 314-362-1253.
Materials provided by Washington University School of Medicine. Note: Content may be edited for style and length.
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