Long-Term Data Presented at ASH Support beti-cel as a Potentially Curative Gene Therapy for β-Thalassemia Patients Who Require Regular Transfusions Through Achievement of Durable Transfusion Independence and Normal or Near-Normal Adult Hb Levels

• Updated data from studies of beti-cel in 63 patients with transfusion-dependent beta-thalassemia showed sustained transfusion independence and improvements in iron management through up to 9 years of follow-up (n=1)
• All four parent studies are complete, and all patients have transitioned to a long-term follow-up study (LTF-303)
• beti-cel is U.S. Food and Drug Administration (FDA) approved and marketed in the U.S. as ZYNTEGLO

SOMERVILLE, Mass.--(BUSINESS WIRE)-- Updated data from bluebird bio inc.’s (NASDAQ: BLUE) gene therapy program in transfusion-dependent (TDT) beta-thalassemia were presented today at the 65th American Society of Hematology (ASH) Annual Meeting & Exposition. Updated follow-up data showed sustained treatment effect, reduced iron management burden and improved quality of life measures in patients with beta-thalassemia who require regular red blood cell transfusions following treatment with betibeglogene autotemcel (beti-cel) (FDA approved and marketed in the U.S. as ZYNTEGLO™).

“Long-term results presented at ASH 2023 showed durable transfusion independence and a continued positive safety profile in patients with beta-thalassemia treated with our beti-cel gene therapy through up to nine years of follow-up,” said Richard Colvin, M.D., Ph.D., chief medical officer, bluebird bio. “These data represent the longest follow-up with a gene therapy for patients with beta-thalassemia requiring regular transfusions and continue to show that beti-cel is a potentially curative therapy across ages and genotypes, through the achievement of durable transfusion independence and normal or near-normal hemoglobin levels.”

As of January 30, 2023, 63 patients had received beti-cel across four clinical studies with a median follow-up of 5 years (60.1 months; range: 23.8-109.5). These include two Phase 3 studies (N=41) that led to the FDA approval of ZYNTEGLO in August 2022 as the first and only gene therapy for patients with beta-thalassemia who require regular red blood cell transfusions.

Sustained Efficacy and Safety Results, and Improved Quality of Life Measures in Adult and Pediatric Patients With Transfusion-Dependent β-Thalassemia Up to 9 Years Post Treatment With Betibeglogene Autotemcel (beti-cel) (poster #1102)

Among patients in the Phase 3 studies, 90.2% (37/41) achieved transfusion independence (TI). As of the data cutoff date, TI was maintained through last follow-up (up to 6 years) across ages and genotypes. Among patients in the Phase 1/2 studies, 68.2% (15/22) achieved TI, with 14 patients sustaining TI through the last follow-up (up to 9 years). One patient, with human immunodeficiency virus complicated by gastrointestinal infection and bleeding, no longer met protocol-defined TI as a result of a hemoglobin level <9 g/dL at year 6. The patient continued to benefit from beti-cell therapy and was not receiving chronic red blood cells transfusions as of the last follow-up.

Among 12 adult patients and 22 pediatric patients in the Phase 1/2 and Phase 3 studies, health-related quality of life (HRQOL) was assessed at baseline and every 6 months. Clinically meaningful improvements in quality of life assessments, including various quality of life assessments for mental, physical and psychosocial health, were demonstrated in both adult and pediatric patients up to 36 months.

As of the cutoff date, the safety results following beti-cel treatment largely reflected the known side effects of hematopoietic stem cell collection and the busulfan conditioning regimen. Overall, 19% of patients experienced ≥1 beti-cel-related AE. The most common beti-cel-related AEs (occurring in ≥3 patients) were abdominal pain (7.9% of patients) and thrombocytopenia (4.8% of patients). Five patients experienced serious veno-occlusive liver disease; all 5 received defibrotide and recovered. No malignancies, insertional oncogenesis, or vector-derived replication-competent lentivirus were reported.

Improvement in Iron Burden in Patients With Transfusion-Dependent β-Thalassemia (TDT) Treated With Betibeglogene Autotemcel (beti-cel) Gene Therapy: Up to 9 Years of Follow-Up (poster #2480)

Additionally, iron management outcomes were presented from patients with transfusion-dependent beta-thalassemia who completed either a Phase 1/2 or Phase 3 beti-cel parent study and subsequently enrolled in the long-term follow-up study and were followed for up to 9 years. Across all studies, 37/51 patients restarted chelation, and 12 received phlebotomy post-infusion; however, 69% (35/51) were able to stop chelation therapy, demonstrating restoration of iron levels over time and reduced iron management burden in those patients.

About ZYNTEGLO™ (betibeglogene autotemcel) or beti-cel

ZYNTEGLO is a first-in-class, one-time ex-vivo LVV gene therapy. It is approved for the treatment of beta-thalassemia in adult and pediatric patients who require regular red blood cell transfusions and was launched commercially more than a year ago. ZYNTEGLO works by adding functional copies of a modified form of the beta-globin gene (β^A-T87Q-globin gene) into a beta-thalassemia patient’s own hematopoietic (blood) stem cells to enable the production of a modified functional adult hemoglobin (HbA^T87Q). Once a patient has the β^A-T87Q-globin gene, they have the potential to increase ZYNTEGLO-derived adult hemoglobin (HbA^T87Q) and total hemoglobin to normal or near normal levels that can eliminate the need for regular red blood cell (RBC) transfusions.

Indication

ZYNTEGLO is indicated for the treatment of adult and pediatric patients with beta-thalassemia who require regular red blood cell (RBC) transfusions.

Important Safety Information

Delayed Platelet Engraftment

Delayed platelet engraftment has been observed with ZYNTEGLO treatment. Bleeding risk is increased prior to platelet engraftment and may continue after engraftment in patients with prolonged thrombocytopenia; 15% of patients had ≥ Grade 3 decreased platelets on or after Day 100.

Patients should be made aware of the risk of bleeding until platelet recovery has been achieved. Monitor patients for thrombocytopenia and bleeding according to standard guidelines. Conduct frequent platelet counts until platelet engraftment and platelet recovery are achieved. Perform blood cell count determination and other appropriate testing whenever clinical symptoms suggestive of bleeding arise.

Risk of Neutrophil Engraftment Failure

There is a potential risk of neutrophil engraftment failure after treatment with ZYNTEGLO. Neutrophil engraftment failure is defined as failure to achieve three consecutive absolute neutrophil counts (ANC) ≥ 500 cells/microliter obtained on different days by Day 43 after infusion of ZYNTEGLO. Monitor neutrophil counts until engraftment has been achieved. If neutrophil engraftment failure occurs in a patient treated with ZYNTEGLO, provide rescue treatment with the back-up collection of CD34+ cells.

Risk of Insertional Oncogenesis

There is a potential risk of LVV mediated insertional oncogenesis after treatment with ZYNTEGLO.

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.

In the event that a malignancy occurs, contact bluebird bio at 1 833-999-6378 for reporting and to obtain instructions on collection of samples for testing.

Hypersensitivity Reactions

Allergic reactions may occur with the infusion of ZYNTEGLO. The dimethyl sulfoxide (DMSO) in ZYNTEGLO may cause hypersensitivity reactions, including anaphylaxis.

Anti-retroviral and Hydroxyurea Use

Patients should not take prophylactic HIV anti-retroviral medications or hydroxyurea for at least one month prior to mobilization, or for 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, then confirm a negative test for HIV before beginning mobilization and apheresis of CD34+ cells.

Interference with Serology Testing

Patients who have received ZYNTEGLO are likely to test positive by polymerase chain reaction (PCR) assays for HIV due to integrated BB305 LVV proviral DNA, resulting in a false-positive test for HIV. Therefore, patients who have received ZYNTEGLO should not be screened for HIV infection using a PCR-based assay.

Adverse Reactions

The most common non-laboratory adverse reactions (≥20%) were mucositis, febrile neutropenia, vomiting, pyrexia, alopecia, epistaxis, abdominal pain, musculoskeletal pain, cough, headache, diarrhea, rash, constipation, nausea, decreased appetite, pigmentation disorder, and pruritus. The most common Grade 3 or 4 laboratory abnormalities (>50%) include neutropenia, thrombocytopenia, leukopenia, anemia, and lymphopenia.

Drug Interactions

Drug-drug interactions between iron chelators and the myeloablative conditioning agent must be considered. Iron chelators should be discontinued at least 7 days prior to initiation of conditioning. The prescribing information for the iron chelator(s) and the myeloablative conditioning agent should be consulted for the recommendations regarding co-administration with CYP3A substrates.

Some iron chelators are myelosuppressive. After ZYNTEGLO infusion, avoid use of these iron chelators for 6 months. If iron chelation is needed, consider administration of non-myelosuppressive iron chelators. Phlebotomy can be used in lieu of iron chelation, when appropriate.

Pregnancy/Lactation

Advise patients of the risks associated with conditioning agents, including on pregnancy and fertility.

ZYNTEGLO should not be administered to women who are pregnant, and pregnancy after ZYNTEGLO infusion should be discussed with the treating physician.

ZYNTEGLO is not recommended for women who are breastfeeding, and breastfeeding after ZYNTEGLO infusion should be discussed with the treating physician.

Females and Males of Reproductive Potential

A negative serum pregnancy test must be confirmed prior to the start of mobilization and re-confirmed prior to conditioning procedures and before ZYNTEGLO administration.

Women of childbearing potential and men capable of fathering a child should use an effective method of contraception (intra uterine device or combination of hormonal and barrier contraception) from start of mobilization through at least 6 months after administration of ZYNTEGLO.

Advise patients of the option to cryopreserve semen or ova before treatment if appropriate.

Please see full Prescribing Information for ZYNTEGLO.

About bluebird bio

bluebird bio is pursuing curative gene therapies to give patients and their families more bluebird days.

Founded in 2010, bluebird has been setting the standard for gene therapy for more than a decade—first as a scientific pioneer and now as a commercial leader. bluebird has an unrivaled track record in bringing the promise of gene therapy out of clinical studies and into the real-world setting, having secured FDA approvals for three therapies in under two years. Today, we are proving and scaling the commercial model for gene therapy and delivering innovative solutions for access to patients, providers, and payers.

With a dedicated focus on severe genetic diseases, bluebird has the largest and deepest ex-vivo gene therapy data set in the field, with industry-leading programs for sickle cell disease, β-thalassemia and cerebral adrenoleukodystrophy. We custom design each of our therapies to address the underlying cause of disease and have developed in-depth and effective analytical methods to understand the safety of our lentiviral vector technologies and drive the field of gene therapy forward.

bluebird continues to forge new paths as a standalone commercial gene therapy company, combining our real-world experience with a deep commitment to patient communities and a people-centric culture that attracts and grows a diverse flock of dedicated birds.

bluebird bio Cautionary Statement Regarding Forward-Looking Statements

Forward-Looking Statements

This press release contains “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995. All statements that are not statements of historical facts are, or may be deemed to be, forward-looking statements, such as statements regarding beti-cel as a potentially curative therapy across ages and genotypes. Such forward-looking statements are based on historical performance and current expectations and projections about bluebird’s future goals, plans and objectives and involve inherent risks, assumptions and uncertainties, including internal or external factors that could delay, divert or change any of them in the next several years, that are difficult to predict, may be beyond bluebird’s control and could cause bluebird’s future goals, plans and objectives to differ materially from those expressed in, or implied by, the statements. No forward-looking statement can be guaranteed. Forward-looking statements in this press release should be evaluated together with the many risks and uncertainties that affect bluebird bio’s business, particularly those identified in the risk factors discussion in bluebird bio’s Annual Report on Form 10-K for the year ended December 31, 2022, as updated by its subsequent Quarterly Reports on Form 10-Q, Current Reports on Form 8-K and other filings with the Securities and Exchange Commission. These risks and uncertainties include, but are not limited to: delays and challenges in bluebird’s commercialization and manufacturing of its products; the internal and external costs required for bluebird’s ongoing and planned activities, and the resulting impact on expense and use of cash, has been, and may in the future be, higher than expected which has caused bluebird, and may in the future cause bluebird to use cash more quickly than it expects or change or curtail some of its plans or both; substantial doubt exists regarding bluebird’s ability to continue as a going concern; bluebird’s expectations as to expenses, cash usage and cash needs may prove not to be correct for other reasons such as changes in plans or actual events being different than its assumptions; the risk that the efficacy and safety results from bluebird’s prior and ongoing clinical trials will not continue or be seen in the commercial context; and the risk of insertional oncogenic or other safety events associated with lentiviral vector, drug product, or myeloablation. The forward-looking statements included in this document are made only as of the date of this document and except as otherwise required by applicable law, bluebird bio undertakes no obligation to publicly update or revise any forward-looking statement, whether as a result of new information, future events, changed circumstances or otherwise.

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