Marcin Kowanetz

Predictive correlates of response to the anti-PD-L1 antibody MPDL3280A in cancer patients

The development of human cancer is a multistep process characterized by the accumulation of genetic and epigenetic alterations that drive or reflect tumour progression. These changes distinguish cancer cells from their normal counterparts, allowing tumours to be recognized as foreign by the immune system. However, tumours are rarely rejected spontaneously, reflecting their ability to maintain an immunosuppressive microenvironment. Programmed death-ligand 1 (PD-L1; also called B7-H1 or CD274), which is expressed on many cancer and immune cells, plays an important part in blocking the ‘cancer immunity cycle’ by binding programmed death-1 (PD-1) and B7.1 (CD80), both of which are negative regulators of T-lymphocyte activation. Binding of PD-L1 to its receptors suppresses T-cell migration, proliferation and secretion of cytotoxic mediators, and restricts tumour cell killing. The PD-L1–PD-1 axis protects the host from overactive T-effector cells not only in cancer but also during microbial infections. Blocking PD-L1 should therefore enhance anticancer immunity, but little is known about predictive factors of efficacy. This study was designed to evaluate the safety, activity and biomarkers of PD-L1 inhibition using the engineered humanized antibody MPDL3280A. Here we show that across multiple cancer types, responses (as evaluated by Response Evaluation Criteria in Solid Tumours, version 1.1) were observed in patients with tumours expressing high levels of PD-L1, especially when PD-L1 was expressed by tumour-infiltrating immune cells. Furthermore, responses were associated with T-helper type 1 (TH1) gene expression, CTLA4 expression and the absence of fractalkine (CX3CL1) in baseline tumour specimens. Together, these data suggest that MPDL3280A is most effective in patients in which pre-existing immunity is suppressed by PD-L1, and is re-invigorated on antibody treatment.

Atezolizumab versus docetaxel for patients with previously treated non-small-cell lung cancer (POPLAR): a multicentre, open-label, phase 2 randomised controlled trial.

BACKGROUND Outcomes are poor for patients with previously treated, advanced or metastatic non-small-cell lung cancer (NSCLC). The anti-programmed death ligand 1 (PD-L1) antibody atezolizumab is clinically active against cancer, including NSCLC, especially cancers expressing PD-L1 on tumour cells, tumour-infiltrating immune cells, or both. We assessed efficacy and safety of atezolizumab versus docetaxel in previously treated NSCLC, analysed by PD-L1 expression levels on tumour cells and tumour-infiltrating immune cells and in the intention-to-treat population. METHODS In this open-label, phase 2 randomised controlled trial, patients with NSCLC who progressed on post-platinum chemotherapy were recruited in 61 academic medical centres and community oncology practices across 13 countries in Europe and North America. Key inclusion criteria were Eastern Cooperative Oncology Group performance status 0 or 1, measurable disease by Response Evaluation Criteria In Solid Tumors version 1.1 (RECIST v1.1), and adequate haematological and end-organ function. Patients were stratified by PD-L1 tumour-infiltrating immune cell status, histology, and previous lines of therapy, and randomly assigned (1:1) by permuted block randomisation (with a block size of four) using an interactive voice or web system to receive intravenous atezolizumab 1200 mg or docetaxel 75 mg/m(2) once every 3 weeks. Baseline PD-L1 expression was scored by immunohistochemistry in tumour cells (as percentage of PD-L1-expressing tumour cells TC3≥50%, TC2≥5% and <50%, TC1≥1% and <5%, and TC0<1%) and tumour-infiltrating immune cells (as percentage of tumour area: IC3≥10%, IC2≥5% and <10%, IC1≥1% and <5%, and IC0<1%). The primary endpoint was overall survival in the intention-to-treat population and PD-L1 subgroups at 173 deaths. Biomarkers were assessed in an exploratory analysis. We assessed safety in all patients who received at least one dose of study drug. This study is registered with ClinicalTrials.gov, number NCT01903993. FINDINGS Patients were enrolled between Aug 5, 2013, and March 31, 2014. 144 patients were randomly allocated to the atezolizumab group, and 143 to the docetaxel group. 142 patients received at least one dose of atezolizumab and 135 received docetaxel. Overall survival in the intention-to-treat population was 12·6 months (95% CI 9·7-16·4) for atezolizumab versus 9·7 months (8·6-12·0) for docetaxel (hazard ratio [HR] 0·73 [95% CI 0·53-0·99]; p=0·04). Increasing improvement in overall survival was associated with increasing PD-L1 expression (TC3 or IC3 HR 0·49 [0·22-1·07; p=0·068], TC2/3 or IC2/3 HR 0·54 [0·33-0·89; p=0·014], TC1/2/3 or IC1/2/3 HR 0·59 [0·40-0·85; p=0·005], TC0 and IC0 HR 1·04 [0·62-1·75; p=0·871]). In our exploratory analysis, patients with pre-existing immunity, defined by high T-effector-interferon-γ-associated gene expression, had improved overall survival with atezolizumab. 11 (8%) patients in the atezolizumab group discontinued because of adverse events versus 30 (22%) patients in the docetaxel group. 16 (11%) patients in the atezolizumab group versus 52 (39%) patients in the docetaxel group had treatment-related grade 3-4 adverse events, and one (<1%) patient in the atezolizumab group versus three (2%) patients in the docetaxel group died from a treatment-related adverse event. INTERPRETATION Atezolizumab significantly improved survival compared with docetaxel in patients with previously treated NSCLC. Improvement correlated with PD-L1 immunohistochemistry expression on tumour cells and tumour-infiltrating immune cells, suggesting that PD-L1 expression is predictive for atezolizumab benefit. Atezolizumab was well tolerated, with a safety profile distinct from chemotherapy. FUNDING F Hoffmann-La Roche/Genentech Inc.

Atezolizumab versus docetaxel in patients with previously treated non-small-cell lung cancer (OAK): a phase 3, open-label, multicentre randomised controlled trial

BACKGROUND Atezolizumab is a humanised antiprogrammed death-ligand 1 (PD-L1) monoclonal antibody that inhibits PD-L1 and programmed death-1 (PD-1) and PD-L1 and B7-1 interactions, reinvigorating anticancer immunity. We assessed its efficacy and safety versus docetaxel in previously treated patients with non-small-cell lung cancer. METHODS We did a randomised, open-label, phase 3 trial (OAK) in 194 academic or community oncology centres in 31 countries. We enrolled patients who had squamous or non-squamous non-small-cell lung cancer, were 18 years or older, had measurable disease per Response Evaluation Criteria in Solid Tumors, and had an Eastern Cooperative Oncology Group performance status of 0 or 1. Patients had received one to two previous cytotoxic chemotherapy regimens (one or more platinum based combination therapies) for stage IIIB or IV non-small-cell lung cancer. Patients with a history of autoimmune disease and those who had received previous treatments with docetaxel, CD137 agonists, anti-CTLA4, or therapies targeting the PD-L1 and PD-1 pathway were excluded. Patients were randomly assigned (1:1) to intravenously receive either atezolizumab 1200 mg or docetaxel 75 mg/m2 every 3 weeks by permuted block randomisation (block size of eight) via an interactive voice or web response system. Coprimary endpoints were overall survival in the intention-to-treat (ITT) and PD-L1-expression population TC1/2/3 or IC1/2/3 (≥1% PD-L1 on tumour cells or tumour-infiltrating immune cells). The primary efficacy analysis was done in the first 850 of 1225 enrolled patients. This study is registered with ClinicalTrials.gov, number NCT02008227. FINDINGS Between March 11, 2014, and April 29, 2015, 1225 patients were recruited. In the primary population, 425 patients were randomly assigned to receive atezolizumab and 425 patients were assigned to receive docetaxel. Overall survival was significantly longer with atezolizumab in the ITT and PD-L1-expression populations. In the ITT population, overall survival was improved with atezolizumab compared with docetaxel (median overall survival was 13·8 months [95% CI 11·8-15·7] vs 9·6 months [8·6-11·2]; hazard ratio [HR] 0·73 [95% CI 0·62-0·87], p=0·0003). Overall survival in the TC1/2/3 or IC1/2/3 population was improved with atezolizumab (n=241) compared with docetaxel (n=222; median overall survival was 15·7 months [95% CI 12·6-18·0] with atezolizumab vs 10·3 months [8·8-12·0] with docetaxel; HR 0·74 [95% CI 0·58-0·93]; p=0·0102). Patients in the PD-L1 low or undetectable subgroup (TC0 and IC0) also had improved survival with atezolizumab (median overall survival 12·6 months vs 8·9 months; HR 0·75 [95% CI 0·59-0·96]). Overall survival improvement was similar in patients with squamous (HR 0·73 [95% CI 0·54-0·98]; n=112 in the atezolizumab group and n=110 in the docetaxel group) or non-squamous (0·73 [0·60-0·89]; n=313 and n=315) histology. Fewer patients had treatment-related grade 3 or 4 adverse events with atezolizumab (90 [15%] of 609 patients) versus docetaxel (247 [43%] of 578 patients). One treatment-related death from a respiratory tract infection was reported in the docetaxel group. INTERPRETATION To our knowledge, OAK is the first randomised phase 3 study to report results of a PD-L1-targeted therapy, with atezolizumab treatment resulting in a clinically relevant improvement of overall survival versus docetaxel in previously treated non-small-cell lung cancer, regardless of PD-L1 expression or histology, with a favourable safety profile. FUNDING F. Hoffmann-La Roche Ltd, Genentech, Inc.

Vascular Endothelial Growth Factor Signaling Pathways: Therapeutic Perspective

The establishment of a vascular supply is one of the earliest and most important events occurring during embryonic development. Growth and maturation of a functional vascular network are complex and still incompletely understood processes involving orchestrated activation of vascular progenitors in the early stages of embryonic development followed by vasculogenesis and angiogenesis. These processes require a tightly regulated activation of several growth factors and their receptors. The role of vascular endothelial growth factors (VEGF) and their receptors has been studied extensively due to their prominent role during blood vessel formation. Mice deficient in various VEGF ligands or receptors show serious defects in vascular formation and maturation. Moreover, members of the VEGF family are involved in other significant biological processes, including lymphangiogenesis, vascular permeability, and hematopoiesis. Importantly, VEGF is released by tumor cells and induces tumor neovascularization. It is now well established that the VEGF axis represents an important target for antitumor therapy. Aberrant VEGF signaling is also a feature of several other pathologic conditions, such as age-related macular degeneration and rheumatoid arthritis.

G-CSF-initiated myeloid cell mobilization and angiogenesis mediate tumor refractoriness to anti-VEGF therapy in mouse models

Recent studies suggest that tumor-associated CD11b+Gr1+ myeloid cells contribute to refractoriness to antiangiogenic therapy with an anti-VEGF-A antibody. However, the mechanisms of peripheral mobilization and tumor-homing of CD11b+Gr1+ cells are unclear. Here, we show that, compared with other cytokines [granulocyte-macrophage colony stimulating factor (GM-CSF), stromal derived factor 1α, and placenta growth factor], G-CSF and the G-CSF-induced Bv8 protein have preferential expression in refractory tumors. Treatment of refractory tumors with the combination of anti-VEGF and anti-G-CSF (or anti-Bv8) reduced tumor growth compared with anti-VEGF-A monotherapy. Anti-G-CSF treatment dramatically suppressed circulating or tumor-associated CD11b+Gr1+ cells, reduced Bv8 levels, and affected the tumor vasculature. Conversely, G-CSF delivery to animals bearing anti-VEGF sensitive tumors resulted in reduced responsiveness to anti-VEGF-A treatment through induction of Bv8-dependent angiogenesis. We conclude that, at least in the models examined, G-CSF expression by tumor or stromal cells is a determinant of refractoriness to anti-VEGF-A treatment.

Granulocyte-colony stimulating factor promotes lung metastasis through mobilization of Ly6G+Ly6C+ granulocytes

Priming of the organ-specific premetastatic sites is thought to be an important yet incompletely understood step during metastasis. In this study, we show that the metastatic tumors we examined overexpress granulocyte-colony stimulating factor (G-CSF), which expands and mobilizes Ly6G+Ly6C+ granulocytes and facilitates their subsequent homing at distant organs even before the arrival of tumor cells. Moreover, G-CSF–mobilized Ly6G+Ly6C+ cells produce the Bv8 protein, which has been implicated in angiogenesis and mobilization of myeloid cells. Anti–G-CSF or anti-Bv8 antibodies significantly reduced lung metastasis. Transplantation of Bv8 null fetal liver cells into lethally irradiated hosts also reduced metastasis. We identified an unexpected role for Bv8: the ability to stimulate tumor cell migration through activation of one of the Bv8 receptors, prokineticin receptor (PKR)-1. Finally, we show that administration of recombinant G-CSF is sufficient to increase the numbers of Ly6G+Ly6C+ cells in organ-specific metastatic sites and results in enhanced metastatic ability of several tumors.

Stable Expression of Angiopoietin-1 and Other Markers by Cultured Pericytes: Phenotypic Similarities to a Subpopulation of Cells in Maturing Vessels During Later Stages of Angiogenesis In Vivo

Pericytes have been difficult cells to study because they do not maintain their characteristic phenotype in vitro, and they begin to express fibroblast markers after only a few days in culture. We now report methods for the isolation, purification, culture, and repurification of human dermal pericytes from mixed cell populations using an immunoaffinity-magnetic bead approach coupled with the 3G5 IgM monoclonal antibody that is specific for a pericyte surface ganglioside. These purified cells could be expanded in culture, and they maintained their pericyte phenotype for up to 8 days. In addition, they strongly expressed angiopoietin-1 (Ang-1) but not angiopoietin-2, Tie-1, or Tie-2; in contrast, dermal microvascular endothelial cells exhibited a reciprocal expression pattern. These findings are important because the close proximity of endothelial cells and pericytes has often made it difficult to determine with certainty the specific cell type(s) that expressed each of these proteins in situ. Extending our in vitro findings to two models of angiogenesis in vivo, we demonstrated a subpopulation of Ang-1–expressing cells that appeared in maturing microvessels during later stages of cutaneous wound healing and vascular permeability factor/vascular endothelial growth factor–induced angiogenesis. Our results provide strong evidence that Ang-1 is expressed by pericytes in vitro and in vivo and that the role proposed for Ang-1 in vessel maturation in development can be extended to vessel maturation after angiogenesis in adult tissues.

PlGF Blockade Does Not Inhibit Angiogenesis during Primary Tumor Growth

It has been recently reported that treatment with an anti-placenta growth factor (PlGF) antibody inhibits metastasis and primary tumor growth. Here we show that, although anti-PlGF treatment inhibited wound healing, extravasation of B16F10 cells, and growth of a tumor engineered to overexpress the PlGF receptor (VEGFR-1), neutralization of PlGF using four novel blocking antibodies had no significant effect on tumor angiogenesis in 15 models. Also, genetic ablation of the tyrosine kinase domain of VEGFR-1 in the host did not result in growth inhibition of the anti-VEGF-A sensitive or resistant tumors tested. Furthermore, combination of anti-PlGF with anti-VEGF-A antibodies did not result in greater antitumor efficacy than anti-VEGF-A monotherapy. In conclusion, our data argue against an important role of PlGF during primary tumor growth in most models and suggest that clinical evaluation of anti-PlGF antibodies may be challenging.

Differential drug class‐specific metastatic effects following treatment with a panel of angiogenesis inhibitors

Inhibiting angiogenesis has become an important therapeutic strategy for cancer treatment but, like other current targeted therapies, benefits experienced for late‐stage cancers can be curtailed by inherent refractoriness or by acquired drug resistance, requiring a need for better mechanistic understanding of such effects. Numerous preclinical studies have demonstrated that VEGF pathway inhibitors suppress primary tumour growth and metastasis. However, it has been recently reported that short‐term VEGF and VEGFR inhibition can paradoxically accelerate tumour invasiveness and metastasis in certain models. Here we comprehensively compare the effects of both antibody and small molecule receptor tyrosine kinase (RTK) inhibitors targeting the VEGF–VEGFR pathway, using short‐term therapy in various mouse models of metastasis. Our findings demonstrate that antibody inhibition of VEGF pathway molecules does not promote metastasis, in contrast to selected small molecule RTK inhibitors at elevated‐therapeutic drug dosages. In particular, a multi‐targeted RTK inhibitor, sunitinib, which most profoundly potentiated metastasis, also increased lung vascular permeability and promoted tumour cell extravasation. Mechanistically, sunitinib, but not anti‐VEGF treatment, attenuated endothelial barrier function in culture and caused a global inhibition of protein tyrosine phosphorylation, including molecules important for maintaining endothelial cell–cell junctions. Together these findings indicate that, rather than a specific consequence of inhibiting the VEGF signalling pathway, pharmacological inhibitors of the VEGF pathway can have dose‐ and drug class‐dependent side‐effects on the host vasculature. These findings also advocate for the continued identification of mechanisms of resistance to anti‐angiogenics and for therapy development to overcome it. Copyright

Oncogenic RAS pathway activation promotes resistance to anti-VEGF therapy through G-CSF–induced neutrophil recruitment

Granulocyte-colony stimulating factor (G-CSF) promotes mobilization of CD11b+Gr1+ myeloid cells and has been implicated in resistance to anti-VEGF therapy in mouse models. High G-CSF production has been associated with a poor prognosis in cancer patients. Here we show that activation of the RAS/MEK/ERK pathway regulates G-CSF expression through the Ets transcription factor. Several growth factors induced G-CSF expression by a MEK-dependent mechanism. Inhibition of G-CSF release with a MEK inhibitor markedly reduced G-CSF production in vitro and synergized with anti-VEGF antibodies to reduce CD11b+Ly6G+ neutrophil mobilization and tumor growth and led to increased survival in animal models of cancer, including a genetically engineered mouse model of pancreatic adenocarcinoma. Analysis of biopsies from pancreatic cancer patients revealed increased phospho-MEK, G-CSF, and Ets expression and enhanced neutrophil recruitment compared with normal pancreata. These results provide insights into G-CSF regulation and on the mechanism of action of MEK inhibitors and point to unique anticancer strategies.