UC San Francisco researchers have safely transplanted a woman’s stem cells into her growing fetus, leading to the live birth of an infant with a normally fatal fetal condition. The infant, who had been critically ill during the second-trimester of pregnancy due to alpha thalassemia, is the first patient enrolled in the world’s first clinical trial using blood stem cells transplanted prior to birth.
The infant was born at UCSF Medical Center at Mission Bay in February, four months after undergoing the transplant to treat the blood disorder, which is caused by a gene carried by nearly 5 percent of the world’s population.
While the ultimate goal will be to assess whether the mother’s stem cells integrate, or engraft, in the fetus’ bone marrow and generate healthy blood cells throughout the child’s life, this phase 1 trial aimed to determine first whether the procedure – which includes infusing the mother’s stem cells along with several blood transfusions – would be safe.
“We are encouraged by how well she and her mother have tolerated this complex treatment,” said Tippi MacKenzie, MD, a pediatric and fetal surgeon at UCSF Benioff Children’s Hospital San Francisco, who performed the pioneering transplant after a decade of research. Normally, women whose fetuses are diagnosed with alpha thalassemia are given a grim prognosis and often terminate the pregnancy due to the low likelihood of a successful birth.
“Her birth suggests that fetal therapy, including fetal transfusions, is a viable option to offer to families with this diagnosis,” MacKenzie said.
During the pregnancy, MacKenzie’s team at the UCSF Fetal Treatment Center treated the fetus with regular in utero blood transfusions, after a medical center near the family’s hometown detected life-threatening swelling, or hydrops, during an ultrasound. The swelling, which included an enlarged heart, was the result of the body’s response to severe anemia and lack of oxygen, which is the hallmark of alpha thalassemia major, the most dangerous variant of the disease.
“Intrauterine blood transfusions were needed to treat the hydrops before the stem cell transplant could be performed,” said Juan Gonzalez Velez, MD, PhD, an obstetrician/gynecologist at the UCSF Division of Maternal-Fetal Medicine, who performed the transfusions. “During the last 30 years, this has been the treatment of choice for patients developing severe fetal anemia and we think that fetuses with alpha thalassemia can also benefit from these transfusions.”
The fetus’ poor prognosis improved slowly with each transfusion during the pregnancy, Gonzalez Velez said. The stem cell transplant took place during one of those transfusions.
The clinical trial, which was funded by a grant from the California Institute for Regenerative Medicine, brings together the unique expertise of both UCSF Benioff Children’s Hospitals. The UCSF Fetal Treatment Center, in San Francisco, is the birthplace of fetal surgery and continues to offer life-saving interventions for fetuses with multiple birth defects. UCSF Benioff Children’s Hospital Oakland established its thalassemia program in 1991 to provide multidisciplinary care to the growing number of thalassemia patients. It is an international leader in stem cell and gene therapy for beta thalassemia.