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USF Health clinical trials at Tampa General test drugs for sickle cell pain

Edna Perez, 53, center, discusses her sickle cell anemia with Tampa General researchers Susan Barnett, left, and Debra Harris. Perez, a nurse, is participating in a drug study.
Edna Perez, 53, center, discusses her sickle cell anemia with Tampa General researchers Susan Barnett, left, and Debra Harris. Perez, a nurse, is participating in a drug study.
Published Feb. 24, 2014

TAMPA — Edna Perez's memories of her early childhood in Puerto Rico are dominated by hospital stays and doctor visits, chronic pain so severe she sometimes couldn't walk, fainting spells and other puzzling symptoms that couldn't be explained or stopped.

Doctors suspected a blood disorder, possibly hemophilia, but suggested the family return to New York, where Perez was born, and consult with specialists. Otherwise, they said, the little girl likely had just months to live.

The news from the specialists was dire: The 6-year-old had sickle cell anemia, an inherited blood disorder the New York doctors predicted would take her life by age 14.

Now 53, Perez works as a registered nurse at Tampa General Hospital. "Even today, I'm old for a sickle cell person," she said. "Most live to about 40 or 50 now."

Sickle cell anemia is the most common genetic disease, affecting an estimated 100,000 Americans, most of African descent, but also Caribbean Hispanics, Middle Easterners, Indians, Asians, American Indians, Latin Americans and people of Mediterranean ancestry.

In sickle cell disease, normally flexible, disc-shaped red blood cells become rigid, sticky and crescent or sickle shaped. That causes them to get stuck in tiny blood vessels, slowing or blocking the flow of oxygen-rich blood through the body. Those misshapen blood cells also tend to break apart and die sooner than expected, in about two weeks instead of the usual 120 days. So patients tend to be low on red blood cells, causing frequent bouts of anemia and fatigue. Pain develops in areas of the body where blood flow is diminished, often the joints.

"One day your hands hurt, the next day it's your knees, then it's your back, or your feet, you just never know where it's going to hurt," Perez said.

Her experience as both nurse and patient makes her an invaluable resource to others with the condition. "Whenever there's a sickle cell patient where I'm working," she said, "they give me the case."

Sickle cell pain can range from mild to debilitating, and can last from hours to weeks. The most severe bouts, known as a pain crisis, usually put patients in the hospital where they can get powerful intravenous pain medication, fluids and other treatment. Some people have a pain crisis every month; others have long periods of remission.

Perez had been able to manage most of her pain episodes at home. But last year she had two, weeklong hospital stays. She sees that as a sign that she needs "to slow down and take better care of myself. I always push myself and try to do too much."

In addition to pain, other symptoms of sickle cell disease include swollen hands, feet and abdomen, fevers, serious infections, breathing difficulties, delayed growth in children and vision problems. Sickle cell patients also are at higher risk than normal for stroke.

Today, most sickle cell disease is diagnosed in infancy, thanks to a newborn screening program that began in the United States in the 1970s but wasn't adopted widely until the mid 1980s, according to the Centers for Disease Control and Prevention.

Treatment of sickle cell disease involves giving antibiotics at the first sign of fever or infection, controlling pain, and remaining well hydrated to promote good blood circulation. There is one FDA approved drug, hydroxyurea, for moderate to severe sickle cell disease, which helps ward off pain crises by helping prevent formation of sickle-shaped blood cells.

"It's a drug used to treat several different types of cancer, as well as sickle cell disease, and, as you might guess, it has a lot of side effects," said Dr. Cameron Tebbi, professor of pediatrics and chief of the division of pediatric hematology-oncology at USF Health and director of pediatric hematology-oncology at Tampa General Hospital. Tebbi and his colleagues at the USF Health Clinics care for about 250 sickle cell patients. "Hydroxyurea suppresses the immune system so patients on it are more prone to infections. In children especially, you have to think twice before prescribing it. There's also a small probability that patients will develop cancer while taking it because it reduces immunity," Tebbi said, "We need a better drug."

Tebbi is overseeing two clinical trials for sickle cell drugs. One is designed to shorten the duration of pain crises, the other to prevent pain crises. Perez is participating in the second trial, testing a new therapy manufactured by Selexys Pharmaceuticals, a monoclonal antibody known as SelG1. It aims to prevent the pain caused by blood vessel blockages and reduce the risk of heart attack, stroke and organ failure. Perez has had one dose during the trial — though she doesn't know if it was the real therapy or a placebo—and said she felt better for a few days after. "I just hope they come through with an answer soon," Perez said. "I've noticed that as I get older, it's getting worse."

Irene Maher can be reached at