Denver, Oct. 20, 1997 -- Researchers at Washington University School of Medicine in St. Louis announced today that a new drug may dramatically increase the nation's supply of platelets, a chronically scarce blood product needed by many cancer patients.
A single injection of the drug, a synthetic human hormone called PEG-rHuMGDF, can triple the number of platelets received from each donor, says Lawrence T. Goodnough, M.D., professor of medicine and of pathology at the School of Medicine. "Platelets are precious, and this drug could help ease the shortage," he says. Goodnough, a lead researcher in a multicenter study of the drug, announced the findings today at the annual American Association of Blood Banks meeting in Denver.
Platelets are blood cells that strengthen blood vessel walls and help seal cuts. Healthy people have hundreds of thousands of platelets in each cubic millimeter of blood. But chemotherapy and radiation therapy can quickly destroy the cells, leaving many cancer patients in dangerously short supply. When platelets are low, microscopic vessels become weak and rupture easily. Patients can have spontaneous nosebleeds, and merely brushing one's teeth can lead to significant bleeding.
Today, platelet transfusions go hand-in-hand with chemotherapy. The transfusions are particularly critical for patients undergoing bone marrow transplants, a procedure that usually involves heavy doses of chemotherapy. It usually takes between four and 10 donations to collect enough platelets for a single bone marrow transplant patient. Because Washington University School of Medicine has one of the largest bone marrow transplant programs in the country, there's constant pressure on the stockpile of cells. "We have barely enough platelet donors to meet the current demand," Goodnough says. "Even people who donate blood regularly don't realize the critical need for platelet donations."
Platelet donors spend about 90 minutes hooked up to a special machine that draws blood, spins it to separate platelets from other cells and then returns the rest of the blood back into the body. The machine processes about four liters of blood, roughly the amount that most people have in their bodies. The procedure, called pheresis, is expensive. According to Goodnough, it costs about $400 to harvest enough platelets for a single transfusion. Some patients need as many as 10 transfusions.
Realizing that increasing the platelet payload from each donation would be a boon to cancer patients, researchers began a multicenter trial of PEG-rHuMGDF on volunteer donors. "Previous studies had shown that the drug helped improve the recovery of platelets in patients undergoing chemotherapy," Goodnough says. "We wanted to see if we could boost platelets in healthy people before they donated."
The drug was developed by Amgen, Inc. of Thousand Oaks, Calif., a biotechnology company that also funded the study. Researchers at the University of Minnesota in Minneapolis and Massachusetts General Hospital in Boston also participated in the study.
The researchers found that, on average, a small dose of the drug given two weeks before donation tripled the number of platelets collected. In some cases, 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 levels returned to normal soon after donation.
Goodnough had surprisingly little trouble finding platelet donors who were willing to try the new drug. "Blood donors in general and platelet donors in particular are very generous people," he says. "Many donors were excited about the prospect of making larger donations."
An increased supply of platelets would give physicians more options for treating chemotherapy patients, Goodnough says. Instead of receiving normal platelet transfusions, many patients would benefit from transfusions that are super-enriched with cells. At the School of Medicine, all of the platelets collected in the study went to patients in the school's bone marrow transplant program. One patient recently received a single platelet transfusion containing six times the normal level of cells. Within one hour, her dangerously low platelet count had risen to healthy levels, and she did not need another transfusion, Goodnough says.
Use of the drug could also make transfusions more affordable. Tripling the number of platelets in each donation should lead to a three-fold decrease in the cost of harvesting platelets, Goodnough says. The calculation does not include the cost of the drug, which is unknown at this point.
Goodnough and colleagues now intend to conduct a follow-up trial with more donors and more patients. "We're very pleased that this drug works, and we believe that it's safe," Goodnough says. "Now we need to collect more data to prove the point." He anticipates FDA approval of the drug in one or two years.
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Editor's note: People in the St. Louis area who want more information about donating platelets can call 314-362-1253.