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474 Outcomes after Reinfusion of CD19-Specific Chimeric Antigen Receptor (CAR)-Modified T Cells in Children and Young Adults with Relapsed/Refractory B-Cell Acute Lymphoblastic Leukemia

Program: Oral and Poster Abstracts
Type: Oral
Session: 704. Cellular Immunotherapies: Cellular Therapies for ALL
Hematology Disease Topics & Pathways:
Clinical Trials, Lymphoid Leukemias, ALL, Clinical Research, Diseases, Lymphoid Malignancies
Sunday, December 12, 2021: 1:15 PM

Regina M. Myers, MD1, Kaitlin Devine, MD1*, Yimei Li, PhD2*, Sophie Lawrence, BS1*, Allison Barz Leahy, MD1*, Hongyan Liu, PhD3*, Lauren Vernau, BA1*, Colleen Callahan, MSN, CRNP1*, Diane Baniewicz, MSN, CRNP1*, Stephan Kadauke, MD, PhD4*, Regina McGuire, BS1*, Margaret A Cameron1*, Amanda M. DiNofia, MD, MSCE1*, Susan R. Rheingold, MD1, Richard Aplenc, MD, PhD1, Carl H June, MD5, Stephan A. Grupp, MD, PhD1, Lisa Wray, MD1* and Shannon L. Maude, MD, PhD1

1Division of Oncology, Children's Hospital of Philadelphia, Philadelphia, PA
2Department of Biostatistics, Epidemiology and Informatics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA
3Children's Hospital of Philadelphia, Philadelphia, PA
4Department of Pathology, Children’s Hospital of Philadelphia, Philadelphia, PA
5Center for Cellular Immunotherapies, University of Pennsylvania, Philadelphia, PA

Background: CAR-modified T cells targeting CD19 have produced remarkable responses in relapsed/refractory B-cell acute lymphoblastic leukemia (B-ALL); however, relapse continues to be a substantial challenge. CD19+ relapses, which account for 33-78% of relapses, are associated with loss of CAR T-cell surveillance due to short persistence. Thus, strategies to improve functional persistence to prevent and treat CD19+ relapsed disease are crucial. Here, we report our experience administering reinfusions of murine or humanized 4-1BB CD19 CAR T cells in an effort to prolong persistence in patients with demonstrated short persistence to mitigate relapse risk, treat CD19+ relapsed disease, and produce responses after nonresponse to initial CAR infusion.

Methods: This analysis included patients aged <30 years treated with a murine CD19 CAR construct, either investigational CTL019 (NCT01626495, NCT02906371) or commercial tisagenlecleucel, or a humanized CD19 CAR construct, huCART19 (NCT02374333), who received ≥1 reinfusion of the same CAR product due to: 1) clinical signs of poor persistence within 6 months (mos) of initial infusion, including peripheral B-cell recovery (BCR) or CD19+ hematogones in the bone marrow, 2) new CD19+ minimal residual disease (MRD) or relapse, or 3) nonresponse to initial infusion. The huCART19 trial included patients who had previously received a CAR T cell product (CAR-exposed), whereas all patients reinfused with CTL019/tisagenlecleucel were CAR-naïve at initial infusion. The primary outcome was complete response (CR) at day 28 after reinfusion, defined as complete remission with establishment or maintenance of B-cell aplasia. Secondary outcomes included CRS incidence, cumulative incidence of relapse (CIR) and overall survival (OS).

Results: Among 229 CAR-naïve and 33 CAR-exposed patients treated with CD19 CAR between 2012-2020, 81 received ≥1 reinfusion (investigational CTL019, n=44; commercial tisagenlecleucel, n=11; huCART19, n=13 CAR-naïve and n=13 CAR-exposed). In addition, 18 patients received PD-1 blockade after their first (n=11) or subsequent (n=7) reinfusions. Indications for first reinfusion were peripheral BCR (CAR-naïve, n=32; CAR-exposed, n=6), hematogones (CAR-naïve, n=21; CAR-exposed, n=4), CD19+ MRD/relapse (CAR-naïve, n=10, CAR-exposed, n=0), and nonresponse to initial infusion (CAR-naïve, n=5, CAR-exposed, n=3). CRS grade ≥2 (Penn scale) occurred in 19 patients (grade 2, n=13; grade 3, n=4; grade 4, n=2). Grade 3-4 events only occurred in patients with active disease at time of reinfusion. Twenty-two patients had an inpatient admission within 30 days of first reinfusion, of which 7 required intensive care unit admission

Among the 63 patients reinfused for relapse prevention, 33 (52%) had a CR at day 28. With a median duration of follow-up of 38 mos, 13 experienced a subsequent relapse (7 CD19+, 4 CD19-, 2 CD19-subset negative), 4 received alternative therapy or allogeneic hematopoietic stem cell transplantation (HSCT) in remission, and 16 remain in remission without further therapy at a median of 39 mos after first reinfusion. The median duration of B-cell aplasia was 8 mos (IQR 2-35) after reinfusion. Of the 30 with no response (NR), 10 had a subsequent CD19+ relapse, 15 received alternative therapy or HSCT, and 5 remain in remission without further therapy at a median of 43 mos after reinfusion. CIR and OS were not statistically significantly different between patients with CR or NR (CIR, p=0.26; OS, p=0.25) (Figure A-B). However, at 24 mos after reinfusion, CIR was 29% (95% CI, 11-44%) for CR compared to 61% (95% CI, 24-80%) for NR; OS was 90% (95% CI, 80-100%) for both groups.

Of the 10 patients reinfused for relapse, 5 (50%) had a CR; 2 subsequently experienced a CD19+ relapse, 2 received an HSCT in remission, and 1 remains in remission without further therapy at 18 mos after reinfusion. Of the 8 patients reinfused for nonresponse to initial infusion, 7 were evaluable; none had a CR, and all died at a median of 2.5 mos after reinfusion.

Conclusions: Reinfusion of CTL019/tisagenlecleucel or huCART19 is safe, may prolong B-cell aplasia in patients with short CAR persistence and reduce relapse risk, and can induce remissions in patients with CD19+ relapsed disease. Thus, reinfusion may provide an alternative to HSCT for short persistence. However, reinfusion is not effective for patients with nonresponse to initial CAR infusion.

Disclosures: Callahan: Novartis: Speakers Bureau. Rheingold: Optinose: Other: Spouse's current employment; Pfizer: Research Funding. June: Tmunity, DeCART, BluesphereBio, Carisma, Cellares, Celldex, Cabaletta, Poseida, Verismo, Ziopharm: Current equity holder in publicly-traded company; Novartis: Patents & Royalties; AC Immune, DeCART, BluesphereBio, Carisma, Cellares, Celldex, Cabaletta, Poseida, Verismo, Ziopharm: Consultancy. Grupp: Novartis, Roche, GSK, Humanigen, CBMG, Eureka, and Janssen/JnJ: Consultancy; Novartis, Adaptimmune, TCR2, Cellectis, Juno, Vertex, Allogene and Cabaletta: Other: Study steering committees or scientific advisory boards; Novartis, Kite, Vertex, and Servier: Research Funding; Jazz Pharmaceuticals: Consultancy, Other: Steering committee, Research Funding. Maude: Novartis Pharmaceuticals Corporation: Consultancy, Research Funding; Wugen: Consultancy.

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