Type: Oral Presentation

 

Session title: Aggressive Lymphoma - CART

 

 

CD19-targeted chimeric antigen receptor (CAR) T-cell therapy has demonstrated about 50~60% of response rate in relapsed or refractory (R/R) B-cell non-Hodgkin lymphoma. However， antigen-escape relapse has emerged as a major challenge for long-term disease control after CD19-targeted therapies. In our previous study， we described a dual-targeted of CD19 and CD22 CAR-T cell cocktail therapy， whichyielded 93.3% of complete remission (CR) rate in R/R B-cell acute lymphoblastic leukemia and could reduce the risk of CD19-negative relapse.

 

 

A phase I/II clinical trial (NCT05206071) was designed to explore the safety and efficacy of CAR19/22 T-cell cocktail therapy for patients with R/R aggressive B-cell lymphoma.

 

 

Eligible R/R aggressive B-cell lymphoma patients were enrolled from July 2020 toDecember 2021. All patients received fludarabine 30 mg/m2/d and cyclophosphamide 250 mg/m2/d for 3 consecutive days (day ?5 to day ?3) followed by cocktail CAR-T cell infusion. CAR-T-cell-related cytokine release syndrome (CRS) was graded to assess the safety. PET-CT was performed on day 28 and 3rd month to evaluate the response rate.

 

 

A total of 26 eligible patients received CAR19/22 cocktail infusion with a median age of 46 years old (4-75) and a median of 3 prior lines of therapies (2-5 lines). Of 26 patients， 4 were Burkitt lymphoma， 2 were follicular lymphoma (grade 3a)， and the rest were diffuse large B-cell lymphoma. Besides， 7 patients were diagnosed with double-hit lymphoma and 4 patients were relapsed after previous CD19 CAR-T cell therapy.

 

Fourteen patients received the murinized CAR-T cells at a median dose of 2.18×106/kg (1-3×106/kg) CAR19 and 1.75×106/kg (1-3×106/kg) CAR22， while 12 patients received the does of the humanized CAR-T cells consisting of 2×106/kg CAR19 and 5×105/kg CAR22.

 

At the day 28 assessment， 12/12 (100%) patients received the humanized CAR-T cells achieved overall response， including 9/12 (75%) CR and 3/12 (25%) partial remission (PR)， while the overall response rate (ORR) and CR rate of the murinized group was 85.71% (12/14) and 42.86% (6/14) respectively. Among of them， all 4 Burkitt lymphoma patients in both groups achieved CR. In 3 months evaluation， 7/10 (70%，2 cases received infusion for less than 3 months) patients in the humanized group maintained in CR， which was higher than the murinized group with CR rate of 5/14 (35.71%). (Figure 1A-B). At a median follow-up of 291 days (range， 31 to 544)， patients in the humanized group had a favorable progression-free survival (PFS) than those in the murinized (1-year PFS of 67.9% vs. 26.8%)， although there was no statistical significance (p=0.08) due to the limited number of patients enrolled (Figure 1E-F). Achieving CR on day 28 (HR: 0.21， 95% CI: 0.06-0.72; P=0.012) and maintaining CR till the 3rd month (HR: 0.18， 95% CI: 0.06-0.59; P=0.004) were found as independent prognostic factors associated with favorable PFS. Maintaining CR till the 3rd month (HR: 0.10， 95% CI: 0.01-0.61; P=0.012) and non-double hit (HR: 0.11， 95% CI: 0.02-0.76， P=0.024) predicted a longer overall survival (OS) (Figure 1G-L). Despite impressive CR rates wereachieved， majority of patients had mild CRS (grade 1-2) in both group. Only 2patients experienced grade 3 CRS， and 2 patients developed grade 3 neurotoxicity.

 

 

This clinical trial demonstrates promising efficacy and safety of CD19/CD22 CAR-T cocktail therapy for R/R aggressive B-cell lymphoma， and patients in the humanized group showed better results than those with murinized ， although this not a randomized trial.

 

Keyword(s): B cell lymphoma， CAR-T

 

 

 

Type: Oral Presentation

 

Session title: Novel insights into the treatment of ALL

 

 

T cell malignancies represent a group of hematologic cancers with high relapse and mortality rates. The shared expression of target antigens between chimeric antigen receptor (CAR) T cells and malignant T cells has limited the development of CAR-T due to unintended CAR-T fratricide. Here， we develop a fratricide-resistant anti-CD7 CAR-T modified by CD7 ablation through CRISPR/CAS9 gene editing (KO7CAR).

 

 

In a phase I clinical trial， we explored the efficacy and safety of KO7CAR T-cells for relapsed or refractory (R/R) T-cell malignancies (NCT04916860 & NCT04938115).

 

 

Peripheral blood mononuclear cells were collected from patients (n=13) or the transplant donor (n=2) by leukapheresis. CD7-ablated CAR T cells (KO7CAR) were derived by electroporation of bulk T cells with CD7-targeting Cas9-gRNA RNP 24 hours before 7CAR transduction. This KO7CAR is a second-generation CAR-T with the co-stimulatory domain of 4-1BB and CD3ζ targeting CD7. Intravenous fludarabine (30mg/m2/d) and cyclophosphamide (300mg/m2/d) were given to all patients on day -5 to day -3 prior to KO7CAR-T cells infusion.

 

 

From Oct. 2020 to Oct. 2021， 15 patients with T-cell acute lymphoblastic leukemia (n=10)， T-cell lymphoblastic lymphoma (n=3)， and mixed phenotype acute leukemia (n=2) were enrolled and received KO7 CAR-T cells (Table 1). The median age was 28 (8-46) years old. Four patients had prior hematopoietic stem cell transplantation (HSCT). At enrollment， 10 patients had bone marrow (BM) blasts >5% by morphology， and 10 patients had the extramedullary disease (EMD， diffuse involvement， n=8， and bulky mediastinal masses， n=2). Both patient- and donor-derived KO7CAR-T cells were successfully generated with a transduction efficiency of 59.0% (22.5%-97.4%). A single dose of KO7CAR-T cells was infused to patients at low dose (1.5~5x105 cells/kg， n=8)， medium dose (1x106 cells/kg， n=6) or high dose (2x106 cells/kg， n=1).

 

On day 28， 15/15 (100%) patients achieved minimal residual disease (MRD) negative complete remission (CR). Among the 10 patients with EMD， 7 achieved EMD CR on day 30， 2 achieved partial response (PR)， and 1 who relapsed post 2nd transplant had no response on day 35 then withdrew. Up to data cutoff Feb.10， 2022， the median follow-up time was of 309 days (35~407 days). About 2 months post KO7CAR， 12 patients bridged into allogeneic HSCT， and all remained progression-free after a median time of 253 (30~388) days after HSCT except for 1 who relapsed on day 147 then died from intracerebral hemorrhage on day 249. The other 2 patients without subsequent HSCT (all had a prior transplant) died from infection on day 78 and GVHD on day 103， respectively， post KO7CAR.

 

Mild cytokine release syndrome (CRS， ≤grade II) occurred in 10/15 (66.7%) patients， and 5/15(33.3%) patients had grade III CRS. One patient had grade I neurotoxicity， and 2 had grade III/IV neurotoxicity. All was controlled after the administration of corticosteroids and/or tocilizumab.

 

Following infusion， the median peak of circulating KO7CAR-T cells was 1.77×105 (0.279~14.3×105) copies/μg genomic DNA which occurred around day 20 (day10~ day25) and 63.47% (23.1%~94.18%) occurring on day15 (day 9~day25) by q-PCR and flow cytometry respectively.

 

 

This study demonstrated KO7CAR-T therapy had a high efficacy for CD7+ T-cell malignancies even for those who relapsed post-transplant. Safety was manageable， however， more data on additional patients and longer observation time are needed to evaluate the efficacy of KO7 CAR-T products further.

 

Keyword(s): CAR-T， Cellular therapy， T cell acute lymphoblastic leukemia