Outcomes in Aggressive B-Cell Non-Hodgkin Lymphomas with Anti-CD19 CAR T-Cell (CTL019) Products Not Meeting Commercial Release Specifications

Introduction: Tisagenlecleucel (CTL019, tisa-cel) was recently approved for treatment of relapsed/refractory diffuse large B-cell lymphoma (r/r DLBCL), high grade B cell lymphoma (r/r HGBCL), and transformed follicular lymphoma (r/r tFL) after second line therapy. Prior to tisa-cel release for commercial use in the United States (US), the final manufactured, patient-specific product must meet specific Lot Release Specifications including requirements that the product's dose contains 0.6 to 6.0 x 10⁸ CAR-positive viable T cells and total cell viability is at least 80%. CAR T cell products that do not meet predetermined release specifications are considered "out of specification" (OOS) and may only be administered via an expanded access protocol or a single patient IND. To date, there are no prospectively reported data with regard to the reasons that commercially manufactured CTL019 products are OOS or clinical outcomes after infusion of OOS CTL019 products.

Methods: We are participating in a prospective, managed access protocol to allow administration of CTL019 to patients (pts) with r/r aggressive B-cell lymphomas meeting the approved prescribing information who are intended for treatment with US commercial tisa-cel but have OOS products. Pts were provided product via this managed access program and consent was obtained from all pts enrolled. Pts were unable to receive commercially manufactured product due to failure of apheresis material to meet acceptance specifications, failure of final manufactured product to meet the commercial release specifications, or failure to meet other product specifications within the prescribing information (e.g., interferon gamma release testing). Response was assessed at 3 months post CTL019 infusion by 2014 Lugano Classification criteria applied to FDG-PET/CT imaging. Adverse events were defined by CTCAE and ASTCT criteria.

Results: From 9/2018 to 7/2019, 16 pts were enrolled at our institution. Nine pts were diagnosed with r/r DLBCL, 5 pts had r/r HGBCL, and 2 pts had r/r tFL; 44% of all pts had "double-hit" lymphoma. Median age at CTL019 infusion was 68 years (range: 42-75 years); 7 pts (44%) were female. Twelve pts (75%) had advanced stage lymphoma at leukapheresis. Median prior therapies before leukapheresis was 3 (range: 2-5). Median ECOG performance status was 0 (range: 0-2). Median absolute lymphocyte count and CD3 count were 900/uL (range: 200-1300/uL) and 614/uL (range: 228-1343/uL), respectively. Median CTL019 dose was 1.3 x 10⁸ CAR-positive viable T cells (range: 0.5 x 10⁸ to 2.1 x 10⁸). Median product viability was 78.4% (range: 70.8-87.4%). Thirteen of 16 pts (81%) were enrolled due to low viability products (viability < 80%). The median viability for pts enrolled due to low product viability was 78.0% (range: 70.8-79.8%). The remaining 3 pts' products did not meet release specifications due to T cell dose below 0.6 x 10⁸ CAR-positive T cells (dose administered, 0.5 x 10⁸; n=1), residual beads by microscopy (n=1), or IFN gamma release level above the upper range (>1000 fg/transduced cell; n=1). All pts with low viability products had CAR-positive T cell doses that were within the product dose specifications for tisa-cel (13 of 13 pts).

Of 16 pts enrolled, 11 pts have at least 3 months follow-up; 3 pts were never treated due to progressive lymphoma and 2 pts have not had 3 month response assessments. Median follow-up is 3.4 months. There were 3 pts with CRS grades 1 or 2 by ASTCT criteria and no pts had neurotoxicity. Of 3 pts with CRS, one received a low dose of CTL019 (grade 2 CRS), one had higher levels of IFN gamma (grade 1 CRS), and one had low viability (grade 1 CRS). For all pts infused with OOS products, the 3-month overall response rate (ORR) was 64% including 6/11 (55%) CR and 1/11 (9%) PR. Progression-free survival (PFS) is 64% at 3 months (median not reached, 95%CI: 30-85%). For OOS products due to low viability, ORR was 4/8 (50%) CR and 4/8 (50%) PD; 3-month PFS was 50% (95%CI: 15-77%).

Conclusions: We report the first experience with commercially produced CTL019 products that do not meet product release specifications, primarily due to low viability. Three-month ORRs appear similar to published tisa-cel outcomes for aggressive B-cell non-Hodgkin lymphomas. Our results suggest that other product release characteristics such as potency and replicative capacity should also be more carefully evaluated prior to establishing criteria for release.