ACALABRUTINIB-CONTAINING REGIMENS SUPERIOR FOR CLL TREATMENT
ELEVATE TN: Phase 3 Study of Acalabrutinib Combined with Obinutuzumab (O) or Alone Vs O Plus Chlorambucil (Clb) in Patients (Pts) with Treatment-Naive Chronic Lymphocytic Leukemia (CLL)
Jeff P. Sharman, MD (Willamette Valley Cancer Institute and Research Center & US Oncology, Eugene OR) discussed a phase 3 study comparing three treatments in patients with treatment-naïve chronic lymphocytic leukemia: acalabrutinib + obinutuzumab (Aca+O), acalabrutinib alone (Aca), or obinutuzumab + chlorambucil (O+C). The primary endpoint of this study was independent review committee-assessed progression free survival (PFS) with Aca+O vs. O+C, while secondary goals included PFS between Aca and O+C, overall response rates (ORR), overall survival (OS), and safety of the treatments.
Outcomes were improved for patients receiving Aca+O compared to O+C, with median PFS not reached in the Aca+O arm, and 22.6 mo in the O+C arm after a median follow-up of 28 months. Across all groups, estimated 24-month PFS rates were 93%, 87%, and 47% for Aca+O, Aca, and O+C, respectively, and the median OS was not reached in any arm of the study. Patients receiving Aca-containing regimens also remained on-treatment for a longer period of time: for both Aca+O and Aca alone, the median treatment duration was 27.7 mo compared to 5.6 mo on O+C. The safety profile was similar across both Aca-containing treatments, with adverse events of interest including any-grade atrial fibrillation and hypertension or grade 3+ bleeding occurring in less than 5% of patients. Overall, Aca-containing regimens significantly improved outcomes over the obinutuzumab + chlorambucil treatment for treatment-naïve chronic lymphocytic leukemia, meriting further investigation.
DENSITY OF CAR MOLECULES IMPACTS TOXICITY AND EFFICACY
Surface Density of CAR Molecules May Modulate the Kinetics of CAR-T Cells In Vivo
Two promoters for CAR-T gene expression were compared in preclinical and clinical studies presented by Jianqiang Li, PhD (Hebei Senlang Biotechnology, Shijiazhuang, China), as the expression levels of CAR molecules have been reported to impact the efficacy and toxicity of CAR-T therapies. One construct (1904A) employed the commonly-used EF1-alpha promoter, while the other (1904B) utilized the myeloproliferative sarcoma virus enhancer, with the negative control region deleted and the dl587 Rev-binding site substituted, known as the MND promoter.
The 1904A construct was found to have a higher expression of the CD19 CAR by flow cytometry over the 1904B cells. In cell culture, this led to higher cytotoxicity and cytokine release by the 1904A cells. In preclinical Raji-luciferase murine models, however, the 1904B cells displayed greater tumor growth inhibition, although both CAR therapies increased survival of mice over the control treatment. In a clinical study comparing the two treatments in patients with relapsed/refractory B-ALL, six patients received 1904A and eight were treated with 1904B. Complete responses were observed in five of the 1904A patients and all eight of those receiving 1904B, with one CD19-negative relapse in the 1904B arm. Altogether, these studies indicated that a lower surface expression of CAR molecules may decrease the intensity of CAR-T cell activation in vivo, resulting in potentially lowered toxicity and prolonged anti-cancer activity.
NK CELL THERAPY REDUCES CD38-RELATED FRATRICIDE AND ENHANCES THERAPEUTIC EFFICACY
FT538: Preclinical Development of an Off-the-Shelf Adoptive NK Cell Immunotherapy with Targeted Disruption of CD38 to Prevent Anti-CD38 Antibody-Mediated Fratricide and Enhance ADCC in Multiple Myeloma When Combined with Daratumumab
In order to enhance the efficacy of daratumumab in treating multiple myeloma, Ryan Bjordahl, PhD (Fate Therapeutics, San Diego CA) and co-workers developed a strategy to mitigate antibody-dependent cellular cytotoxicity (ADCC)-mediated natural killer (NK) cell fratricide. Since daratumumab targets CD38, found on both myeloma and NK cells, NK cells are often depleted and treatment efficacy is reduced. The team circumvented this issue through adoptive cellular therapy with FT538 NK cells engineered to lack CD38 expression and to express an IL-15 receptor alpha fusion protein (IL-15RF) and a high-affinity non-cleavable CD16 (hnCD16), to increase persistence and ADCC, respectively.
An engineered induced pluripotent stem cell line was created to enable cGMP manufacturing and development, which, upon differentiation and expansion, demonstrated a mature NK cell phenotype. In an in vitro fratricide assay, the engineered CD38-knockout NK cells demonstrated increased resistance, with minimal loss of engineered cells compared to a high level fratricide in peripheral blood-derived NK cells incubated with daratumumab. This CD38-mediated fratricide also resulted in reduced cytotoxicity toward myeloma cells in cytotoxic re-stimulation assays by naïve NK cells (~15% loss of activity after re-stimulation), while the combination of FT538 and daratumumab exhibited a 20-fold increase in viable NK cells over the controls and subsequently enhanced cancer cell killing. The improved persistence and ADCC provided by the IL-15RF and hnCD16 modifications also improved cancer cell cytotoxicity. Therefore, this off-the-shelf NK therapy may enhance treatment outcomes for multiple myeloma patients in the future.
DUAL-TARGETING MAY ENHANCE CAR THERAPY OF MULTIPLE MYELOMA
Optimal Dual-Targeted CAR Construct Simultaneously Targeting Bcma and GPRC5D Prevents Bcma-Escape Driven Relapse in Multiple Myeloma
To prevent BCMA-negative multiple myeloma relapse, Carlos Fernandez de Larrea, MD, PhD (University of Barcelona, Barcelona, Spain) and colleagues designed dual-targeted CAR T cell therapies, binding both BCMA and the G protein-coupled receptor class C group 5 member D (GPRC5D). The investigators compared several production approaches: two parallel strategies, developing individual BCMA- and GPRC5D-targeted CAR cells for dual transduction, and three single-vector targeting approaches with both CAR molecules expressed by a single engineered cell. Of these three single-vector approaches, two were bicistronic vectors varying in their costimulatory domain downstream of the GPRC5D-targeting element and one was a tandem vector. To maximize clinical utility, all five approaches utilized the BCMA(125)/4-1BB CAR (BCMA scFv 125; Smith EL. Mol Ther 2018), which is currently under multi-center clinical investigation.
All five dual-targeted therapies were able to successfully control BCMA+GPRC5D+ multiple myeloma in mouse models at high adoptive cellular doses. Mice were then re-challenged with BCMA knockout myeloma cells, and only those mice initially treated with a dual-targeted construct, but not with a BCMA mono-targeted CAR, were resistant to re-challenge. When a combination of both wild type and BCMA knockout myeloma cells were engrafted in mice, differences in the therapeutic efficacy across the dual-targeted constructs were observed. Those GPRC5D-targeting CARs with CD28 costimulation were unable to eradicate the disease, hypothesized to result from greater activation-induced cell death in these CAR cells. Therefore, the 4-1BB approaches were compared, with the highest efficacy measured with the bicistronic dual 4-1BB design. This dual-targeted bicistronic CAR T cell approach may represent a novel treatment option for multiple myeloma as a result.
ANTI-CD5 CAR T CELLS SHOW PROMISE IN T CELL MALIGNANCIES
Safety and Anti-Tumor Activity of CD5 CAR T-Cells in Patients with Relapsed/Refractory T-Cell Malignancies
LaQuisa C. Hill, MD (Houston Methodist Hospital, Houston TX) presented a phase I dose escalation study of a CD5 CAR T cell construct in patients with T cell malignancies. The CAR construct, developed from autologous PBMCs, contains a CD28 costimulatory domain and displayed minimal fratricide of CD5-expressing normal T cells.
Eleven patients were treated to date, at dose levels of 1x107 CAR T cells/m2 and 5x107 CAR T cells/m2, and peak expansion was noted from 1-4 weeks post-infusion. After the pre-treatment conditioning and CAR infusion, a transient decrease was noted in peripheral blood CD3+ cells, suggesting minimal and limited fratricide. Cytokine release syndrome of grade 1-2 occurred in four patients and responded to management. Four patients exhibited an objective response, including three patients with the higher dose of CAR cells, and three of these were complete responses. The other responding patient was classified as a mixed response due to the appearance of a new lesion; however, after a second administration of CD5 CAR T cells, this patient remained in complete response at nine months post-HSCT. CD5 CAR T cell therapy therefore represents a promising option for management of heavily pretreated T cell malignancies.
CYTOKINE INDUCED KILLER CELLS TESTED IN B-ALL
Donor-Derived CD19 CAR Cytokine Induced Killer (CIK) Cells Engineered with Sleeping Beauty Transposon for Relapsed B-Cell Acute Lymphoblastic Leukemia (B-ALL)
To create an allogeneic adoptive cellular therapy, Chiara F. Magnani (University of Milano-Bicoc, Monza, Italy) and co-workers developed a cytokine induced killer T cell therapy, engineered by the non-viral Sleeping Beauty transposon. The donor cells were also engineered with the CD19.CAR/pTMNDU3 plasmid to enable CD19 targeting. This dose-escalation study aimed to evaluate the maximum tolerated dose and safety of the therapy, known as CARCIK-CD19.
Following successful manufacturing of 17/19 batches of CAR cells, four pediatric and nine adult patients have been treated with a single dose of the CARCIK-CD19 cells. Adverse events of note resulting from the therapy included a grade 1 and a grade 2 cytokine release syndrome and an infusion-related DMSO-associated seizure. No dose-limiting toxicities were observed. Most patients displayed expansion of the cells in vivo, with the magnitude of expansion related to the CD19+ disease burden extent. The cells persisted for a mean of 70 days as well. Together, these findings translated to a CR/CRi for 8/10 patients treated with doses of at least 3x106 cells/kg, with six of these patients also MRD-negative. As the cellular therapy demonstrated encouraging results in this initial study, the authors plan to expand the investigation.
GVHD INCIDENCE REDUCED THROUGH CD83 CAR T THERAPY
Human CD83 Targeted Chimeric Antigen Receptor T Cell for the Prevention of Graft Versus Host Disease and Treatment of Myeloid Leukemia
Bishwas Shrestha, PhD (Moffitt Cancer Center and Research Institute, Tampa FL) presented an investigation of a CD83-targeted CAR T construct, utilized to prevent graft-versus-host disease (GVHD) and also target CD83-expressing acute myeloid leukemia. CD83 is found on allo-activated conventional T cells, as well as on pro-inflammatory dendritic cells; therefore, prophylactic elimination of these cells may provide protection from GVHD.
To test this hypothesis, allogeneic mixed leukocyte reactions were employed. By mixing autologous T cells and allogeneic monocyte-derived dendritic cells at various ratios and adding in the CD83 CAR T cells, it was determined that the CD83 CARs were able to efficiently reduce alloreactive T cell proliferation. This also resulted in depletion of both CD83+ conventional T cells and pro-inflammatory dendritic cells within two days. A murine model was also investigated, wherein mice were administered human PBMCs and the autologous CD83 CAR or mock transduced T cells. Consistent with in vitro studies, mice treated with the CD83 CAR cells demonstrated prolonged survival compared to the mock-transduced constructs, and also displayed far less GVHD target organ damage and a higher ratio of regulatory to alloreactive T cells. A similar study wherein the CAR cells were administered after the onset of GVHD demonstrated effective remediation of the disease as well. In another set of studies, the CD83 CAR T cells were also able to eradicate acute myeloid leukemia cell lines, as they also express CD83. These studies point to the potential of engineered immune cells not only for treating cancer, but also for controlling toxicities resulting from other therapies.
POSSIBLE SYNERGY WITH GAMMA SECRETASE INHIBITOR AND BCMA CAR T CELLS
Efficacy and Safety of Fully Human Bcma CAR T Cells in Combination with a Gamma Secretase Inhibitor to Increase Bcma Surface Expression in Patients with Relapsed or Refractory Multiple Myeloma
In order to improve outcomes for patients with multiple myeloma on BCMA-targeted CAR T cell therapy, Andrew J. Cowan, MD (University of Washington and Fred Hutchinson Cancer Research Center, Seattle WA) and colleagues conducted a first-in-human study combining a BCMA CAR T therapy with an oral gamma secretase inhibitor (GSI, specifically JSMD194). BCMA is regularly cleaved from the cell surface and GSIs have been shown to inhibit this process, the addition of JSMD194 lead to a 20-fold median increase in BCMA surface density on cancer cells, this combination approach may reduce BCMA-negative myeloma relapses by eliminating resistant cells.
Patients were first treated with a “run-in” regimen of three doses of JSMD194, after which the percentage of plasma cells expressing BCMA increased from 75% to 99%, while soluble BCMA decreased by a factor of two. After the run-in doses and lymphodepletion, BCMA CAR T cells were administered along with JSMD194. Of the ten evaluable patients, all experienced a response, including five VGPRs, 2 PRs, 1 CR, and 2 sCRs. None of the patients relapsed after the treatment to date; however, one patient did develop cytokine release syndrome and concurrent fungal infection, resulting in death. Most patients experienced some grade of cytokine release syndrome (100%) and/or neurotoxicity (70%). While the follow-up of these patients is rather short, at 20 weeks, and high incidences of adverse events were noted, the fact that all treated patients responded to this combination treatment strategy warrants continued investigation.
LISO-CELL DEMONSTRATES SIMILAR EFFICACY, ENHANCED SAFETY FOR R/R DLBCL
Pivotal Safety and Efficacy Results from Transcend NHL 001, a Multicenter Phase 1 Study of Lisocabtagene Maraleucel (liso-cel) in Relapsed/Refractory (R/R) Large B Cell Lymphomas
A long-term follow-up of patients with diffuse large B cell lymphoma treated with lisocabtagene maraleucel (liso-cel) was presented by Jeremy S. Abramson, MD, MMSc (Massachusetts General Hospital Cancer Center, Boston MA). Patients received doses of the anti-CD19 CAR T treatment ranging from 50x106 to 150x106 viable CAR+ T cells and were followed to evaluate the primary endpoints of treatment-emergent adverse events (TEAEs) and overall response rate.
Outcomes were similar across all CAR dose groups, so results were pooled. A total of 269 heavily pre-treated patients received liso-cel therapy, and 79% of these patients experienced any TEAE of grade 3 or greater. Any-grade cytokine release syndrome occurred in 42% of patients, with only 2% of grade 3 or higher, while neurologic events were observed in 30% (10% grade 3+). Four grade 5 events related to the therapy occurred, not related to CRS or NE. The overall response rate in evaluable patients was 73% with a 53% complete response rate as well. For those patients experiencing a CR the duration of response was not reached, while for those with a PR the DOR was 1.9 months. The progression-free survival of patients on liso-cel (overall at 6.8 months) was notably longer than the patients’ PFS on their immediate prior therapy, indicating a clinical benefit of this treatment. Overall, the response rates with liso-cel were comparable to other CAR T therapies on the market, with a lower incidence of CRS and neurotoxicity, indicating a potential safety benefit with this agent.
TARGETING CD19 AND CD22 MAY BENEFIT R/R DLBCL
Phase 1/2 Study of AUTO3 the First Bicistronic Chimeric Antigen Receptor (CAR) Targeting CD19 and CD22 Followed By an Anti-PD1 in Patients with Relapsed/Refractory (r/r) Diffuse Large B Cell Lymphoma (DLBCL): Results of Cohort 1 and 2 of the Alexander Study
Kirit M. Ardeshna, MBBChir (University College London Hospital NHS Foundation Trust, London, UK) presented a phase 1/2 study of a CD19- and CD22-targeted CAR T construct combined with pembrolizumab to treat diffuse large B cell lymphomas. A novel bicistronic retroviral vector was employed to develop the CAR cells, incorporating an OX40 co-stimulatory domain with the CD19 CAR and the CD22 CAR in combination with a 4-1BB domain. The goal of the combination treatment was to prevent relapses due to CD19 antigen loss or PD-L1 upregulation, with this initial study evaluating the safety of the treatment.
As of data cut-off, sixteen patients had been treated with the CAR construct, known as AUTO3. Four of these patients received AUTO3 alone, and the remaining twelve also were administered pembrolizumab after CAR infusion. After a minimum of FOUR weeks follow-up, no dose-limiting toxicities or deaths had occurred. Notable high-grade (3+) toxicities emergent on-treatment included neutropenia, thrombocytopenia, anemia, and infection; at the same time, no cytokine release syndromes greater than grade 1 were observed. Among patients receiving a lower dose of AUTO3, 4/7 patients experienced a PR or CR. At the higher dose levels (150 or 450x106 cells), 3 patients had a CR and another one had a PR. Given the relative safety and promising efficacy of this treatment, the investigators continue to enroll patients at higher dose levels.