Mending malfunctioning machinery: The search for better Diamond-Blackfan anemia syndrome treatments

When a factory grinds to a halt due to broken machinery, it becomes imperative to assess the situation and replace the faulty parts to maintain production and efficiency. Such is the case when treating Diamond-Blackfan anemia syndrome (DBAS), a rare bone marrow failure disorder that typically reveals itself in patients within a few months of birth. 

Although DBAS manifests in different ways, impaired red blood cell production is the most common. Hemoglobin, the protein that transports oxygen through blood, is the predominant component of mature red blood cells. Each red blood cell carries hundreds of thousands of copies of hemoglobin. However, mutations in the genes responsible for the cell’s protein factory, the ribosome, can drastically reduce hemoglobin and red blood cell production, leading to oxygen deprivation and other severe complications.

“This huge machinery — the ribosome — comprises lots of different smaller ribosomal proteins that work together to synthesize proteins,” said Senthil Bhoopalan, MBBS, PhD, Department of Bone Marrow Transplantation & Cellular Therapy. “Out of the 83 different proteins that constitute a ribosome, 23 have been implicated in DBAS. There are two copies of each gene; if you have a mutation in one copy of any one of those 23, then you will get DBAS.”

Treatment challenges and sample scarcity throw a wrench in research efforts

Many hypotheses regarding the cause of DBAS, along with many ineffective treatments, abounded when it was first described in the 1930s. What eventually worked to treat the disease was corticosteroids, an immunosuppressive drug class.

“It’s not functioning as an immunosuppressive medication in this case,” explained Bhoopalan. “We don’t completely understand how it works, but it’s causing an expansion of red blood cell progenitors.” 

Corticosteroids, along with regular red blood cell transfusions, became the standard of care for DBAS and have remained so for the last 50 years. Corticosteroid treatments would begin in patients as young as a year old and then taper off, administering low doses to maintain response to the drug. Patients may maintain their drug response for a time after weaning, but it is not uncommon for the response to fade eventually or for patients to develop adverse effects from the steroids and necessitate regular blood transfusions again. 

Regular transfusions present many challenges to patients, including issues related to access, frequent needle pokes and high levels of iron deposited in the body, which can lead to other disorders such as diabetes, liver disease, heart failure and pituitary problems. Allogeneic bone marrow transplantation is currently the only cure for blood problems associated with DBAS; however, it presents complications of its own, including conditioning exposure, graft-versus-host disease and immunosuppression. 

These many complications have spurred researchers, including Bhoopalan, to explore better options for children with DBAS. To assess the biology of any disease and develop treatment protocols, researchers need to study patient samples. That presents a challenge in DBAS research because the disease is rare, affecting approximately 5-10 children per one million live births. In addition, bone marrow, where affected blood-forming stem cells reside, is not readily available for research due to practical and ethical concerns. These limitations have made it difficult for researchers to identify the underlying disease mechanisms and develop newer therapies.

The absence of DBAS–affected cells compounds those complications. When examining bone marrow tissue samples at the time of a DBAS diagnosis, other types of blood cells (white blood cells and platelets) are usually unaffected. However, there are significantly fewer erythroid progenitor cells, the branch of blood stem cells that eventually gives rise to red blood cells. Thus, the very cells that DBAS researchers wish to study are difficult or impossible to find.

The conundrum is not lost on researchers. “It’s very challenging to try to figure out why something is missing when that particular thing is missing,” said Bhoopalan.

Despite these roadblocks, Bhoopalan and his team have made progress in developing another potentially curative treatment.

Engineering the right tools

Bhoopalan began studying DBAS six years ago as a postdoctoral fellow working in the lab of Mitchell Weiss, MD, PhD, Department of Hematology chair. Part of the problem with the existing DBAS research, Bhoopalan surmised, was a need for more robust disease models. Using blood stem cells and progenitor cells from healthy donors and CRISPR-Cas9–derived genome editors, he and his colleagues disrupted RPS19, the most commonly mutated gene in DBAS.

The gene RPS19 encodes key ribosomal components, and mutations in RPS19 account for 25%-30% of DBAS cases. St. Jude researchers, led by Bhoopalan, knocked out one copy of RPS19 in the sample blood-forming stem cells and transplanted them into mice because patients with the disease have only one functional copy of the gene. They found that when that one copy of RPS19 was knocked out in the blood stem cells, fewer red blood cells were generated.

“These kinds of models provide us new mechanistic insights to develop novel therapeutic approaches and also serve as a model system in which we can test these approaches,” said Bhoopalan.

Building on the vector used by St. Jude scientists to cure X-linked severe combined immunodeficiency (SCID-X1), the group then engineered a lentiviral vector to safely provide functional copies of RPS19 in the blood-forming stem cells. “We took the lentiviral vector backbone, replaced the gene they used for SCID-X1 with RPS19, and then did the same studies,” Bhoopalan said. “We knocked out RPS19 and added the lentiviral vector to provide additional functional copies of the missing gene. Now, we have two or more copies of RPS19. This improved the ability to generate red blood cells in our model. It provided a nice way to test this potentially therapeutic approach.” 

The findings, published in Molecular Therapy in 2025, showed that the lentiviral addition of functional RPS19 to the model not only increased red blood cell production but also provided gene-rescued blood-forming stem cells a competitive advantage over the uncorrected DBAS stem cells. The findings also showed that RPS19’s unique biology protected against overexpression in cells, thus demonstrating preclinical safety and efficacy.

“As a postdoctoral fellow and instructor in my lab in the Department of Hematology, Senthil developed a new human cellular model of DBAS, which he used to deepen our understanding of the disease and to design a new curative strategy,” said Weiss. “Now, as an independent faculty member in the Department of Bone Marrow Transplantation & Cellular Therapy, he is generating fundamental insights into ribosome biology and translating his preclinical findings into a clinical trial planned to open next year. Senthil’s ability to translate his scientific discoveries into a novel therapy for a devastating childhood disease embodies the St. Jude mission and distinguishes him as an outstanding physician-scientist.”

Shifting gears: Moving the research from bench to bedside

The preclinical results laid the foundation for autologous gene therapy, which would correct the genetic mutation in the patient’s own cells using the lentiviral vector rather than replacing the DBAS stem cells with someone else’s through bone marrow transplantation. Because autologous gene therapy involves a patient’s own cells instead of a donor’s, there would be no risk of graft-versus-host disease or need for immune suppression. 

“This is an exciting period; there’s a lot of effort in this direction. This is a thrilling time for gene therapy in general. But challenges remain. This is all experimental, so we still need to study this clinically and rigorously, with long-term follow-up,” Bhoopalan said. 

The group is preparing to launch a clinical trial, led by Shruthi Suryaprakash, MD, Departments of Hematology and Bone Marrow Transplantation & Cellular Therapy, to test the approach’s safety and efficacy. “It is incredibly exciting to see scientific discovery in Diamond-Blackfan anemia move from bench to bedside,” said Suryaprakash. “While there is still much to learn, this new therapeutic approach has the potential to transform how we care for patients with RPS19-mutated DBAS in the future.”

Clinical research will rely on the extensive infrastructure and experts from St. Jude, with support from external mentors and advisors, including parent advocacy groups. “It’s a huge village,” said Bhoopalan. “St. Jude has the infrastructure to do it all in one place. We can test these therapies, advance them beyond our own campus and learn from these studies, bringing things back from the bedside to the bench. This study sets us up to learn a lot about DBAS and its biology and advance gene therapy for bone marrow failure disorders.”