A Phase 1 Multicenter Study Evaluating the Safety and Tolerability of KTE-X19 in Adult Subjects with Relapsed/Refractory Chronic Lymphocytic Leukemia and Small Lymphocytic Lymphoma

The primary objective of this study is to evaluate the safety and tolerability of
brexucabtagene autoleucel (KTE-X19) in adults with relapsed/refractory chronic lymphocytic
leukemia (r/r CLL) and small lymphocytic lymphoma (r/r SLL) who have received at least 2
prior lines of treatment, one of which must include a Bruton's tyrosine kinase (BTK)
inhibitor.

After the end of KTE-C19-108, participants who received an infusion of brexucabtagene
autoleucel will complete the remainder of the 15-year follow-up assessments in a separate
Long-term Follow-up study, KT-US-982-5968 (NCT05041309).

Key Inclusion Criteria:

- Documentation of relapsed or refractory CLL and SLL; must have received at least 2
prior lines of treatment, one of which must include a Bruton's tyrosine kinase (BTK)
inhibitor.

- Cohort 1 and 2: Participants with r/r CLL who have received at least 2 prior
lines of treatment, one of which must include a BTK inhibitor.

- Cohort 3: Participants with r/r CLL and SLL must present with ≤ 1% circulating
tumor cells in peripheral blood or absolute lymphocyte count (ALC) < 5000
cells/μL. Participants must have received at least 2 prior lines of treatment,
one of which must include a BTK inhibitor.

- Cohort 4: Participants with r/r CLL who have received at least 2 prior lines of
treatment and must have received ibrutinib as a single agent or in comibation
with anti-cluster of differentiate 20 (CD20) antibodies, B-cell lymphoma 2
(BCL-2) inhibitors, and phosphoinositide 3-kinase inhibitor (PI3k) inhibitors for
at least 6 months as the last line of therapy prior to screening. Ibrutinib
administration will continue up to 30 hours prior to leukapheresis. In case of
treatment interruption with ibrutinib, the principal investigator should reach
out to the medical monitor to discuss.

- An indication for treatment per International Workshop on Chronic Lymphocytic Leukemia
(IWCLL) 2018 criteria and radiographically measurable disease (at least 1 lesion > 1.5
cm in diameter)

- Adequate hematologic function as indicated by:

- Platelet count ≥ 50 × 10^9/L

- Neutrophil count ≥ 0.5 × 10^9/L

- Hemoglobin ≥ 8 g/dL unless lower values are attributable to CLL

- Adequate renal, hepatic, cardiac and pulmonary function defined as:

- Creatinine clearance (as estimated by Cockcroft-Gault) ≥ 60 mL/min

- Serum alanine aminotransferase (ALT)/aspartate aminotransferase (AST) ≤ 2.5 x
upper limit of normal (ULN)

- Total bilirubin ≤ 1.5 mg/dL unless participant has Gilbert's syndrome

- Left ventricular ejection fraction (LVEF) ≥ 50%, no evidence of pericardial
effusion, no New York Heart Association (NYHA) class III or IV functional
classification, no clinically significant arrhythmias

- No clinically significant pleural effusion

- Baseline oxygen saturation > 92% on room air

- Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1

- At least 2 weeks or 5 half-lives, whichever is shorter, must have elapsed since any
prior systemic therapy or BTKi (ibrutinib or acalabrutinib) at the time the
participant is planned for leukapheresis, except for systemic inhibitory/stimulatory
immune checkpoint therapy. At least 3 half-lives must have elapsed from any prior
systemic inhibitory/stimulatory immune checkpoint molecule therapy at the time the
participant is planned for leukapheresis (eg, ipilimumab, nivolumab, pembrolizumab,
atezolizumab, OX40 agonists, 4-1BB agonists)

Key Exclusion Criteria:

- A history of treatment including any of the following:

- Prior cluster of differentiate 19 (CD19) directed therapy

- Prior allogeneic hematopoietic stem cell transplant (SCT) or donor lymphocyte
infusion (DLI) within 6 months prior to enrollment

- History of autoimmune disease resulting in end-organ injury unless attributable to CLL
(eg, idiopathic thrombocytopenic purpura (ITP), autoimmune hemolytic anemia (AIHA))

- Diagnosis of Richter's transformation or a history of malignancy other than
non-melanoma skin cancer or carcinoma in situ (eg, skin, cervix, bladder, breast),
superficial bladder cancer, asymptomatic localized low grade prostate cancer for which
watch-and-wait approach is standard of care, or any other cancer that has been in
remission for > 3 years prior to enrollment

- History of severe hypersensitivity reaction attributed to aminoglycosides

Note: Other protocol defined Inclusion/Exclusion criteria may apply.