Preclinical Solid Tumor Models Research Articles

Preclinical development of T cells engineered to express a T cell antigen coupler (TAC) targeting Claudin 18.2-positive solid tumors.

The T cell antigen coupler (TAC) is a chimeric receptor that facilitates tumor antigen-specific activation of T cells by co-opting the endogenous T cell receptor complex in the absence of tonic signaling. Previous data demonstrates that TAC affords T cells with the ability to induce durable and safe anti-tumor responses in preclinical models of hematological and solid tumors. Here, we describe the preclinical pharmacology and safety of an autologous Claudin 18.2 (CLDN18.2)-directed TAC T cell therapy, TAC01-CLDN18.2, in preparation for a Phase I/II clinical study in subjects with CLDN18.2-positive solid tumors. Following a screen of putative TAC constructs, the specificity, activity, and cytotoxicity of TAC T cells expressing the final CLDN18.2-TAC receptor were evaluated in vitro and in vivo using gastric, gastroesophageal, and pancreatic tumor models as well as human cells derived from normal tissues. CLDN18.2-specific activity and cytotoxicity of CLDN18.2-TAC T cells were observed in coculture with various 2D tumor cultures naturally expressing CLDN18.2 as well as tumor spheroids. These effects occurred in models with low antigen levels and was positively associated with increasing CLDN18.2 expression. CLDN18.2-TAC T cells effectively eradicated established tumor xenografts in mice in the absence of observed off-target or on-target/off-tumor effects, elicited durable efficacy in recursive killing and tumor rechallenge experiments, and remained unreactive in coculture with human cells representing vital organs. Thus, the data demonstrate that CLDN18.2-TAC T cells can induce a specific and long-lasting anti-tumor response in various CLDN18.2-positive solid tumor models without notable TAC-dependent toxicities, supporting the clinical development of TAC01-CLDN18.2.

254 (PB242): HMPL-500, a potent and selective EZH1/EZH2 dual inhibitor, demonstrates superior anti-tumor activity in preclinical models of hematological malignancies and solid tumors

254 (PB242): HMPL-500, a potent and selective EZH1/EZH2 dual inhibitor, demonstrates superior anti-tumor activity in preclinical models of hematological malignancies and solid tumors

BP1003 Decreases STAT3 Expression and Its Pro-Tumorigenic Functions in Solid Tumors and the Tumor Microenvironment.

Overexpression and aberrant activation of signal transducer and activator of transcription 3 (STAT3) contribute to tumorigenesis, drug resistance, and tumor-immune evasion, making it a potential cancer therapeutic target. BP1003 is a neutral liposome incorporated with a nuclease-resistant P-ethoxy antisense oligodeoxynucleotide (ASO) targeting the STAT3 mRNA. Its unique design enhances BP1003 stability, cellular uptake, and target affinity. BP1003 efficiently reduces STAT3 expression and enhances the sensitivity of breast cancer cells (HER2+, triple negative) and ovarian cancer cells (late stage, invasive ovarian cancer) to paclitaxel and 5-fluorouracil (5-FU) in both 2D and 3D cell cultures. Similarly, ex vivo and in vivo patient-derived models of pancreatic ductal adenocarcinoma (PDAC) show reduced tissue viability and tumor volume with BP1003 and gemcitabine combination treatments. In addition to directly affecting tumor cells, BP1003 can modulate the tumor microenvironment. Unlike M1 differentiation, monocyte differentiation into anti-inflammatory M2 macrophages is suppressed by BP1003, indicating its potential contribution to immunotherapy. The broad anti-tumor effect of BP1003 in numerous preclinical solid tumor models, such as breast, ovarian, and pancreatic cancer models shown in this work, makes it a promising cancer therapeutic.

JAK inhibition enhances checkpoint blockade immunotherapy in patients with Hodgkin lymphoma.

Unleashing antitumor T cell activity by checkpoint inhibitor immunotherapy is effective in cancer patients, but clinical responses are limited. Cytokine signaling through the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway correlates with checkpoint immunotherapy resistance. We report a phase I clinical trial of the JAK inhibitor ruxolitinib with anti-PD-1 antibody nivolumab in Hodgkin lymphoma patients relapsed or refractory following checkpoint inhibitor immunotherapy. The combination yielded a best overall response rate of 53% (10/19). Ruxolitinib significantly reduced neutrophil-to-lymphocyte ratios and percentages of myeloid suppressor cells but increased numbers of cytokine-producing T cells. Ruxolitinib rescued the function of exhausted T cells and enhanced the efficacy of immune checkpoint blockade in preclinical solid tumor and lymphoma models. This synergy was characterized by a switch from suppressive to immunostimulatory myeloid cells, which enhanced T cell division.

A first-in-human, phase I, dose-escalation study to evaluate pharmacokinetics, safety, and tolerability of KD6001, a novel anti-CTLA-4 monoclonal antibody (mAb) in patients with advanced solid tumors.

e14501 Background: KD6001, a novel fully human anti-CTLA4 IgG1 monoclonal antibody, exhibits immunomodulatory effects, enhances T-cell-mediated antitumor immune response and shows promising activity in preclinical models of solid tumors. Here we present the pharmacokinetics, safety and tolerability data from the phase 1 study of KD6001 (NCT05230290) in patients with advanced solid tumors. Methods: patients were enrolled in a 3+3 dose escalation phase 1 study with the following pre-defined KD6001 cohorts: 0.2mg/kg, 1mg/kg, 3mg/kg or 6mg/kg, every 2 weeks via intravenous infusion for 4 cycles. The primary objective was to evaluate the safety and tolerability of KD6001 and determine the MTD/RP2D. The secondary objectives were to measure antitumor activity, immunogenicity and pharmacokinetics (PK). All AEs are graded using NCI CTCAE v5.0. Efficacy assessments are per RECIST 1.1. Blood samples are obtained for pharmacokinetics (PK) and for immunogenicity assessments, measured by the development of anti-drug antibodies. Results: The study had been completed. Thirteen pts with melanoma had been enrolled and treated at 0.2 mg/kg (n = 1), 1mg/kg (n = 3), 3 mg/kg (n = 6) and 6mg/kg (n = 3) at Beijing Cancer Hospital. The average age was 57.2 years (range 34-68). Baseline ECOG scores were 0 (n = 5), 1(n = 8) with all pts. Seven pts (53.85%) received ≥ 2 lines of previous systemic therapies and 12 pts (92.31%) received previous PD-1/PD-L1 treatment. KD6001 was well-tolerated with no dose-limiting toxicities (DLTs) observed, nor was the MTD reached at the highest doses administered. All the thirteen pts had at least one adverse event during treatment, and eleven of them (84.62%) had Treatment Related Adverse Events (TRAEs), most of which were Grades 1-2. There were no permanent drug discontinuation or deaths due to adverse events. Pharmacokinetic analysis indicated a linear correlate between the drug exposure (Cmax, AUC0-t and AUC0-inf) and study drug dosages evaluated. The geometric mean T1/2 was 10 days (CV%: 31%). The peak concentration and exposure level increased proportionally to dose from 0.2mg/kg to 6 mg/kg. No anti-drug antibodies were detected in any of the patient’s serum samples. Clinical efficacy was observed in 12 evaluable pts: 3 patients at 3mg/kg had a stable disease (SD) and 1 patient at 3mg/kg had a confirmed partial response (PR). The ORR of the 3mg/kg dose group was 16.7% (1/6), the DCR was 66.67% (4/6). The median PFS was 109 days and the median OS was not reached. Conclusions: KD6001 showed promising antitumor activity and a tolerable safety profile in patients with advanced solid tumors. Hence, 3mg/kg was selected as the RP2D. Clinical trial information: NCT05230290 .

A phase 1, first-in-human study of autologous monocytes engineered to express an anti-HER2 chimeric antigen receptor (CAR) in participants with HER2-overexpressing solid tumors.

TPS2682 Background: Myeloid cells are actively recruited to the solid tumor microenvironment (TME) and have the potential to mediate tumor control via phagocytosis, TME remodeling, and T cell activation. We previously developed human chimeric antigen receptor macrophages (CAR-M) and have shown potent anti-tumor activity in pre-clinical solid tumor models. The anti-HER2 CAR-M cell therapy product, CT-0508, is currently being evaluated in a Phase I trial as a monotherapy and in combination with pembrolizumab. Early clinical data have shown feasibility, safety, and validated the mechanism of action. We have developed a next-generation CAR monocyte (CAR-Mono) platform to increase the dose, improve tumor trafficking and engraftment, and shorten the manufacturing and vein-to-vein time as compared to CAR-M therapy. CT-0525 is an autologous anti-HER2 CAR-Mono cell therapy based on CD14+ monocytes engineered with an Ad5f35 adenoviral vector to express an anti-HER2 CAR. Pre-clinical studies have demonstrated the feasibility, phenotype, pharmacokinetics, durable CAR expression, cellular fate, antigen specificity, and anti-tumor activity of CT-0525. Pre-clinical studies have shown that CT-0525 differentiated into pro-inflammatory CAR-M in vivo and controlled tumor growth. The CT-0525 manufacturing process takes one day and enables the production of up to 10 billion cells from a single apheresis. CT-0525 is being investigated in a first-in-human, open-label, multi-center, Phase I study in patients with HER2 overexpressing solid tumors. Methods: This Phase 1, first-in-human study evaluates the feasibility, safety, tolerability, trafficking, TME activation, and preliminary evidence of efficacy of the investigational CAR-Mono product CT-0525 in 6 participants (pts) with locally advanced unresectable/metastatic solid tumors overexpressing HER2. Pts previously treated with anti-HER2 therapies are eligible. Filgrastim mobilized autologous CD14+ monocytes are collected by apheresis, followed by manufacturing and cryopreservation. The 1st cohort of pts (n=3) will receive 3 x 109 CT-0525 CAR positive monocytes administered IV in one infusion. If tolerated as per the modified toxicity probability interval algorithm (mTPI), the 2nd cohort of pts (n=3) will receive up to 10 x 109 CT-0525 CAR positive monocytes in one infusion. CT-0525 will be administered without conditioning chemotherapy. Primary endpoints include assessment of safety and tolerability, as well as manufacture feasibility. Correlative assessments include pre- and post-treatment biopsies and blood samples for safety, immunogenicity, pharmacokinetics, tumor trafficking, TME modulation, epitope spreading, and other translational biomarkers. Clinical trial information: NCT06254807 .

Safety, pharmacokinetics (PK), pharmacodynamics (PD) and efficacy of KT-253, a targeted protein degrader of MDM2, in patients with relapsed/refractory (R/R) solid tumors, lymphoma, high grade myeloid malignancies and acute lymphoblastic leukemia (ALL).

3084 Background: The tumor suppressor p53 is mutated in approximately 50% of cancers. In those cancers with wild-type p53, its activity is controlled by mouse double minute 2 (MDM2), an E3 ligase that tags p53 for degradation. KT-253 is a novel, highly potent heterobifunctional MDM2 degrader that upregulates p53 activity and overcomes the p53-MDM2 feedback loop, resulting in >200-fold higher potency compared to MDM2 inhibitors. In preclinical PDX models of sensitive p53WT solid tumors, AML and ALL, KT-253 robustly activates p53, induces apoptosis, and results in tumor regressions with every 3-week dosing. The ability to rapidly induce an acute apoptotic response and dose intermittently may result in a therapeutic index that has eluded previous MDM2 targeting agents. Methods: The ongoing open-label Phase 1 study evaluates safety, PK, PD and preliminary efficacy of IV KT-253 administered on Day 1 of 21-day cycles. Patients (pts) with advanced (≥2 prior therapies) solid tumors (ST)/lymphomas (Arm A) and relapsed/refractory (R/R) high grade myeloid malignancies (AML, high/very-high risk myelodysplastic syndrome (MDS), MDS/myeloproliferative neoplasms) and ALL (Arm B) are eligible. Blood samples are collected for KT-253 PK/PD analyses. Results: As of 26 January 2024, 18 pts have been treated, 13 in Arm A dose levels (A: DL) 1-4 and 5 in Arm B dose levels (B: DL) 1-2, with mean number of 3 and 2 doses, respectively. The most common solid tumor types were Merkel cell carcinoma ((MCC) n=3), adenoid cystic carcinoma ((ACC) n=2) and uveal melanoma (n=2). Arm B included 5 pts with R/R AML. The median age was 61 years (yrs) (range 42, 81) in Arm A and 66 yrs (range 57, 70) in Arm B. The most common adverse events (AEs) in > 20% of pts included nausea, fatigue, headache, and vomiting. There was 1 DLT of AEs leading to discontinuation that included Grade (G) 2 nausea and fatigue in A: DL4. There were no neutropenia or thrombocytopenia AEs in either arm. KT-253 related SAEs included G3 hypotension in a pt with decreased oral intake (A: DL1). Overall best response: 1 CR (B: DL2, AML); 2 PRs (A: DL1, MCC; B: DL1, AML); 3 SD (A: DL1, fibromyxoid sarcoma; DL2, ACC; DL3, renal cell cancer). PD data from A: DL1-4 and B: DL1-2 demonstrated rapid upregulation of plasma GDF-15 protein and upregulation of CDKN1A and PHLDA3 mRNA levels in blood. KT-253 demonstrated dose-dependent increase in plasma exposure with levels approximating efficacious doses. Conclusions: KT-253 results in potent upregulation of p53-dependent biomarkers and has demonstrated early signs of anti-tumor activity including objective responses in MCC and AML at doses that are well tolerated. Dose escalation is ongoing at DL4 in Arm A and at DL2 in Arm B and analyses from additional pts will be presented at the meeting. Clinical trial information: NCT05775406 .

Evaluating antitumor activity and response determinants to trastuzumab deruxtecan in pediatric solid tumors.

10049 Background: Trastuzumab deruxtecan (T-DXd) is an anti-HER2 antibody-drug conjugate (ADC) linked to a topoisomerase inhibitor FDA-approved for several indications, including the treatment of HER2+ breast and gastric cancer. Although HER2 amplification is uncommon in pediatric cancers, recent demonstration of T-DXd efficacy in HER2-low breast cancer patients prompted us to examine the potential clinical relevance of T-DXd in pediatrics by evaluating HER2 expression and activity of T-DXd in preclinical pediatric solid tumor models. Methods: Cell viability was assessed in a panel of histologically diverse pediatric solid tumor cell lines and 2 HER2-amplified adult cancer cell lines treated with T-DXd, payload (DXd), and a control IgG-ADC. HER2 protein expression in patient-derived xenograft (PDX) tumors was evaluated by immunohistochemistry (IHC) using 5 clinically validated anti-HER2 antibodies. RNAseq was performed on clinical (n=290) and PDX (n=184) tumors to determine relative expression of ERBB2. In vivo activity of T-DXd was evaluated in osteosarcoma (OS, n=10), Wilms tumor (WT, n=1) and malignant rhabdoid tumor (MRT, n=1) PDX models and a desmoplastic small round cell tumor (DSRCT) cell line xenograft model. Differences in tumor volume and time to disease progression was assessed and compared across treatments and models. Responses were correlated with HER2 expression by IHC. Results: In vitro, HER2-amplified control cell lines demonstrated a >30-fold reduction of IC50 when comparing T-DXd to ADC control. In contrast, the ADC control IC50 was nearly identical to T-DXd across all pediatric cancer cell lines, consistent with the absence of HER2 amplification in these models. We observed focal and membranous staining of HER2 by IHC in PDXs but was quite variable across antibodies tested: WT 0-17% HER2+ cases (n=6), MRT 0-40% (n=5), DSRCT 0-33% (n=24), OS 0-7% (n=30). ERBB2 gene expression was highest in DSRCT followed by WT, OS and MRT. In vivo efficacy studies demonstrated complete and partial responses in OS, WT, and DSRCT and improved disease control rates (OS: 67%, p=0.006, Mann-Whitney; WT: 100%; DSRCT: 100%). However, T-DXd and ADC control demonstrated similar activity in all tumor types with no consistent correlation between in vivo response and HER2 expression. Consistent with these preclinical studies, 4 patients with progressive DSRCT were treated with T-DXd via compassionate/off-label access with signs of clinical and radiographic responses. Conclusions: T-DXd shows significant preclinical antitumor activity across multiple pediatric solid tumors but little correlation with HER2 expression suggesting a mechanism of action similar to the clinical activity observed in HER2-low breast cancer. Xenograft efficacy studies and preliminary clinical experience with T-DXd in DSRCT patients warrant formal clinical trial investigation in this largely incurable disease.

A phase I trial of intratumoral STX-001: A novel self-replicating mRNA expressing IL-12 alone or with pembrolizumab in advanced solid tumors.

TPS2696 Background: STX-001 is a multi-mechanistic lipid nanoparticle encapsulated synthetic self-replicating mRNA, engineered to express the IL-12 cytokine for an extended duration when administered intratumorally. A murine surrogate of STX-001 induces deep durable responses in multiple preclinical solid tumor models. This Phase 1 open-label, multi-center first-in-human dose-escalation trial evaluates the safety, tolerability, pharmacokinetics (PK), pharmacodynamics (PD), and preliminary antitumor activity of STX-001 alone, or in combination with pembrolizumab in patients with treatment refractory advanced cancers. Methods: Approximately 30 adults ≥18 years of age with histologically confirmed advanced solid tumors that are refractory to standard treatments will be enrolled. The study will consist of two arms, an STX-001 monotherapy arm and an STX-001 + pembrolizumab combination arm, enrolling approximately 15 patients each. Key eligibility criteria include ECOG status 0 or 1, a tumor lesion amendable to injection, and confirmed prior disease progression. STX-001 will be administered every 3 weeks (q3w) for 3 doses and then every 6 weeks (q6w) for a further 3 doses. Tumor biopsies will be obtained at baseline and after the first STX-001 administration. Primary endpoints will include safety and maximum tolerated dose (MTD), with secondary endpoints encompassing pharmacokinetics and preliminary efficacy as measured by RECIST 1.1. To determine the MTD, this study will employ the Bayesian optimal interval (BOIN) design, with the 3 + 3 design run-in and a recommended phase 2 dose (RP2D) will be determined. Tumor response will be assessed using RECIST 1.1 criteria. Exploratory pharmacodynamic analyses will assess tumor-infiltrating lymphocytes and STX-001 mRNA in baseline and on-treatment biopsies, evaluate inflammatory cytokine profiles in plasma, determine immune activation in circulating immune cells, and measure circulating tumor DNA (ctDNA) for molecular response assessment. Clinical trial information: NCT06249048 .

Preclinical development of novel PD-L1 tracers and first-in-human study of [68Ga]Ga-NOTA-RW102 in patients with lung cancers

BackgroundThe programmed cell death protein-1 (PD-1)/programmed death receptor ligand 1 (PD-L1) axis critically facilitates cancer cells’ immune evasion. Antibody therapeutics targeting the PD-1/PD-L1 axis have shown remarkable efficacy in various...

Abstract 4012: SOT302: Dual expression of exogenous glutamine oxaloacetate transaminase (GOT2) and TP53-induced glycolysis and apoptosis regulator (TIGAR) enhance CAR T cell activity in preclinical solid tumor models

Abstract Background: Despite success in hematological malignancies, CAR T therapy has had limited efficacy against solid tumors. The suppressive tumor microenvironment limits CAR T activity through various mechanisms including competition for available nutrients and chronic stimulation resulting in reduced effector functions or T cell exhaustion. CAR T cells with enhanced metabolic fitness or more durable memory phenotype could potentially improve the clinical outcome in solid tumors. GOT2 plays an important role in mitochondrial function and maintenance of redox homeostasis. We have previously demonstrated enhancement of CAR T cells overexpressing GOT2. TIGAR is an enzyme known to promote antioxidative activites and reduce reactive oxygen species and has a role in protecting against apoptosis. Here we tested SOT302 CAR T cells expressing both GOT2 and TIGAR in preclinical solid tumor models. Results: Expression of GOT2 and TIGAR transgenes were confirmed by qRT-PCR and western blot. Activity of GOT2 and TIGAR were confirmed by measuring aminotransferase activity (AST) and glutathione production, respectively. Compared to control CAR T cells, SOT302 is enriched for CD8+ Tscm cells and has a higher percentage functional, non-senescent (CD28+CD57-) cells. SOT302 has similar cytokine expression and cytotoxicity in standard co-culture assays compared to controls. SOT302 cells were chronically stimulated with plate-bound antigen every 3-4 days for 4 rounds. SOT302 had greater expansion of cells and were less exhausted and had better cytolytic capacity compared to controls. SOT302 cells were then evaluated in tumor xenograft mouse models. Consistent with our previous findings, CAR T cells expressing the single GOT2 transgene were more efficacious compared to CAR T cells alone. Expression of the single TIGAR transgene had no apparent benefit over CAR alone, however SOT302 cells expressing both GOT2 and TIGAR had superior anti-tumor activity compared to CAR alone and CAR+GOT2. No overt toxicity or significant body weight loss was observed. Ex vivo analyses to measure peripheral expansion, tumor infiltration and exhaustion were also performed. Preliminary findings indicate that SOT302 has better peripheral expansion compared to CAR alone and similar expansion compared to CAR+GOT2 controls. SOT302 cells had better tumor infiltration compared to both the CAR alone and CAR+GOT2 cells. Tumor infiltrating SOT302 cells also exhibited lower levels of exhaustion compared to CAR alone or CAR+GOT2 controls. Summary: SOT302 cells express exogenous GOT2 and TIGAR transgenes and have superior anti-tumor activity in preclinical solid tumor models. These data suggest that SOT302 may be a promising candidate for patients with solid tumor cancers. Citation Format: Emily Kuiper, Samyabrata Bhaduri, Daniel Garafola, Kshitij Sharma, Jennifer Coccia, Kathleen Whiteman, Amy Jensen-Smith. SOT302: Dual expression of exogenous glutamine oxaloacetate transaminase (GOT2) and TP53-induced glycolysis and apoptosis regulator (TIGAR) enhance CAR T cell activity in preclinical solid tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4012.

Abstract 6332: Evaluating the relationship of affinity, functional avidity, and in vivo potency in KIR-CAR T cells

Abstract Chimeric antigen receptors (CARs) targeting CD19 demonstrate remarkable clinical outcomes in patients (pts) with B-cell malignancies. Importantly, all four FDA-approved CD3ζ-based CAR T cell therapies use the same FMC63-derived single-chain variable fragment (scFv) to target CD19+ tumors. Although response rates are high in diffuse large B cell lymphoma, only ~40% of pts achieve durable, long-term remissions. Improved CAR T cell therapies are therefore needed. We have previously shown that a novel killer immunoglobulin receptor (KIR)-based CAR expressed in T cells as a multichain receptor with DAP12 (KIR-CAR T) has enhanced anti-tumor activity in several preclinical solid tumor models suggesting that this platform may show better activity in lymphoma. Some recent studies report that lower-affinity CD19 binders compared to the benchmark FMC63-scFv yield equivalent or increased anti-tumor activity of CAR T in pts, raising the question of optimal affinity for a KIR-based CAR. In this study, we aimed to evaluate the relationship of affinity, functional avidity, and in vivo potency of CD19 binders in a KIR-based CAR T cell. Using a highly-diverse 40-billion member canine scFv phage display library, we generated 19 unique human CD19-specific binders that compete with FMC63 binder supporting a similar binding epitope. Different KIR-CAR T cells were generated, and relative affinities were compared via binding to a recombinant (rec) CD19 protein. We found that although CAR receptor expression was similarly expressed, the concentration of soluble rec CD19 protein required to saturate the surface CAR varied more than 2-log among the different scFv binders suggesting a range of affinities relative to FMC63. We selected several scFvs with lower, and equivalent CD19 binding MFI compared to the FMC63-scFv and found that all scFvs could mediate similarly robust in vitro potency. In vivo anti-tumor efficacy was next assessed using the NSG xenograft mouse model of B-cell leukemia NALM6 cells. Interestingly, despite their comparable in vitro functions, some binders with relatively similar binding MFI failed to control the tumors. In contrast, two binders with an ~30-fold apparent affinity relative to FMC63 exhibited robust anti-tumor activity comparable to the benchmark scFv. These preliminary data suggest that the in vivo functional activity of chimeric KIR-based immunoreceptors is insensitive to binder affinity over a wide range of affinities. The failure of some scFvs with comparable affinity and binding epitope suggest that other, yet to be characterized attributes of the binder may be critical for optimal function. Further characterization of these binders is being conducted to understand the relationship between affinity, functional avidity, antigen density, and in vivo potency. This study paves the way for developing an improved CD19-specific KIR-CAR T cell therapy for treating pts with B-cell malignancies. Citation Format: Jun Xu, Selene Nunez-Cruz, John M. Leferovich, Gayathri Gulendran, Chune Zhang, Nora D. Yucel, Megan C. Blair, William S. Stanley, Laura A. Johnson, Don L. Siegel, Michael C. Milone. Evaluating the relationship of affinity, functional avidity, and in vivo potency in KIR-CAR T cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6332.

Elimusertib has Antitumor Activity in Preclinical Patient-Derived Pediatric Solid Tumor Models.

The small-molecule inhibitor of ataxia telangiectasia and Rad3-related protein (ATR), elimusertib, is currently being tested clinically in various cancer entities in adults and children. Its preclinical antitumor activity in pediatric malignancies, however, is largely unknown. We here assessed the preclinical activity of elimusertib in 38 cell lines and 32 patient-derived xenograft (PDX) models derived from common pediatric solid tumor entities. Detailed in vitro and in vivo molecular characterization of the treated models enabled the evaluation of response biomarkers. Pronounced objective response rates were observed for elimusertib monotherapy in PDX, when treated with a regimen currently used in clinical trials. Strikingly, elimusertib showed stronger antitumor effects than some standard-of-care chemotherapies, particularly in alveolar rhabdomysarcoma PDX. Thus, elimusertib has strong preclinical antitumor activity in pediatric solid tumor models, which may translate to clinically meaningful responses in patients.

Abstract C077: STC-15, a small molecule inhibitor of the RNA methyltransferase METTL3, activates anti-tumor immunity and reshapes the tumor microenvironment

Abstract Background METTL3 is the RNA methyltransferase responsible for the deposition of N-6-methyladenosine modification (m6A) on mRNA, to regulate its stability, splicing and protein translation. Small molecule inhibitors of METTL3 catalytic activity have previously demonstrated anti-tumor efficacy in pre-clinical models of acute myeloid leukemia (AML) and solid tumors. Inhibition of METTL3 was shown to induce a cell-intrinsic innate immune response through activation of the double strand RNA (dsRNA) sensing machinery and interferon (IFN) signalling. Here we present new pre-clinical data, investigating the combination of METTL3 inhibitor (METTL3i) with DNA damaging therapies. We show that METTL3 inhibition profoundly changes the tumor microenvironment (TME), and we further demonstrate the generation of durable immune memory in mice treated with METTL3i, with or without anti-PD1 therapy. Materials & Methods The orally bioavailable small molecule clinical-stage METTL3i STC-15, or the equipotent tool compound STM3675 were used in these studies. To characterise transcriptomic changes following METTL3 inhibition, RNA sequencing was performed. Induction of specific genes was validated by Western Blot, and cytokine secretion assessed by ELISA. In-vitro cell viability was assessed by Cell TiterGlo (Promega). In vivo efficacy studies used subcutaneous MC38 and GL261 syngeneic tumor models, and characterisation of the TME was performed by flow cytometry. Results Treatment with METTL3i sensitized cells to DNA damaging agents such as doxorubicin. On the molecular level, further enhancement of the IFN pathway by the combination treatment was observed. Moreover, combination of METTL3i with radiation treatment (RT) in vivo in the MC38 colorectal syngeneic mouse model demonstrated a clear benefit of the combination over each of the single treatments. METTL3i alone or in combination with RT led to a major TME remodulation, reducing the number of Tregs, M2 macrophages and neutrophils, and increasing the number of M1 macrophages and CD8+ T-cells in tumors. The GL261 syngeneic glioma model is exquisitely sensitive to anti-PD1 treatment. Similarly, METTL3i treatment led to multiple complete regressions, and the combination of METTL3i and anti-PD1 further accelerated the occurrence of regressions. Following a 3-weeks’ observation period, tumor free mice were re-inoculated with GL261 cells. All tumor-free mice remained tumor free after the rechallenge. Conclusions In pre-clinical cancer models, treatment with METTL3i such as STC-15 resulted in activation of innate immune pathways and subsequent enhancement of cytotoxic T-cell activity. In-vivo, STC-15 had a profound effect on the TME, shifting it from an immunosuppressive, pro-tumorigenic state to an immunostimulatory, anti-tumor state. In combination with anti-PD1, METTL3 inhibitors generate a durable anti-tumor response and lasting immune memory. A First-in-Human dose escalating study evaluating STC-15 monotherapy in patients with solid tumors is ongoing (NCT05584111). Citation Format: Yaara Ofir-Rosenfeld, Lina Vasiliauskaitė, Joanna Obacz, Georgia Tsagkogeorga, Josefin-Beate Holz, Jerry McMahon, Oliver Rausch. STC-15, a small molecule inhibitor of the RNA methyltransferase METTL3, activates anti-tumor immunity and reshapes the tumor microenvironment [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr C077.

Abstract B157: Preclinical evaluation of the blood-brain barrier permeability and intracranial efficacy of the next-generation RET inhibitor Vepafestinib

Abstract Background. Drug resistance and central nervous system (CNS) metastasis often hampers response to precision therapy for RET-rearranged solid tumors. Vepafestinib (Vepa) is a clinical-stage, potent and selective RET tyrosine-kinase inhibitor (TKI) with proven activity against on-target resistance mutations that arise post first-generation RET TKI. Here, we utilized an array of structural and pharmacokinetic methods to determine blood-brain barrier (BBB) permeability of vepa compared with other RET TKIs. Furthermore, we correlate BBB penetrability of RET inhibitors with in vivo efficacy in preclinical models of RET-rearranged intracranial solid tumors. Methods. RET inhibitors were generated by rational chemical design to identify agents which penetrate BBB more effectively than currently approved RET TKIs, and with reduced efflux transporter susceptibility. Transcellular transport assays were conducted in LLC-PK1 and MDCK II cells expressing P-gp and BCRP, respectively. Brain penetrability was assessed by total (Kp) and unbound (Kp,uu) brain:plasma concentration ratios in male Balb/c mice and microdialysis studies in freely-moving male Wistar rats. Models of CNS metastasis were generated by implanting cells labelled with luciferase into the cerebellum of mice. Studies were conducted in comparison with selpercatinib (Selp), pralsetinib (Pral) and TPX-0046. Results. Assessment of Kp and Kp,uu parameters of analogs revealed an excellent structure-activity relationship where modification at the 6-position of the pyrrolopyrimidine core resulted in improved BBB penetrability. The analog with the most favorable physiochemical and biological properties was Vepa. Vepa showed poor susceptibility to P-gp and BCRP-mediated efflux and better CNS penetrability (Kp,uu: 1.3) and retention than Sel, Pral and TPX-0046. The ratio of the observed concentrations of Vepa in microdialysates from the prefrontal cortex, cerebrospinal fluid (CSF) and plasma free fraction was approximately 1:1:1; these ratios were maintained from 2h to 6.5h after Vepaadministration (up to 8h for CSF). Importantly, Vepa was more effective than Selp at causing regression of intracranial xenograft tumors of RET fusion-driven malignancies (lung adenocarcinoma and sarcoma), thus extending survival of tumor-bearing animals. Common first-generation RET TKI resistance mutations at the solvent front (G810A/C/S/R), gatekeeper (V804L/M), hinge (Y806C) and roof (L730Q/R) regions remained sensitive to Vepa. Vepa was more selective than Selp, Pral and TPX-0046, inhibiting only RET when profiled against a panel of 256 kinases. In contrast, Selp, Pral and TPX-0045 also inhibited VEGFR2, and 4, 11 and 39 additional kinases, respectively. Conclusions. Vepafestinib is a structurally distinct and specific RET inhibitor, with superior brain penetration and retention kinetics. It is more effective than selpercatinib in controlling CNS disease. Vepafestinib is currently undergoing phase 1 and 2 clinical trial for patients with advanced solid tumors with RET alterations (margaRET, NCT04683250). Citation Format: Igor Odintsov, Kentaro Wakayama, Tom Zhang, Satoru Iguchi, Masanori Kato, Allan JW Lui, Inna Khodos, Morana Vojnic, Claudio Giuliano, Annalisa Bonifacio, Monika A Davare, Elisa de Stanchina, Emanuela Lovati, Marc Ladanyi, Isao Miyazaki, Romel Somwar. Preclinical evaluation of the blood-brain barrier permeability and intracranial efficacy of the next-generation RET inhibitor Vepafestinib [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr B157.

Cooperative Armoring of CAR and TCR T Cells by T Cell-Restricted IL15 and IL21 Universally Enhances Solid Tumor Efficacy.

Chimeric antigen receptor (CAR) and T-cell receptor (TCR) T-cell therapies are effective in a subset of patients with solid tumors, but new approaches are needed to universally improve patient outcomes. Here, we developed a technology to leverage the cooperative effects of IL15 and IL21, two common cytokine-receptor gamma chain family members with distinct, pleiotropic effects on T cells and other lymphocytes, to enhance the efficacy of adoptive T cells. We designed vectors that induce the constitutive expression of either membrane-tethered IL15, IL21, or IL15/IL21. We used clinically relevant preclinical models of transgenic CARs and TCRs against pediatric and adult solid tumors to determine the effect of the membrane-tethered cytokines on engineered T cells for human administration. We found that self-delivery of these cytokines by CAR or TCR T cells prevents functional exhaustion by repeated stimulation and limits the emergence of dysfunctional natural killer (NK)-like T cells. Across different preclinical murine solid tumor models, we observed enhanced regression with each individual cytokine but the greatest antitumor efficacy when T cells were armored with both. The coexpression of membrane-tethered IL15 and IL21 represents a technology to enhance the resilience and function of engineered T cells against solid tumors and could be applicable to multiple therapy platforms and diseases. See related commentary by Ruffin et al., p. 1431.

MAP kinase ERK5 modulates cancer cell sensitivity to extrinsic apoptosis induced by death-receptor agonists

Death receptor ligand TRAIL is a promising cancer therapy due to its ability to selectively trigger extrinsic apoptosis in cancer cells. However, TRAIL–based therapies in humans have shown limitations, mainly due inherent or acquired resistance of tumor cells. To address this issue, current efforts are focussed on dissecting the intracellular signaling pathways involved in resistance to TRAIL, to identify strategies that sensitize cancer cells to TRAIL-induced cytotoxicity. In this work, we describe the oncogenic MEK5-ERK5 pathway as a critical regulator of cancer cell resistance to the apoptosis induced by death receptor ligands. Using 2D and 3D cell cultures and transcriptomic analyses, we show that ERK5 controls the proteostasis of TP53INP2, a protein necessary for full activation of caspase-8 in response to TNFα, FasL or TRAIL. Mechanistically, ERK5 phosphorylates and induces ubiquitylation and proteasomal degradation of TP53INP2, resulting in cancer cell resistance to TRAIL. Concordantly, ERK5 inhibition or genetic deletion, by stabilizing TP53INP2, sensitizes cancer cells to the apoptosis induced by recombinant TRAIL and TRAIL/FasL expressed by Natural Killer cells. The MEK5-ERK5 pathway regulates cancer cell proliferation and survival, and ERK5 inhibitors have shown anticancer activity in preclinical models of solid tumors. Using endometrial cancer patient-derived xenograft organoids, we propose ERK5 inhibition as an effective strategy to sensitize cancer cells to TRAIL-based therapies.

Combretastatin A-4 suppresses the invasive and metastatic behavior of glioma cells and induces apoptosis in them: in-vitro study.

The most common primary brainmalignancy, glioblastoma multiforme, is tremendously resistant to conventionaltreatmentsdue to its potency for metastasis to surrounding brain tissue. Temozolomide is a chemotherapeutic agent that currently is administrated during the treatment procedure. Studies have attempted to investigate new agents with higher effectiveness and fewer side effects. Combretastatin A-4 (CA-4), a natural compound derived from Combretum caffrum, has been recently considered for its potent antitumor activities in a wide variety of preclinical solid tumor models. Our findings have shown that CA-4 exerts potent anti-proliferative and apoptotic effects on glioma cells, and ROS generation may be involved in these cellular events. CA-4 has imposed G2 arrest in U-87 cells. We also observed that CA-4 significantly reduced the migration and invasion capability of U-87 cells. Furthermore, the gene expression and enzyme activity of MMP-2 and MMP-9 were significantly inhibited in the presence of CA-4. We also observed a considerable decrease in PI3K and Akt protein expression following treatment with CA-4. In conclusion, our findings showed significant apoptogenic and anti-metastatic effects of CA-4 on glioma cells and also suggested that the PI3K/Akt/MMP-2/-9 and also ROS pathway might play roles in these cellular events.

First-in-human, phase I study of KC1036, a multiple kinase inhibitor, as a single agent in patients with advanced solid tumors.

e15000 Background: KC1036 is a novel and selective multi-kinase inhibitor that targets cell proliferation, angiogenesis, metastasis and drug resistance by inhibiting receptor tyrosine kinases (AXLs and VEGFRs) involved in the tumor microenvironment. KC1036 has demonstrated anti-tumor activity in preclinical models of solid tumors, including non-small cell lung cancer (NSCLC). Methods: This phase I, first-in-human study of KC1036 (NCT04387916) enrolled adult patients (pts) with advanced or metastatic solid tumors. This study was comprised of dose escalation (Part A: With the accelerated titration of the 10 mg QD, in which only one patient was enrolled, a standard 3+3 design was applied for 20, 40, 60, and 80 mg QD) followed by dose expansion (Part B) and recommended phase II dose (RP2D) expansion (Part C). The primary safety endpoints were to determine dose limiting toxicities (DLTs) and RP2D. Secondary endpoints included pharmacokinetics (PK) and preliminary efficacy evaluated per RECIST v1.1 criterion. Results: As of November 30, 2022, a total of 41 pts had received at least 1 dose of KC1036 orally with 13 pts in Part A (10 mg [n = 1], 20 mg [n = 3], 40 mg [n = 3], 60 mg [n = 4], 80 mg [n = 3]) and 28 pts in Part B (60 mg [n = 21], 80 mg [n = 7]). In Part A, no DLTs were observed, and the maximum tolerated dose (MTD) has not been reached. Consequently, 60 mg and 80 mg were recommended for Part B. Pts most commonly had NSCLC (31.7%, 13/41), esophageal cancer (14.6%, 6/41), colorectal cancer (12.1%, 5/41). All pts were heavily pre-treated with 65% (27/41) receiving three or more lines of therapy, and average targeted tumor size was 58.7 mm with the largest 162 mm. Of the 41 pts, the median duration of KC1036 exposure was 105.0 days (range, 51.0-168.0). Any-grade TRAEs occurred in 39 pts (95.1%), with 16 pts (39.0%) reported with ≥ Grade 3. The most commonly reported ≥ Grade 3 TRAEs at 60 mg was hypertension (16.7%, 4/24), and that at 80 mg was diarrhea (30.0%, 3/10). PK analysis showed that KC1036 exhibited with dose-proportional increases in exposure over the range of 10 to 40 mg, but increased less proportionally within the range of 40-80 mg. Of 36 pts who had at least one efficacy evaluation, 5 (13.9%) had a best response of partial response (PR) and 24 (66.7%) had stable disease (SD). Thus, ORR was 13.9% (95% CI: 4.7, 29.5) and DCR was 80.6% (95% CI: 64.0, 91.2). Among the 9 evaluable pts with lung adenocarcinoma (6 on 60 mg and 3 on 80 mg), 2 pts had PR, 5 had SD and 2 had progressive disease (PD) as best response. Sustainable PR for 42 weeks was observed in 1 patient with lung adenocarcinoma on 60 mg. Conclusions: KC1036 demonstrated a manageable safety profile and preliminary antitumor activity in pts with advanced solid tumors. Taking safety, efficacy and clinical PK into consideration, 60 mg QD was recommended as RP2D for Part C, and this part was ongoing. Further studies in pts with lung adenocarcinoma would be considered promising. Clinical trial information: NCT04387916 .

Abstract 2660: HMBD-501 - a novel Fc engineered, exatecan-based next generation HER3 targeting antibody drug conjugate shows robust efficacy and tolerability in pre-clinical solid tumor models

Abstract HER3 is a member of the epidermal growth factor receptor (ERBB) family of tyrosine kinase receptors overexpressed in a broad range of tumors and is associated with disease progression and poor survival. For example, more than 50% of melanoma, cervical, lung, gastric, colorectal, and ovarian cancers show overexpression of HER3, while in breast, pancreatic and prostate cancers the overexpression ranges between 25-40%. In addition, recent studies show that HER3 expression is significantly induced in tumors during metastasis (in colorectal) and during acquired resistance to tyrosine kinase inhibitors (TKI) in lung cancers. This widespread overexpression of HER3 makes it an ideal target for antibody drug conjugates (ADCs). ADCs are a therapeutic modality that harness an antibody’s target specificity to selectively deliver cytotoxic payloads to tumors. Patritumab-Deruxtecan (U3-1402), a HER3-targeting ADC, showed clinical response in a subset of EGFR mutant and TKI resistant lung cancers in a Phase 1 study, albeit with toxicities including severe interstitial lung disease (ILD) and high grade cytopenias. Mechanistic studies show that these ADC-related toxicities are likely driven by Fc- or micropinocytosis-mediated uptake of ADCs by normal cells. We have developed HMBD-501, a novel anti-HER3 ADC with (i) a high-affinity Fab, which can bind to HER3 in the presence or absence of its ligand NRG1, (ii) an engineered Fc-domain to avoid FcgR binding and potential toxicities, and (iii) site-specific conjugation to a next generation cleavable linker and exatecan-based payload. In our preclinical studies, HMBD-501 demonstrates superior inhibition of tumor growth compared to other exatecan-based anti-HER3 ADCs, in a variety of in vitro and in vivo cancer models with a range of HER3 expression. Additionally, the optimized Fc engineering of HMBD-501 shows enhanced tolerability in vivo indicating a potential reduction in Fc mediated toxicities. Finally, the next generation site-specific conjugation-linker-payload technology of HMBD-501 allows optimal plasma stability and pharmacokinetic profile. In conclusion, HMBD-501 represents a next generation HER3 targeting ADC that has a potentially best-in-class efficacy and tolerability profile. Our findings strongly support the development of HMBD-501 as a promising candidate in the treatment of HER3 expressing solid tumors. Citation Format: Suhail Ahmed Kabeer Rasheed, Dipti Thakkar, Shalini Paliwal, Wen Jie Chin, Akshaya Bansal, Ben Ayers, Che Theng ng, Brendon Hanson, Piers Ingram, Jerome Boyd-Kirkup. HMBD-501 - a novel Fc engineered, exatecan-based next generation HER3 targeting antibody drug conjugate shows robust efficacy and tolerability in pre-clinical solid tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2660.