A bedside to bench study of anti-PD-1, anti-CD40, and anti-CSF1R indicates that more is not necessarily better

BACKGROUND

Stimulating inflammatory tumor associated macrophages can overcome resistance to PD-(L)1 blockade. We previously conducted a phase I trial of cabiralizumab (anti-CSF1R), sotigalimab (CD40-agonist) and nivolumab. Our current purpose was to study the activity and cellular effects of this three-drug regimen in anti-PD-1-resistant melanoma.

METHODS

We employed a Simon's two-stage design and analyzed circulating immune cells from patients treated with this regimen for treatment-related changes. We assessed various dose levels of anti-CSF1R in murine melanoma models and studied the cellular and molecular effects.

RESULTS

Thirteen patients were enrolled in the first stage. We observed one (7.7%) confirmed and one (7.7%) unconfirmed partial response, 5 patients had stable disease (38.5%) and 6 disease progression (42.6%). We elected not to proceed to the second stage. CyTOF analysis revealed a reduction in non-classical monocytes. Patients with prolonged stable disease or partial response who remained on study for longer had increased markers of antigen presentation after treatment compared to patients whose disease progressed rapidly. In a murine model, higher anti-CSF1R doses resulted in increased tumor growth and worse survival. Using single-cell RNA-sequencing, we identified a suppressive monocyte/macrophage population in murine tumors exposed to higher doses.

CONCLUSIONS

Higher anti-CSF1R doses are inferior to lower doses in a preclinical model, inducing a suppressive macrophage population, and potentially explaining the disappointing results observed in patients. While it is impossible to directly infer human doses from murine studies, careful intra-species evaluation can provide important insight. Cabiralizumab dose optimization is necessary for this patient population with limited treatment options.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03502330.

Combinatorial Immunotherapy with Agonistic CD40 Activates Dendritic Cells to Express IL12 and Overcomes PD-1 Resistance

Checkpoint inhibitors have revolutionized cancer treatment, but resistance remains a significant clinical challenge. Myeloid cells within the tumor microenvironment can modulate checkpoint resistance by either supporting or suppressing adaptive immune responses. Using an anti-PD-1-resistant mouse melanoma model, we show that targeting the myeloid compartment via CD40 activation and CSF1R blockade in combination with anti-PD-1 results in complete tumor regression in a majority of mice. This triple therapy combination was primarily CD40 agonist-driven in the first 24 hours after therapy and showed a similar systemic cytokine profile in human patients as was seen in mice. Functional single-cell cytokine secretion profiling of dendritic cells (DC) using a novel microwell assay identified a CCL22+CCL5+ IL12-secreting DC subset as important early-stage effectors of triple therapy. CD4+ and CD8+ T cells are both critical effectors of treatment, and systems analysis of single-cell RNA sequencing data supported a role for DC-secreted IL12 in priming T-cell activation and recruitment. Finally, we showed that treatment with a novel IL12 mRNA therapeutic alone was sufficient to overcome PD-1 resistance and cause tumor regression. Overall, we conclude that combining myeloid-based innate immune activation and enhancement of adaptive immunity is a viable strategy to overcome anti-PD-1 resistance.

Type 2 Dendritic Cells Orchestrate a Local Immune Circuit to Confer Antimetastatic Immunity

The progression of transformed primary tumors to metastatic colonization is a lethal determinant of disease outcome. Although circulating adaptive and innate lymphocyte effector responses are required for effective antimetastatic immunity, whether tissue-resident immune circuits confer initial immunity at sites of metastatic dissemination remains ill defined. Here we examine the nature of local immune cell responses during early metastatic seeding in the lung using intracardiac injection to mimic monodispersed metastatic spread. Using syngeneic murine melanoma and colon cancer models, we demonstrate that lung-resident conventional type 2 dendritic cells (DC2) orchestrate a local immune circuit to confer host antimetastatic immunity. Tissue-specific ablation of lung DC2, and not peripheral DC populations, led to increased metastatic burden in the presence of an intact T cell and NK cell compartment. We demonstrate that DC nucleic acid sensing and transcription factors IRF3 and IRF7 signaling are required for early metastatic control and that DC2 serve as a robust source of proinflammatory cytokines in the lung. Critically, DC2 direct the local production of IFN-γ by lung-resident NK cells, which limits the initial metastatic burden. Collectively, our results highlight, to our knowledge, a novel DC2-NK cell axis that colocalizes around pioneering metastatic cells to orchestrate an early innate immune response program to limit initial metastatic burden in the lung.

Abstract 3287: A bedside to bench study of anti-PD-1, anti-CD40, and anti-CSF1R indicates that more is not necessarily better

Stimulating innate immunity can potentially enable us to overcome resistance to PD-(L)1 blockade. We previously conducted a phase 1 trial of cabiralizumab (anti-CSF1R) with sotigalimab (CD40 agonistic antibody) and nivolumab. Our purpose was to determine safety and the effects of this regimen on circulating and tumor-infiltrating immune cells and to determine the activity of this regimen in a phase 1b trial for melanoma patients whose disease had progressed on anti-PD-(L)1. CyTOF analysis on circulating immune cells taken before and during treatment revealed a reduction in non-classical monocytes and an increase in dendritic cells. Patients with prolonged stable disease had less T-regulatory cells and more circulating antigen presenting cells after treatment compared to patients that were treated for a shorter time. In the phase 1b component of the trial in 13 melanoma patients, objective response rates were: 1 confirmed partial response (7.7%), 1 unconfirmed partial response (7.7%), 5 stable disease (38.5%) and 6 disease progression (42.6%). Despite therapy-induced changes in circulating immune cells and previous preclinical studies supporting rationale for this combination, responses in humans were insufficient to proceed to the second stage of the phase 1b trial. Given the challenges with translating doses from mice to humans, we proceeded to study various doses of anti-CSF1R in combination with CD40 agonist and anti-PD-1 in a murine model. Higher dose anti-CSF1R in mice was associated with increased tumor growth, worse survival and by single-cell RNA-sequencing analyses, we identified a more suppressive monocyte/macrophage profile in murine tumors. Our study suggests that more anti-CSF1R might not be better. Further optimization of cabiralizumab dosing is necessary to evaluate the clinical potential in combination with anti-PD-1 and anti-CD40 in a difficult-to treat patient population whose therapeutic options are limited.

Citation Format: Dijana Djureinovic, Sarah A. Weiss, Irina Krykbaeva, Rihao Qu, Ioannis Vathiotis, Myrto Moutafi, Lin Zhang, Ana L. Perdigoto, Wei Wei, Gail Anderson, William Damsky, Michael Hurwitz, Barbara Johnson, Amit Mahajan, Frank Hsu, Kathryn Miller-Jensen, Yuval Kluger, Mario Sznol, Susan M. Kaech, Marcus Bosenberg, Lucia Jilaveanu, Harriet M. Kluger. A bedside to bench study of anti-PD-1, anti-CD40, and anti-CSF1R indicates that more is not necessarily better [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 3287.

Abstract 2166: Ibuprofen induces ferroptosis to potentiate antitumor immunity

Ferroptosis is an iron-dependent regulated cell death pathway that has recently emerged as a promising target for cancer therapy. PTGS2 has been identified as a marker of ferroptosis due to its upregulation in cells after treatment with ferroptosis inducers. Nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit the protein product of PTGS2 and have been shown to enhance antitumor immunity. We hypothesized that NSAIDs induce ferroptosis and that this mechanism is essential for their effect on antitumor immunity. To test this, we first determined that ibuprofen and other NSAIDs induce cell death in YUMMER-1.7 melanoma and MC38 colorectal cancer cells in vitro. Cell death occurred progressively over 24 hours and could be blocked by multiple ferroptosis inhibitors. Treatment with NSAIDs also increased intracellular lipid peroxides and decreased levels of reduced glutathione and ferrous iron. This indicated that ibuprofen and other NSAIDs induce ferroptosis in vitro, so we next evaluated whether ibuprofen also induces ferroptosis in vivo. Analysis of ibuprofen-treated YUMMER-1.7 or MC38 tumors showed increased levels of lipid peroxides and lipid peroxide intermediates, 4-hydroxynonenal and malondialdehyde, compared to untreated tumors. Treatment of tumor-bearing mice with ibuprofen alone resulted in approximately 60% tumor clearance and survival, whereas a combination of multiple ferroptosis inhibitors with ibuprofen completely abrogated this effect. Since it has been demonstrated by that CD8+ T cells can release IFN-γ to induce ferroptosis in tumor cells, we next tested the dependence of the antitumor effect of ibuprofen on CD4+ T cells, CD8+ T cells, and IFN-γ using depleting antibodies. Depletion of any of these was sufficient to prevent the antitumor effect of ibuprofen. Given the need to identify pathways that enhance responses to existing immunotherapies, we determined whether treatment with ibuprofen synergizes with PD-1 checkpoint blockade. The combination of α-PD-1 with ibuprofen resulted in a 100% tumor clearance and survival rate, whereas α-PD-1 or ibuprofen alone resulted in 40% and 60% tumor clearance and survival rates, respectively. Furthermore, treatment with ibuprofen also sensitized α-PD-1-resistant tumors to PD-1 in two distinct models of α-PD-1 resistance. Overall, these findings establish ibuprofen and other NSAIDs as inducers of ferroptosis and underscore the potential for ferroptosis inducers to be used in combination with existing immunotherapy regimens.

Citation Format: Ronan Talty, Michelle Ferreira, Irina Krykbaeva, Marcus Bosenberg. Ibuprofen induces ferroptosis to potentiate antitumor immunity [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 2166.

A Phase I Study of APX005M and Cabiralizumab with or without Nivolumab in Patients with Melanoma, Kidney Cancer, or Non-Small Cell Lung Cancer Resistant to Anti-PD-1/PD-L1

PURPOSE

PD-1/PD-L1 inhibitors are approved for multiple tumor types. However, resistance poses substantial clinical challenges.

PATIENTS AND METHODS

We conducted a phase I trial of CD40 agonist APX005M (sotigalimab) and CSF1R inhibitor cabiralizumab with or without nivolumab using a 3+3 dose-escalation design (NCT03502330). Patients were enrolled from June 2018 to April 2019. Eligibility included patients with biopsy-proven advanced melanoma, non-small cell lung cancer (NSCLC), or renal cell carcinoma (RCC) who progressed on anti-PD-1/PD-L1. APX005M was dose escalated (0.03, 0.1, or 0.3 mg/kg i.v.) with a fixed dose of cabiralizumab with or without nivolumab every 2 weeks until disease progression or intolerable toxicity.

RESULTS

Twenty-six patients (12 melanoma, 1 NSCLC, and 13 RCC) were enrolled in six cohorts, 17 on nivolumab-containing regimens. Median duration of follow-up was 21.3 months. The most common treatment-related adverse events were asymptomatic elevations of lactate dehydrogenase (n = 26), creatine kinase (n = 25), aspartate aminotransferase (n = 25), and alanine aminotransferase (n = 19); periorbital edema (n = 17); and fatigue (n = 13). One dose-limiting toxicity (acute respiratory distress syndrome) occurred in cohort 2. The recommended phase 2 dose was APX005M 0.3 mg/kg, cabiralizumab 4 mg/kg, and nivolumab 240 mg every 2 weeks. Median days on treatment were 66 (range, 23-443). Median cycles were 4.5 (range, 2-21). One patient had unconfirmed partial response (4%), 8 stable disease (31%), 16 disease progression (62%), and 1 unevaluable (4%). Pro-inflammatory cytokines were upregulated 4 hours post-infusion. CD40 and MCSF increased after therapy.

CONCLUSIONS

This first in-human study of patients with anti-PD-1/PD-L1-resistant tumors treated with dual macrophage-polarizing therapy, with or without nivolumab demonstrated safety and pharmacodynamic activity. Optimization of the dosing frequency and sequence of this combination is warranted.

Conventional type 2 dendritic cells and natural killer cells mediate control of early metastatic seeding

The multistep progression of transformed primary tumors to metastatic dissemination and seeding of distant site is a lethal determinant of disease. Although the role of immune cells and immune sensors in promoting or restricting metastatic growth is well described, whether immune cells are capable of detecting and controlling metastatic cells during peripheral tissue seeding is unknown. Here we examine if local immune cells can confer early anti-metastatic control in the lung using intracardiac injection to mimic metastatic spread. Using a syngeneic mouse model of YUMMER1.7 melanoma expressing GFP and luciferase (YMR1.7-G/L), we demonstrate that lung resident conventional type 2 dendritic cells (cDC2) and extravascular NK cells confer host anti-tumor immunity during the first three days following intracardiac injection. Rapid production of IFN-γ by NK cells serves an essential role to limit metastatic burden. Using mice deficient in innate sensors and signaling pathways, we demonstrate that the transcription factors IRF3 and IRF7 are required for early metastatic control in a type I IFN-independent manner. In contrast, ablation of adaptive immune cells had no effect to initial metastatic burden. Collectively our results highlight a novel cDC2 - NK cell axis that orchestrates a non-redundant innate immune response program to limit initial metastatic burden in the lung.

Evaluating the role of the COX2/PGE2 pathway in anti-melanoma immunity

e14114

Background: Checkpoint inhibitors such as anti-PD1 (aPD1) have revolutionized treatment of metastatic melanoma. However, a large subset of patients receiving such treatment fails to respond to aPD1 monotherapy due to mechanisms such as PD-L1 upregulation within the tumor and T cell exhaustion in the tumor microenvironment. The PGE2/COX2 signaling pathway is one of the pathways implicated in T cell exhaustion and PD1/PD-L1 upregulation and thus represents an attractive pharmacologic target to enhance effects of aPD1 therapy due to the availability and safety of inhibitors such as aspirin or NSAIDs. There is evidence that PGE2/COX2 pathway inhibitors act synergistically with aPD1 therapy in murine melanoma and breast cancer models. Here we aimed to further characterize this synergism using the YUMMER (Yale University Mouse Melanoma Exposed to Radiation) 1.7 model, an irradiated, syngeneic cell line originating from BrafV600E; Pten-/-; and Cdkn2a -/- genetically engineered mouse melanomas. YUMMER1.7 cells implanted into the flanks of C57BL6/j mice show reproducible but partial responses to intraperitoneal aPD1 therapy and thus serves as an ideal platform to study whether concurrent PGE2/COX2 pathway blockade may result in additive effects to aPD1 therapy. Methods: 6-7 week old male C57BL6/j mice (n = 20) were injected with 500K YUMMER1.7 cells and treated with aPD1 therapy alone starting on day 7 after tumor implantation (n = 10) or with aPD1 therapy starting on day 7 in addition to ibuprofen dissolved in drinking water at a concentration of 1 mg/mL started on the day of tumor implantation (n = 10). Using an average daily water consumption estimate of 6 mL/day, this translates to a human equivalent of roughly 1200 mg/day, a moderate dose of ibuprofen. Tumor growth was monitored and tracked to an endpoint of 1cm3. Results: Tumor volume at day 17 significantly differed between the two groups (p < 0.0001). Survival curves were significantly different between the two groups (p < 0.0001); all tumors treated with aPD1 alone grew to endpoint by day 32, while all tumors treated with aPD1 + ibuprofen regressed with 8 out of 10 showing complete regression by day 32. Conclusions: We have shown that ibuprofen strongly synergizes with aPD1 therapy in a murine model of melanoma, complementing existing evidence. This suggests that PGE2/COX2 inhibitors such as NSAIDs, which are over-the-counter agents with a well-studied safety profile, may serve as a promising means of enhancing the response to aPD1 therapies such as nivolumab in melanoma patients who initially fail aPD1 monotherapy.

KDM5B Promotes Drug Resistance by Regulating Melanoma-Propagating Cell Subpopulations

Tumor heterogeneity is a major challenge for cancer treatment, especially due to the presence of various subpopulations with stem cell or progenitor cell properties. In mouse melanomas, both CD34⁺p75^- (CD34⁺) and CD34^-p75^- (CD34^-) tumor subpopulations were characterized as melanoma-propagating cells (MPC) that exhibit some of those key features. However, these two subpopulations differ from each other in tumorigenic potential, ability to recapitulate heterogeneity, and chemoresistance. In this study, we demonstrate that CD34⁺ and CD34^- subpopulations carrying the BRAF^V600E mutation confer differential sensitivity to targeted BRAF inhibition. Through elevated KDM5B expression, melanoma cells shift toward a more drug-tolerant, CD34^- state upon exposure to BRAF inhibitor or combined BRAF inhibitor and MEK inhibitor treatment. KDM5B loss or inhibition shifts melanoma cells to the more BRAF inhibitor-sensitive CD34⁺ state. These results support that KDM5B is a critical epigenetic regulator that governs the transition of key MPC subpopulations with distinct drug sensitivity. This study also emphasizes the importance of continuing to advance our understanding of intratumor heterogeneity and ultimately develop novel therapeutics by altering the heterogeneous characteristics of melanoma.

Inhibition of isoprenylation synergizes with MAPK blockade to prevent growth in treatment-resistant melanoma, colorectal, and lung cancer

This study evaluates the use of HMG-CoA reductase inhibitors, or statins, as an adjunctive to BRAF and MEK inhibition as a treatment in melanomas and other tumors with driver mutations in the MAPK pathway. Experiments used simvastatin in conjunction with vemurafenib and selumetinib in vitro and simvastatin with vemurafenib in vivo to demonstrate additional growth abrogation beyond MAPK blockade alone. Additional studies demonstrated that statin anti-tumor effects appeared to depend on inhibition of isoprenoid synthesis given rescue with add-back of downstream metabolites. Ultimately, we concluded that statins represent a possible useful adjunctive therapy in MAPK-driven tumors when given with current approved targeted therapy.

Widespread macromolecular interaction perturbations in human genetic disorders

How disease-associated mutations impair protein activities in the context of biological networks remains mostly undetermined. Although a few renowned alleles are well characterized, functional information is missing for over 100,000 disease-associated variants. Here we functionally profile several thousand missense mutations across a spectrum of Mendelian disorders using various interaction assays. The majority of disease-associated alleles exhibit wild-type chaperone binding profiles, suggesting they preserve protein folding or stability. While common variants from healthy individuals rarely affect interactions, two-thirds of disease-associated alleles perturb protein-protein interactions, with half corresponding to "edgetic" alleles affecting only a subset of interactions while leaving most other interactions unperturbed. With transcription factors, many alleles that leave protein-protein interactions intact affect DNA binding. Different mutations in the same gene leading to different interaction profiles often result in distinct disease phenotypes. Thus disease-associated alleles that perturb distinct protein activities rather than grossly affecting folding and stability are relatively widespread.

A quantitative chaperone interaction network reveals the architecture of cellular protein homeostasis pathways

Chaperones are abundant cellular proteins that promote the folding and function of their substrate proteins (clients). In vivo, chaperones also associate with a large and diverse set of cofactors (cochaperones) that regulate their specificity and function. However, how these cochaperones regulate protein folding and whether they have chaperone-independent biological functions is largely unknown. We combined mass spectrometry and quantitative high-throughput LUMIER assays to systematically characterize the chaperone-cochaperone-client interaction network in human cells. We uncover hundreds of chaperone clients, delineate their participation in specific cochaperone complexes, and establish a surprisingly distinct network of protein-protein interactions for cochaperones. As a salient example of the power of such analysis, we establish that NUDC family cochaperones specifically associate with structurally related but evolutionarily distinct β-propeller folds. We provide a framework for deciphering the proteostasis network and its regulation in development and disease and expand the use of chaperones as sensors for drug-target engagement.

The mammalian-membrane two-hybrid assay (MaMTH) for probing membrane-protein interactions in human cells

Cell signaling, one of key processes in both normal cellular function and disease, is coordinated by numerous interactions between membrane proteins that change in response to stimuli. We present a split ubiquitin-based method for detection of integral membrane protein-protein interactions (PPIs) in human cells, termed mammalian-membrane two-hybrid assay (MaMTH). We show that this technology detects stimulus (hormone or agonist)-dependent and phosphorylation-dependent PPIs. MaMTH can detect changes in PPIs conferred by mutations such as those in oncogenic ErbB receptor variants or by treatment with drugs such as the tyrosine kinase inhibitor erlotinib. Using MaMTH as a screening assay, we identified CRKII as an interactor of oncogenic EGFR(L858R) and showed that CRKII promotes persistent activation of aberrant signaling in non-small cell lung cancer cells. MaMTH is a powerful tool for investigating the dynamic interactomes of human integral membrane proteins.

Chaperones as thermodynamic sensors of drug-target interactions reveal kinase inhibitor specificities in living cells

The interaction between the HSP90 chaperone and its client kinases is sensitive to the conformational status of the kinase, and stabilization of the kinase fold by small molecules strongly decreases chaperone interaction. Here we exploit this observation and assay small-molecule binding to kinases in living cells, using chaperones as 'thermodynamic sensors'. The method allows determination of target specificities of both ATP-competitive and allosteric inhibitors in the kinases' native cellular context in high throughput. We profile target specificities of 30 diverse kinase inhibitors against >300 kinases. Demonstrating the value of the assay, we identify ETV6-NTRK3 as a target of the FDA-approved drug crizotinib (Xalkori). Crizotinib inhibits proliferation of ETV6-NTRK3-dependent tumor cells with nanomolar potency and induces the regression of established tumor xenografts in mice. Finally, we show that our approach is applicable to other chaperone and target classes by assaying HSP70/steroid hormone receptor and CDC37/kinase interactions, suggesting that chaperone interactions will have broad application in detecting drug-target interactions in vivo.

Widespread regulation of translation by elongation pausing in heat shock

Global repression of protein synthesis is a hallmark of the cellular stress response and has been attributed primarily to inhibition of translation initiation, although this mechanism may not always explain the full extent of repression. Here, using ribosome footprinting, we show that 2 hr of severe heat stress triggers global pausing of translation elongation at around codon 65 on most mRNAs in both mouse and human cells. The genome-wide nature of the phenomenon, its location, and features of protein N termini suggested the involvement of ribosome-associated chaperones. After severe heat shock, Hsp70's interactions with the translational machinery were markedly altered and its association with ribosomes was reduced. Pretreatment with mild heat stress or overexpression of Hsp70 protected cells from heat shock-induced elongation pausing, while inhibition of Hsp70 activity triggered elongation pausing without heat stress. Our findings suggest that regulation of translation elongation in general, and by chaperones in particular, represents a major component of cellular stress responses.