A groundbreaking bone marrow transplant procedure developed by researchers at the Johns Hopkins Kimmel Cancer Center has demonstrated remarkable success in treating sickle cell disease, offering a more accessible and cost-effective alternative to gene therapy.
The multicenter trial, conducted across approximately 20 cancer centers in the United States and London, showed that 95% of patients were alive two years post-transplant, with 88% achieving complete cure from the disease. These findings will be published in The New England Journal of Medicine Evidence.
Treatment Approach and Innovation
The procedure, known as reduced-intensity haploidentical bone marrow transplantation, accepts donors who are only half-matched with recipients, significantly expanding the pool of potential donors. Compatible donors can include parents, siblings, children, or extended family members, requiring only a 50% match in immune system proteins.
The treatment protocol involves:
- Low-dose chemotherapy and total body irradiation pre-transplant
- Cyclophosphamide administration post-transplant to prevent graft-versus-host disease
- Continued medication for up to one year following the procedure
Clinical Trial Results
The phase II trial, conducted from 2017 to 2021, enrolled 42 patients with severe sickle cell disease. The study population demographics included:
- Median age: 22 years
- 59% male participants
- 92% Black participants
- 4% Hispanic participants
- Average follow-up period: 37 months
Safety and Efficacy Profile
Dr. Richard Jones, professor of oncology and director of the bone marrow transplantation program at the Kimmel Cancer Center, emphasized that the results match or exceed those seen with gene therapy. The procedure showed limited serious complications:
- Three cases of graft failure
- 22% occurrence of moderate to severe graft-versus-host disease
- Two deaths in the first year (including one from COVID-19)
Cost and Accessibility Advantages
The transplant procedure offers significant practical advantages over gene therapy:
- Estimated cost of $467,747 compared to $2-3 million for gene therapy
- Average hospital stay of 8 days versus 6-8 weeks for gene therapy
- Median of 6 blood transfusions needed compared to 50 for gene therapy
- Primarily outpatient treatment
Clinical Implications
Dr. Robert Brodsky, the Johns Hopkins Family Professor of Medicine and Oncology, addressed common misconceptions about transplantation for sickle cell disease. He emphasized that neither a perfect donor match nor high mortality rates are accurate concerns, as demonstrated by this and other studies.
The procedure represents a significant advancement in treating sickle cell disease, which affects approximately 100,000 Americans, predominantly in the Black community. This treatment option provides a more accessible and economically viable alternative to gene therapy, while maintaining high efficacy rates.
