B7-H3 Specific CAR T Cells for the Naturally Occurring, Spontaneous Canine Sarcoma Model

One obstacle for human solid tumor immunotherapy research is the lack of clinically relevant animal models. In this study, we sought to establish a chimeric antigen receptor (CAR) T-cell treatment model for naturally occurring canine sarcomas as a model for human CAR T-cell therapy. Canine CARs specific for B7-H3 were constructed using a single-chain variable fragment derived from the human B7-H3-specific antibody MGA271, which we confirmed to be cross-reactive with canine B7-H3. After refining activation, transduction, and expansion methods, we confirmed target killing in a tumor spheroid three-dimensional assay. We designed a B7-H3 canine CAR T-cell and achieved consistently high levels of transduction efficacy, expansion, and in vitro tumor killing. Safety of the CAR T cells were confirmed in two purposely bred healthy canine subjects following lymphodepletion by cyclophosphamide and fludarabine. Immune response, clinical parameters, and manifestation were closely monitored after treatments and were shown to resemble that of humans. No severe adverse events were observed. In summary, we demonstrated that similar to human cancers, B7-H3 can serve as a target for canine solid tumors. We successfully generated highly functional canine B7-H3-specific CAR T-cell products using a production protocol that closely models human CAR T-cell production procedure. The treatment regimen that we designed was confirmed to be safe in vivo. Our research provides a promising direction to establish in vitro and in vivo models for immunotherapy for canine and human solid tumor treatment.

Integrated -omics approach reveals persistent DNA damage rewires lipid metabolism and histone hyperacetylation via MYS-1/Tip60

Although DNA damage is intricately linked to metabolism, the metabolic alterations that occur in response to DNA damage are not well understood. We use a DNA repair-deficient model of ERCC1-XPF in Caenorhabditis elegans to gain insights on how genotoxic stress drives aging. Using multi-omic approach, we discover that nuclear DNA damage promotes mitochondrial β-oxidation and drives a global loss of fat depots. This metabolic shift to β-oxidation generates acetyl-coenzyme A to promote histone hyperacetylation and an associated change in expression of immune-effector and cytochrome genes. We identify the histone acetyltransferase MYS-1, as a critical regulator of this metabolic-epigenetic axis. We show that in response to DNA damage, polyunsaturated fatty acids, especially arachidonic acid (AA) and AA-related lipid mediators, are elevated and this is dependent on mys-1. Together, these findings reveal that DNA damage alters the metabolic-epigenetic axis to drive an immune-like response that can promote age-associated decline.

Analysis of representative mutants for key DNA repair pathways on healthspan in Caenorhabditis elegans

Although the link between DNA damage and aging is well accepted, the role of different DNA repair proteins on functional/physiological aging is not well-defined. Here, using Caenorhabditis elegans, we systematically examined the effect of three DNA repair genes involved in key genome stability pathways. We assayed multiple health proxies including molecular, functional and resilience measures to define healthspan. Loss of XPF-1/ERCC-1, a protein involved in nucleotide excision repair (NER), homologous recombination (HR) and interstrand crosslink (ICL) repair, showed the highest impairment of functional and stress resilience measures along with a shortened lifespan. brc-1 mutants, with a well-defined role in HR and ICL are short-lived and highly sensitive to acute stressors, specifically oxidative stress. In contrast, ICL mutant, fcd-2 did not impact lifespan or most healthspan measures. Our efforts also uncover that DNA repair mutants show high sensitivity to oxidative stress with age, suggesting that this measure could act as a primary proxy for healthspan. Together, these data suggest that impairment of multiple DNA repair genes can drive functional/physiological aging. Further studies to examine specific DNA repair genes in a tissue specific manner will help dissect the importance and mechanistic role of these repair systems in biological aging.

Identification of MALT1 feedback mechanisms enables rational design of potent antilymphoma regimens for ABC-DLBCL

MALT1 inhibitors are promising therapeutic agents for B-cell lymphomas that are dependent on constitutive or aberrant signaling pathways. However, a potential limitation for signal transduction-targeted therapies is the occurrence of feedback mechanisms that enable escape from the full impact of such drugs. Here, we used a functional genomics screen in activated B-cell-like (ABC) diffuse large B-cell lymphoma (DLBCL) cells treated with a small molecule irreversible inhibitor of MALT1 to identify genes that might confer resistance or enhance the activity of MALT1 inhibition (MALT1i). We find that loss of B-cell receptor (BCR)- and phosphatidylinositol 3-kinase (PI3K)-activating proteins enhanced sensitivity, whereas loss of negative regulators of these pathways (eg, TRAF2, TNFAIP3) promoted resistance. These findings were validated by knockdown of individual genes and a combinatorial drug screen focused on BCR and PI3K pathway-targeting drugs. Among these, the most potent combinatorial effect was observed with PI3Kδ inhibitors against ABC-DLBCLs in vitro and in vivo, but that led to an adaptive increase in phosphorylated S6 and eventual disease progression. Along these lines, MALT1i promoted increased MTORC1 activity and phosphorylation of S6K1-T389 and S6-S235/6, an effect that was only partially blocked by PI3Kδ inhibition in vitro and in vivo. In contrast, simultaneous inhibition of MALT1 and MTORC1 prevented S6 phosphorylation, yielded potent activity against DLBCL cell lines and primary patient specimens, and resulted in more profound tumor regression and significantly improved survival of ABC-DLBCLs in vivo compared with PI3K inhibitors. These findings provide a basis for maximal therapeutic impact of MALT1 inhibitors in the clinic, by disrupting feedback mechanisms that might otherwise limit their efficacy.

Abstract A19: MALT1 inhibition as an anchor for combinatorial therapy of ABC-DLBCL

MALT1 (Mucossa Associated Lymphoid tissue Lymphoma Translocated protein 1) is critical for the proliferation and survival of Activated B-cell like Diffuse Large B-cell Lymphoma (ABC-DLBCL), the most chemo-resistant form of DLBCL. MALT1 mediates activation of the B-cell receptor pathway (BCR) downstream of characteristic somatic mutations in CD79, CARD11 or MYD88 that lead to chronically activated NF-κB. MALT1 is a paracaspase and the effector enzyme of the CARD11/Bcl10/MALT1 signalosome, a high order assembly that functions as an amplifier of BCR signaling to NF-κB. MALT1 constitutes a compelling therapeutic target because: i) it is the only paracaspase in humans, ii) MALT1 knockout mice are viable, and iii) ABC-DLBCLs are biologically dependent on MALT1 paracaspase activity.

MALT1 is only active when forming multimeric complexes. In order to identify potential MALT1 inhibitors we engineered a leucine zipper-MALT1, obliged and enzymatically active dimer, and established a paracaspase enzymatic assay for high throughput screening. Screening a ~50,000 compound chemical diversity library allowed us the identification and validation of 19 distinct chemical scaffolds that inhibited MALT1 with an IC50<20 μM. Three compounds significantly induced selective dose-dependent suppression of MALT1-dependent ABC-DLBCL cells (MI-2, p<0.0001; MI-4, p=0.006; MI-11, p<0.0001). The most potent compound in cell-based assays was MI-2 with a GI25 in the low nanomolar range. MI-2 analogs also displayed nanomolar activity. In depth analysis using NMR and LC-MS revealed that MI-2 binds covalently to the active site of MALT1. In DLBCL cells, MI-2 inhibited MALT1 cleavage of its targets TNFAIP3, BCL10 and RelB, as well as nuclear translocation of c-REL and overall NF-κB activation. MI-2 inhibited proliferation by inducing G1 arrest and ultimately promoted apoptosis in ABC-DLBCLs including those with mutations that bypass BTK inhibitors, like CARD11 activating mutation. MI-2 was non toxic in vivo and potently and specifically inhibited the growth of xenotransplanted ABC-DLBCLs (p=0.014, t-test) but not GCB-DLBCLs. Moreover, MI-2 selectively killed primary human ABC-DLBCL specimens ex vivo.

Given that multiple pathways contribute to ABC-DLBCL pathogenesis, we hypothesized that MALT1 inhibitors would be most effective within combinatorial therapy regimens. Along these lines MI-2 strongly enhanced the activity of CHOP chemotherapy drugs against ABC-DLBCL cells. The addition of MI-2 to doxorubicin allowed for 2.5 to 13-fold reduction in the doxorubicin dose as determined by the dose-reduction index that was specific for the doxorubicin resistant cell lines (GI50 > 200 nM). Because the BCR pathway constitutes a complex network of signaling molecules beyond NF-κB activation, we tested combination of MI-2 with inhibitors of other proteins in this pathway affecting other branches of this pathway. Combination of MI-2 with the pan PI3K inhibitor BKM120, that was in our hands the most effective against a broad group of ABC-DLBCL cell lines, resulted in synergistic cell killing of OCI-Ly10 and Rc-K8 and had an additive effect in HBL-1 while it was less than additive for OCI-Ly3 and TMD8. These cell lines harbor mutations in different proteins of the pathway, which may contribute to the differences in response to the combination. Finally MI-2 strongly synergized with BH3 mimetics (most notably ABT-737) that target fundamental complementary survival pathways to BCR signaling in ABC-DLBCLs. Synergistic killing was at least partially due to induction of apoptosis, as concurrent administration of the two drugs induced increased apoptosis assessed by Caspase-7/3 activity and Annexin V+ DAPI- flow cytometry.

In summary, we identified the first specific MALT1 inhibitor drug and demonstrated a promising role for MALT1 targeted therapy as an anchor of rational combinatorial therapy against ABC-DLBCL.

Citation Format: Lorena Fontan, Chenghua Yang, Himaly Shinglot, Venkataraman Kabaleeswaran, Volpon Laurent, Michael Osborne, Elena Beltran, Monica Rosen, Rita Shaknovich, Shao N. Yang, Randy D. Gascoyne, Leandro Cerchietti, Jose A. MArtinez-Climent, J Fraser Glickman, KAtherine Borden, Hao Wu, Ari Melnick. MALT1 inhibition as an anchor for combinatorial therapy of ABC-DLBCL. [abstract]. In: Proceedings of the AACR Special Conference on Hematologic Malignancies: Translating Discoveries to Novel Therapies; Sep 20-23, 2014; Philadelphia, PA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(17 Suppl):Abstract nr A19.

Efficacy and toxicity management of 19-28z CAR T cell therapy in B cell acute lymphoblastic leukemia

We report on 16 patients with relapsed or refractory B cell acute lymphoblastic leukemia (B-ALL) that we treated with autologous T cells expressing the 19-28z chimeric antigen receptor (CAR) specific to the CD19 antigen. The overall complete response rate was 88%, which allowed us to transition most of these patients to a standard-of-care allogeneic hematopoietic stem cell transplant (allo-SCT). This therapy was as effective in high-risk patients with Philadelphia chromosome-positive (Ph(+)) disease as in those with relapsed disease after previous allo-SCT. Through systematic analysis of clinical data and serum cytokine levels over the first 21 days after T cell infusion, we have defined diagnostic criteria for a severe cytokine release syndrome (sCRS), with the goal of better identifying the subset of patients who will likely require therapeutic intervention with corticosteroids or interleukin-6 receptor blockade to curb the sCRS. Additionally, we found that serum C-reactive protein, a readily available laboratory study, can serve as a reliable indicator for the severity of the CRS. Together, our data provide strong support for conducting a multicenter phase 2 study to further evaluate 19-28z CAR T cells in B-ALL and a road map for patient management at centers now contemplating the use of CAR T cell therapy.