Three-year results from phase I of ZUMA-4: KTE-X19 in pediatric relapsed/refractory acute lymphoblastic leukemia

Here we present the 3-year results of ZUMA-4, a phase I/II multicenter study evaluating the safety and efficacy of KTEX19, an autologous anti-CD19 chimeric antigen receptor (CAR) T-cell therapy, in pediatric/adolescent patients with relapsed/refractory B-cell acute lymphoblastic leukemia. Phase I explored two dose levels and formulations. The primary endpoint was the incidence of dose-limiting toxicities. Thirty-one patients were enrolled; KTE-X19 was administered to 24 patients (median age 13.5 years, range 3-20; median follow-up 36.1 months). No dose-limiting toxicities were observed. All treated patients had grade ≥3 adverse events, commonly hypotension (50%) and anemia (42%). Grade 3 cytokine release syndrome rates were 33% in all treated patients, 75% in patients given the dose of 2×106 CAR T cells/kg, 27% in patients given the dose of 1×106 cells/kg in the 68 mL formulation, and 22% in patients given the dose of 1×106 cells/kg in the 40 mL formulation; the percentages of patients experiencing grade ≥3 neurologic events were 21%, 25%, 27%, and 11% respectively. Overall complete remission rates (including complete remission with incomplete hematologic recovery) were 67% in all treated patients, 75% in patients given 2×106 CAR T cells/kg, 64% in patients given 1×106 cells/kg in the 68 mL formulation, and 67% in patients given 1×106 cells/kg in the 40 mL formulation. Overall minimal residual diseasenegativity rates were 100% among responders; 88% of responders underwent subsequent allogeneic stem-cell transplantation. In the 1×106 (40 mL) group (recommended phase II dose), the median duration of remission censored at allogeneic stem-cell transplantation and median overall survival were not reached. Pediatric/adolescent patients with relapsed/refractory B-cell acute lymphoblastic leukemia achieved high minimal residual disease-negative remission rates with a manageable safety profile after a single dose of KTE-X19. Phase II of the study is ongoing at the dose of 1×106 CAR T cells/kg in the 40 mL formulation. ClinicalTrials.gov: NCT02625480.

207 Enhanced antigen capture, antigen-presenting cell (APC)-like function, and cytotoxic responses with chimeric engulfment receptor (CER) T cells

Background

Activated T cells have limited antigen presenting capability due to inefficient capture.1 This process can be enhanced through novel chimeric engulfment receptors (CERs) expressing a human Tim-4 phagocyte receptor that recognizes phosphatidylserine (Ptd-Ser)2 fused to T cell and macrophage/dendritic cell-derived signaling domains. CERs can facilitate antigen capture, processing, and presentation, and impart target-dependent cytotoxic function when expressed in T cells. This combined function is hypothesized to improve tumor clearance and durability of response, making CER T cell products ideal clinical candidates.

Methods

We generated Tim-4 receptors fused to toll-like receptor (TLR)-2 or -8, CD28 or CD3 zeta and tested phagocytic, antigen presentation and cytotoxic function in healthy donor T cells. To assess phagocytosis, target cells treated with a small molecule to induce Ptd-Ser externalization were labeled with pH-Rodo followed by co-culture with CER T cells. Activated CER T cells were evaluated by transmission electron microscopy (TEM) or flow cytometry (FC) for lysosomal uptake of cell fragments. Antigen capture and presentation were characterized by FC for the capacity of human papilloma virus 16 (HPV 16) E7 peptide-pulsed CER T cells to activate and induce proliferation of autologous HPV 16 E7-TCR transduced T cells. Cytotoxic function was evaluated in co-culture assays of CER T cells in the presence of subtherapeutic doses of BTKi (ibrutinib)-treated JeKo-1 lymphoma cells.

Results

TEM imaging demonstrated that CER T cells engulfed target cell fragments, illustrated by multi-vesicular bodies containing tumor fragments (some measuring >0.5 uM) and pseudo-pod like formations around apoptotic target cell blebs. RNA analysis revealed upregulation of TLR, myeloid differentiation, and antigen presentation pathways. In the HPV 16 E7 co-culture model, T-cell surface activation markers CD25 and CD69 were upregulated 41% and 23%, respectively, on E7-TCR-T cells relative to controls. In addition, the percentage of dividing E7-TCR-T cells was increased (44% vs 8%) after 6 days in co-culture. Addition of CER T cells to JeKo- 1 target cells in the presence of BTKi at low effector: target ratios enhanced cytotoxicity by over 99%, demonstrating synergy with a targeted small molecule to fully eliminate lymphoma cells.

Conclusions

Novel Tim-4/TLR containing CERs can capture tumor cell fragments and present soluble antigen, a function previously demonstrated to be a barrier to effective antigen presentation in T cells. Enhanced T-cell antigen capture and presentation capability alongside inducible and target-specific cytotoxic function in single T cells represents a significant advancement in the potential for chimeric receptor-based therapies.

References

Lanzavecchia A, Roosnek E, Gregory T, Berman P, Abrignani S. T cells can present antigens such as HIV gp120 targeted to their own surface molecules. Nature 1988 Aug 11;334(6182):530–2.

Caronni N, Piperno GM, Simoncello F, Romano O, Vodret S, Yanagihashi Y, et al. TIM4 expression by dendritic cells mediates uptake of tumor-associated antigens and anti-tumor responses. Nat Commun 2021 Apr 14;12(1):2237.

KTE-X19 for relapsed or refractory adult B-cell acute lymphoblastic leukaemia: phase 2 results of the single-arm, open-label, multicentre ZUMA-3 study

BACKGROUND

Despite treatment with novel therapies and allogeneic stem-cell transplant (allo-SCT) consolidation, outcomes in adult patients with relapsed or refractory B-precursor acute lymphoblastic leukaemia remain poor, underlining the need for more effective therapies.

METHODS

We report the pivotal phase 2 results of ZUMA-3, an international, multicentre, single-arm, open-label study evaluating the efficacy and safety of the autologous anti-CD19 chimeric antigen receptor (CAR) T-cell therapy KTE-X19 in adult patients with relapsed or refractory B-precursor acute lymphoblastic leukaemia. Patients were enrolled at 25 sites in the USA, Canada, and Europe. Eligible patients were aged 18 years or older, with Eastern Cooperative Oncology Group performance status of 0-1, and morphological disease in the bone marrow (>5% blasts). After leukapheresis and conditioning chemotherapy, patients received a single KTE-X19 infusion (1 × 10⁶ CAR T cells per kg bodyweight). The primary endpoint was the rate of overall complete remission or complete remission with incomplete haematological recovery by central assessment. Duration of remission and relapse-free survival, overall survival, minimal residual disease (MRD) negativity rate, and allo-SCT rate were assessed as secondary endpoints. Efficacy and safety analyses were done in the treated population (all patients who received a dose of KTE-X19). This study is registered with ClinicalTrials.gov, NCT02614066.

FINDINGS

Between Oct 1, 2018, and Oct 9, 2019, 71 patients were enrolled and underwent leukapheresis. KTE-X19 was successfully manufactured for 65 (92%) patients and administered to 55 (77%). The median age of treated patients was 40 years (IQR 28-52). At the median follow-up of 16·4 months (13·8-19·6), 39 patients (71%; 95% CI 57-82, p<0·0001) had complete remission or complete remission with incomplete haematological recovery, with 31 (56%) patients reaching complete remission. Median duration of remission was 12·8 months (95% CI 8·7-not estimable), median relapse-free survival was 11·6 months (2·7-15·5), and median overall survival was 18·2 months (15·9-not estimable). Among responders, the median overall survival was not reached, and 38 (97%) patients had MRD negativity. Ten (18%) patients received allo-SCT consolidation after KTE-X19 infusion. The most common adverse events of grade 3 or higher were anaemia (27 [49%] patients) and pyrexia (20 [36%] patients). 14 (25%) patients had infections of grade 3 or higher. Two grade 5 KTE-X19-related events occurred (brain herniation and septic shock). Cytokine release syndrome of grade 3 or higher occurred in 13 (24%) patients and neurological events of grade 3 or higher occurred in 14 (25%) patients.

INTERPRETATION

KTE-X19 showed a high rate of complete remission or complete remission with incomplete haematological recovery in adult patients with relapsed or refractory B-precursor acute lymphoblastic leukaemia, with the median overall survival not reached in responding patients, and a manageable safety profile. These findings indicate that KTE-X19 has the potential to confer long-term clinical benefit to these patients.

FUNDING

Kite, a Gilead Company.

Abstract CT055: Phase 1/2 primary analysis of ZUMA-6: Axicabtagene ciloleucel (Axi-Cel) in combination With atezolizumab (Atezo) for the treatment of patients (Pts) with refractory diffuse large B cell lymphoma (DLBCL)

Background: Axi-cel is a US and EU-approved autologous anti-CD19 chimeric antigen receptor (CAR) T cell therapy for the treatment of adult relapsed/refractory LBCL after ≥ 2 prior lines of therapy. In ZUMA-1, the objective response rate (ORR) was 83% (58% complete response [CR] rate; Locke et al. Lancet Oncol. 2019). As checkpoint proteins (eg, PD-1, PD-L1) have been shown to be upregulated after CAR T cell infusion (Perez et al. ASH 2015. #2042; Galon et al. ASCO 2017. #3025; Neelapu et al. ASH 2017. #578; Arihara et al. SITC 2019. #P210), ZUMA-6 examined outcomes of axi-cel combined with the anti-PD-L1 antibody atezo (NCT02926833). Methods: Adult pts (≥18 y) with refractory DLBCL who received prior CD20-targeting and anthracycline-containing regimen, had ECOG ≤ 1, and had adequate bone marrow and organ function were eligible. Pts received conditioning (fludarabine 30 mg/m2/d + cyclophosphamide 500 mg/m2/d for 3 days) followed by a targeted 2 × 106 CAR T cells/kg. In Phase 1, atezo was given at 1200 mg every 21 days for 4 doses starting on Day 21, 14, and 1 post-axi-cel infusion for Cohorts 1, 2, and 3, respectively. Given Phase 1 results, pts received the Cohort 3 atezo (Day +1) dosing schedule in Phase 2. The primary endpoint was incidence of dose-limiting toxicities for Phase 1 and CR rate for Phase 2. Secondary endpoints included adverse events (AEs), response, and CAR T cell levels. Pooled data are reported for Phase 1 Cohort 3 and Phase 2 pts. Results: As of 2/21/19, 28 pts received axi-cel and ≥ 1 atezo dose; 18/28 pts received all 4 atezo doses. Median age was 58 y (range, 42 - 71). Most pts (86%) had received ≥ 2 prior therapies (4 had primary refractory disease), and 46% had an IPI score of 3 or 4. All pts experienced ≥ 1 AE (86% Grade [Gr] ≥ 3). There was 1 Gr 5 AE of multiple organ dysfunction syndrome unrelated to axi-cel or atezo. Gr ≥ 3 CRS occurred in 4% of pts, and Gr ≥ 3 neurologic events (NEs) occurred in 29%. With a median follow-up of 10.2 mo, the best ORR was 75% (46% CR rate); 46% of pts were in ongoing response. Median DOR, PFS, and OS were not reached; KM estimated 6-mo rates were 62%, 50%, and 71%, respectively. Median peak CAR T cell levels were similar in ZUMA-6 and ZUMA-1 (ZUMA-6: 37 cells/µL [range, 0.07 - 196]; ZUMA-1: 32 cells/µL [range, 1 - 1513]). Median CAR T cell expansion as measured by area under the curve in the first 28 days was also similar (ZUMA-6: 497 cells/µL × days [range, 0.002 - 2222]; ZUMA-1: 357 cells/µL × days [range, 5 - 11,507]). Levels of key cytokines, including those related to CRS and/or NEs, will be presented. Conclusions: PD-L1 blockade with atezo after axi-cel has a manageable safety profile, consistent with that observed in ZUMA-1, with no significant evidence of increased incidence of AEs. Efficacy outcomes and CAR T cell level results of axi-cel combined with atezo were similar to those of pts treated with axi-cel alone.

Citation Format: Caron A. Jacobson, Jason R. Westin, David B. Miklos, Alex F. Herrera, Jennifer Lee, Judy Seng, John M. Rossi, Jennifer Sun, Jinghui Dong, Zachary J. Roberts, Remus Vezan, Mauro P. Avanzi, Frederick L. Locke. Phase 1/2 primary analysis of ZUMA-6: Axicabtagene ciloleucel (Axi-Cel) in combination With atezolizumab (Atezo) for the treatment of patients (Pts) with refractory diffuse large B cell lymphoma (DLBCL) [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr CT055.

End of phase I results of ZUMA-3, a phase 1/2 study of KTE-X19, anti-CD19 chimeric antigen receptor (CAR) T cell therapy, in adult patients (pts) with relapsed/refractory (R/R) acute lymphoblastic leukemia (ALL)

7006

Background: KTE-X19 is an autologous anti-CD19 CAR T cell therapy under investigation for adult R/R ALL. In an interim analysis of Phase 1 of ZUMA-3, we reported manageable safety and encouraging efficacy of KTE-X19; 72% of pts achieved a complete remission (CR) or CR with incomplete bone marrow (BM) recovery (CRi; Wierda et al, ASH 2018. #897). Here, we present end of Phase 1 results. Methods: Adults with R/R B cell ALL, > 5% BM blasts, and ECOG 0-1 received 2, 1, or 0.5 × 106 KTE-X19 cells/kg after conditioning chemotherapy. Revised adverse event management (rAE mgmt) was implemented for additional pts in a 1 × 106 dose cohort: corticosteroids were given earlier at onset of Grade ≥ 2 neurologic events (NEs) and tocilizumab was used only for active toxicity. The primary endpoint was the dose-limiting toxicity (DLT) rate. Key additional endpoints were KTE-X19 levels, incidence of AEs, minimal residual disease (MRD), and CR/CRi rate. Results: As of 9/27/18, 45 pts had received KTE-X19 (median follow-up [f/u], 16 mo). The median age was 46 y (range, 18–77); 30 pts (66%) had ≥ 3 prior therapies and the median pre-conditioning BM blasts was 70% (range, 0–97). Six, 23, and 16 pts received 2, 1, and 0.5 × 106 cells/kg, respectively. There were no DLTs in the DLT-evaluable pts. The most common Grade ≥ 3 AEs were hypotension (38%), pyrexia (38%) and thrombocytopenia (31%). There were 2 previously reported KTE-X19–related Grade 5 AEs of cerebral infarction and multiorgan failure, both in the context of CRS. Grade ≥ 3 CRS and NEs occurred in 13 (29%) and 17 (38%) pts, respectively. Of 41 pts with ≥ 2 mo of f/u, 68% had CR/CRi, and 73% had undetectable MRD. Of 19 pts with ≥ 2 mo of f/u treated with 1 × 106 cells/kg, 16 (84%) had a CR/CRi and the median event-free survival was 15 mo. In 9 pts treated with 1 × 106 cells/kg and rAE mgmt, 2 (22%) had Grade 3 CRS and 1 (11%) had Grade 3 NE with no Grade 4/5 events. Conclusions: KTE-X19 dosing and safety mgmt have been successfully refined by testing 3 cell doses and evaluating a new AE mgmt guideline with altered corticosteroids/tocilizumab use for NE/CRS. Pivotal Phase 2 is ongoing at the 1 × 106 dose with rAE mgmt. Clinical trial information: NCT02614066.

Long-term follow-up of the RESONATE phase 3 trial of ibrutinib vs ofatumumab

Ibrutinib, a once-daily oral inhibitor of Bruton tyrosine kinase, has greatly improved outcomes for patients with chronic lymphocytic leukemia (CLL). The phase 3 RESONATE trial, which compared single-agent ibrutinib to ofatumumab in high-risk, relapsed patients with CLL, provided support for approval of ibrutinib in the United States and Europe. We describe long-term follow-up of patients treated in RESONATE, where continued superiority of progression-free survival (PFS) (hazard ratio [HR], 0.133; 95% confidence interval [CI], 0.099-0.178) was observed. Overall survival benefit continues (HR, 0.591; 95% CI, 0.378-0.926), although with decreased magnitude relative to that seen before crossover to ibrutinib was implemented for patients on ofatumumab (HR, 0.426; 95% CI, 0.220-0.823). Notably, overall response to ibrutinib increased over time, with 91% of patients attaining a response. The PFS benefit with ibrutinib was independent of baseline risk factors, although patients with ≥2 prior therapies had shorter PFS than those with <2 prior therapies, and the presence of TP53 or SF3B1 mutations showed a trend toward shorter PFS vs without these factors. Median duration of ibrutinib was 41 months, with 46% remaining on treatment at a median follow-up of 44 months. Grade ≥3 adverse events generally decreased over time, causing only a small proportion of patients to cease therapy. Ibrutinib was discontinued due to progressive disease in 27% of patients. This long-term study provides support for sustained efficacy and safety of ibrutinib in relapsed/refractory CLL and consideration of study provisions that allow crossover to investigational therapy when benefit has been clearly demonstrated. This trial was registered at www.clinicaltrials.gov as #NCT01578707.

ACCELERATE and European Medicine Agency Paediatric Strategy Forum for medicinal product development for mature B-cell malignancies in children

Paediatric Strategy Forums have been created by the multistakeholder organisation, ACCELERATE, and the European Medicines Agency to facilitate dialogue between all relevant stakeholders and suggest strategies in critical areas of paediatric oncology drug development. As there are many medicines being developed for B-cell malignancies in adults but comparatively few in children with these malignancies, a Paediatric Strategy Forum was held to discuss the best approach to develop these products for children. It was concluded that as current frontline therapy is highly successful, despite associated acute toxicity, de-escalation of this or substitution of presently used drugs with new medicines can only be undertaken when there is an effective salvage regimen, which is currently not available. Therefore priority should be given to developing treatment for patients with relapsed and refractory mature B-cell lymphomas. The consensus of the clinicians attending the meeting was that CAR T-cells, T-cell engagers and antibody drug conjugates (excluding those with a vinca alkaloid-like drug) presently have the greatest probability of providing benefit in relapse in view of their mechanism of action. However, as producing autologous CAR T-cells currently takes at least 4 weeks, they are not products which could be quickly employed initially at relapse in rapidly progressing mature B-cell malignancies but only for the consolidation phase of the treatment. Global, industry-supported, academic-sponsored studies testing compounds from different pharmaceutical companies simultaneously should be considered in rare populations, and it was proposed that an international working group be formed to develop an overarching clinical trials strategy for these disease groups. Future Forums are planned for other relevant paediatric oncologic diseases with a high unmet medical need and relevant molecular targets.

Safety and efficacy of abexinostat, a pan-histone deacetylase inhibitor, in non-Hodgkin lymphoma and chronic lymphocytic leukemia: results of a phase II study

Histone deacetylase inhibitors are members of a class of epigenetic drugs that have proven activity in T-cell malignancies, but little is known about their efficacy in B-cell lymphomas. Abexinostat is an orally available hydroxamate-containing histone deacetylase inhibitor that differs from approved inhibitors; its unique pharmacokinetic profile and oral dosing schedule, twice daily four hours apart, allows for continuous exposure at concentrations required to efficiently kill tumor cells. In this phase II study, patients with relapsed/refractory non-Hodgkin lymphoma or chronic lymphocytic leukemia received oral abexinostat at 80 mg BID for 14 days of a 21-day cycle and continued until progressive disease or unacceptable toxicity. A total of 100 patients with B-cell malignancies and T-cell lymphomas were enrolled between October 2011 and July 2014. All patients received at least one dose of study drug. Primary reasons for discontinuation included progressive disease (56%) and adverse events (25%). Grade 3 or over adverse events and any serious adverse events were reported in 88% and 73% of patients, respectively. The most frequently reported grade 3 or over treatment-emergent related adverse events were thrombocytopenia (80%), neutropenia (27%), and anemia (12%). Among the 87 patients evaluable for efficacy, overall response rate was 28% (complete response 5%), with highest responses observed in patients with follicular lymphoma (overall response rate 56%), T-cell lymphoma (overall response rate 40%), and diffuse large B-cell lymphoma (overall response rate 31%). Further investigation of the safety and efficacy of abexinostat in follicular lymphoma, T-cell lymphoma, and diffuse large B-cell lymphoma implementing a less dose-intense week-on-week-off schedule is warranted. (Trial registered at: EudraCT-2009-013691-47)

A phase 1 dose-escalation study of the oral histone deacetylase inhibitor abexinostat in combination with standard hypofractionated radiotherapy in advanced solid tumors

Current treatments for advanced solid tumors tend to be only palliative. Although radiotherapy is administered with a curative intent, radioresistance and dose-limiting toxicities pose limitations to treatment. Abexinostat, an oral pan-histone deacetylase inhibitor, demonstrated enhanced sensitivity to radiation in various solid tumor cell lines. We conducted an exploratory, phase 1, dose-escalation study of abexinostat in combination with standard hypofractionated radiotherapy in patients with advanced solid tumors treated in a palliative setting. Among 58 treated patients, the median age was 61.5 years (range, 20-82); 47% of the patients had M1 stage disease, and 95% had received previous chemotherapy alone or chemotherapy in combination with surgery and/or radiotherapy. The recommended phase 2 dose was determined to be 90 mg/m² (140 mg). Of the 51 patients evaluable for response, best overall response was 8% (1 complete response [CR], 3 partial responses [PRs]), and best loco-regional response was 12% (1 CR and 5 PRs) at a median follow-up of 16 weeks. Of note, patients with target or non-target brain lesions showed encouraging responses, with 1 patient achieving a best loco-regional response of CR. Treatment-emergent grade ≥3 adverse events (AEs) were few, with most common being thrombocytopenia (17%), lymphopenia (12%), and hypokalemia (7%). Six patients (10%) discontinued treatment due to AEs. No grade ≥3 prolongation of the QTc interval was observed, with no treatment discontinuations due to this AE. Oral abexinostat combined with radiotherapy was well tolerated in patients with advanced solid tumors. The combination may have potential for treatment of patients with brain lesions.

Phase 1 dose-escalation study of oral abexinostat for the treatment of patients with relapsed/refractory higher-risk myelodysplastic syndromes, acute myeloid leukemia, or acute lymphoblastic leukemia

Histone deacetylase (HDAC) inhibitor abexinostat is under investigation for the treatment of various cancers. Epigenetic changes including aberrant HDAC activity are associated with cancers, including myelodysplastic syndromes (MDS), acute myeloid leukemia (AML), and acute lymphoblastic leukemia (ALL). In this phase 1 dose-escalation study, 17 patients with relapsed/refractory higher-risk MDS, AML, or ALL received oral abexinostat (60, 80 [starting dose], 100, or 120 mg) twice daily (bid) on Days 1-14 of 21-day cycles. The most common treatment-related grade ≥3 adverse events were thrombocytopenia (29%) and neutropenia (24%), none of which led to discontinuation. Maximum-tolerated dose was not reached. Of 12 evaluable patients, best response was stable disease in 1 patient. This study was closed due to limited clinical benefit. Future development of oral abexinostat 100 mg bid in patients with MDS, AML, or ALL should focus on combination regimens. ISRCTN registry: 99680465.