Sickle Cell Disease Treatments — Hydroxyurea to CRISPR Gene Therapy

Hydroxyurea — the cornerstone of disease modification

Hydroxyurea (brand name Droxia, also available generic) was the first FDA-approved disease-modifying therapy for SCD, approved in adults in 1998 and in children aged 2 and older in 2017. It induces fetal hemoglobin (HbF), which doesn't sickle, reducing crisis frequency, hospitalization rates, and mortality. NHLBI and ASH guidelines recommend hydroxyurea for every patient with HbSS or HbSβ0 over nine months old, regardless of prior crisis history. Every U.S. state Medicaid program covers it. Starting dose is typically 15-20 mg/kg/day with quarterly CBC monitoring.

L-glutamine (Endari)

L-glutamine, marketed as Endari, was FDA-approved in 2017 for reducing acute complications in patients 5 and older. Oral powder, twice daily. Evidence base is smaller than for hydroxyurea; it is typically used as an add-on for patients with breakthrough crises on hydroxyurea.

Voxelotor (Oxbryta) — status

Voxelotor was FDA-approved in 2019 as a hemoglobin oxygen-affinity modulator that reduces polymerization of sickle hemoglobin. In September 2024, Pfizer voluntarily withdrew voxelotor from the market after post-approval safety data raised concerns, particularly around vaso-occlusive crises and mortality in certain subgroups. Patients previously on voxelotor should consult their hematologist about alternatives.

Crizanlizumab (Adakveo) — status

Crizanlizumab is a monthly IV anti-P-selectin antibody approved by FDA in 2019. The European Medicines Agency withdrew its approval in 2023 after a confirmatory study failed to replicate the original effect size; the FDA's U.S. indication remains under ongoing review.

Casgevy (exa-cel) and Lyfgenia (lovo-cel) — CRISPR gene therapy

In December 2023, the FDA approved two one-time gene therapies for severe SCD in patients 12 and older:

• Casgevy (exagamglogene autotemcel), from Vertex Pharmaceuticals + CRISPR Therapeutics, uses CRISPR-Cas9 to edit the BCL11A enhancer, re-activating fetal hemoglobin. List price: ~$2.2M per patient.
• Lyfgenia (lovotibeglogene autotemcel), from bluebird bio, uses a lentiviral vector to insert a modified β-globin gene that produces anti-sickling hemoglobin. List price: ~$3.1M per patient.

Both require myeloablative conditioning (essentially a stem-cell transplant) and are administered at a limited number of authorized treatment centers nationally. See our center directory filtered to CRISPR-authorized centers, and see individual state pages for Medicaid coverage status.

Stem-cell transplant (allogeneic HSCT)

Allogeneic hematopoietic stem-cell transplant from a matched sibling donor is the only conventionally curative therapy for SCD and has been used for roughly 40 years in pediatric patients with severe disease. The 5-year event-free survival rate is above 90% for matched-sibling recipients. Matched-unrelated-donor and haplo-identical transplants are under continued protocol refinement.