A Study Evaluating the Safety and Efficacy of BEAM-201 in Relapsed/Refractory T-Cell Acute Lymphoblastic Leukemia (T-ALL) or T-Cell Lymphoblastic Lymphoma (T-LL)

Key Inclusion Criteria:

1. Ages 18 to ≤ 50 years.

2. Ages ≥ 1 year to < 18 years, after health authority approval.

3. T-ALL/T-LL that is CD7-positive (defined as at least 20% of blasts positive for CD7by flow cytometry or immunohistochemistry based on assessment of the study site'sCLIA [Clinical Laboratory Improvement Amendments of 1988] certified facility) insecond or greater relapse, first relapse post-transplant relapse, orchemotherapy-refractory disease. Specifically:

4. Second or greater relapse or post-transplant relapse, defined as:

• BM with ≥ 5% lymphoblasts by morphologic assessment or evidence ofextramedullary disease at screening after second documented CR; OR
• Flow cytometric confirmation of relapsed T-ALL of at least 0.1% aftersecond CR documented to have been MRD negative < 0.1%; OR
• Any detectable relapsed disease post-allogeneic HSCT with flow cytometricconfirmation of T-ALL of at least 0.1%; OR
• Biopsy confirmed evidence of relapsed T-LL on lymph node biopsy aftersecond CR; OR
• Any detectable disease post-allogeneic transplant with biopsy confirmedevidence of T-LL on lymph node biopsy

2. Refractory disease, defined as:

• Primary refractory T-ALL or T-LL, defined as failure to achieve CR afterinduction chemotherapy, per investigator assessment and based onbiopsy-confirmed evidence of residual T-ALL or T-LL; OR
• Relapsed, refractory disease, defined as > 5% BM blasts orbiopsy-confirmed evidence of residual TLL after 1 course of re-inductionchemotherapy for patients who have relapsed after previously achieving aCR NOTE: Patients with mixed phenotype acute leukemia with T-cell dominantphenotype may be enrolled if the aforementioned criteria are met.

4. Eligible for myeloablative conditioning for and allogeneic HSCT based on theinvestigator's assessment with an available donor identified by a FACT accreditedtransplant center.

Key Exclusion Criteria:

1. CNS involvement meeting any of the following criteria: CNS-3 disease, progressiveCNS involvement despite therapy, CNS parenchymal or cranial nerve lesions onimaging.

2. Clinically active CNS dysfunction or known history of irreversible neurologicaltoxicity related to prior antileukemic therapy.

3. Receipt of prior CD7 targeted therapy.

4. Systemic antileukemic therapy intended to induce or maintain remission within 14days prior to completion of screening.