The search for therapeutic targets in lung cancer: Preclinical and human studies of carcinoembryonic antigen-related cell adhesion molecule 5 expression and its associated molecular landscape.

OBJECTIVES: CEACAM5 is a cell-surface glycoprotein expressed on epithelial cells of some solid tumors. Tusamitamab ravtansine (SAR408701), a humanized antibody-drug conjugate targeting CEACAM5, is in clinical development for nonsquamous non-small cell lung cancer (NSQ-NSCLC) with CEACAM5 high expression (HE), defined as membranous CEACAM5 immunohistochemistry staining at ≥ 2+ intensity in ≥ 50% of tumor cells. MATERIALS AND METHODS: We investigated correlations between CEACAM5 expression by immunohistochemistry, CEACAM5 protein expression by ELISA, and CEACAM5 RNA expression by RNA-seq in NSQ-NSCLC patient-derived xenograft (PDX) models, and tumor responses to tusamitamab ravtansine in these models. We assessed prevalence of CEACAM5 HE, clinicopathologic characteristics and molecular markers in patients with NSQ-NSCLC in clinical cohorts. RESULTS: In a lung PDX set of 10 NSQ-NSCLC specimens, correlations between CEACAM5 by IHC, ELISA and RNA-seq ranged from 0.72 to 0.88. In a larger lung PDX set, higher H-scores were present in NSQ- (n = 93) vs SQ-NSCLC (n = 128) models, and in 12 of these NSQ-NSCLC models, more tumor responses to tusamitamab ravtansine occurred in CEACAM5 HE (5/8; 62.5%) versus moderate or negative expression (1/4; 25%), including 3 with KRAS mutations among the 6 responders. In clinical NSQ-NSCLC samples, CEACAM5 HE prevalence was (52/214; 24.3%) in primary tumors and (6/17; 35.3%) in metastases. In NSQ-NSCLC primary tumors, CEACAM5 HE prevalence was significantly higher in KRAS-altered versus wild-type (35.0% vs 19.5%; P = 0.028) and in programmed cell death ligand 1 (PD-L1) negative (tumor cells 0%)/low (1-49%) versus high (≥50%) (33.3%, 26.1%, 5.0%; P = 0.031), but not significantly different in EGFR-mutated versus wild-type (20.0% vs 25.7%, P = 0.626). CONCLUSIONS: In NSQ-NSCLC tumors, CEACAM5 HE prevalence was 24.3% overall and was higher with KRAS altered and with PD-L1 negative/low tumors but similar regardless of EGFR mutation status. These findings support targeting CEACAM5 and the clinical development of tusamitamab ravtansine for patients with NSQ-NSCLC with CEACAM5 HE.

Control of acute myeloid leukemia by a trifunctional NKp46-CD16a-NK cell engager targeting CD123.

CD123, the alpha chain of the IL-3 receptor, is an attractive target for acute myeloid leukemia (AML) treatment. However, cytotoxic antibodies or T cell engagers targeting CD123 had insufficient efficacy or safety in clinical trials. We show that expression of CD64, the high-affinity receptor for human IgG, on AML blasts confers resistance to anti-CD123 antibody-dependent cell cytotoxicity (ADCC) in vitro. We engineer a trifunctional natural killer cell engager (NKCE) that targets CD123 on AML blasts and NKp46 and CD16a on NK cells (CD123-NKCE). CD123-NKCE has potent antitumor activity against primary AML blasts regardless of CD64 expression and induces NK cell activation and cytokine secretion only in the presence of AML cells. Its antitumor activity in a mouse CD123+ tumor model exceeds that of the benchmark ADCC-enhanced antibody. In nonhuman primates, it had prolonged pharmacodynamic effects, depleting CD123+ cells for more than 10 days with no signs of toxicity and very low inflammatory cytokine induction over a large dose range. These results support clinical development of CD123-NKCE.

AMEERA-1 phase 1/2 study of amcenestrant, SAR439859, in postmenopausal women with ER-positive/HER2-negative advanced breast cancer.

AMEERA-1 is a Phase 1/2 open-label single-arm study evaluating once-daily (QD) amcenestrant, an orally bioavailable selective estrogen receptor (ER) degrader, in postmenopausal women with ER+/HER2- advanced breast cancer (NCT03284957), who were mostly heavily pretreated (including targeted therapies and fulvestrant). In the dose escalation phase (Part A: n = 16), patients received amcenestrant 20-600 mg QD. Based on absence of dose-limiting toxicities, paired functional 18F-fluoroestradiol positron emission tomography, and pharmacokinetics, 400 mg QD was selected as recommended Phase 2 dose (RP2D) for the dose expansion phase (Part B: n = 49). No Grade ≥3 treatment-related adverse events or clinically significant cardiac/eye toxicities were reported. The Part B primary endpoint, confirmed objective response rate (ORR) was 3/45 at the interim analysis and 5/46 (10.9%) at the final analysis. The overall clinical benefit rate (CBR) was 13/46 (28.3%). CBRs among patients with baseline wild-type and mutated ESR1 were 9/26 (34.6%) and 4/19 (21.1%), respectively. Paired tumor biopsy and cell-free DNA analyses revealed ER inhibition and degradation, and a reduction in detectable ESR1 mutations, including Y537S. In conclusion, amcenestrant at RP2D of 400 mg QD for monotherapy is well-tolerated with no dose-limiting toxicities, and demonstrates preliminary antitumor activity irrespective of baseline ESR1 mutation status.

Two Patient Studies of a Companion Diagnostic Immuno-Positron Emission Tomography (PET) Tracer for Measuring Human CA6 Expression in Cancer for Antibody Drug Conjugate (ADC) Therapy.

An antigen binding fragment (BFab) derived from a tumor-associated mucin 1-sialoglycotope antigen (CA6) targeting antibody (huDS6) was engineered. We synthesized a companion diagnostic positron emission tomography (PET) tracer by radiolabeling BFab with [64Cu] to measure CA6 expression on cancer tissues prior to anti-human CA6 (huDS6-DM4 antibody-drug conjugate) therapy for ovarian and breast cancer patients. After chemotherapy, the ovarian patient received PET scan with 18F-2-fluoro-2-deoxyglucose ([18F]FDG: 10 mCi), followed by [64Cu]-DOTA-BFab ([64Cu]BFab; 5.5 mCi) 1 week later for PET scanning of CA6 expression and subsequent surgery. The breast cancer patient was treated with chemotherapy before primary tumor resection and subsequent [18F]FDG-PET scan. 4 weeks later the patient received of [64Cu]BFab (11.7 mCi) for CA6 PET scan. Whole body [18F]FDG-PET of the breast cancer patient indicated FDG-avid tumor metastases to the liver, bilateral hila and thoracic spine, but no uptake was observed for the ovarian patient. Each patient was also imaged by PET/CT with [64Cu]BFab at 1 and 24 hours after tracer administration. The [64Cu]BFab tracer was well tolerated by both patients without adverse effects, and no significant tracer uptake was observed in both patients. Immunohistochemistry (IHC) data indicated CA6 expressions were weak to intermediate and matched with the [64Cu]BFab-PET signals.

Establishment and Characterization of a Reliable Xenograft Model of Hodgkin Lymphoma Suitable for the Study of Tumor Origin and the Design of New Therapies.

To identify the cells responsible for the initiation and maintenance of Hodgkin lymphoma (HL) cells, we have characterized a subpopulation of HL cells grown in vitro and in vivo with the aim of establishing a reliable and robust animal model for HL. To validate our model, we challenged the tumor cells in vivo by injecting the alkylating histone-deacetylase inhibitor, EDO-S101, a salvage regimen for HL patients, into xenografted mice. Methodology: Blood lymphocytes from 50 HL patients and seven HL cell lines were used. Immunohistochemistry, flow cytometry, and cytogenetics analyses were performed. The in vitro and in vivo effects of EDO-S101 were assessed. Results: We have successfully determined conditions for in vitro amplification and characterization of the HL L428-c subline, containing a higher proportion of CD30-/CD15- cells than the parental L428 cell line. This subline displayed excellent clonogenic potential and reliable reproducibility upon xenografting into immunodeficient NOD-SCID-gamma (-/-)(NSG) mice. Using cell sorting, we demonstrate that CD30-/CD15- subpopulations can gain the phenotype of the L428-c cell line in vitro. Moreover, the human cells recovered from the seventh week after injection of L428-c cells into NSG mice were small cells characterized by a high frequency of CD30-/CD15- cells. Cytogenetic analysis demonstrated that they were diploid and showed high telomere instability and telomerase activity. Accordingly, chromosomal instability emerged, as shown by the formation of dicentric chromosomes, ring chromosomes, and breakage/fusion/bridge cycles. Similarly, high telomerase activity and telomere instability were detected in circulating lymphocytes from HL patients. The beneficial effect of the histone-deacetylase inhibitor EDO-S101 as an anti-tumor drug validated our animal model. Conclusion: Our HL animal model requires only 10³ cells and is characterized by a high survival/toxicity ratio and high reproducibility. Moreover, the cells that engraft in mice are characterized by a high frequency of small CD30-/CD15- cells exhibiting high telomerase activity and telomere dysfunction.

Tasquinimod modulates tumor-infiltrating myeloid cells and improves the antitumor immune response to PD-L1 blockade in bladder cancer.

The infiltration of myeloid cells helps tumors to overcome immune surveillance and imparts resistance to cancer immunotherapy. Thus, strategies to modulate the effects of these immune cells may offer a potential therapeutic benefit. We report here that tasquinimod, a novel immunotherapy which targets S100A9 signaling, reduces the immunosuppressive properties of myeloid cells in preclinical models of bladder cancer (BCa). As single anticancer agent, tasquinimod treatment was effective in preventing early stage tumor growth, but did not achieve a clear antitumor effect in advanced tumors. Investigations of this response revealed that tasquinimod induces an increase in the expression of a negative regulator of T cell activation, Programmed-death-ligand 1 (PD-L1). This markedly weakens its antitumor immunity, yet provokes an "inflamed" milieu rendering tumors more prone to T cell-mediated immune attack by PD-L1 blockade. Interestingly, the combination of tasquinimod with an Anti-PD-L1 antibody enhanced the antitumor immune response in bladder tumors. This combination synergistically modulated tumor-infiltrating myeloid cells, thereby strongly affecting proliferation and activation of effector T cells. Together, our data provide insight into the rational combination of therapies that activate both innate and adaptive immune system, such as the association of S100A9-targeting agents with immune checkpoints inhibitors, to improve the response to cancer immunotherapeutic agents in BCa.

Tasquinimod triggers an early change in the polarization of tumor associated macrophages in the tumor microenvironment.

BACKGROUND: Tasquinimod (a quinoline-3-carboxyamide) is a small molecule immunotherapy with demonstrated effects on the tumor microenvironment (TME) involving immunomodulation, anti-angiogenesis and inhibition of metastasis. A target molecule of tasquinimod is the inflammatory protein S100A9 which has been shown to affect the accumulation and function of suppressive myeloid cell subsets in tumors. Given the major impact of myeloid cells to the tumor microenvironment, manipulation of this cell compartment is a desirable goal in cancer therapeutics. METHODS: To understand the consequences of tasquinimod treatment on the TME, we evaluated early treatment effects in tumor infiltrating myeloid cells. Cellular phenotypes were studied by flow cytometry while gene expression both in tumor tissue and in isolated CD11b(+) cells or tumor cells were measured by real time-PCR. Effects on angiogenesis were monitored by changes in CD31 levels and by gene expression in tumor tissue. Effects on cytokine levels in tumor tissue and serum were determined by multiplex analysis. RESULTS: The MC38-C215 colon carcinoma tumors showed a substantial infiltration of primarily myeloid cells that were dominated by Ly6C(low)F4/80(+)CD206(+) M2-polarized tumor associated macrophages (TAMs), an immuno-suppressive and pro-angiogenic cell population. Here, we show that tasquinimod treatment induces an anti-tumor effect which is subsequent to a reduction in tumor infiltrating CD206(+) M2 macrophages and a simultaneous increase in M1 macrophages expressing MHC class II and CD86. The tasquinimod-induced changes in TAM polarization were evident within 24 h of exposure, emphasizing the ability of tasquinimod to rapidly reprogram the tumor microenvironment. This change in the tumor associated myeloid compartment preceded an increased IL12-production within the tumor and a decrease in tumor neovascularization. The switch in TAM polarization by tasquinimod was confirmed in the 4T1 breast cancer model where tasquinimod also reduce lung metastasis development. CONCLUSION: Our data show that tasquinimod affects tumor infiltrating myeloid cells early after exposure, leading to a change in phenotype from pro-angiogenic and immunosuppressive M2-like TAMs to pro-inflammatory M1-like macrophages. These changes are consistent with the effects of tasquinimod seen on tumor vascularization, immune suppression and metastasis giving further insights to the anti-tumor mechanism of action of tasquinimod.

Preeclampsia-like symptoms induced in mice by fetoplacental expression of STOX1 are reversed by aspirin treatment.

Preeclampsia (PE) is a common human-specific pregnancy disorder defined by hypertension and proteinuria during gestation and responsible for maternal and fetal morbimortality. STOX1, encoding a transcription factor, was the first gene associated with PE as identified by positional cloning approaches. Its overexpression in choriocarcinoma cells mimics the transcriptional consequences of PE in the human placenta. Here, we created transgenic mouse strains overexpressing human STOX1. Wild-type female mice crossed with transgenic male mice reproduce accurately the symptoms of severe PE: gestational hypertension, proteinuria, and elevated plasma levels of soluble fms-like tyrosine kinase 1 and soluble endoglin. Placental and kidney histology were altered. Symptoms were prevented or alleviated by aspirin treatment. STOX1-overexpressing mice constitute a unique model for studying PE, allow testing therapeutic approaches, and assessing the long-term effects of the preeclamptic syndrome.

Characterization of novel genomic alterations and therapeutic approaches using acute megakaryoblastic leukemia xenograft models.

Acute megakaryoblastic leukemia (AMKL) is a heterogeneous disease generally associated with poor prognosis. Gene expression profiles indicate the existence of distinct molecular subgroups, and several genetic alterations have been characterized in the past years, including the t(1;22)(p13;q13) and the trisomy 21 associated with GATA1 mutations. However, the majority of patients do not present with known mutations, and the limited access to primary patient leukemic cells impedes the efficient development of novel therapeutic strategies. In this study, using a xenotransplantation approach, we have modeled human pediatric AMKL in immunodeficient mice. Analysis of high-throughput RNA sequencing identified recurrent fusion genes defining new molecular subgroups. One subgroup of patients presented with MLL or NUP98 fusion genes leading to up-regulation of the HOX A cluster genes. A novel CBFA2T3-GLIS2 fusion gene resulting from a cryptic inversion of chromosome 16 was identified in another subgroup of 31% of non-Down syndrome AMKL and strongly associated with a gene expression signature of Hedgehog pathway activation. These molecular data provide useful markers for the diagnosis and follow up of patients. Finally, we show that AMKL xenograft models constitute a relevant in vivo preclinical screening platform to validate the efficacy of novel therapies such as Aurora A kinase inhibitors.

A mammary gland adenomyoepithelioma in a C57BL/6 mouse.

Mammary gland adenomyoepitheliomas are benign complex mammary gland tumors composed of neoplastic cells of epithelial and myoepithelial origins, described in many species (humans, dogs, cats, rats) and rarely in mice. We report here an adenomyoepithelioma in a C57BL/6 female mouse. Histologically, tubes and cords formed by neoplastic epithelial cells were separated by bundles of neoplastic myoepithelial cells in a clear and partially mucinous matrix. The tumor displayed characteristics of a benign neoplastic proliferation with a compressive growth pattern, and moderate cellular pleomorphism and mitotic index. At immunohistochemistry, the epithelial cells were strongly cytokeratin positive; the myoepithelial cells were weakly cytokeratin positive and strongly smooth muscle actin positive. This is to our knowledge, the first report of a mammary gland adenomyoepithelioma in a C57BL/6 mouse.

An atypical case of histiocytic sarcoma in a Wistar rat (Rattus norvegicus).

Histiocytic sarcoma is the most frequent hematopoietic tumor in rats. We report here a histiocytic sarcoma infiltrating the liver, the spleen and the pancreas from a Wistar rat. In the liver, the tumor was associated with oval cell and bile duct hyperplasia. The cells looked like neoplastic histocytic cells described in this species but with some particularities (e.g. lack of multinucleated giant cells). At immunohistochemistry, neoplastic cells in the liver were vimentine positive but lysozyme and CD68 negative. In the kidney, lysozyme-positive cytoplasmic droplets were observed. We describe here an atypical case of histiocytic sarcoma in the rat and we compare the nature of these neoplastic cells to other species.