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Background: This phase 1b study (NCT02323191) evaluated the safety, antitumor activity, pharmacokinetics, and pharmacodynamics of colony-stimulating factor-1 receptor-blocking monoclonal antibody (mAb) emactuzumab in combination with the programmed cell death-1 ligand (PD-L1)-blocking mAb atezolizumab in patients with advanced solid tumors naïve or experienced for immune checkpoint blockers (ICBs)., Methods: Emactuzumab (500-1350 mg flat) and atezolizumab (1200 mg flat) were administered intravenously every 3 weeks. Dose escalation of emactuzumab was conducted using the 3+3 design up to the maximum tolerated dose (MTD) or optimal biological dose (OBD). Extension cohorts to evaluate pharmacodynamics and clinical activity were conducted in metastatic ICB-naive urothelial bladder cancer (UBC) and ICB-pretreated melanoma (MEL), non-small cell lung cancer (NSCLC) and UBC patients., Results: Overall, 221 patients were treated. No MTD was reached and the OBD was determined at 1000 mg of emactuzumab in combination with 1200 mg of atezolizumab. Grade ≥3 treatment-related adverse events occurred in 25 (11.3%) patients of which fatigue and rash were the most common (14 patients (6.3%) each). The confirmed objective response rate (ORR) was 9.8% for ICB-naïve UBC, 12.5% for ICB-experienced NSCLC, 8.3% for ICB-experienced UBC and 5.6% for ICB-experienced MEL patients, respectively. Tumor biopsy analyses demonstrated increased activated CD8 +tumor infiltrating T lymphocytes (TILs) associated with clinical benefit in ICB-naïve UBC patients and less tumor-associated macrophage (TAM) reduction in ICB-experienced compared with ICB-naïve patients., Conclusion: Emactuzumab in combination with atezolizumab demonstrated a manageable safety profile with increased fatigue and skin rash over usual atezolizumab monotherapy. A considerable ORR was particularly seen in ICB-experienced NSCLC patients. Increase ofCD8 +TILs under therapy appeared to be associated with persistence of a TAM subpopulation., Competing Interests: Competing interests: CG-R: Invited Speaker: BMS, Eisai, Pierre Fabre, Roche/Genentech; Coordinating PI: BMS; Steering Committee Member: BMS; Local PI: Foundation Medicine; Steering Committee Member: Genentech; Research Grant: Roche/Genentech; AM: Stock ownership Pegascy, Hifibio Therapeutics, Shattuck Labs, Centessa Pharmaceuticals; Honoraria: BMS, AstraZeneca/MedImmune, Oncovir; Consulting and advisory activities: Lytix Biopharma, Eisai, Pierre Fabre, AstraZeneca, Servier, Roche, Redx Pharma, Sotio, Innate Pharma, ImCheck Therapeutics, MSD, OSE Immunotherapeutics, HIFIBIO Therapeutics, MedinCell, Centessa Pharmaceuticals; Speaker’s bureau: BMS; Research funding: BMS, Boehringer Ingelheim, Transgene, MSD; Travel expenses: MSD, AstraZeneca; SC: Honoraria: Amgen, AstraZeneca, BMS, EISAI, Janssen, MSD, Novartis and Roche; Principal Investigator of Clinical Trials for: Amgen, MSD, Sanofi Aventis, Transgene; Advisory Board: Alderaan Biotechnology, Amgen, AstraZeneca, Oncovita, Seagen, Ultrahuman; Travel and congress: AstraZeneca, MSD, Roche; Principal/sub-investigator of clinical trials for: Abbvie, Adaptimmune, Adlai Nortye USA Inc, Aduro Biotech, Agios Pharmaceuticals, Amgen, Argen-X Bvba, Astex Pharmaceuticals, Astra Zeneca Ab, Aveo, Basilea Pharmaceutica International Ltd, Bayer Healthcare Ag, Bbb Technologies Bv, Beigene, BicycleTx Ltd, Blueprint Medicines, Boehringer Ingelheim, Boston Pharmaceuticals, Bristol Myers Squibb, Ca, Celgene Corporation, Chugai Pharmaceutical Co, Clovis Oncology, Cullinan-Apollo, Curevac, Daiichi Sankyo, Debiopharm, Eisai, Eisai Limited, Eli Lilly, Exelixis, Faron Pharmaceuticals Ltd, Forma Tharapeutics, Gamamabs, Genentech, Glaxosmithkline, H3 Biomedicine, Hoffmann La Roche Ag, Imcheck Therapeutics, Innate Pharma, Institut De Recherche Pierre Fabre, Iris Servier, Iteos Belgium SA, Janssen Cilag, Janssen Research Foundation, Kura Oncology, Kyowa Kirin Pharm. Dev, Lilly France, Loxo Oncology, Lytix Biopharma As, Medimmune, Menarini Ricerche, Merck Sharp & Dohme Chibret, Merrimack Pharmaceuticals, Merus, Millennium Pharmaceuticals, Molecular Partners Ag, Nanobiotix, Nektar Therapeutics, Novartis Pharma, Octimet Oncology Nv, Oncoethix, Oncopeptides, Orion Pharma, Ose Pharma, Pfizer, Pharma Mar, Pierre Fabre, Medicament, Roche, Sanofi Aventis, Seattle Genetics, Sotio A.S, Syros Pharmaceuticals, Taiho Pharma, Tesaro, Turning Point Therapeutics, Xencor; Research Grants from: Astrazeneca, BMS, Boehringer Ingelheim, GSK, INCA, Janssen Cilag, Merck, Novartis, Pfizer, Roche, SanofiNon-financial support (drug supplied) from Astrazeneca, Bayer, BMS, Boringher Ingelheim, GSK, Medimmune, Merck, NH TherAGuiX, Pfizer, Roche; SA: Speakers bureau: Pfizer, Roche, Sanofi and BMSAdvisory board: Sanofi; PC: Honoraria: Novartis, Roche/Genentech, Amgen, Astra Zeneca, Merck Serono; Research Funding: Novartis, Roche/Genentech, Lilly, lueprint Medicines, Bayer, Astra Zeneca, Celgene, Plexxikon, Abbvie, BMS, Merck Serono, Merck Sharp and Dohme, Taiho Pharmaceutical, Toray Industries, Transgene, Loxo, GSK, Innate Pharma, Janssen; Travel expenses: Roche, Amgen, Novartis, BMS, MSD, Netris Pharma, Bayer, Merck Serono; DZ: Reports research support from: Roche, Astra Zeneca, and Plexxikon; Personal/consultancy fees from Synlogic Therapeutics, GSK, Roche, Xencor, Memgen, Immunos, Celldex, Calidi, and Agenus; J-PM: Advisory board member or speaker with honoraria: Pfizer, Roche, Astra/Zeneca, Bayer, Innate, Merck Serono, Boerhinger, BMS, Novartis, Janssen, Incyte, Cue Biopharma, ALX Oncology, iTEOS, eTheRNATravel expenses: Amgen, BMS, Pfizer, MSDData safety monitoring board with honoraria: Debio, Nanobiotix, Psioxus; Uncompensated advisory role: MSD; JLPG; Research grants and support: Roche, BMS, MSD, Seattle Genetics. Speakers bureau and advisory boards: Roche, BMS, Ipsen, MSD, Seattle Genetics. Travel support: Roche, MSD, BMS; FSH: Consulting: BMS, Merck, EMD Serono, Novartis, Sanofi, Psioxus Therapeutics, Pieris Pharmacutical, Corner Therapeutics, Eisai, Idera, Takeda, Genentech/Roche; Advisory Board: Compass Therapeutics, Apricity Scientific, Pionyr, Torque, Rheos, Bicara, Checkpoint Therapeutics, Bioentre, Gossamer, Iovance; ATG: Personal fees from: Boehringer-Ingelheim, BMS, MSD, Roche, Pfizer, Astra Zeneca, Tesaro-GSK and non-financial support from Boehringer-Ingelheim, Lilly and RocheMaria Martinez Garcia; Research grants and support: Roche, BMS, MSD, Seattle Genetics; Speakers bureau and advisory boards: Roche, BMS, Ipsen, MSD, Seattle Genetics; Travel support: Roche, MSD, BMS; VB: Consulting or Advisory Role: Puma Biotechnology; Ideaya Biosciences; Loxo Therapeutics, CytomX Therapeutics; Guidepoint; Oncoart; Amunix; Institutional financial support for clinical trials from: Abbvie, ACEO, Adaptaimmune, Amcure, AMGEN, AstraZeneca, BMS, Cytomx, GSK, Genentech/Roche, H3, Incyte, Janssen, Kura, Lilly, Loxo, Nektar, Macrogenics, Menarini, Merck, Merus, Nanobiotix, Novartis, Pfizer, PharmaMar, Principia, PUMA, Sanofi, Taiho, Tesaro, BeiGene, Transgene, Takeda, Incyte, Innovio, MSD, PsiOxus, Seattle Genetics, Mersana, GSK, Daiichi, Nektar, Astellas, ORCA, Boston Therapeutics, Dynavax, DebioPharm, Boehringen Ingelheim, Regeneron, Millenium, Synthon, Spectrum, Rigontec, Zenith; JPE: The author declares no potential conflicts of interest. NH: The author declares no potential conflicts of interest. RS: Consultant/advisory boards: Asana Biosciences, AstraZeneca, Bristol-Myers Squibb, Eisai, Iovance, Merck, Novartis, OncoSec, Pfizer, Replimune; Research funding: Amgen, Merck; DM: Consulting and honoraria: BMS, Pfizer, Merck, Alkermes Inc., EMD Serono, Eli Lilly and Company, Iovance, Eisai Inc., Werewolf Therapeutics, Calithera Biosciences; Research support: BMS, Merck, Genentech, Pfizer, Exelixis, X4 Pharma, Alkermes Inc; MAC: Sponsor employee and sponsor stock ownership; A-MJ: Former sponsor employee and has patent issued in the use of emactuzumab; WJ: Sponsor employee and sponsor stock ownership; CR: Former Roche employee and has patent issued in the use of emactuzumab. Consultant for Verseau Therapeutics, Ridgeline Discovery, iOmx Therapeutics AG; KK: Sponsor employee and Roche stocks; GB: Sponsor employee; FM: Sponsor employee; RC: Sponsor employee and Roche stocks; CW: Sponsor consultantGeorgina Meneses-LorenteSponsor employee; MW: Sponsor employee, stock options, and has patent issued in the use of emactuzumab; DR: Sponsor employee, sponsor stock ownership and has patent issued in the use of emactuzumab; J-PD: Consulting/Advisory: Novartis, Roche/Genentech, BMS, MSD; Research funding: Genentech, BMS, MSD, Astra Zeneca, Transgene; CT: Research funding GSK, travel expenses Mundipharma., (© Author(s) (or their employer(s)) 2022. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Colony-stimulating factor 1 receptor (CSF1R) blockade abates tumor-associated macrophage (TAM) infiltrates and provides marked clinical benefits in diffuse-type tenosynovial giant cell tumors. However, facial edema is a common adverse event associated with TAM elimination in patients. In this study, we examined molecular and cellular events associated with edema formation in mice and human patients with cancer treated with a CSF1R blocking antibody. Extended antibody treatment of mice caused marked body weight gain, an indicator of enhanced body fluid retention. This was associated with an increase of extracellular matrix-remodeling metalloproteinases (MMPs), namely MMP2 and MMP3, and enhanced deposition of hyaluronan (HA) and proteoglycans, leading to skin thickening. Discontinuation of anti-CSF1R treatment or blockade of MMP activity restored unaltered body weight and normal skin morphology in the mice. In patients, edema developed at doses well below the established optimal biological dose for emactuzumab, a CSF1R dimerization inhibitor. Patients who developed edema in response to emactuzumab had elevated HA in peripheral blood. Our findings indicate that an early increase of peripheral HA can serve as a pharmacodynamic marker for edema development and suggest potential interventions based on MMP inhibition for relieving periorbital edema in patients treated with CSF1R inhibitors., (Copyright © 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Objectives: This study investigated the safety, clinical activity and patient-reported outcomes of patients with diffuse-type tenosynovial giant-cell tumour (dTGCT) of the soft tissue who were treated with emactuzumab, a humanised anti-colony stimulating factor 1 receptor (CSF1R) monoclonal antibody and were followed up for up to 2 years after the start of treatment., Methods: In this open-label phase 1 study (ClinicalTrials.govNCT01494688), patients received intravenous (IV) emactuzumab from 900 to 2000 mg every two weeks in the dose-escalation phase and at the optimal biological dose of 1000 mg with different schedules in the dose-expansion phase. Adverse event (AE) rates and biomarker assessments from tumour biopsies were analysed. Quality of life was assessed using a standard questionnaire (EuroQol-5D-3L) and the WOMAC® 3.1 Osteoarthritis Index. Tumour responses were determined with magnetic resonance imaging., Results: Altogether, 63 patients were enrolled into the study. The most frequently reported AEs were pruritus, asthenia and oedema. In 36 patients for whom biopsy tissue was available a substantial decrease of CSF1R-positive and CD68/CD163-positive macrophages was detected. The independently reviewed best overall objective response rate (ORR) (Response Evaluation Criteria in Solid Tumors version 1.1) was 71%. Responses were durable, and an ORR of 70% and 64% was determined after one or two years after enrolment into the study. Clinical activity was accompanied by an improvement in EuroQol-5D-3L and particularly the joint disorder-specific WOMAC score., Conclusions: Systemic therapy of dTGCT patients with emactuzumab resulted in pronounced and durable responses associated with symptomatic improvement and a manageable safety profile., (Copyright © 2020 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Background: By understanding prognostic biomarkers, we gain insights into disease biology and may improve design, conduct, and data analysis of clinical trials and real-world data. In this context, we used the Flatiron Health Electronic Health Record-derived deidentified database that provides treatment outcome and biomarker data from >280 oncology centers in the USA, organized into 17 cohorts defined by cancer type., Patients and Methods: In 122 694 patients, we analyzed demographic, clinical, routine hematology, and blood chemistry parameters within a Cox proportional hazard framework to derive a multivariable prognostic risk model for overall survival (OS), the 'Real wOrld PROgnostic score (ROPRO)'. We validated ROPRO in two independent phase I and III clinical studies., Results: A total of 27 variables contributed independently and homogeneously across cancer indications to OS. In the largest cohort (advanced non-small-cell lung cancer), for example, patients with elevated ROPRO scores (upper 10%) had a 7.91-fold (95% confidence interval 7.45-8.39) increased death hazard compared with patients with low scores (lower 10%). Median survival was 23.9 months (23.3-24.5) in the lowest ROPRO quartile Q1, 14.8 months (14.4-15.2) in Q2, 9.4 months (9.1-9.7) in Q3, and 4.7 months (4.6-4.8) in Q4. The ROPRO model performance indicators [C-index = 0.747 (standard error 0.001), 3-month area under the curve (AUC) = 0.822 (0.819-0.825)] strongly outperformed those of the Royal Marsden Hospital Score [C-index = 0.54 (standard error 0.0005), 3-month AUC = 0.579 (0.577-0.581)]. We confirmed the high prognostic relevance of ROPRO in clinical Phase 1 and III trials., Conclusions: The ROPRO provides improved prognostic power for OS. In oncology clinical development, it has great potential for applications in patient stratification, patient enrichment strategies, data interpretation, and early decision-making in clinical studies., Competing Interests: Disclosure JW, WVS, AF, MW, FS, DR, and AB-M are employed by Roche. All remaining authors have declared no conflicts of interest., (Copyright © 2020 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Background: This phase Ib study evaluated the safety, clinical activity, pharmacokinetics, and pharmacodynamics (PD) of emactuzumab (anti-colony stimulating factor 1 receptor monoclonal antibody (mAb)) in combination with selicrelumab (agonistic cluster of differentiation 40 mAb) in patients with advanced solid tumors., Methods: Both emactuzumab and selicrelumab were administered intravenously every 3 weeks and doses were concomitantly escalated (emactuzumab: 500 to 1000 mg flat; selicrelumab: 2 to 16 mg flat). Dose escalation was conducted using the product of independent beta probabilities dose-escalation design. PD analyzes were performed on peripheral blood samples and tumor/skin biopsies at baseline and on treatment. Clinical activity was evaluated using investigator-based and Response Evaluation Criteria In Solid Tumors V.1.1-based tumor assessments., Results: Three dose-limiting toxicities (all infusion-related reactions (IRRs)) were observed at 8, 12 and 16 mg of selicrelumab together with 1000 mg of emactuzumab. The maximum tolerated dose was not reached at the predefined top doses of emactuzumab (1000 mg) and selicrelumab (16 mg). The most common adverse events were IRRs (75.7%), fatigue (54.1%), facial edema (37.8%), and increase in aspartate aminotransferase and creatinine phosphokinase (35.1% both). PD analyzes demonstrated an increase of Ki67 + -activated CD8 + T cells accompanied by a decrease of B cells and the reduction of CD14 Dim CD16 bright monocytes in peripheral blood. The best objective clinical response was stable disease in 40.5% of patients., Conclusion: Emactuzumab in combination with selicrelumab demonstrated a manageable safety profile and evidence of PD activity but did not translate into objective clinical responses., Trialregistration Number: NCT02760797., Competing Interests: Competing interests: Jean-Pascal Machiels: Advisory board consulting for Pfizer, Roche, AstraZeneca, Bayer, Innate, Merck Serono, Boerhinger, BMS, Novartis, Janssen, Incyte, Cue Biopharma and ALX Oncology; travel expenses from Amgen, BMS, Pfizer, MSD; data safety monitoring board support for Debio, Nanobiotix and PsiOxus. Carlos Gomez-Roca: Consultancy for AstraZeneca and BMS; travel grant from Boehringer Ingelheim, BMS, Pierre Fabre, Roche and Sanofi Aventis; honoraria from BMS, Pierre Fabre and Roche; Jean-Marie Michot: Consultancy from Celgene, Bristol Myers Squibb, AstraZeneca and Janssen; travel grant and non-financial support from AstraZeneca, Roche, Novartis, Gilead, Celgene and Bristol Myers Squibb; Dmitriy Zamarin: Consultancy fees from Merck, Synlogic Therapeutics, Biomed Valley Discoveries, Trieza Therapeutics, Tesaro, and Agenus; Tara Mitchell: Advisory board consulting for Merck, BMS and Array; Gaetan Catala: Travel grants from Roche, Pharmamar, MSD and AstraZeneca; advisory role for MSD. Lauriane Eberst: None. Wolfgang Jacob: Sponsor employee and sponsor stock ownership. Anna-Maria Jegg: Former sponsor employee and has patent issued in the use of emactuzumab. Michael A Cannarile: Sponsor employee and sponsor stock ownership. Carl Watson: Sponsor consultant. Galina Babitzki: Sponsor employee. Konstanty Korski: Sponsor employee. Irina Klaman: Sponsor employee. Priscila C Teixeira: Sponsor employee. Sabine Hoves: Sponsor employee, sponsor stock ownership and has patent issued in the use of emactuzumab. Carola Ries: Former sponsor employee and has patent issued in the use of emactuzumab. Georgina Meneses-Lorente: Sponsor employee. Francesca Michielin: Sponsor employee. Randolph Christen: Sponsor employee and sponsor stock ownership. Dominik Rüttinger: Sponsor employee, sponsor stock ownership and has patent issued in the use of emactuzumab. Martin Weisser: Sponsor employee and sponsor stock ownership. Jean-Pierre Delord: Consulting or advisory role for Novartis, Roche/Genentech, Bristol Myers Squibb, MSD Oncology; research funding from Genentech, Bristol Myers Squibb, MSD Oncology. Philippe Cassier: Honoraria from Novartis, Roche/Genentech, Blueprint Medicines, Amgen and AstraZeneca; research funding from Novartis, Roche/Genentech, Eli Lilly, Blueprint Medicines, Bayer, AstraZeneca, Celgene, Plexxikon, AbbVie, Bristol Myers Squibb, Merck Serono, Merck Sharp & Dohme, Taiho Pharmaceuticals, Toray Industries, Transgene, Loxo, GlaxoSmithKline, Innatre Pharma and Janssen; travel grants from Roche, Amgen, Novartis, Bristol Myers Squibb, Merck Sharp & Dohme and Netris Pharma., (© Author(s) (or their employer(s)) 2020. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Purpose: Paget's disease (PD) of the breast is an uncommon disease of the nipple usually accompanied by an underlying carcinoma, often HER2 + , and accounting for 0.5-5% of all breast cancer. To date, histogenesis of PD of the breast remains controversial, as two theories-transformation and epidermotropic-have been proposed to explain this disease. Currently, animal models recapitulating PD of the nipple have not been described., Methods: HER2-enriched DT13 breast cancer cells were injected into the mammary fat pad of NOD scid gamma null (NSG) female mice. Immunohistochemical staining and pathological studies were performed on tumor samples, and diagnosis of PD of the nipple was confirmed by expression of proteins characteristic of Paget cells (epidermal growth factor 2 (HER2), androgen receptor (AR), cytokeratin 7 (CK7), cytokeratin 8/18 (CK8/18), and mucin 1 (MUC1)). In addition, DT13 cells grown in 2D culture and in soft agar assays were sensitive to in vitro treatment with pharmacological inhibitors targeting Her2, adenylyl cyclase, mTOR, and PI3K signaling pathways., Results: Mice developed tumors and nipple lesions that were detected exclusively on the tumor-bearing mammary fat pad. Tumor cells were positive for proteins characteristic of Paget cells. In vitro, DT13 cells were sensitive to inhibition of Her2, adenylyl cyclase, mTOR, and PI3K signaling pathways., Conclusions: Our results suggest that injection of HER2 + DT13 cells into the mammary fat pad of NSG mice recapitulates critical aspects of the pathophysiology of PD of the nipple, supporting the epidermotropic theory as the more likely to explain the histogenesis of this disease.

Background: Emactuzumab is a monoclonal antibody against the colony-stimulating factor-1 receptor and targets tumor-associated macrophages (TAMs). This study assessed the safety, clinical activity, pharmacokinetics (PK) and pharmacodynamics (PD) of emactuzumab, as monotherapy and in combination with paclitaxel, in patients with advanced solid tumors., Patients and Methods: This open-label, phase Ia/b study comprised two parts (dose escalation and dose expansion), each containing two arms (emactuzumab, every 2 or 3 weeks, as monotherapy or in combination with paclitaxel 80 mg/m2 weekly). The dose-escalation part explored the maximum tolerated dose and optimal biological dose (OBD). The dose-expansion part extended the safety assessment and investigated the objective response rate. A PK/PD analysis of serial blood, skin and tumor biopsies was used to explore proof of mechanism and confirm the OBD., Results: No maximum tolerated dose was reached in either study arm, and the safety profile of emactuzumab alone and in combination does not appear to preclude its use. No patients receiving emactuzumab monotherapy showed an objective response; the objective response rate for emactuzumab in combination with paclitaxel was 7% across all doses. Skin macrophages rather than peripheral blood monocytes or circulating colony-stimulating factor-1 were identified as an optimal surrogate PD marker to select the OBD. Emactuzumab treatment alone and in combination with paclitaxel resulted in a plateau of immunosuppressive TAM reduction at the OBD of 1000 mg administered every 2 weeks., Conclusions: Emactuzumab showed specific reduction of immunosuppressive TAMs at the OBD in both treatment arms but did not result in clinically relevant antitumor activity alone or in combination with paclitaxel. (ClinicalTrials.gov Identifier: NCT01494688)., (© The Author(s) 2019. Published by Oxford University Press on behalf of the European Society for Medical Oncology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

The tumor-permissive and immunosuppressive characteristics of tumor-associated macrophages (TAM) have fueled interest in therapeutically targeting these cells. In this context, the colony-stimulating factor 1 (CSF1)/colony-stimulating factor 1 receptor (CSF1R) axis has gained the most attention, and various approaches targeting either the ligands or the receptor are currently in clinical development. Emerging data on the tolerability of CSF1/CSF1R-targeting agents suggest a favorable safety profile, making them attractive combination partners for both standard treatment modalities and immunotherapeutic agents. The specificity of these agents and their potent blocking activity has been substantiated by impressive response rates in diffuse-type tenosynovial giant cell tumors, a benign connective tissue disorder driven by CSF1 in an autocrine fashion. In the malignant disease setting, data on the clinical activity of immunotherapy combinations with CSF1/CSF1R-targeting agents are pending. As our knowledge of macrophage biology expands, it becomes apparent that the complex phenotypic and functional properties of macrophages are heavily influenced by a continuum of survival, differentiation, recruitment, and polarization signals within their specific tissue environment. Thus, the role of macrophages in regulating tumorigenesis and the impact of depleting and/or reprogramming TAM as therapeutic approaches for cancer patients may vary greatly depending on organ-specific characteristics of these cells. We review the currently available clinical safety and efficacy data with CSF1/CSF1R-targeting agents and provide a comprehensive overview of ongoing clinical studies. Furthermore, we discuss the local tissue macrophage and tumor-type specificities and their potential impact on CSF1/CSF1R-targeting treatment strategies for the future.

Background: Diffuse-type tenosynovial giant cell tumour (dt-GCT) of the soft tissue (alternatively known as pigmented villonodular synovitis), an orphan disease with unmet medical need, is characterised by an overexpression of colony-stimulating factor 1 (CSF1), and is usually caused by a chromosomal translocation involving CSF1. CSF1 receptor (CSF1R) activation leads to the recruitment of CSF1R-expressing cells of the mononuclear phagocyte lineage that constitute the tumor mass in dt-GCT. Emactuzumab (RG7155) is a novel monoclonal antibody that inhibits CSF1R activation. We have assessed the safety, tolerability and activity of emactuzumab in patients with Dt-GCT of the soft tissue., Methods: In this phase 1, first-in-human dose-escalation and dose-expansion study, eligible patients were aged 18 years or older with dt-GCT of the soft tissue with locally advanced disease or resectable tumours requiring extensive surgery, an Eastern Cooperative Oncology Group performance status of 1 or less, measurable disease according to Response Evaluation Criteria In Solid Tumors version 1.1, and adequate end-organ function. Patients with GCT of the bone were not eligible. Patients received intravenous emactuzumab at 900 mg, 1350 mg, or 2000 mg every 2 weeks in the dose-escalation phase and at the optimal biological dose in a dose-expansion phase. The primary objective was to evaluate the safety and tolerability of emactuzumab, and to determine the maximum tolerated dose or optimal biological dose. All treated patients were included in the analyses. Expansion cohorts are currently ongoing. This study is registered with ClinicalTrials.gov, number NCT01494688., Findings: Between July 26, 2012, and Oct 21, 2013, 12 patients were enrolled in the dose-escalation phase. No dose-limiting toxicities were noted in the dose-escalation cohort; on the basis of pharmacokinetic, pharmacodynamic, and safety information, we chose a dose of 1000 mg every 2 week for the dose-expansion cohort, into which 17 patients were enrolled. Owing to different cutoff dates for safety and efficacy readouts, the safety population comprised 25 patients. Common adverse events after emactuzumab treatment were facial oedema (16 [64%] of 25 patients), asthenia (14 [56%]), and pruritus (14 [56%]). Five serious adverse events (periorbital oedema, lupus erythematosus [occurring twice], erythema, and dermohypodermitis all experienced by one [4%] patient each) were reported in five patients. Three of the five serious adverse events-periorbital oedema (one [4%]), lupus erythematosus (one [4%]), and dermohypodermitis (one [4%])-were assessed as grade 3. Two other grade 3 events were reported: mucositis (one [4%]) and fatigue (one [4%]). 24 (86%) of 28 patients achieved an objective response; two (7%) patients achieved a complete response., Interpretation: Further study of dt-GCT is warranted and different possibilities, such as an international collaboration with cooperative groups to assure appropriate recruitment in this rare disease, are currently being assessed., Funding: F Hoffmann-La Roche., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Truncated-ERBB2 isoforms (t-ERBB2s), resulting from receptor proteolysis or alternative translation of the ERBB2 mRNA, exist in a subset of human breast tumors. t-ERBB2s lack the receptor extracellular domain targeted by therapeutic anti-ERBB2 antibodies and antibody-drug conjugates, including trastuzumab, trastuzumab-DM1 and pertuzumab. In clinical studies, expression of t-ERBB2 in breast tumors correlates with metastasis as well as trastuzumab resistance. By using a novel immuno-microarray method, we detect a significant t-ERBB2 fraction in 18 of 31 (58%) of immunohistochemistry (IHC)3+ ERBB2+ human tumor specimens, and further show that t-ERBB2 isoforms are phosphorylated in a subset of IHC3+ samples (10 of 31, 32%). We investigated t-ERBB2 biological activity via engineered expression of full-length and truncated ERBB2 isoforms in human mammary epithelial cells (HMECs), including HMEC and MCF10A cells. Expression of p110 t-ERBB2, but not p95m (m=membrane, also 648CTF) or intracellular ERBB2s, significantly enhanced cell migration and invasion in multiple cell types. In addition, only expression of the p110 isoform led to human breast epithelial cell (HMLE) xenograft formation in vivo. Expression of t-ERBB2s did not result in hyperactivation of the phosphoinositide kinase-3/AKT or mitogen-activated protein kinase signaling pathways in these cells; rather, phosphoproteomic array profiling revealed attenuation of phosphorylated signal transducer and activator of transcription 5 (STAT5) in p110-t-ERBB2-expressing cells compared to controls. Short hairpin-mediated silencing of STAT5 phenocopied p110-t-ERBB2-driven cell migration and invasion, while expression of constitutively active STAT5 reversed these effects. Thus, we provide novel evidence that (1) expression of p110 t-ERBB2 is sufficient for full transformation of HMEC, yielding in vivo xenograft formation, and (2) truncated p110 t-ERBB2 expression is associated with decreased phosphorylation of STAT5.

Therapies targeting the ERBB2 receptor, including the kinase inhibitor lapatinib (Tykerb, GlaxoSmithKline), have improved clinical outcome for women with ERBB2-amplified breast cancer. However, acquired resistance to lapatinib remains a significant clinical problem, and the mechanisms governing resistance remain poorly understood. We sought to define molecular alterations that confer an acquired lapatinib resistance phenotype in ER-/ERBB2+ human breast cancer cells. ERBB2-amplified SKBR3 breast cancer cells were rendered resistant to lapatinib via culture in increasing concentrations of the drug, and molecular changes associated with a resistant phenotype were interrogated using a collaborative enzyme-enhanced immunoassay platform and immunoblotting techniques for detection of phosphorylated signaling cascade proteins. Interestingly, despite apparent inactivation of the PI3K/AKT signaling pathway, resistant cells exhibited constitutive activation of mammalian target of rapamycin complex 1 (mTORC1) and were highly sensitive to mTOR inhibition with rapamycin and the dual PI3K/mTOR inhibitor NVP-BEZ235. These data demonstrate a role for downstream activation of mTORC1 in the absence of molecular alterations leading to PI3K/AKT hyperactivation as a potential mechanism of lapatinib resistance in this model of ERBB2+ breast cancer and support the rationale of combination or sequential therapy using ERBB2 and mTOR-targeting molecules to prevent or target resistance to lapatinib. Moreover, our data suggest that assessment of mTOR substrate phosphorylation (i.e., S6) may serve as a more robust biomarker to predict sensitivity to mTOR inhibitors in the context of lapatinib resistance than PI3K mutations, loss of PTEN and p-AKT levels.