Functional host-specific adaptation of the intestinal microbiome in hominids

Fine-scale knowledge of the changes in composition and function of the human gut microbiome compared that of our closest relatives is critical for understanding the evolutionary processes underlying its developmental trajectory. To infer taxonomic and functional changes in the gut microbiome across hominids at different timescales, we perform high-resolution metagenomic-based analyzes of the fecal microbiome from over two hundred samples including diverse human populations, as well as wild-living chimpanzees, bonobos, and gorillas. We find human-associated taxa depleted within non-human apes and patterns of host-specific gut microbiota, suggesting the widespread acquisition of novel microbial clades along the evolutionary divergence of hosts. In contrast, we reveal multiple lines of evidence for a pervasive loss of diversity in human populations in correlation with a high Human Development Index, including evolutionarily conserved clades. Similarly, patterns of co-phylogeny between microbes and hosts are found to be disrupted in humans. Together with identifying individual microbial taxa and functional adaptations that correlate to host phylogeny, these findings offer insights into specific candidates playing a role in the diverging trajectories of the gut microbiome of hominids. We find that repeated horizontal gene transfer and gene loss, as well as the adaptation to transient microaerobic conditions appear to have played a role in the evolution of the human gut microbiome.

Brentuximab Vedotin-Driven Microtubule Disruption Results in Endoplasmic Reticulum Stress Leading to Immunogenic Cell Death and Antitumor Immunity

Brentuximab vedotin, a CD30-directed antibody-drug conjugate (ADC), is approved for clinical use in multiple CD30-expressing lymphomas. The cytotoxic payload component of brentuximab vedotin is monomethyl auristatin E (MMAE), a highly potent microtubule-disrupting agent. Preclinical results provided here demonstrate that treatment of cancer cells with brentuximab vedotin or free MMAE leads to a catastrophic disruption of the microtubule network eliciting a robust endoplasmic reticulum (ER) stress response that culminates in the induction of the classic hallmarks of immunogenic cell death (ICD). In accordance with the induction of ICD, brentuximab vedotin-killed lymphoma cells drove innate immune cell activation in vitro and in vivo. In the "gold-standard" test of ICD, vaccination of mice with brentuximab vedotin or free MMAE-killed tumor cells protected animals from tumor rechallenge; in addition, T cells transferred from previously vaccinated animals slowed tumor growth in immunodeficient mice. Immunity acquired from killed tumor cell vaccination was further amplified by the addition of PD-1 blockade. In a humanized model of CD30+ B-cell tumors, treatment with brentuximab vedotin drove the expansion and recruitment of autologous Epstein-Barr virus-reactive CD8+ T cells potentiating the activity of anti-PD-1 therapy. Together, these data support the ability of brentuximab vedotin and MMAE to drive ICD in tumor cells resulting in the activation of antigen-presenting cells and augmented T-cell immunity. These data provide a strong rationale for the clinical combination of brentuximab vedotin and other MMAE-based ADCs with checkpoint inhibitors.

SGN-B7H4V, an investigational vedotin ADC directed to the immune checkpoint ligand B7-H4, shows promising activity in preclinical models

BACKGROUND

SGN-B7H4V is a novel investigational vedotin antibody-drug conjugate (ADC) comprising a B7-H4-directed human monoclonal antibody conjugated to the cytotoxic payload monomethyl auristatin E (MMAE) via a protease-cleavable maleimidocaproyl valine citrulline (mc-vc) linker. This vedotin linker-payload system has been clinically validated in multiple Food and Drug Administration approved agents including brentuximab vedotin, enfortumab vedotin, and tisotumab vedotin. B7-H4 is an immune checkpoint ligand with elevated expression on a variety of solid tumors, including breast, ovarian, and endometrial tumors, and limited normal tissue expression. SGN-B7H4V is designed to induce direct cytotoxicity against target cells by binding to B7-H4 on the surface of target cells and releasing the cytotoxic payload MMAE upon internalization of the B7-H4/ADC complex.

METHODS

B7-H4 expression was characterized by immunohistochemistry across multiple solid tumor types. The ability of SGN-B7H4V to kill B7-H4-expressing tumor cells in vitro and in vivo in a variety of xenograft tumor models was also evaluated. Finally, the antitumor activity of SGN-B7H4V as monotherapy and in combination with an anti-programmed cell death-1 (PD-1) agent was evaluated using an immunocompetent murine B7-H4-expressing Renca tumor model.

RESULTS

Immunohistochemistry confirmed B7-H4 expression across multiple solid tumors, with the highest prevalence in breast, endometrial, and ovarian tumors. In vitro, SGN-B7H4V killed B7-H4-expressing tumor cells by MMAE-mediated direct cytotoxicity and antibody-mediated effector functions including antibody-dependent cellular cytotoxicity and antibody-dependent cellular phagocytosis. In vivo, SGN-B7H4V demonstrated strong antitumor activity in multiple xenograft models of breast and ovarian cancer, including xenograft tumors with heterogeneous B7-H4 expression, consistent with the ability of vedotin ADCs to elicit a bystander effect. In an immunocompetent murine B7-H4-expressing tumor model, SGN-B7H4V drove robust antitumor activity as a monotherapy that was enhanced when combined with an anti-PD-1 agent.

CONCLUSION

The immune checkpoint ligand B7-H4 is a promising molecular target expressed by multiple solid tumors. SGN-B7H4V demonstrates robust antitumor activity in preclinical models through multiple potential mechanisms. Altogether, these preclinical data support the evaluation of SGN-B7H4V as a monotherapy in the ongoing phase 1 study of SGN-B7H4V in advanced solid tumors (NCT05194072) and potential future clinical combinations with immunotherapies.

HER2-Selective and Reversible Tyrosine Kinase Inhibitor Tucatinib Potentiates the Activity of T-DM1 in Preclinical Models of HER2-positive Breast Cancer

The oncogenic receptor HER2 is overexpressed in many cancers, including up to 20% of breast cancers. Despite the availability of HER2-targeted treatments, patients’ disease often progresses during therapy, underscoring the need for novel treatment strategies. The addition of tucatinib, a reversible, highly selective HER2 tyrosine kinase inhibitor (TKI), to treatment with trastuzumab and capecitabine significantly improved survival outcomes of patients with HER2-positive metastatic breast cancer, including those with active brain metastases. We rationalized that combining tucatinib with other HER2-targeting agents with complementary mechanisms of action would further increase efficacy against tumors. We characterized the activity of tucatinib with the antibody–drug conjugate T-DM1 in preclinical models of breast cancer, including HER2-positive breast cancer cells and patient-derived xenograft (PDX) models. Mechanistic details on tucatinib activity were obtained in internalization and catabolism studies. In combination, tucatinib and T-DM1 showed an enhanced, often synergistic, cytotoxic response and demonstrated improved antitumor activity in vivo, including in PDX models refractory to T-DM1 single-agent activity. Mechanistically, tucatinib mediated an increase in inactive HER2 molecules at the cell surface through inhibition of HER2 ubiquitination, resulting in increased internalization and catabolism of T-DM1. The combination was correlated with enhanced HER2 pathway inhibition, decreased proliferation, and increased apoptosis. In a xenograft model of brain metastasis, tucatinib penetrated intracranial tumor tissues, inhibiting tumor growth and improving survival. These results suggest that tucatinib may be the optimal TKI partner for HER2-targeted therapies and support clinical studies of its combination with T-DM1, including in patients with brain metastases.

SIGNIFICANCE

The preclinical findings in breast cancer models presented here demonstrate that combining tucatinib with T-DM1 enhances the antitumor activity of either agent alone, supporting clinical studies of the combination in HER2-positive breast cancer, including in patients with brain metastases, which remains an important unmet medical need.

Sex differences in anxiety and threat avoidance in GAD65 knock-out mice

Anxiety disorders have been linked to a disbalance of excitation and inhibition in a network of brain structures comprising frontal cortical regions, the amygdala and the hippocampus, among others. Recent imaging studies suggest sex differences in the activation of this anxiety network during the processing of emotional information. Rodent models with genetically altered ϒ-amino butyric acid (GABA) neurotransmission allow studying the neuronal basis of such activation shifts and their relation to anxiety endophenotypes, but to date sex effects have rarely been addressed. Using mice with a null mutation of the GABA synthetizing enzyme glutamate decarboxylase 65 (GAD65-/-), we started to compare anxiety-like behavior and avoidance in male vs. female GAD65-/- mice and their wildtype littermates. In an open field, female GAD65-/- mice displayed increased activity, while male GAD65-/- mice showed an increased adaptation of anxiety-like behavior over time. GAD65-/- mice of both sexes had a higher preference for social interaction partners, which was further heightened in male mice. In male mice higher escape responses were observed during an active avoidance task. Together, female mice showed more stable emotional responses despite GAD65 deficiency. To gain insights into interneuron function in network structures controlling anxiety and threat perception, fast oscillations (10-45 Hz) were measured in ex vivo slice preparations of the anterior cingulate cortex (ACC). GAD65-/- mice of both sexes displayed increased gamma power in the ACC and a higher density of PV-positive interneurons, which are crucial for generating such rhythmic activity. In addition, GAD65-/- mice had lower numbers of somatostatin-positive interneurons in the basolateral amygdala and in the dorsal dentate gyrus especially in male mice, two key regions important for anxiety and active avoidance responses. Our data suggest sex differences in the configuration of GABAergic interneurons in a cortico-amygdala-hippocampal network controlling network activity patterns, anxiety and threat avoidance behavior.

Abstract 1522: SGN-B6A induces immunogenic cell death as an additional mechanism of action

SGN-B6A is a novel investigational antibody-drug conjugate (ADC) directed to integrin beta-6 and uses the clinically validated vedotin drug-linker platform that delivers the microtubule disrupting agent, monomethyl auristatin E (MMAE). SGN-B6A is designed to bind and internalize the integrin beta-6/ADC complex from the surface of malignant cells and release the cytotoxic payload MMAE. We have previously demonstrated the antitumor activity of SGN-B6A in cell line-derived xenograft models originating from multiple carcinomas as well as patient-derived xenograft models of non-small cell lung cancer (NSCLC). Other clinically validated vedotin ADCs that deliver MMAE have been shown to induce immunogenic cell death (ICD) in preclinical models and have demonstrated promising clinical activity in combination with immunotherapy. Since the induction of ICD appeared to be a consequence of the activity of MMAE, and is independent of the antibody that delivers it, we hypothesized that this mechanism of action may also apply to SGN-B6A.

Consistent with this hypothesis, we observed that tumor cells treated with SGN-B6A in vitro showed key hallmarks of immunogenic cell death, including markers of endoplasmic reticulum (ER) stress, exposure of calreticulin, and release of ATP and high mobility group protein B1 (HMGB1). Further, in vivo studies demonstrated that treatment with SGN-B6A led to immune activation and recruitment of immune cells to the tumor environment. In an integrin beta-6-expressing syngeneic model, a vedotin ADC directed to integrin beta-6 has shown combinatorial activity with immunotherapy.

Preclinical models suggest that, like other vedotin ADCs, SGN-B6A induces immunogenic cell death which then promotes activation and recruitment of immune cells to the tumor. We have recently reported promising single-agent activity of SGN-B6A in non-small cell lung, head and neck squamous cell, and esophageal cancer observed in interim results of a phase I study (NCT04389632). The combination of SGN-B6A with immunotherapy may be utilized as a potential treatment for integrin-beta-6-expressing tumors including NSCLC, head and neck squamous cell carcinoma, and esophageal carcinoma. Altogether, our preclinical and initial clinical results support the ongoing evaluation of SGN-B6A as a single agent and in combination with immune checkpoint inhibitors.

Citation Format: Vivian H. Trang, Rebecca C. Mazahreh, John J. Gosink, Michelle Ulrich, Devra Olson, Allana Ubben, Sean Allred, Li-Ya Huang, Kelly Hensley, Piper M. Treuting, Kerry Klussman, Shaylin Higgins, Patrick Younan, Roma Yumul, Natalya Nazarenko, Robert P. Lyon. SGN-B6A induces immunogenic cell death as an additional mechanism of action [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 1522.

Abstract 1281: SGN-B7H4V shows immunomodulatory activity through induction of immunogenic cell death

SGN-B7H4V is a novel investigational antibody-drug conjugate composed of a B7-H4-directed human monoclonal antibody conjugated to the validated vedotin drug linker, which incorporates the microtubule disrupting agent monomethyl auristatin E (MMAE) via a protease-cleavable peptide linkage. This vedotin drug linker system has been clinically validated by multiple ADC programs, including brentuximab vedotin, enfortumab vedotin, tisotumab vedotin, and polatuzumab vedotin. B7-H4 is an immune checkpoint ligand with elevated expression on a variety of solid tumor types, including breast, ovarian, and endometrial tumors. SGN-B7H4V is designed to bind and internalize the B7-H4/ADC complex from the surface of malignant cells and release the cytotoxic payload MMAE. The antitumor activity of SGN-B7H4V may be multimodal as SGN-B7H4V can induce tumor cell death through several mechanisms, including MMAE-mediated direct cytotoxicity and bystander killing as well as antibody-mediated functions including antibody-dependent cellular cytotoxicity (ADCC) and phagocytosis (ADCP). Previously, vedotin ADCs have been described to elicit antitumor immune responses in part through induction of immunogenic cell death (ICD) mediated by the MMAE payload. These immunomodulatory effects potentially position vedotin ADCs to uniquely synergize with checkpoint inhibitors, supported by recent clinical activity observed when vedotin ADCs are paired with anti-PD1 agents. Here, we characterize SGN-B7H4V-mediated ICD and subsequent immunomodulatory activity. We also evaluate the contribution of SGN-B7H4V-induced immune activation to antitumor activity in combination with an anti-PD1 agent in an immunocompetent mouse model. In vitro, tumor cells treated with SGN-B7H4V showed several hallmarks of immunogenic cell death, including calreticulin exposure and release of ATP. In vivo, treatment of B7-H4-expressing tumors with SGN-B7H4V led to immune changes in the tumor microenvironment, including recruitment of macrophages and T cells. Finally, SGN-B7H4V drove robust, curative activity in an immunocompetent tumor model as a monotherapy and paired well with an anti-PD1 agent. Altogether, these data support the evaluation of SGN-B7H4V as a monotherapy in a first-in-human phase 1 clinical study and potential future clinical combinations with immunotherapies.

Citation Format: Elizabeth E. Gray, Michelle Ulrich, Angela Epp, Patrick Younan, Kelly Hensley, Sean Allred, Julie Hahn, Kristen Gahnberg, Piper M. Treuting, John J. Gosink, Robert Thurman, Alyson J. Smith, Jason Schrum, Natalya Nazarenko, Shyra J. Gardai. SGN-B7H4V shows immunomodulatory activity through induction of immunogenic cell death [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 1281.

854 SGN-B7H4V, a novel, investigational vedotin antibody-drug conjugate directed to the T cell checkpoint ligand B7-H4, shows promising activity in preclinical models

Background

SGN-B7H4V is a novel, investigational vedotin antibody drug conjugate (ADC) directed to B7-H4, a member of the B7 family of immune checkpoint ligands. B7-H4 expression is elevated on a variety of solid tumors including breast, ovarian, and endometrial tumors.1 SGN-B7H4V is composed of a fully human IgG1 anti-B7-H4 monoclonal antibody (mAb) conjugated to the microtubule disrupting agent monomethyl auristatin E (MMAE) via a protease-cleavable peptide linker. SGN-B7H4V is designed to bind and internalize the immune checkpoint ligand B7-H4/ADC complex from the surface of malignant cells and release the cytotoxic payload MMAE. This ”vedotin” drug linker system has been clinically validated by multiple ADC programs, including brentuximab vedotin, enfortumab vedotin, and polatuzumab vedotin.2–4 Here, we characterize the target antigen B7-H4 and evaluate SGN-B7H4V activity in preclinical models.

Methods

B7-H4 expression was characterized by RNA expression and immunohistochemistry across multiple solid tumor types. The ability of SGN-B7H4V to kill B7-H4-expressing tumor cells in vitro and in vivo in a variety of xenograft tumor models was also evaluated. Finally, the tolerability of SGN-B7H4V was assessed in rodent and non-human primate toxicology studies.

Results

Immunohistochemistry confirmed expression of B7-H4 across multiple solid tumor types, including ovarian and breast tumors. In vitro, upon binding to SGN-B7H4V, the immune checkpoint ligand B7-H4 was rapidly internalized and delivered the cytotoxic payload MMAE. Moreover, SGN-B7H4V killed B7-H4-expressing tumor cells in vitro by MMAE-mediated cytotoxicity, antibody-dependent cellular cytotoxicity (ADCC), and antibody-dependent cellular phagocytosis (ADCP). In vivo, SGN-B7H4V demonstrated strong anti-tumor activity in multiple xenograft models, including ovarian and breast cancer models. Activity was observed in models with both uniformly high and heterogeneous expression of B7-H4, consistent with robust bystander activity of vedotin ADCs. Finally, SGN-B7H4V was tolerated in both rat and non-human primate (NHP) toxicology studies at doses consistent with approved vedotin ADCs.

Conclusions

B7-H4 is a promising ADC target expressed by several solid tumor types. SGN-B7H4V demonstrates robust anti-tumor activity in preclinical models through multiple potential mechanisms and is tolerated in rat and NHP toxicity studies. Altogether, these data support further evaluation of SGN-B7H4V in a planned, first-in-human phase 1 clinical study.

Acknowledgements

We would like to thank Kellie Spahr for conjugation support and Martha Anderson for in vivo biology support.

References

Leong SR, Liang WC, Wu Y, Crocker L, Cheng E, Sampath D, et al. An anti-B7-H4 antibody-drug conjugate for the treatment of breast cancer. Mol Pharm 2015;12(6):1717–29. Epub 2015/04/09. doi: 10.1021/mp5007745. PubMed PMID: 25853436.

Rosenberg JE, O’Donnell PH, Balar AV, McGregor BA, Heath EI, Yu EY, et al. Pivotal trial of enfortumab vedotin in urothelial carcinoma after platinum and anti-programmed death 1/programmed death ligand 1 therapy. J Clin Oncol 2019;37(29):2592–600. Epub 2019/07/30. doi: 10.1200/JCO.19.01140. PubMed PMID: 31356140; PubMed Central PMCID: PMC.

Senter PD, Sievers EL. The discovery and development of brentuximab vedotin for use in relapsed Hodgkin lymphoma and systemic anaplastic large cell lymphoma. Nat Biotechnol 2012;30(7):631–7. Epub 2012/07/12. doi: 10.1038/nbt.2289. PubMed PMID: 22781692.

Tilly H, Morschhauser F, Bartlett NL, Mehta A, Salles G, Haioun C, et al. Polatuzumab vedotin in combination with immunochemotherapy in patients with previously untreated diffuse large B-cell lymphoma: an open-label, non-randomised, phase 1b-2 study. Lancet Oncol 2019;20(7):998–1010. Epub 2019/05/19. doi: 10.1016/S1470-2045(19)30091–9. PubMed PMID: 31101489.

Ethics Approval

All animal studies were conducted in accordance with protocols reviewed and approved by the Institutional Animal Care and Use Committee at Seagen or the external testing facility that conducted the studies.

Activity of loggerhead turtles during the U-shaped dive: insights using angular velocity metrics

Understanding the behavioural ecology of endangered taxa can inform conservation strategies. The activity budgets of the loggerhead turtle Caretta caretta are still poorly understood because many tracking methods show only horizontal displacement and ignore dives and associated behaviours. However, time-depth recorders have enabled researchers to identify flat, U-shaped dives (or type 1a dives) and these are conventionally labelled as resting dives on the seabed because they involve no vertical displacement of the animal. Video- and acceleration-based studies have demonstrated this is not always true. Focusing on sea turtles nesting on the Cabo Verde archipelago, we describe a new metric derived from magnetometer data, absolute angular velocity, that integrates indices of angular rotation in the horizontal plane to infer activity. Using this metric, we evaluated the variation in putative resting behaviours during the bottom phase of type 1a dives for 5 individuals over 13 to 17 d at sea during a single inter-nesting interval (over 75 turtle d in total). We defined absolute resting within the bottom phase of type 1a dives as periods with no discernible acceleration or angular movement. Whilst absolute resting constituted a significant proportion of each turtle’s time budget for this 1a dive type, turtles allocated 16-38% of their bottom time to activity, with many dives being episodic, comprised of intermittent bouts of rest and rotational activity. This implies that previously considered resting behaviours are complex and need to be accounted for in energy budgets, particularly since energy budgets may impact conservation strategies.

Dynamic optical coherence tomography shows characteristic alterations of blood vessels in malignant melanoma

BACKGROUND

Dynamic optical coherence tomography (D-OCT) allows in vivo visualization of blood vessels in the skin and in malignant tumours. Vessel patterns in malignant melanoma may be associated with tumour stage.

OBJECTIVE

The aim of this study was to describe blood vessel patterns in melanomas and to correlate them with stage.

METHODS

One hundred fifty-nine malignant melanomas were assessed in a multicentre study. Every tumour was imaged using D-OCT prior to surgery and histologic evaluation. The tumour data such as thickness and ulceration as well as the staging at primary diagnosis and a follow-up of at least 40 months resulted in a stage classification. The vessel patterns were assessed according to predefined categories, compared with healthy adjacent skin, and correlated to stage.

RESULTS

Melanomas contained more blood vessels in different patterns compared with healthy adjacent skin. In particular, irregular vascular shapes such as blobs, coils, curves and serpiginous vessels were more common in melanomas. In addition, these patterns were significantly more often found in high-risk and metastatic melanomas than in low-risk lesions.

CONCLUSION

In melanomas, the density of the blood vessels is increased, and irregular vascular patterns are more frequent. At higher stages, especially in metastatic melanomas, these atypical vessels are significantly more common.

Experimentelle Forschung an der Klinik und Poliklinik für Dermatologie und Venerologie

Seit Antritt von Prof. Dr. med. Steffen Emmert als Ordinarius der Klinik und Poliklinik für Dermatologie und Venerologie im Jahr 2015 konnte das dermatologische Forschungslabor sukzessive aufgebaut und erweitert werden. Im Einklang mit dem onkologischen Schwerpunkt der Universitätsmedizin Rostock sowie dem von der Landesregierung forcierten „Gesundheitsland Mecklenburg-Vorpommern“ wird grundlagenorientierten und translationalen Projekten nachgegangen. Das vorwiegend drittmittelfinanzierte und stetig wachsende Forschungsteam bearbeitet diverse Fragestellungen in den Bereichen der Dermato-Onkologie, Plasmamedizin und seltenen Hauterkrankungen. Inzwischen auf einem soliden Fundament stehend, befindet sich der Forschungsbereich weiterhin in einem dynamischen Entwicklungsprozess. Nicht nur personell, sondern auch thematisch und methodisch wird er derzeit durch die Integration weiterer Arbeitsgruppen unter der Leitung von Ärzten aus der Klinik ergänzt und ausgebaut. Diverse Kollaborationen an der Universitätsmedizin Rostock und im Land zeugen von einem freundlichen, unterstützenden und kollegialen Umfeld, das die Integration am Standort befördert hat.

Abstract 1062: Development and characterization of patient-derived xenograft models for acute myeloid leukemia

Drug development for acute myeloid leukemia (AML) remains challenging, in part, due to the lack of preclinical models that reflect the biology of AML patients. For example, while the majority of AML patients express both CD33 and CD123, only a small fraction of AML cell lines express CD123. Similarly, most AML cell lines have a differentiated phenotype, which may bias the evaluation towards certain types of AML. To address these challenges, we developed a dozen patient derived xenograft (PDX) models to aid preclinical development of AML drugs. Bone marrow samples from 32 AML patients were implanted intravenously into NSG mice. Thirteen of them led to successful expansion of human CD45+ cells in the bone marrow, as demonstrated by flow cytometry. Twelve of these established disease in a secondary passage. Using multicolor flow cytometry analysis, we found that expression of CD33 and CD123 were preserved from AML patients and engrafted disease in NSG mice. Moreover, RNA-sequencing analysis demonstrated that gene expression largely remained consistent between the first two passages. Detailed genetic analysis demonstrated the preservation AML-relevant mutations, such as FLT3-ITD mutations and IDH2 mutations in the PDX model. In summary, we have successfully established AML PDX models that reflect the antigen expression and molecular genetics of AML patients. These models may facilitate the future development of antibody-based therapeutics.

Citation Format: Michelle Ulrich, Martha Anderson, Robert Thurman, Fu Li. Development and characterization of patient-derived xenograft models for acute myeloid leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1062.

Characterization of SGN-CD123A, A Potent CD123-Directed Antibody-Drug Conjugate for Acute Myeloid Leukemia

Treatment choices for acute myelogenous leukemia (AML) patients resistant to conventional chemotherapies are limited and novel therapeutic agents are needed. IL3 receptor alpha (IL3Rα, or CD123) is expressed on the majority of AML blasts, and there is evidence that its expression is increased on leukemic relative to normal hematopoietic stem cells, which makes it an attractive target for antibody-based therapy. Here, we report the generation and preclinical characterization of SGN-CD123A, an antibody-drug conjugate using the pyrrolobenzodiazepine dimer (PBD) linker and a humanized CD123 antibody with engineered cysteines for site-specific conjugation. Mechanistically, SGN-CD123A induces activation of DNA damage response pathways, cell-cycle changes, and apoptosis in AML cells. In vitro, SGN-CD123A-mediated potent cytotoxicity of 11/12 CD123⁺ AML cell lines and 20/23 primary samples from AML patients, including those with unfavorable cytogenetic profiles or FLT3 mutations. In vivo, SGN-CD123A treatment led to AML eradication in a disseminated disease model, remission in a subcutaneous xenograft model, and significant growth delay in a multidrug resistance xenograft model. Moreover, SGN-CD123A also resulted in durable complete remission of a patient-derived xenograft AML model. When combined with a FLT3 inhibitor quizartinib, SGN-CD123A enhanced the activity of quizartinib against two FLT3-mutated xenograft models. Overall, these data demonstrate that SGN-CD123A is a potent antileukemic agent, supporting an ongoing trial to evaluate its safety and efficacy in AML patients (NCT02848248). Mol Cancer Ther; 17(2); 554-64. ©2017 AACR.

Diagnostic accuracy of confocal microscopy imaging vs. punch biopsy for diagnosing and subtyping basal cell carcinoma

Background

In vivo reflectance confocal microscopy (RCM) is a promising non‐invasive skin imaging technique that could facilitate early diagnosis of basal cell carcinoma (BCC) instead of routine punch biopsies. However, the clinical value and utility of RCM vs. a punch biopsy in diagnosing and subtyping BCC is unknown.

Objective

To assess diagnostic accuracy of RCM vs. punch biopsy for diagnosing and subtyping clinically suspected primary BCC.

Methods

A prospective, consecutive cohort of 100 patients with clinically suspected BCC were included at two tertiary hospitals in Amsterdam, the Netherlands, between 3 February 2015 and 2 October 2015. Patients were randomized between two test‐treatment pathways: diagnosing and subtyping using RCM imaging followed by direct surgical excision (RCM one‐stop‐shop) or planned excision based upon the histological diagnosis and subtype of punch biopsy (standard care). The primary outcome was the agreement between the index tests (RCM vs. punch biopsy) and reference standard (excision specimen) in correctly diagnosing BCC. The secondary outcome was the agreement between the index tests and reference standard in correctly identifying the most aggressive BCC subtypes.

Results

Sensitivity to detect BCC was similar for RCM and punch biopsy (100% vs. 93.94%), but a punch biopsy was more specific than RCM (79% vs. 38%). RCM expert evaluation for diagnosing BCC had a sensitivity of 100% and a specificity of 75%. The agreement between RCM and excision specimen in identifying the most aggressive BCC subtype ranged from 50% to 85% vs. 77% by a punch biopsy.

Conclusion

Reflectance confocal microscopy and punch biopsy have comparable diagnostic accuracy to diagnose and subtype BCC depending on RCM experience. Although experienced RCM users could accurately diagnose BCC at a distance, we found an important difference in subtyping BCC. Future RCM studies need to focus on diagnostic accuracy, reliability and specific criteria to improve BCC subtype differentiation.

Tumor-Associated Macrophages Can Contribute to Antitumor Activity through FcγR-Mediated Processing of Antibody-Drug Conjugates

The primary mechanism of antibody-drug conjugates (ADC) is targeted delivery of a cytotoxic payload to tumor cells via cancer-associated membrane receptors. However, the tumor microenvironment likely plays a role in ADC penetration, distribution, and processing and thus impacts the overall antitumor activity. Here, we report on the potential contribution of Fc-FcγR interactions between ADCs and tumor-associated macrophages (TAM) to the preclinical antitumor activities of ADCs. In the CD30⁺ L-428 Hodgkin lymphoma model, anti-CD30-vcMMAE and a non-binding control (hIgG-vcMMAE) demonstrated similar antitumor activity as well as similar payload release in the tumors. IHC analysis revealed L-428 tumors contained highly abundant TAMs, which were confirmed to bind ADCs by IHC and flow cytometry. The infiltration of TAMs was further found to correlate with the antitumor activity of the non-binding hIgG-vcMMAE in five additional xenograft models. hIgG1V1-vcMMAE, bearing a mutation in the Fc region which ablates Fc gamma receptor (FcγR) binding, lost antitumor activity in three TAM-high xenograft models, suggesting Fc-FcγR interactions modulate the TAM-ADC interaction. Our results suggest that TAMs can contribute to ADC processing through FcγR interaction in preclinical tumor models and may represent an important additional mechanism for drug release from ADCs. Correlative studies in clinical trials will further shed light on whether TAMs play a role in patients' response to ADC therapies. Mol Cancer Ther; 16(7); 1347-54. ©2017 AACR.

The dendritic cell high-affinity IgE receptor is overexpressed in both asthma and severe COPD

BACKGROUND

The reduction of asthma exacerbations following omalizumab treatment has been related to the suppression of the high-affinity IgE receptor (FcεRI) on plasmacytoid dendritic cells (DCs). However, the FcεRI expression on DCs in chronic obstructive pulmonary disease (COPD) is unknown.

OBJECTIVE

To compare FcεRI expression on DCs in COPD with patients with allergic asthma and healthy controls, and to relate the findings to clinical parameters, blood eosinophil concentrations and serum immunoglobin E (IgE) concentrations.

METHODS

Using four-colour flow cytometry, FcεRI expression on blood myeloid DCs and plasmacytoid DCs was analyzed in 64 patients with COPD, 20 patients with allergic asthma, 41 asymptomatic never smokers and 21 asymptomatic current smokers.

RESULTS

As compared with never smokers, current smokers displayed an increased expression of the FcεRI on myeloid and plasmacytoid DCs. In patients with COPD, the expression of the FcεRI on plasmacytoid DCs, but not myeloid DCs, increased from spirometric GOLD stage 2 to GOLD stage 4, and was correlated with several lung function parameters. Patients with severe COPD and patients with allergic asthma displayed a similar FcεRI overexpression on plasmacytoid DCs. In all groups, there was a positive correlation between total IgE serum concentrations and the FcεRI expression on plasmacytoid DCs.

CONCLUSIONS AND CLINICAL RELEVANCE

Severe COPD and allergic asthma are characterized by a similar overexpression of the high-affinity IgE receptor on plasmacytoid DCs. In view of the effect of anti-IgE on exacerbations in asthma, trials investigating the effect of anti-IgE on exacerbations in severe COPD appear to be warranted.

Anti-angiogenic effects of novel cyclin-dependent kinase inhibitors with a pyrazolo[4,3-d]pyrimidine scaffold

BACKGROUND AND PURPOSE

Cyclin-dependent kinase 5 (CDK5) has recently emerged as an attractive target in several tumour entities. Inhibition of CDK5 has been shown to have anti-angiogenic effects in vitro and in vivo. However, potent inhibitors of CDK5, which can be applied in vivo, are still scarce. We have recently developed a new series of 5-substituted 3-isopropyl-7-[4-(2-pyridyl)benzyl]amino-1(2)H-pyrazolo[4,3-d]pyrimidines that show a preference for inhibiting CDK5 and tested them in vitro and in vivo in a murine model of hepatocellular carcinoma.

EXPERIMENTAL APPROACH

All compounds were initially examined for effects on proliferation of HUVECs. The most potent compounds were then tested on migration, and one of them, LGR2674, was selected for assessing effects on nuclear fragmentation, cell cycle, cell viability and metabolic activity. Furthermore, LGR2674 was tested in a tube formation assay and in vivo in a murine model of hepatocellular carcinoma, induced by s.c. injection of HUH7 cells (measurement of in vivo toxicity, tumour vascularization, tumour cell proliferation and tumour size).

KEY RESULTS

LGR2674 showed an EC50 in the low nanomolar range in the proliferation and migration assays. Cytotoxic effects started at 50 nM, a concentration that did not influence the cell cycle. In vivo, LGR2674 was well tolerated and caused a clear reduction in vessel density in the tumours; also tumour cell proliferation was inhibited and tumour growth retarded.

CONCLUSIONS AND IMPLICATIONS

Pyrazolo[4,3-d]pyrimidine is a novel scaffold for the development of potent CDK inhibitors with in vivo potential. Such structures are good candidates for broadening our pharmacological arsenal against various tumours.

Abstract 2082: Fc-FcγR interaction impacts the clearance and antitumor activity of antibody-drug conjugates in NSG mice

Majority of preclinical efficacy studies for cancer therapeutics are performed on tumor models implanted in immune-deficient mouse strains, including athymic nude, severe combined immunodeficiency (SCID), or NOD-SCID/IL2Rgamma null (NSG) mice. To better understand the correlation between drug exposure and preclinical antitumor activity of biologics, we evaluated the pharmacokinetic (PK) profiles of antibodies and antibody-drug conjugates (ADC) in four strains of mice commonly used in cancer research, including BALB/c, athymic nude, SCID, and NSG. To our surprise, antibodies and ADCs had an abnormally short serum half-life in NSG mice, compared to other strains of mice.

We hypothesized that the fast clearance from plasma in NSG mice may reduce the overall exposure of xenografts to the ADCs, resulting in underestimation of antitumor activity. This was confirmed by comparing cAC10-vcMMAE in CD30+ Karpas-299 tumors implanted in either SCID mice or NSG mice. A single dose of 1 mg/kg cAC10-vcMMAE ADC resulted in complete remission of Karpas-299 tumors implanted in SCID mice (5/5). In contrast, the same treatment regimen had no effect on Karpas-299 tumors implanted in NSG mice (0/5). This observation suggests indeed the shortened exposure penalizes ADC efficacy in NSG models.

We then hypothesized that the fast clearance of ADCs from plasma in NSG mice could be mediated by Fc-FcγR interaction; compromising this interaction may improve the serum half-lives of antibodies and ADCs and thus enhance ADC-mediated antitumor effects in NSG mice. To test this, we utilized a mutant antibody with the amino acid substitutions of E233P:L234V:L235 in its Fc domain that result in significantly reduced FcγR binding (G1V1). These mutations restored the serum exposure in NSG mice to that level comparable to other strains of mice. As a result, treatment of 1 mg/kg cAC10G1V1-vcMMAE led to tumor remission in Karpas-299 tumors grown in NSG mice, correlating with extended exposure. In parallel, pretreatment with human IV immunoglobulin also enhanced ADC exposure and antitumor activity in the NSG mice.

In summary, these results suggest preclinical PK/PD assessment should be performed in the same strains of mice, especially when NSG xenograft models are used to evaluate activities. Moreover, reduced FcγR binding may enhance ADC exposure and allow a better assessment of therapeutic potential of biologics in NSG-based xenograft models.

Citation Format: Fu Li, Michelle Ulrich, Joshua Hunter, Lori Westendorf, Devra Olson, Cassie Baker Lee, Dennis Benjamin, Che-Leung Law. Fc-FcγR interaction impacts the clearance and antitumor activity of antibody-drug conjugates in NSG mice. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2082.

Abstract 2966: Preclinical combinations of the antibody-drug conjugate SGN-LIV1A with chemotherapies show increased activity

SGN-LIV1A is an antibody-drug conjugate (ADC) currently being evaluated in a phase 1 clinical trial for metastatic breast cancer. SGN-LIV1A consists of the microtubule disrupting agent, monomethyl auristatin E (MMAE), conjugated to the anti-LIV-1 humanized monoclonal antibody hLIV22. LIV-1, as a downstream target of STAT3, promotes the epithelial to mesenchymal transition that is important in the malignant progression to metastasis. We have previously shown that as a single agent, SGN-LIV1A displays target specific internalization and cytotoxic activity against a breast cancer cell line in vitro and also demonstrates antitumor activity in in vivo preclinical xenograft models with significant delay of tumor growth. We report here additive and synergistic effects when combining SGN-LIV1A with current chemotherapeutic modalities used in the treatment of metastatic breast cancer. Specifically, we show synergy between SGN-LIV1A in combination with either doxorubicin or Abraxane in MCF-7 breast cancer tumor model. In addition, we show additive effects when carboplatin or protein kinase inhibitors are dosed in combination with SGN-LIV1A in this tumor model. These findings support further evaluation and development of SGN-LIV1A in combination with standard of care chemotherapeutic agents for the treatment of breast cancer.

Citation Format: Fu Li, Martha Anderson, Joshua Hunter, Jaime Miyamoto, Michelle Ulrich, Ana Kostic, Che-Leung Law, Django Sussman. Preclinical combinations of the antibody-drug conjugate SGN-LIV1A with chemotherapies show increased activity. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2966.

Interleukin-4 and interferon-γ orchestrate an epithelial polarization in the airways

Interferon-γ (IFN-γ) and interleukin-4 (IL-4) are key effector cytokines for the differentiation of T helper type 1 and 2 (Th1 and Th2) cells. Both cytokines induce fate-decisive transcription factors such as GATA3 and TBX21 that antagonize the polarized development of opposite phenotypes by direct regulation of each other's expression along with many other target genes. Although it is well established that mesenchymal cells directly respond to Th1 and Th2 cytokines, the nature of antagonistic differentiation programs in airway epithelial cells is only partially understood. In this study, primary normal human bronchial epithelial cells (NHBEs) were exposed to IL-4, IFN-γ, or both and genome-wide transcriptome analysis was performed. The study uncovers an antagonistic regulation pattern of IL-4 and IFN-γ in NHBEs, translating the Th1/Th2 antagonism directly in epithelial gene regulation. IL-4- and IFN-γ-induced transcription factor hubs form clusters, present in antagonistically and polarized gene regulation networks. Furthermore, the IL-4-dependent induction of IL-24 observed in rhinitis patients was downregulated by IFN-γ, and therefore IL-24 represents a potential biomarker of allergic inflammation and a Th2 polarized condition of the epithelium.