A one-time gene therapy, managed through a highly coordinated and personalized process1

ZYNTEGLO can only be administered at Qualified Treatment Centers (QTCs).

The primary hematologist’s role is pivotal in identifying and referring potential patients for ZYNTEGLO, and they may be involved in collaborating with the QTC during and after the treatment process.

If you are considering a patient for treatment with ZYNTEGLO, contact a Qualified Treatment Center to discuss the patient’s eligibility and next steps

The time frames provided below are approximate and should be used as guidelines. Times may vary per patient.


Patient undergoes hematopoietic stem cell collection

Stem cell

(~1 week)

The patient’s cells are sent to a manufacturing site to produce ZYNTEGLO.


(~70-90 days)

While remaining in the QTC, the patient receives ZYNTEGLO intravenously, after which they will be monitored during a recovery period of several weeks


(4 days + at least 48 hours washout)

Stem Cell

(~1 week)
  • Patient undergoes hematopoietic stem cell mobilization (5–6 days) followed by apheresis (2–3 days) to obtain CD34+ stem cells for ZYNTEGLO manufacturing. Apheresis generally occurred on mobilization days 5 and 6
Additional information
  • The treating physician should confirm HSC transplantation is appropriate for the patient and perform screening for HBV, HCV, HTLV, and HIV before mobilization and apheresis are initiated
    • Patients should not take prophylactic HIV anti-retroviral medications or hydroxyurea for at least one month prior to mobilization or the expected duration for elimination of the medications, and until all cycles of apheresis are completed
    • If a patient requires anti-retrovirals for HIV prophylaxis, mobilization and apheresis of CD34+ cells should be delayed until a negative test for HIV is confirmed
  • Patients should be maintained at a hemoglobin (Hb) ≥11 g/dL for at least 30 days prior to mobilization
  • If the minimum dose of 5.0 x 106 CD34+ cells/kg is not met, mobilization and apheresis may be repeated to obtain collection of sufficient stem cells
  • A back-up collection of CD34+ stem cells of ≥1.5 x 106 CD34+ cells/kg (if collected by apheresis) or >1.0 x 108 TNC/kg (if collected by bone marrow harvest) is required
    • The back-up collection may be needed for rescue treatment if there is a compromise of hematopoietic stem cells or ZYNTEGLO before infusion, primary engraftment failure, or loss of engraftment after infusion with ZYNTEGLO

HBV = hepatitis B virus; HCV= hepatitis C virus; HIV = human immunodeficiency virus; HSC = hematopoietic stem cells; HTLV = human T-lymphotropic virus [HTLV-1, HTLV-2]; TNC = total nucleated cell count.


(~70-90 days)
  • The patient’s cells are sent to a manufacturing site to produce ZYNTEGLO. ZYNTEGLO is then supplied in one or more infusion bags
  • ZYNTEGLO is specifically manufactured for each individual patient by adding functional copies of a modified β-globin gene into the patient’s CD34+ stem cells
  • ZYNTEGLO is then cryopreserved and, after passing quality release testing, stored until it is ready to be shipped to the QTC


(4 days + at least
48 hours washout)
  • Full myeloablative conditioning (chemotherapy given over 4 days) must be administered before infusion of ZYNTEGLO
  • In clinical trials, all patients received full myeloablative conditioning with busulfan
  • After completion of the conditioning, a minimum of 48 hours of washout should be allowed for before ZYNTEGLO infusion
  • Conditioning should not begin until the ZYNTEGLO has been received and stored at the treatment center and the availability of the back-up collection is confirmed
  • Like mobilization, patients should be maintained at a Hb ≥11 g/dL for at least 30 days prior to myeloablative conditioning
  • Iron chelation should be stopped at least 7 days prior to conditioning
  • Prophylaxis for hepatic veno-occlusive disease (VOD) is recommended and should be considered for seizures


Zynteglo Qualified Treatment Center 


(~30 min/bag)

Zynteglo post-infusion monitoring 

Post-Infusion Monitoring

(~3–6 weeks)


(~30 min/bag)
  • Each infusion bag of ZYNTEGLO is administered via intravenous infusion over a period of less than 30 minutes per bag. ZYNTEGLO is supplied in up to four infusion bags
  • Coordinate the timing of ZYNTEGLO thaw and infusion. ZYNTEGLO must be administered within 4 hours after thawing


(~3–6 weeks)
  • Patients should be prepared to remain hospitalized and monitored for an additional 3-6 weeks after infusion. Time may vary by patient
  • The patient will remain at the Qualified Treatment Center until the treating physician determines that they are ready to go home

In the clinical trials, patients treated with ZYNTEGLO (N=41) stayed in the hospital for an average of 44 days (~6 weeks) with a range of 29-92 days (~4-13 weeks). Time frame defined as admission for conditioning through post-infusion discharge.2


Zynteglo Long-Term Follow-Up
and Registry 

Long-Term Follow-Up
and Registry

(At least 15 Years)


(At least 15 Years)
  • Patients treated with ZYNTEGLO may develop hematologic malignancies and should be monitored lifelong. Monitor for hematologic malignancies with a complete blood count (with differential) at Month 6 and Month 12 and then at least annually for at least 15 years after treatment with ZYNTEGLO, and integration site analysis at Months 6, 12, and as warranted
    • If a hematologic malignancy is detected, the treating physician should contact bluebird bio at 1-833-999-NEST (6378) for reporting and to obtain instructions on collection of samples for testing
  • Restarting iron chelation may be necessary. Phlebotomy can be used in lieu of iron chelation, when appropriate
  • Irradiate any blood products required within the first 3 months after ZYNTEGLO infusion
  • Granulocyte-colony stimulating factor (G-CSF) is not recommended for 21 days after ZYNTEGLO infusion
  • Patients should be encouraged to enroll in the product registry, which collects data on the safety and efficacy of treatment for up to 15 years

Patient Counseling

Ensure your patient or their caregiver understands the risks associated with ZYNTEGLO and
the treatment process prior to consent.
Patients should understand:
  • Risk of manufacturing failure; if this occurs or there is the need for additional cells, additional HSC collection and manufacturing of ZYNTEGLO would be needed
  • Risks associated with mobilization and myeloablative conditioning agents
Additionally, advise patients of the following:
  • Delayed platelet engraftment
    A risk of bleeding exists after myeloablative conditioning and before platelet engraftment, and may continue after engraftment in patients who have continued thrombocytopenia
  • Risk of neutrophil engraftment failure
    Patients who experience neutrophil engraftment failure will receive rescue treatment with their back-up collection of CD34+ cells
  • Risk of insertional oncogenesis
    There is a potential risk of insertional oncogenesis after treatment with ZYNTEGLO. Patients should be monitored lifelong. Monitoring will include assessment for hematologic malignancies with a complete blood count at Month 6 and Month 12 and then at least annually for at least 15 years after treatment with ZYNTEGLO. This will include integration site analysis at Months 6, 12, and as warranted

Advise patients to read the Patient Information.


Advise patients of the need to:

Seek immediate attention if new or worsening bleeding or bruising occurs. Platelet recovery following ZYNTEGLO infusion could be delayed, potentially resulting in an increased risk of bruising or bleeding until platelet recovery has been achieved

  • Monitor for signs and symptoms of bleeding and have frequent blood draws for platelet counts, until platelet recovery has been achieved 
  • Have their treating physician contact bluebird bio at 1-833-999-NEST (6378) if they are diagnosed with a malignancy
Advise patients that:
  • They should not donate blood, organs, tissues, or cells at any time in the future
  • They may test positive for HIV if tested using a PCR assay after being treated with ZYNTEGLO

PCR = polymerase chain reaction.

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