T cell lymphoma and secondary primary malignancy risk after commercial CAR T cell therapy

We report a T cell lymphoma (TCL) occurring 3 months after anti-CD19 chimeric antigen receptor (CAR) T cell immunotherapy for non-Hodgkin B cell lymphoma. The TCL was diagnosed from a thoracic lymph node upon surgery for lung cancer. The TCL exhibited CD8+ cytotoxic phenotype and a JAK3 variant, while the CAR transgene was very low. The T cell clone was identified at low levels in the blood before CAR T infusion and in lung cancer. To assess the overall risk of secondary primary malignancy after commercial CAR T (CD19, BCMA), we analyzed 449 patients treated at the University of Pennsylvania. At a median follow-up of 10.3 months, 16 patients (3.6%) had a secondary primary malignancy. The median onset time was 26.4 and 9.7 months for solid and hematological malignancies, respectively. The projected 5-year cumulative incidence is 15.2% for solid and 2.3% for hematological malignancies. Overall, one case of TCL was observed, suggesting a low risk of TCL after CAR T.

Melanoma Brain Metastases in the Era of Target Therapies: An Overview

Malignant melanoma is the third most common type of tumor that causes brain metastases. Patients with cerebral involvement have a dismal prognosis and their treatment is an unmet medical need. Brain involvement is a multistep process involving several signaling pathways such as Janus kinase/signal Transducer and Activator of Transcription (JAK/STAT), Phosphoinositide 3-kinase/Protein Kinase B (PI3K/AKT), Vascular Endothelial Growth Factor and Phosphatase and Tensin Homolog (PTEN). Recently therapy that targets the MAPK signaling (BRAF/MEK inhibitors) and immunotherapy (anti-CTLA4 and anti-PD1 agents) have changed the therapeutic approaches to stage IV melanoma. In contrast, there are no solid data about patients with brain metastases, who are usually excluded from clinical trials. Retrospective data showed that BRAF-inhibitors, alone or in combination with MEK-inhibitors have interesting clinical activity in this setting. Prospective data about the combinations of BRAF/MEK inhibitors have been recently published, showing an improved overall response rate. Short intracranial disease control is still a challenge. Several attempts have been made in order to improve it with combinations between local and systemic therapies. Immunotherapy approaches seem to retain promising activity in the treatment of melanoma brain metastasis as showed by the results of clinical trials investigating the combination of anti-CTL4 (Ipilimumab) and anti-PD1(Nivolumab). Studies about the combination or the sequential approach of target therapy and immunotherapy are ongoing, with immature results. Several clinical trials are ongoing trying to explore new approaches in order to overcome tumor resistance. At this moment the correct therapeutic choices for melanoma with intracranial involvement is still a challenge and new strategies are needed.

Alternative splicing of its 5'-UTR limits CD20 mRNA translation and enables resistance to CD20-directed immunotherapies

Aberrant skipping of coding exons in CD19 and CD22 compromises the response to immunotherapy in B-cell malignancies. Here, we showed that the MS4A1 gene encoding human CD20 also produces several messenger RNA (mRNA) isoforms with distinct 5' untranslated regions. Four variants (V1-4) were detected using RNA sequencing (RNA-seq) at distinct stages of normal B-cell differentiation and B-lymphoid malignancies, with V1 and V3 being the most abundant. During B-cell activation and Epstein-Barr virus infection, redirection of splicing from V1 to V3 coincided with increased CD20 positivity. Similarly, in diffuse large B-cell lymphoma, only V3, but not V1, correlated with CD20 protein levels, suggesting that V1 might be translation-deficient. Indeed, the longer V1 isoform contained upstream open reading frames and a stem-loop structure, which cooperatively inhibited polysome recruitment. By modulating CD20 isoforms with splice-switching morpholino oligomers, we enhanced CD20 expression and anti-CD20 antibody rituximab-mediated cytotoxicity in a panel of B-cell lines. Furthermore, reconstitution of CD20-knockout cells with V3 mRNA led to the recovery of CD20 positivity, whereas V1-reconstituted cells had undetectable levels of CD20 protein. Surprisingly, in vitro CD20-directed chimeric antigen receptor T cells were able to kill both V3- and V1-expressing cells, but the bispecific T-cell engager mosunetuzumab was only effective against V3-expressing cells. To determine whether CD20 splicing is involved in immunotherapy resistance, we performed RNA-seq on 4 postmosunetuzumab follicular lymphoma relapses and discovered that in 2 of them, the downregulation of CD20 was accompanied by a V3-to-V1 shift. Thus, splicing-mediated mechanisms of epitope loss extend to CD20-directed immunotherapies.

High BRAF variant allele frequencies are associated with distinct pathological features and responsiveness to target therapy in melanoma patients

Background

BRAF mutant melanoma patients are commonly treated with anti-BRAF therapeutic strategies. However, many factors, including the percentage of BRAF-mutated cells, may contribute to the great variability in patient outcomes.

Patients and methods

The BRAF variant allele frequency (VAF; defined as the percentage of mutated alleles) of primary and secondary melanoma lesions, obtained from 327 patients with different disease stages, was assessed by pyrosequencing. The BRAF mutation rate and VAF were then correlated with melanoma pathological features and patients’ clinical characteristics. Kaplan–Meier curves were used to study the correlations between BRAF VAF, overall survival (OS), and progression-free survival (PFS) in a subset of 62 patients treated by anti-BRAF/anti-MEK therapy after metastatic progression.

Results

A highly heterogeneous BRAF VAF was identified (3%-90%). Besides being correlated with age, a higher BRAF VAF level was related to moderate lymphocytic infiltration (P = 0.017), to melanoma thickness according to Clark levels, (level V versus III, P = 0.004; level V versus IV, P = 0.04), to lymph node metastases rather than cutaneous (P = 0.04) or visceral (P = 0.03) secondary lesions. In particular, a BRAF VAF >25% was significantly associated with a favorable outcome in patients treated with the combination of anti-BRAF/anti-MEK drug (OS P = 0.04; PFS P = 0.019), retaining a significant value as an independent factor for the OS and the PFS in the multivariate analysis (P = 0.014 and P = 0.003, respectively).

Conclusion

These results definitively support the role of the BRAF VAF as a potential prognostic and predictive biomarker in melanoma patients in the context of BRAF inhibition.

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In melanoma the response to anti-BRAF targeted therapies is heterogeneous and influenced by several features.

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The role of the BRAF VAF as provider of sensitivity to target therapies is debated.

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We found that high BRAF VAFs are associated with patient age, melanoma thickness, non-brisk TILs and lymph node metastases.

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We proved the independent prognostic value of high BRAF VAFs in melanoma patients treated with targeted therapies.

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The quantitative evaluation of BRAF mutations allows stratifying melanoma patients to the BRAF/MEK targeted treatment.

Current Controversies and Challenges on BRAF V600K-Mutant Cutaneous Melanoma

About 50% of melanomas harbour a BRAF mutation. Of these 50%, 10% have a V600K mutation. Although it is the second most common driver mutation after V600E, no specific studies have been conducted to identify a clinical and therapeutic gold standard for this patient subgroup. We analysed articles, including registrative clinical trials, to identify common clinical and biological traits of the V600K melanoma population, including different adopted therapeutic strategies. Melanoma V600K seems to be more frequent in Caucasian, male and elderly populations with a history of chronic sun damage and exposure. Prognosis is poor and no specific prognostic factor has been identified. Recent findings have underlined how melanoma V600K seems to be less dependent on the ERK/MAPK pathway, with a higher expression of PI3KB and a strong inhibition of multiple antiapoptotic pathways. Both target therapy with BRAF inhibitors + MEK inhibitors and immunotherapy with anti-checkpoint blockades are effective in melanoma V600K, although no sufficient evidence can currently support a formal recommendation for first line treatment choice in IIIC unresectable/IV stage patients. Still, melanoma V600K represents an unmet medical need and a marker of poor prognosis for cutaneous melanoma.

Alternative splicing of its 5'-UTR limits CD20 mRNA translation and enables resistance to CD20-directed immunotherapies

Aberrant skipping of coding exons in CD19 and CD22 compromises responses to immunotherapy for B-cell malignancies. Here, we show that the MS4A1 gene encoding human CD20 also produces several mRNA isoforms with distinct 5' untranslated regions (5'-UTR). Four variants (V1-4) were detectable by RNA-seq in distinct stages of normal B-cell differentiation and B-lymphoid malignancies, with V1 and V3 being the most abundant by far. During B-cell activation and Epstein-Barr virus infection, redirection of splicing from V1 to V3 coincided with increased CD20 positivity. Similarly, in diffuse large B-cell lymphoma only V3, but not V1, correlated with CD20 protein levels, suggesting that V1 might be translation-deficient. Indeed, the longer V1 isoform was found to contain upstream open reading frames (uORFs) and a stem-loop structure, which cooperatively inhibited polysome recruitment. By modulating CD20 isoforms with splice-switching Morpholino oligomers, we enhanced CD20 expression and anti-CD20 antibody rituximab-mediated cytotoxicity in a panel of B-cell lines. Furthermore, reconstitution of CD20-knockout cells with V3 mRNA led to the recovery of CD20 positivity, while V1-reconstituted cells had undetectable levels of CD20 protein. Surprisingly, in vitro CD20-directed CAR T cells were able to kill both V3- and V1-expressing cells, but the bispecific T cell engager mosunetuzumab was only effective against V3-expressing cells. To determine whether CD20 splicing is involved in immunotherapy resistance, we performed RNA-seq on four post-mosunetuzumab follicular lymphoma relapses and discovered that in two of them downregulation of CD20 was accompanied by the V3-to-V1 shift. Thus, splicing-mediated mechanisms of epitope loss extend to CD20-directed immunotherapies.

Key Points

In normal & malignant human B cells, CD20 mRNA is alternatively spliced into four 5'-UTR isoforms, some of which are translation-deficient.The balance between translation-deficient and -competent isoforms modulates CD20 protein levels & responses to CD20-directed immunotherapies.

Explanation of Novelty

We discovered that in normal and malignant B-cells, CD20 mRNA is alternatively spliced to generate four distinct 5'-UTRs, including the longer translation-deficient V1 variant. Cells predominantly expressing V1 were still sensitive to CD20-targeting chimeric antigen receptor T-cells. However, they were resistant to the bispecific anti-CD3/CD20 antibody mosunetuzumab, and the shift to V1 were observed in CD20-negative post-mosunetuzumab relapses of follicular lymphoma.

The BTLA-HVEM axis restricts CAR T cell efficacy in cancer

The efficacy of T cell-based immunotherapies is limited by immunosuppressive pressures in the tumor microenvironment. Here we show a predominant role for the interaction between BTLA on effector T cells and HVEM (TNFRSF14) on immunosuppressive tumor microenvironment cells, namely regulatory T cells. High BTLA expression in chimeric antigen receptor (CAR) T cells correlated with poor clinical response to treatment. Therefore, we deleted BTLA in CAR T cells and show improved tumor control and persistence in models of lymphoma and solid malignancies. Mechanistically, BTLA inhibits CAR T cells via recruitment of tyrosine phosphatases SHP-1 and SHP-2, upon trans engagement with HVEM. BTLA knockout thus promotes CAR signaling and subsequently enhances effector function. Overall, these data indicate that the BTLA-HVEM axis is a crucial immune checkpoint in CAR T cell immunotherapy and warrants the use of strategies to overcome this barrier.

Apoptosis: a Janus bifrons in T-cell immunotherapy

Immunotherapy has revolutionized the treatment of cancer. In particular, immune checkpoint blockade, bispecific antibodies, and adoptive T-cell transfer have yielded unprecedented clinical results in hematological malignancies and solid cancers. While T cell-based immunotherapies have multiple mechanisms of action, their ultimate goal is achieving apoptosis of cancer cells. Unsurprisingly, apoptosis evasion is a key feature of cancer biology. Therefore, enhancing cancer cells' sensitivity to apoptosis represents a key strategy to improve clinical outcomes in cancer immunotherapy. Indeed, cancer cells are characterized by several intrinsic mechanisms to resist apoptosis, in addition to features to promote apoptosis in T cells and evade therapy. However, apoptosis is double-faced: when it occurs in T cells, it represents a critical mechanism of failure for immunotherapies. This review will summarize the recent efforts to enhance T cell-based immunotherapies by increasing apoptosis susceptibility in cancer cells and discuss the role of apoptosis in modulating the survival of cytotoxic T lymphocytes in the tumor microenvironment and potential strategies to overcome this issue.

Abstract 2812: CSPG4-specific CAR.CIK lymphocyte-based immunotherapy to eliminate HLA class I-defective melanoma tumors

Purpose of this study is to explore the preclinical efficacy of Chondroitin Sulfate Proteoglycan 4 (CSPG4)-specific CAR-engineered Cytokine-Induced Killer lymphocytes (CIK) to eradicate melanoma cells with defective HLA class I (HLA-I). The latter abnormality plays a major role in clinical resistance to Checkpoint Inhibitors (CI). CSPG4 was selected as the target because of its high expression on melanoma and its restricted distribution in normal tissues. Our approach is based on CAR.CIK redirected against CSPG4. CIK, ex vivo expanded T-NK lymphocytes endowed with intrinsic HLA-independent antitumor activity, were used as effectors.

Experimental procedure. CAR.CIK were generated by retroviral transduction of patient derived PBMC with a vector encoding a 2nd generation CSPG4-CAR with 4-1BB co-stimulation. Surface HLA-I expression was evaluated by flow cytometry on melanoma cell lines (Mel), derived by surgical biopsies. These cells also served as targets for CSPG4 CAR.CIK. The activity of CSPG4 CAR.CIK was analyzed in vitro and in immunodeficient mice grafted with a patient-derived HLA-defective melanoma. Mice were treated intravenously with 3x106 CAR.CIK (5 cells infusions in total).

Results. CAR.CIK were efficiently generated from 4 melanoma patients. Mean expression of CSPG4-CAR was 48±8%, the rate of ex vivo expansion (84 fold) and phenotypic characteristics (CD3+CD8+=71±13%, CD3+ CD56+=22.5±13%, NKG2D+= 68±32.3%) were comparable with unmodified controls. Membrane HLA-I molecules were detected in 23/24 Mel samples, with a variable membrane density per cell (median 21232, range 787-49871). Sample Mel17 did not express HLA-I because of a start lost mutation (p.Met1Ile) in β2microglobulin. CSPG4 was intensely expressed by all Mel (78±5%), with no correlation to HLA-I levels. CSPG4 CAR.CIK efficiently killed 10 Mel samples in vitro, including Mel17 (HLA-I negative) and 2 Mel with the lowest HLA-I density (Mel71, Mel72). Mean Mel-specific killing by CSPG4 CAR.CIK was significantly higher compared with unmodified CIK especially at low effector/target (E/T) ratios (85% vs 40% at E/T=1:1; 46% vs 9% at E/T=1:8, p<0.0001). In vivo, CSPG4 CAR.CIK caused a significant inhibition of the HLA-negative Mel17 tumor growth (p<0.0001) as compared to controls. Antitumor activity was confirmed by the reduction of tumor weight and metabolic activity (by fluorescent glucose uptake) measured on the residual explanted tumors. Antitumor response persisted up to 2 weeks after end of the treatment.

Conclusions. We reported the activity of CSPG4 CAR.CIK against melanoma, including those with low or defective HLA-I expression. CIK may provide a valid platform for CAR-based strategies against melanoma and solid tumors in general. Our data provide the rationale to implement clinical studies exploring the proposed strategy in melanoma patients not responding or relapsing after immunotherapy with CI.

Citation Format: Giulia Cattaneo, Lidia Giraudo, Loretta Gammaitoni, Ilenia Iaia, Fabrizio Carnevale-Schianca, Alberto Pisacane, Enrico Berrino, Caterina Marchiò, Luca Paruzzo, Andrea Michela Biolato, Chiara Donini, Marco Basiricò, Elisa Landoni, Soldano Ferrone, Valeria Leuci, Massimo Aglietta, Gianpietro Dotti, Dario Sangiolo. CSPG4-specific CAR.CIK lymphocyte-based immunotherapy to eliminate HLA class I-defective melanoma tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2812.

Safety and efficacy of a novel anti-CD19 chimeric antigen receptor T cell product targeting a membrane-proximal domain of CD19 with fast on- and off-rates against non-Hodgkin lymphoma: a first-in-human study

BACKGROUND

Commercial anti-CD19 chimeric antigen receptor T-cell therapies (CART19) are efficacious against advanced B-cell non-Hodgkin lymphoma (NHL); however, most patients ultimately relapse. Several mechanisms contribute to this failure, including CD19-negative escape and CAR T dysfunction. All four commercial CART19 products utilize the FMC63 single-chain variable fragment (scFv) specific to a CD19 membrane-distal epitope and characterized by slow association (on) and dissociation (off) rates. We hypothesized that a novel anti-CD19 scFv that engages an alternative CD19 membrane-proximal epitope independent of FMC63 and that is characterized by faster on- and off-rates could mitigate CART19 failure and improve clinical efficacy.

METHODS

We developed an autologous CART19 product with 4-1BB co-stimulation using a novel humanized chicken antibody (h1218). This antibody is specific to a membrane-proximal CD19 epitope and harbors faster on/off rates compared to FMC63. We tested h1218-CART19 in vitro and in vivo using FMC63-CART19-resistant models. We conducted a first-in-human multi-center phase I clinical trial to test AT101 (clinical-grade h1218-CART19) in patients with relapsed or refractory (r/r) NHL.

RESULTS

Preclinically, h1218- but not FMC63-CART19 were able to effectively eradicate lymphomas expressing CD19 point mutations (L174V and R163L) or co-expressing FMC63-CAR19 as found in patients relapsing after FMC63-CART19. Furthermore, h1218-CART19 exhibited enhanced killing of B-cell malignancies in vitro and in vivo compared with FMC63-CART19. Mechanistically, we found that h1218-CART19 had reduced activation-induced cell death (AICD) and enhanced expansion compared to FMC63-CART19 owing to faster on- and off-rates. Based on these preclinical results, we performed a phase I dose-escalation trial, testing three dose levels (DL) of AT101 (the GMP version of h1218) using a 3 + 3 design. In 12 treated patients (7 DLBCL, 3 FL, 1 MCL, and 1 MZL), AT101 showed a promising safety profile with 8.3% grade 3 CRS (n = 1) and 8.3% grade 4 ICANS (n = 1). In the whole cohort, the overall response rate was 91.7%, with a complete response rate of 75.0%, which improved to 100% in DL-2 and -3. AT101 expansion correlates with CR and B-cell aplasia.

CONCLUSIONS

We developed a novel, safe, and potent CART19 product that recognizes a membrane-proximal domain of CD19 with fast on- and off-rates and showed significant efficacy and promising safety in patients with relapsed B-cell NHL.

TRIAL REGISTRATION

NCT05338931; Date: 2022-04-01.

Nontuberculous mycobacterial infections following teclistamab in multiple myeloma

Not available.

CD5 deletion enhances the antitumor activity of adoptive T cell therapies

Most patients treated with US Food and Drug Administration (FDA)-approved chimeric antigen receptor (CAR) T cells eventually experience disease progression. Furthermore, CAR T cells have not been curative against solid cancers and several hematological malignancies such as T cell lymphomas, which have very poor prognoses. One of the main barriers to the clinical success of adoptive T cell immunotherapies is CAR T cell dysfunction and lack of expansion and/or persistence after infusion. In this study, we found that CD5 inhibits CAR T cell activation and that knockout (KO) of CD5 using CRISPR-Cas9 enhances the antitumor effect of CAR T cells in multiple hematological and solid cancer models. Mechanistically, CD5 KO drives increased T cell effector function with enhanced cytotoxicity, in vivo expansion, and persistence, without apparent toxicity in preclinical models. These findings indicate that CD5 is a critical inhibitor of T cell function and a potential clinical target for enhancing T cell therapies.

Efficacy and safety of bendamustine for lymphodepletion before lisocabtagene maraleucel

Bendamustine has been retrospectively shown to be an effective and safe lymphodepletion regimen prior to the anti-CD19 chimeric antigen receptor T cell (CART) products tisagenlecleucel and axicabtagene ciloleucel, as well as the anti-BCMA CART products idecabtagene vicleucel and ciltacabtagene autoleucel. However, bendamustine as lymphodepletion prior to lisocabtagene maraleucel (liso-cel), a 4-1BB co-stimulated, fixed CD4:CD8 ratio anti-CD19 CART product, has not been described yet. Thus, we studied a cohort of sequentially-treated patients with large B-cell lymphomas who received bendamustine lymphodepletion before liso-cel at the University of Pennsylvania between 5/2021 and 12/2023 (n = 31). Patients were evaluated for toxicities and responses. Of note, 7 patients (22.6%) would have dnot met the inclusion criteria for the registrational liso-cel clinical trials, mostly due to older age. Overall and complete response rates were 76.9% and 73.1%, respectively. At a median follow-up of 6.3 months, the 6-month progression-free and overall survival were 59.9% and 91.1%, respectively. Rates of cytokine-release syndrome (CRS) and neurotoxicity (ICANS) of any grade were 9.7% and 9.7%, respectively, with no grade ≥ 3 events. No infections were reported during the first 30 days following liso-cel infusion. Neutropenia ≥ grade 3 was observed in 29.0% of patients; thrombocytopenia ≥ grade 3 occurred in 9.7%. In conclusion, bendamustine lymphodepletion before liso-cel appears to be a strategy that can drive tumor responses while ensuring a mild toxicity profile.

Directed evolution-based discovery of ligands for in vivo restimulation of CAR-T cells

Chimeric antigen receptor (CAR) T cell therapy targeting CD19 elicits remarkable clinical efficacy in B-cell malignancies, but many patients relapse due to failed expansion and/or progressive loss of CAR-T cells. We recently reported a strategy to potently restimulate CAR-T cells in vivo, enhancing their functionality by administration of a vaccine-like stimulus comprised of surrogate peptide ligands for a CAR linked to a lymph node-targeting amphiphilic PEG-lipid (termed CAR-T-vax). Here, we demonstrate a general strategy to generate and optimize peptide mimotopes enabling CAR-T-vax generation for any CAR. Using the clinical CD19 CAR FMC63 as a test case, we employed yeast surface display to identify peptide binders to soluble IgG versions of FMC63, which were subsequently affinity matured by directed evolution. CAR-T vaccines using these optimized mimotopes triggered marked expansion of both murine CD19 CAR-T cells in a syngeneic model and human CAR-T cells in a humanized mouse model of B cell acute lymphoblastic leukemia (B-ALL), and enhanced control of leukemia progression. This approach thus enables vaccine boosting to be applied to any clinically-relevant CAR-T cell product.

Recent Advances in Immune-Based Therapies for Acute Myeloid Leukemia

Despite advancements, acute myeloid leukemia (AML) remains unconquered by current therapies. Evidence of immune evasion during AML progression, such as HLA loss and T-cell exhaustion, suggests that antileukemic immune responses contribute to disease control and could be harnessed by immunotherapy. In this review, we discuss a spectrum of AML immunotherapy targets, encompassing cancer cell-intrinsic and surface antigens as well as targeting in the leukemic milieu, and how they can be tailored for personalized approaches. These targets are overviewed across major immunotherapy modalities applied to AML: immune checkpoint inhibitors, antibody-drug conjugates, therapeutic vaccines, bispecific/trispecific antibodies, and chimeric antigen receptor (CAR)-T and CAR-NK cells. Significance: Immune therapies in AML treatment show evolving promise. Ongoing research aims to customize approaches for varied patient profiles and clinical scenarios. This review covers immune surveillance mechanisms, therapy options like checkpoint inhibitors, antibodies, CAR-T/NK cells, and vaccines, as well as resistance mechanisms and microenvironment considerations.

Predictive Factors in Metastatic Melanoma Treated with Immune Checkpoint Inhibitors: From Clinical Practice to Future Perspective

The introduction of immunotherapy revolutionized the treatment landscape in metastatic melanoma. Despite the impressive results associated with immune checkpoint inhibitors (ICIs), only a portion of patients obtain a response to this treatment. In this scenario, the research of predictive factors is fundamental to identify patients who may have a response and to exclude patients with a low possibility to respond. These factors can be host-associated, immune system activation-related, and tumor-related. Patient-related factors can vary from data obtained by medical history (performance status, age, sex, body mass index, concomitant medications, and comorbidities) to analysis of the gut microbiome from fecal samples. Tumor-related factors can reflect tumor burden (metastatic sites, lactate dehydrogenase, C-reactive protein, and circulating tumor DNA) or can derive from the analysis of tumor samples (driver mutations, tumor-infiltrating lymphocytes, and myeloid cells). Biomarkers evaluating the immune system activation, such as IFN-gamma gene expression profile and analysis of circulating immune cell subsets, have emerged in recent years as significantly correlated with response to ICIs. In this manuscript, we critically reviewed the most updated literature data on the landscape of predictive factors in metastatic melanoma treated with ICIs. We focus on the principal limits and potentiality of different methods, shedding light on the more promising biomarkers.

Bendamustine as Lymphodepletion for Brexucabtagene Autoleucel Therapy of Mantle Cell Lymphoma

Brexucabtagene autoleucel (brexu-cel) is an autologous CD19-directed chimeric antigen receptor (CAR) T-cell therapy approved for treatment of relapsed/refractory mantle cell lymphoma (MCL). During a fludarabine shortage, we used bendamustine as an alternative to standard cyclophosphamide/fludarabine (cy/flu) lymphodepletion (LD) prior to brexu-cel. We assessed MCL patient outcomes as well as CAR T-cell expansion and persistence after brexu-cel following bendamustine or cy/flu LD at our center. This was a retrospective single institution study that utilized prospectively banked blood and tissue samples. Clinical efficacy was assessed by 2014 Lugano guidelines. CAR T-cell expansion and persistence in peripheral blood were assessed on day 7 and at ≥month 6 for patients with available samples. Seventeen patients received bendamustine and 5 received cy/flu. For the bendamustine cohort, 14 (82%) received bridging therapy and 4 (24%) had CNS involvement. Fifteen patients (88%) developed CRS with 4 (24%) ≥grade 3 events. Six (35%) patients developed ICANS with 4 (24%) events ≥grade 3. No patient had ≥grade 3 cytopenias at day 90. Best objective (BOR) and complete response (CRR) rates were 82% and 65%, respectively. At 24.5 months median follow-up, 12-month progression-free survival (PFS) was 45%, 24-month PFS was 25%, and median duration of response was 19 months. Median OS was not reached. BOR was 25% (1/4) for patients with CNS involvement. CAR transgene expansion after bendamustine LD was observed on day 7 in all (4/4) patients tested and persisted at ≥6 months (2/2), regardless of response. Bendamustine LD before brexu-cel for MCL is feasible and safe with a lower frequency and shorter duration of cytopenias than reported for cy/flu. Both CAR T-cell expansion and persistence were observed after bendamustine LD. Outcomes appear comparable to the real world outcomes reported with cy/flu LD.

CAR T-Cell Immunotherapy in Minority Patients with Lymphoma

BACKGROUND

Administration of anti-CD19 chimeric antigen receptor T-cell (CART19) immunotherapy for large B-cell lymphomas (LBCLs), a subset of non-Hodgkin lymphoma (NHL), involves high costs and access to specialized tertiary care centers. We investigated whether minority health populations (MHPs) have equal access to CART19 and whether their outcomes are similar to those of non-MHPs.

METHODS

We analyzed the prevalence and clinical outcomes of patients treated with commercial CART19 at two geographically and socioeconomically different institutions: the Abramson Cancer Center (ACC, Philadelphia, Pennsylvania) and the Knight Cancer Institute (KCI, Portland, Oregon).

RESULTS

In the ACC catchment area, 8956 patients were diagnosed with NHL between 2015 and 2019 (latest available data from the state registry), including 17.9% MHPs. In the ACC, between 2018 and 2022 (CART became available in 2018), 1492 patients with LBCL were treated, and 194 received CART19. The proportion of MHPs was 15.7% for the entire LBCL cohort but only 6.7% for the CART19 cohort. During the same time, in the KCI catchment area, 4568 patients were diagnosed with NHL, including 4.2% MHPs. In the KCI, 396 patients with LBCL were treated, and 47 received CART19. The proportion of MHPs was 6.6% for the entire LBCL cohort and 4.2% for the CART19 cohort. The 3-month response, survival, and toxicities after CART19 infusion showed similar results, although the number of patients who were treated was limited.

CONCLUSIONS

This study shows that the access of MHPs to tertiary centers for LBCL care was preserved but appeared reduced for commercial CART19 immunotherapy. Although clinical outcomes of MHPs seemed similar to those of non-MHPs, the small sample size precludes drawing firm conclusions. Further studies are needed. (Funded by the Laffey McHugh Foundation and others.).

Extramedullary Multiple Myeloma: Challenges and Opportunities

Extramedullary multiple myeloma (EMM), defined in this review as soft tissue plasmacytomas resulting from hematogenous spread, is characterized by the ability of MM cells to proliferate outside of the bone marrow microenvironment. It is aggressive, often associated with high-risk cytogenetics and early relapse, and independently portends significantly shorter progression-free and overall survival, even in the era of highly effective immunotherapies. The molecular and microenvironmental factors underlying extramedullary MM dissemination continue to be studied to inform the development of better treatments. In this review, we discuss our current understanding of the biology of EMM, focusing on its distinct molecular and microenvironmental characteristics vis-à-vis MM. We also review the current treatment strategies, acknowledging the paucity of large, randomized studies specific to this population.

Bendamustine lymphodepletion before axicabtagene ciloleucel is safe and associates with reduced inflammatory cytokines

ABSTRACT

Lymphodepletion (LD) is an integral component of chimeric antigen receptor T-cell (CART) immunotherapies. In this study, we compared the safety and efficacy of bendamustine (Benda) to standard fludarabine/cyclophosphamide (Flu/Cy) LD before CD19-directed, CD28-costimulated CART axicabtagene ciloleucel (axi-cel) for patients with large B-cell lymphoma (LBCL) and follicular lymphoma (FL). We analyzed 59 patients diagnosed with LBCL (n = 48) and FL (n = 11) consecutively treated with axi-cel at the University of Pennsylvania. We also analyzed serum samples for cytokine levels and metabolomic changes before and after LD. Flu/Cy and Benda demonstrated similar efficacy, with complete remission rates of 51.4% and 50.0% (P = .981), respectively, and similar progression-free and overall survivals. Any-grade cytokine-release syndrome occurred in 91.9% of patients receiving Flu/Cy vs 72.7% of patients receiving Benda (P = .048); any-grade neurotoxicity after Flu/Cy occurred in 45.9% of patients and after Benda in 18.2% of patients (P = .031). In addition, Flu/Cy was associated with a higher incidence of grade ≥3 neutropenia (100% vs 54.5%; P < .001), infections (78.4% vs 27.3%; P < .001), and neutropenic fever (78.4% vs 13.6%; P < .001). These results were confirmed both in patients with LBCL and those with FL. Mechanistically, patients with Flu/Cy had a greater increase in inflammatory cytokines associated with neurotoxicity and reduced levels of metabolites critical for redox balance and biosynthesis. This study suggests that Benda LD may be a safe alternative to Flu/Cy for CD28-based CART CD19-directed immunotherapy with similar efficacy and reduced toxicities. Benda is associated with reduced levels of inflammatory cytokines and increased anabolic metabolites.

Streamlined measurement of chimeric antigen receptor T-cell concentration, size, viability and two-color phenotyping during manufacturing

BACKGROUND AIMS

The successful development of CD19-targeted chimeric antigen receptor (CAR) T-cell therapies has led to an exponential increase in the number of patients recieving treatment and the advancement of novel CAR T products. Therefore, there is a strong need to develop streamlined platforms that allow rapid, cost-effective, and accurate measurement of the key characteristics of CAR T cells during manufacturing (i.e., cell number, cell size, viability, and basic phenotype).

METHODS

In this study, we compared the novel benchtop cell analyzer Moxi GO II (ORFLO Technologies), which enables simultaneous evaluation of all the aforementioned parameters, with current gold standards in the field: the Multisizer Coulter Counter (cell counter) and the BD LSRFortessa (flow cytometer).

RESULTS

Our results demonstrated that the Moxi GO II can accurately measure cell number and cell size (i.e., cell volume) while simultaneously assessing simple two-color flow cytometry parameters, such as CAR T-cell viability and CD4 or CAR expression.

CONCLUSIONS

These measurements are comparable with those of gold standard instruments, demonstrating that the Moxi GO II is a promising platform for quickly monitoring CAR T-cell growth and phenotype in research-grade and clinical samples.

EZH1/EZH2 inhibition enhances adoptive T cell immunotherapy against multiple cancer models

Tumor resistance to chimeric antigen receptor T cell (CAR-T) and, in general, to adoptive cell immunotherapies (ACTs) is a major challenge in the clinic. We hypothesized that inhibiting the tumor drivers' methyltransferases EZH2 and EZH1 could enhance ACT by rewiring cancer cells to a more immunogenic state. In human B cell lymphoma, EZH2 inhibition (tazemetostat) improved the efficacy of anti-CD19 CAR-T by enhancing activation, expansion, and tumor infiltration. Mechanistically, tazemetostat-treated tumors showed upregulation of genes related to adhesion, B cell activation, and inflammatory responses, and increased avidity to CAR-T. Furthermore, tazemetostat improved CAR- and TCR-engineered T cell efficacy in multiple liquid (myeloma and acute myeloid leukemia) and solid (sarcoma, ovarian, and prostate) cancers. Lastly, combined EZH1/EZH2 inhibition (valemetostat) further boosted CAR-T efficacy and expansion in multiple cancers. This study shows that EZH1/2 inhibition reprograms tumors to a more immunogenic state and potentiates ACT in preclinical models of both liquid and solid cancers.

CSPG4 CAR-redirected Cytokine Induced Killer lymphocytes (CIK) as effective cellular immunotherapy for HLA class I defective melanoma

BACKGROUND

Even acknowledging the game-changing results achieved in the treatment of metastatic melanoma with the use of immune checkpoint inhibitors (ICI), a large proportion of patients (40-60%) still fail to respond or relapse due to the development of resistance. Alterations in the expression of Human Leukocyte Antigen class I (HLA-I) molecules are considered to play a major role in clinical resistance to ICI. Cellular immunotherapy with HLA-independent CAR-redirected lymphocytes is a promising alternative in this challenging setting and dedicated translational models are needed.

METHODS

In this study, we propose an HLA-independent therapeutic strategy with Cytokine Induced Killer lymphocytes (CIK) genetically engineered with a Chimeric Antigen Receptor (CAR) targeting the tumor antigen CSPG4 as effector mechanism. We investigated the preclinical antitumor activity of CSPG4-CAR.CIK in vitro and in a xenograft murine model focusing on patient-derived melanoma cell lines (Mel) with defective expression of HLA-I molecules.

RESULTS

We successfully generated CSPG4-CAR.CIK from patients with metastatic melanoma and reported their intense activity in vitro against a panel of CSPG4-expressing patient-derived Mel. The melanoma killing activity was intense, even at very low effector to target ratios, and not influenced by the expression level (high, low, defective) of HLA-I molecules on target cells. Furthermore, CAR.CIK conditioned medium was capable of upregulating the expression of HLA-I molecules on melanoma cells. A comparable immunomodulatory effect was replicated by treatment of Mel cells with exogenous IFN-γ and IFN-α. The antimelanoma activity of CSPG4-CAR.CIK was successfully confirmed in vivo, obtaining a significant tumor growth inhibition of an HLA-defective Mel xenograft in immunodeficient mice.

CONCLUSIONS

In this study we reported the intense preclinical activity of CSPG4-CAR.CIK against melanoma, including those with low or defective HLA-I expression. Our findings support CSPG4 as a valuable CAR target in melanoma and provide translational rationale for clinical studies exploring CAR-CIK cellular immunotherapies within the challenging setting of patients not responsive or relapsing to immune checkpoint inhibitors.