First-in-human data of ALLO-501 and ALLO-647 in relapsed/refractory large B-cell or follicular lymphoma (R/R LBCL/FL): ALPHA study.

8002 Background: Allogeneic (off the shelf) chimeric antigen receptor (CAR) T cell therapy addresses the logistical challenges and variable product quality of autologous CAR T therapy. ALLO-501 is a genetically modified anti-CD19 CAR T cell product in which the TCR alpha constant gene is disrupted to reduce the risk of graft-versus-host disease (GvHD) and the CD52 gene is disrupted to permit the use of ALLO-647, an anti-CD52 mAb, for selective and prolonged host lymphodepletion. Methods: This is an open-label, Phase 1 trial (NCT03939026) in adults with R/R LBCL/FL who have received ≥ 2 prior lines of therapy; prior anti-CD19 cell therapy is allowed. Patients (pts) receive fludarabine (flu) 90 mg/m 2 , cyclophosphamide (cy) 900 mg/m 2 , and ALLO-647 39 or 90 mg followed by ALLO-501 at 1 of 3 dose levels (DL) in a 3+3 design: 40, 120, and 360 × 10 6 CAR+ T cells. Results: As of 20 January 2020, 12 pts were enrolled: 9 received ALLO-501 at 3 DLs (4, 4 & 1 pts in DL1, DL2 and DL3 respectively), 1 pt discontinued due to kidney injury prior to lymphodepletion and 2 are starting treatment. Of the 9 treated pts aged 42 to 70 years: 5 had LBCL, 2 were female, 3 had primary refractory disease, and 3 had prior autologous stem cell transplants. The median number of prior lines of therapies was 3 (range 2 to 4). All treated pts received 39 mg of ALLO-647. No DLTs or GvHD have been observed to date. Most common Grade (Gr) ≥ 3 adverse events were neutropenia (55.6%), leukopenia (33.3%) and anemia (22.2%). Two pts (22.2%) developed cytokine release syndrome (1 Gr1 and 1 Gr2) that resolved within 72 hrs without steroids or tocilizumab. One pt developed Gr1 neurotoxicity that resolved without treatment. Infections included upper respiratory tract infection (Gr2), CMV (Gr3) and EBV viremia (Gr1), all reported in a single pt and resolved. One pt had a Gr2 infusion reaction to ALLO-647 which resolved with antihistamines. The overall response rate is 78% (95% exact CI: 40%, 97%): 3 complete and 4 partial responses. With a median follow up of 2.7 mos, 4 pts have ongoing responses and 3 pts progressed at 2, 4 and 6 mos. ALLO-501 cell expansion by qPCR was observed in 4 of 6 pts in varying degrees. Conclusions: These early data suggest that ALLO-501 and ALLO-647 have a manageable safety profile. ALLO-647 may be an effective and selective lymphodepleting agent with CD52 gene editing, and ALLO-501 shows evidence of clinical activity in pts with advanced NHL. Enrollment is ongoing, and updated safety, efficacy, PK/PD data will be presented including pts treated with increasing doses of ALLO-647. Clinical trial information: NCT03939026 .