Preliminary Report of the Academic CAR-T (ISIKOK-19) Cell Clinical Trial in Turkey: Characterization of Product and Outcomes of Clinical Application

Objective: Chimeric antigen receptor T (CAR-T) cell therapies have already made an impact on the treatment of B-cell malignancies. Although CAR-T cell therapies are promising, there are concerns about commercial products regarding their affordability and sustainability. In this preliminary study, the results of the first production and clinical data of an academic CAR-T cell (ISIKOK-19) trial in Turkey are presented. Materials and
Methods: A pilot clinical trial (NCT04206943) designed to assess the safety and feasibility of ISIKOK-19 T-cell therapy for patients with relapsed and refractory CD19+ tumors was conducted and participating patients received ISIKOK-19 infusions between October 2019 and July 2021. The production data of the first 8 patients and the clinical outcome of 7 patients who received ISIKOK-19 cell infusions are presented in this study.
Results: Nine patients were enrolled in the trial [5 with acute lymphoblastic leukemia (ALL) and 4 with non-Hodgkin lymphoma (NHL)], but only 7 patients could receive treatment. Two of the 3 participating ALL patients and 3 of the 4 NHL patients had complete/partial response (overall response rate: 72%). Four patients (57%) had CAR-T-related toxicities (cytokine release syndrome, CAR-T-related encephalopathy syndrome, and pancytopenia). Two patients were unresponsive and had progressive disease following CAR-T therapy. Two patients with partial response had progressive disease during follow-up.
Conclusion: Production efficacy and fulfillment of the criteria of quality control were satisfactory for academic production. Response rates and toxicity profiles were also acceptable for this heavily pretreated/refractory patient group. ISIKOK-19 cells appear to be a safe, economical, and efficient treatment option for CD19+ tumors. However, the findings of this study need to be supported by the currently ongoing ISIKOK-19 clinical trial. ©Copyright 2022 by Turkish Society of Hematology | Turkish Journal of Hematology, Published by Galenos Publishing House

Introduction

Chimeric antigen receptor T cell (CAR-T) therapies have already revolutionized the treatment of B-cell malignancies [1,2]. The commercial availability of CAR-T cell products provides significant real-world experience in treating relapsed or refractory B-cell malignancies, but there are concerns in many countries about commercial products regarding their affordability and sustainability [3,4]. These concerns raised the need for more economical academic and local production. Hence, several countries are exploring alternative T-cell production models that have comparable clinical outcomes to commercial products [5]. ISIKOK-19 is the first local CD19 CAR-T cell product in Turkey, arising from the need to address economical and accessibility concerns related to the use of commercialized products.

Results of the clinical data of the academic CAR-T cell product ISIKOK-19 from Turkey are presented in this preliminary report. Production data for ISIKOK-19 have already been published [6] and are presented as supplementary data in this report.

Materials and Methods

A pilot clinical trial (NCT04206943) designed to assess the safety and feasibility of ISIKOK-19 T-cell therapy in patients with relapsed and refractory CD19+ tumors was conducted at Acıbadem Altunizade Hospital. The clinical research protocol was approved by the respective institutional review board and the Blood, Organ, and Tissue Transplantation Department of the Turkish Ministry of Health [(56733164/203)/(2019-11/6)]. All patients provided written informed consent. The participating patients received ISIKOK-19 infusions between October 2019 and July 2021. Production data for the first 8 patients and the clinical outcomes of 7 patients who received ISIKOK-19 cell infusions are presented in this study. Data on ISIKOK-19 cell production and quality control tests are included in Supplementary Data File 1.

The academic CAR-T cell product presented in this study, ISIKOK-19, encodes the anti-CD19 CAR construct with the single-chain variable fragment (scFv) of an anti-CD19 monoclonal antibody (FMC63) conjugated with the CD8 hinge region, CD28 transmembrane (TM), and co-stimulatory domain, and the CD3z pro-activator signaling domain along with a truncated form of the epidermal growth factor receptor (EGFRt) cell surface protein as a co-expression marker and a safety switch mechanism. Product characterization, in vivo expansion, and persistence of CAR-T cells are presented in Supplementary Data File 2.

CAR-T cell treatment details, eligibility criteria, and primary/secondary outcomes of the study are presented in Supplementary Data File 3.

Results

Nine patients were enrolled in the trial [5 with acute lymphoblastic leukemia (ALL) and 4 with non-Hodgkin lymphoma (NHL)], but only 7 patients could receive treatment (Table 1, Supplementary Data File 4). Three patients with diffuse large B-cell lymphoma (DLBCL), three patients with ALL, and one with double-hit lymphoma (DHL) were treated. One patient had DLBCL transformed from chronic lymphocytic leukemia (CLL) and the patient with DHL had experienced transformation from follicular lymphoma. All four lymphoma patients had refractory disease and two of the ALL patients had extramedullary involvement.

Table 1

Patient characteristics.

Clinical data illustrate that the study group was very heavily pretreated (median lines of previous therapies = 4), with all except one having a previous history of hematopoietic stem cell transplantation (HSCT), including four patients who underwent allogeneic HSCT. Time from HSCT to ISIKOK-19 infusion was 19,14, 8, and 7 months and donor chimerism at the time of leukapheresis was 100%, 98%, 73%, and 0%, respectively. One of the patients received checkpoint inhibitor therapy (nivolumab) 6 months prior to the ISIKOK-19 infusion. No graft-versus-host disease was observed following the infusion of ISIKOK-19.

Two of the 3 participating ALL patients and 3 of 4 NHL patients had complete/partial response (overall response rate: 72%). All of the patients with DLBCL obtained partial response after infusion of CAR-T cells. All three of the DLBCL patients had bulky disease at the time of CAR-T infusion. The DHL patient had progressive disease following CAR-T cell infusion. Two of the patients with ALL obtained complete response and the other ALL patient was unresponsive to treatment. Four patients (57%) had CAR-T-related toxicities [cytokine release syndrome (CRS), immune effector cell-associated neurotoxicity syndrome (ICANS), and pancytopenia] (Table 2).

Table 2

Clinical outcomes according to diagnosis.

Infusion of ISIKOK-19 was associated with mild and transient toxicity; one patient had grade 1 CRS and another one had grade 1 ICANS, both of which resolved without intervention. One patient with grade 2 CRS needed a single dose of tocilizumab and recovered afterwards. One patient had grade 2 CRS, grade 1 ICANS, and hematological toxicity with pancytopenia. He required both tocilizumab and dexamethasone treatment for recovery. The hematological toxicity resolved by the end of the second month of treatment. All four patients who had CRS or ICANS were responsive to ISIKOK-19 therapy. All patients with the exception of one experienced B-cell aplasia following ISIKOK-19 infusion. B-cell aplasia lasted longer in responding patients.

Discussion

In this study, 8 peripheral mononuclear cell aphereses were performed for 8 patients. One production attempt failed and the patient died just before CAR-T cell infusion. Seven of the eight production attempts resulted in successful outcomes that met all the criteria for release and quality control. The products also had the advantage of cost-effectiveness as previously demonstrated by Ran et al. [7], who reported the low cost of decentralized CAR-T cell production in an academic nonprofit setting.

Four of 7 patients in this study had a history of allogeneic HSCT prior to CAR-T cell infusion. Three of these 4 patients had high ratios of donor chimerism (100%, 98%, and 73%) at the time of leukapheresis and one of them was non-chimeric. The patients with high donor chimerism showed responses to CAR-T cell treatment, whereas the non-chimeric patient was unresponsive. This finding is in accordance with previous CAR-T cell reports from patients with high donor chimerism [8]. We speculate that the satisfactory results in cases with high donor chimerism may have been due to the non-exhausted T-cells of donors in comparison to the probably exhausted T-cells of heavily pretreated patients. This finding is encouraging for CAR-T cell treatments from allogeneic sources.

Overall, the toxicity observed in this study was mild. Grade 2 CRS was noted in 2 patients who required intervention. All responders had adverse events, whereas non-responders had no toxicity. This finding is supportive of observations regarding a positive correlation between adverse events and the efficacy of CAR-T cell therapy in previous reports [9,10]. Although a high tumor burden is associated with more adverse events in CAR-T cell therapy [11], it has been illustrated that fractionated dosing with intra-patient dose modification optimizes safety without compromising efficacy [12]. The low toxicity rates in this study, which mainly included patients with high tumor burdens, can be explained by the dose administration being split over 3 days.

Regarding the in vivo expansion of CAR-T cells, study data indicate higher vector copy numbers for responders. Lasting high CAR-T copy numbers and vanishing CD19 positivity in responsive patients were evidence of the efficacy of ISIKOK-19 cells. In the responsive lymphoma patients, biopsy specimens following disease progression showed that progression occurred in the CD19- lymphoma cell population. This finding is in accordance with previously reported high rates of CD19 negativity in relapses that mostly occurred within the first 4 months following CAR-T cell therapy [13].

Study Limitations

One limitation of this study was the inclusion of mainly heavily pretreated refractory patients. This influenced the clinical outcome in this small group of patients. Furthermore, the COVID-19 pandemic led to the death of one of the study patients. The findings of this study need to be supported by the current ongoing larger ISIKOK-19 clinical trial.

Conclusion

This report has presented the production and clinical outcomes of the first academic CAR-T cell trial in Turkey. Production efficacy and the criteria of quality control were fulfilled for academic production. Response rates and toxicity profiles were acceptable for this heavily pretreated/refractory patient group. ISIKOK-19 cells appear to be a safe, economical, and effective treatment option for CD19+ tumors.