Bone Marrow Transplant vs Gene Therapy for Sickle Cell

Between bone marrow transplant and gene therapy for sickle cell disease, transplant is the established cure: it needs a matched donor, carries real risks and has mature data. Gene therapy uses the patient's own modified stem cells, needs no donor and avoids graft-versus-host disease, but takes months to prepare, is held back by cost and is not yet available in India. Where money is a constraint, Dr. Sukriti Gupta recommends a transplant.

That recommendation, from Dr. Sukriti Gupta, Sr. Consultant, BMT, Haematopoietic Stem Cell Transplant, Hematology, Oncology, Paediatric Haemato-Oncology & BMT, Artemis Hospitals, Gurugram, India, came at the end of a long exchange in her November 2025 masterclass about the hardest choice in sickle cell care. This article sets out who should be considered for a cure, how a transplant works and what can go wrong, her centre's outcomes and costs, how gene therapy works, and the framework she uses to help families choose. Earlier stages of care are covered in the complete guide to sickle cell disease and in sickle cell treatment: supportive care, hydroxyurea and pregnancy.

How a bone marrow transplant cures sickle cell disease

Bone marrow is the tissue inside the bones that produces red cells, white cells and platelets. In a bone marrow transplant, more precisely an allogeneic haematopoietic stem cell transplant, the patient's own blood-forming stem cells are replaced with healthy stem cells from a donor. From then on, the blood the body produces is healthy: normal red cells, normal white cells and normal platelets.

The curative potential was first seen by chance. In 1984, a child with sickle cell disease who received a bone marrow transplant for acute leukaemia was found to be cured of sickle cell disease as well. Since then, transplant has been regarded as the curative treatment, and it is used for many red and white cell disorders, of which sickle cell disease is one.

Dr. Gupta makes a point families often need to hear: despite its name, a bone marrow transplant is not surgery. There is no cutting. It is entirely a medical procedure.

Bone marrow transplant indications in sickle cell disease

A transplant comes into play when symptoms remain significant despite hydroxyurea and red cell exchange, compromise organ function, or leave the patient with a debilitated lifestyle. Dr. Gupta lists the indications for a definitive treatment as:

• any episode of stroke, which is an absolute indication
• acute chest syndrome, especially two episodes
• transfusion dependence
• painful crises requiring hospital visits more than three times a year
• cardiomyopathy or tricuspid valve regurgitation found on regular screening

A strong family history combined with a fully matched donor is a further reason. In that situation her team will offer a transplant at an earlier age, even with fewer symptoms, because the success rate in young, well-matched patients is very high.

The prerequisites for success

Dr. Gupta names four:

1. a younger patient
2. well-preserved organ function
3. a suitable donor
4. financial implications understood by the whole family and the team before starting

Finding a donor: HLA matching

Matching depends on human leucocyte antigens (HLA), proteins coded by a cluster of genes on chromosome 6 that the immune system uses to tell self from non-self. Donor and patient are compared across the key class I and class II genes. The best match is a full 10 out of 10, or 12 out of 12, across the alleles tested. A report with a single mismatch is still a very good match.

Who can donate

Dr. Gupta's answers to doctors' questions about donors give a realistic picture.

• A full-match sibling is always the best donor. The chance that a brother or sister with the same two parents is a full match is usually 25%.
• A half-match (haploidentical) sibling is better than a parent, in her experience, because the patient forms fewer antibodies against a sibling's cells and accepts them better. Some siblings, however, are no match at all.
• Parents are always half matches, but not all are fit to donate. A parent who has sickle cell disease, compromised organ function or a significant illness cannot donate. In African settings, she noted, a parent being HIV positive is a common reason a parent cannot donate.
• Aunts, uncles and cousins are usually not even half matches.
• An unrelated donor from a registry is the remaining option when the family has no suitable match (see matched unrelated donor BMT cost).

Because donating stem cells is non-surgical and carries no significant complication for the donor, Dr. Gupta finds immediate family members easier to persuade to donate for a half-match transplant. In kidney transplantation, by contrast, she observed that the main obstacle is often the family's mindset rather than donor availability. For donor options in detail, see Dr. Vikas Dua on bone marrow donors for sickle cell patients from Africa and Dr. Dharma Choudhary on sickle cell transplant donor options.

The transplant process, step by step

A bone marrow transplant runs in five steps, from preparing the donor to engraftment of the new cells.

1. Donor mobilisation. The donor receives injections of filgrastim, a granulocyte colony-stimulating factor that pushes stem cells out of the bone marrow into the blood, for four days.
2. Collection. On the fifth day the stem cells are collected from the donor's bloodstream. The donor's bone marrow does not need to be punctured. The cells are stored in the blood bank.
3. Conditioning. The patient receives high-dose chemotherapy that destroys their own bone marrow's capacity to make blood.
4. Infusion. The donor stem cells are given through a normal vein, just like a blood transfusion.
5. Engraftment. The donor cells find their way to the patient's bone marrow and begin producing healthy blood cells.

Why conditioning intensity is the crucial decision

Up to the infusion, the process is usually simple and well tolerated. The critical choice is the intensity of the conditioning chemotherapy. More intensive conditioning reduces the chance that the disease returns, but it raises the risk of organ damage, infection and death unrelated to relapse. Dr. Gupta argues that centres in resource-limited settings should not simply adopt protocols built on US data: the regimen has to be calculated to prevent complications while still achieving a good success rate.

Engraftment

Engraftment, signalled above all by a rising count of neutrophils (the white cells that fight bacterial infection), usually takes about two weeks and can take up to three, depending on the intensity of the regimen. It is the most important step, and, as Dr. Gupta put it, every transplanter is anxious until the patient has engrafted.

Transplant complications and how they are managed

The main transplant complications are infection, graft-versus-host disease, graft failure and organ toxicity. All complications are more frequent with half-match or unrelated donors than with a full-match sibling.

Infections

Infection is the most important complication, and the organisms change with time:

• early phase: bacterial infections are most common, sometimes fungal infections
• later, around engraftment: atypical bacterial and atypical viral infections
• beyond 100 days, with graft-versus-host disease: encapsulated organisms

Every patient receives preventive antibiotics, antifungals and antivirals at the appropriate times, with close monitoring for signs of infection.

Graft-versus-host disease

Graft-versus-host disease (GVHD) is the second most common complication. Donor T cells recognise the patient's tissues as foreign and attack them.

Medicines to prevent GVHD are given throughout, and patients are monitored for its early signs.

Graft failure and organ toxicity

The donor cells may function poorly or fail altogether, in which case the sickle cell disease can return. The conditioning chemotherapy can also damage organs.

Follow-up after the patient returns home

The success of a transplant, Dr. Gupta stressed, depends entirely on follow-up: timely detection and treatment of GVHD, organ damage or infection after the patient has gone home and is under the care of a local physician, paediatrician or general practitioner. Her schedule is review twice a month in the early months, then monthly until at least one year after transplant. Many of her patients over the past three years stay in contact by WhatsApp, reporting symptoms so that the team can advise them to seek care promptly. Dr. Dharma Choudhary's article on sickle cell transplant aftercare covers this phase in more depth.

Outcomes at Dr. Gupta's centre

Dr. Gupta shared her own transplant data, consolidated from her hospital's registers, and was explicit that she would not present inflated figures. Her centre has performed equal numbers of full-match and half-match transplants.

• About 80% of full-match transplant recipients have survived.
• About 60% of half-match recipients have survived well.
• In the most recent year, half-match (haploidentical) results reached 80%, a clear improvement on the two previous years.

The causes of death were major infections in the early period, acute GVHD, chronic GVHD that developed after return to the home country, and relapse. Of these, she regards chronic GVHD and relapse as preventable, provided medicines are taken and follow-up continues in the home country. That is why she sees doctors in the patient's home country as essential partners. For comparison across centres, see Dr. Vikas Dua on sickle cell transplant cure rates.

Bone marrow transplant cost for sickle cell disease

At Dr. Gupta's centre, a bone marrow transplant for sickle cell disease costs about USD 24,000 to 25,000 with a full-match donor and about USD 33,000 to 34,000 with a half-match or unrelated registry donor. The figures she quoted:

A full-match transplant costs less because the conditioning regimen is less toxic and the hospital stay, medicines and supportive care are all reduced. The figure also depends on age: for a young child of two to four years the cost is lower, and it reaches the quoted level for patients beyond 15 years, whose body weight is that of an adult. Half-match and registry transplants cost about the same: registry charges are high, but complications and donor charges are lower. Indicative package ranges are on the matched sibling donor BMT cost and haploidentical BMT cost pages, and for registry donors on the unrelated donor BMT cost page.

Is there an upper age limit for a sickle cell transplant?

Dr. Gupta does not treat age as a fixed cut-off; overall organ function matters most. The oldest patient she has transplanted was 26, with a full-match donor, and that patient's course was turbulent. When the moderator raised a successful half-match transplant in a patient in their late twenties at another centre, she cautioned against drawing conclusions from one case. The question is how many patients aged 25 to 30 have been transplanted across a region, with what profiles and what results; if only four or five of 20 survived well, she would be sceptical, and the selection of the survivors would itself be a source of bias. For patients above 25 she plans in great detail, with kidney function scanning and cardiac assessment. With well-preserved kidney and heart function and a fully willing family, age is not always a fixed barrier.

How gene therapy for sickle cell disease works

Gene therapy for sickle cell disease collects the patient's own stem cells, modifies them in the laboratory and returns them, so no donor is needed.

1. The patient receives filgrastim for four days to mobilise stem cells, which are then collected.
2. In the laboratory, the cells are modified, either by gene editing with CRISPR-Cas9 (a molecular tool that cuts DNA at a chosen point) or by gene addition with a viral vector. This step currently takes around six months.
3. The patient receives chemotherapy to clear their own stem cells.
4. The modified cells are infused and begin producing healthy red cells.

The two approaches differ in what they change. The approved CRISPR-based therapy, exagamglogene autotemcel, disrupts a genetic switch (the BCL11A enhancer) that normally turns off fetal haemoglobin after birth, so red cells produce protective HbF again. The gene addition therapy, lovotibeglogene autotemcel, uses a viral vector to insert a functional, modified beta-globin gene that makes a non-sickling haemoglobin; the original faulty gene remains.

Because the cells are the patient's own, the risk of graft-versus-host disease is largely removed, and Dr. Gupta expects infections and other complications to be much less frequent than after a donor transplant.

Where gene therapy is available

The FDA first approved these therapies in December 2023, for patients aged 12 years and older, not younger children. Dr. Gupta listed availability in the United States, European countries, Switzerland, Saudi Arabia and Bahrain. Indian research institutes, including the CSIR Institute of Genomics and Integrative Biology (CSIR-IGIB), are developing gene therapy, and her centre collaborates with CSIR-IGIB by providing autologous cells (the patients' own cells). The government indicates approval may come within two to three years; what it will cost is not yet known.

Bone marrow transplant vs gene therapy for sickle cell: Dr. Gupta's framework

For families deciding now, Dr. Gupta recommends a transplant whenever money or urgency is a constraint, even though she expects gene therapy to become the better option in time. Asked for her view, she reasoned by analogy with inherited metabolic and immunodeficiency diseases she treats as a paediatrician. Those diseases also have two options, enzyme replacement therapy and bone marrow transplant. Patients on enzyme replacement do beautifully, with minimal side effects, and cost is the only prohibitive factor; transplant is somewhat toxic, although modern protocols and monitoring have significantly reduced that toxicity. On that basis, she believes gene therapy should become the best therapy once its cost comes down.

For families deciding now, her advice follows a clear sequence.

1. The decision must be informed and seen through. Whatever a family chooses, they must complete it.
2. If cost is no barrier at all, she would recommend gene therapy, once it is better studied and available in her own practice.
3. If the disease is urgent, a patient with recent severe crises or a stroke-like episode cannot wait six to eight months for gene therapy, and a transplant should be given a chance.
4. If finances are even a slight barrier, she prefers an allogeneic transplant. In experienced hands its results are excellent and its data are mature. There may be a 10 to 15% gap in outcomes, but families should not wait on that margin and risk being unable to complete gene therapy. She does not recommend that any family exhaust all its resources for the disease.

Donor availability remains a separate problem that has to be solved for each family. The doctors' questions on age limits, costs, donors and gene therapy are collected in the Live Discussion.