Preclinical Characterization of Linrodostat Mesylate, a Novel, Potent, and Selective Oral Indoleamine 2,3-Dioxygenase 1 Inhibitor

Tumors can exploit the indoleamine 2,3-dioxygenase 1 (IDO1) pathway to create an immunosuppressive microenvironment. Activated IDO1 metabolizes tryptophan into immunosuppressive kynurenine, leading to suppressed effector T-cell (Teff) proliferation, allowing for tumor escape from host immune surveillance. IDO1 inhibition counteracts this immunosuppressive tumor microenvironment and may improve cancer outcomes, particularly when combined with other immunotherapies. Linrodostat mesylate (linrodostat) is a potent, selective oral IDO1 inhibitor that occupies the heme cofactor-binding site to prevent further IDO1 activation and is currently in multiple clinical trials for treatment of patients with advanced cancers. Here, we assess the in vitro potency, in vivo pharmacodynamic (PD) activity, and preclinical pharmacokinetics (PKs) of linrodostat. Linrodostat exhibited potent cellular activity, suppressing kynurenine production in HEK293 cells overexpressing human IDO1 and HeLa cells stimulated with IFNγ, with no activity against tryptophan 2,3-dioxygenase or murine indoleamine 2,3-dioxygenase 2 detected. Linrodostat restored T-cell proliferation in a mixed-lymphocyte reaction of T cells and allogeneic IDO1-expressing dendritic cells. In vivo, linrodostat reduced kynurenine levels in human tumor xenograft models, exhibiting significant PD activity. Linrodostat demonstrated a PK/PD relationship in the xenograft model, preclinical species, and samples from patients with advanced cancers, with high oral bioavailability in preclinical species and low to moderate systemic clearance. Our data demonstrate that linrodostat potently and specifically inhibits IDO1 to block an immunosuppressive mechanism that could be responsible for tumor escape from host immune surveillance with favorable PK/PD characteristics that support clinical development.

The Value of PD-L1 Expression as Predictive Biomarker in Metastatic Renal Cell Carcinoma Patients: A Meta-Analysis of Randomized Clinical Trials

Immune checkpoint inhibitors (ICIs) are soluble antibodies that have dramatically changed the outcomes including overall survival in a subset of kidney tumors, specifically in renal cell carcinoma (RCC). To date, there is no a single predictive biomarker approved to be used to select the patients that achieve benefit from ICIs targeting. It seems reasonable to analyze whether the programmed death-ligand 1 (PD-L1) expression could be useful. To assess the role of PD-L1 expression as a potential predictive biomarker for benefit of ICIs in RCC patients, we performed a search of randomized clinical trials (RCTs) comparing ICIs (monotherapy or in combination with other therapies) to standard of care in metastatic RCC patients according to PRISMA guidelines. Trials must have included subgroup analyses evaluating the selected outcomes (progression-free survival (PFS) and overall survival (OS)) in different subsets of patients according to PD-L1 expression on tumor samples. Hazard ratios with confidence intervals were used as the measure of efficacy between groups. A total of 4635 patients (six studies) were included (ICIs arm: 2367 patients; standard of care arm: 2268 patients). Globally, PFS and OS results favored ICIs. Differential expression of PD-L1 on tumor samples could select a subset of patients who could benefit more in terms of PFS (those with higher levels; p-value for difference between subgroups: <0.0001) but it did not seem to impact in OS results (p-value for difference: 0.63). As different methods to assess PD-L1 positivity were used among trials, this heterogeneity could have an influence on the results. PD-L1 could represent a biomarker to test PFS in clinical trials but its value for OS is less clear. In this meta-analysis, the usefulness of PD-L1 expression as a predictive biomarker to select treatment in metastatic RCC patients was not clearly shown.

Programmed Cell Death 1 (PD-1) Ligand (PD-L1) Expression in Solid Tumors As a Predictive Biomarker of Benefit From PD-1/PD-L1 Axis Inhibitors: A Systematic Review and Meta-Analysis

PURPOSE

Drugs targeting the programmed cell death 1 (PD-1)/programmed cell death ligand 1 (PD-L1) pathway show significant clinical activity across several tumor types. However, a majority of patients do not respond to these agents. Use of biomarker assays to predict response to these agents is an active area of research; however, the predictive value of PD-L1 immunohistochemistry (IHC) assays is largely inconsistent across clinical trials. In this meta-analysis of clinical trials of PD-1/PD-L1-targeted agents, we evaluate the predictive value of a tumor and tumor-infiltrating immune cell PD-L1 IHC assay as a biomarker for objective response to PD-1/PD-L1 inhibitors.

METHODS

We searched databases (PubMed, Medline, ASCO abstracts, European Society for Medical Oncology abstracts, and Scopus) up until December 2016 for clinical trials using PD-1/PD-L1 inhibitors with reported PD-L1 biomarker data. Objective response rates (primary end point) from all phase I to III trials investigating nivolumab, pembrolizumab, atezolizumab, durvalumab, and avelumab in advanced solid tumors were collected. Odds ratios (ORs) for response in PD-L1-positive patients compared with PD-L1-negative patients were calculated using the DerSimonian-Laird random effects model to combine trials. We performed meta-analysis as per the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

RESULTS

Forty-one distinct trials with 6,664 patients were identified. PD-L1 expression was predictive of favorable response across all tumor types (OR, 2.26; 95% CI, 1.85 to 2.75; P < .001), with the significantly largest effect observed in non-small-cell lung cancer (OR, 2.51; 95% CI, 1.99 to 3.17; P < .001). A subgroup analysis across all non-small-cell lung cancer trials using nivolumab and Dako clone 28-8 (Dako, Carpinteria, CA) IHC antibody assay yielded a significantly higher objective response rate in patients with tumor PD-L1 expression even at the minimum cutoff value of 1% (OR, 2.17; 95% CI, 1.03 to 4.57).

CONCLUSION

Our meta-analysis shows that tumor and tumor-infiltrating immune cell PD-L1 overexpression based on IHC is associated with significantly higher response rates to PD-1/PD-L1 axis inhibitors across a range of malignant solid tumors.

Nivolumab in the treatment of advanced renal cell carcinoma: clinical trial evidence and experience

Renal cell carcinoma (RCC) is considered an immunogenic tumor with a prominent dysfunctional immune cell infiltrate, unable to control tumor growth. Cytokine-based immunotherapies, including interferon-α and interleukin-2, have been used for the treatment of metastatic RCC (mRCC). Long-term responses and complete remissions were observed, but durable clinical benefit efficacy in the overall population was limited and associated with significant toxicity. As a consequence, new generation agents targeting the vascular endothelial growth factor (VEGF) and mammalian target of rapamycin (mTOR) pathways replaced interferon alpha (IFN-α). Strategies of tumor immune evasion include T-cell suppression by negative signals deriving from the interaction between programmed death-1 (PD-1) on the T cell and its ligand (PDL-1) on the tumor cells. Nivolumab, a programmed death 1 checkpoint inhibitor, blocks this pathway, thus reversing T-cell suppression and activating antitumor responses. The aim of this review is to summarize the safety and efficacy data of nivolumab in mRCC. Objective responses and safety profile of single-agent nivolumab are favorable in both previously treated and treatment-naïve mRCC patients. Despite toxic effects, combination therapies with nivolumab have shown promising results, indicating a potential role in the treatment of mRCC. Tailoring immunotherapy on a patient-to-patient basis represents a major challenge for the future.

Checkpoint inhibitors and other novel immunotherapies for advanced renal cell carcinoma

The management of advanced renal cell carcinoma (RCC) has dramatically changed over the past decade. Therapies that target the vascular endothelial growth factor (VEGF) and mammalian target of rapamycin (mTOR) pathways have considerably expanded treatment options; however, most patients with advanced RCC still have limited overall survival. Increased understanding of the mechanisms of T cell-antigen recognition and function has led to the development of novel immunotherapies to treat cancer, chief among them inhibitors of checkpoint receptors - molecules whose function is to restrain the host immune response. In 2015, the FDA approved the first checkpoint inhibitor nivolumab for patients with advanced RCC following treatment with antiangiogenic therapy based on improved overall survival compared with the standard of care. Ongoing phase III trials are comparing checkpoint-inhibitor-based combination regimens with antiangiogenesis agents in the first-line setting. The field is evolving rapidly, with many clinical trials already testing several checkpoint inhibitors alone, in combination, or with other targeted therapies. In addition, different novel immune therapies are being investigated including vaccines, T-cell agonists, and chimeric antigen receptor T cells. Determining which patients will benefit from these therapies and which combination approaches will result in better response will be important as this field evolves.

Predictive and prognostic biomarkers of targeted agents and modern immunotherapy in renal cell carcinoma

In the past decade, several agents targeting angiogenesis and signal transduction pathways have replaced the use of cytokines as standard of care treatment for metastatic renal cell carcinoma (RCC) after showing improved clinical benefit and survival. Currently, several novel immunotherapy agents targeting the programmed cell death-1 (PD-1) and cytotoxic T-lymphocyte-associated protein-4 (CTLA-4) pathways are being tested in metastatic RCC and are bound to revolutionise the management of this disease. However, the success of both antiangiogenic drugs and new immunotherapy agents still depends on our ability to select patients most likely to respond to treatment. This article will review the current available evidence on prognostic and predictive biomarkers of response to signal transduction pathways-targeted agents and modern immunotherapy in metastatic RCC.

Prognostic Significance of PD-L1 in Patients with Non-Small Cell Lung Cancer: A Large Cohort Study of Surgically Resected Cases

INTRODUCTION

The aim of our analysis was to evaluate the prognostic effect of programmed cell death ligand-1 (PD-L1) expression in patients with non-small cell lung cancer (NSCLC).

METHODS

PD-L1 expression among 1070 surgically resected NSCLC specimens was evaluated by immunohistochemical analysis. Data were analyzed using Cox proportional hazard models adjusting for age, sex, smoking status, histologic type, stage, and performance status.

RESULTS

Sixty-eight patients (6%) were strongly PD-L1 positive and 410 (38%) were weakly PD-L1 positive. A significantly higher prevalence of PD-L1 positivity was observed among patients with squamous cell carcinoma and among stage IIIB and IV patients. PD-L1 expression may be associated with poorer overall survival, with an adjusted hazard ratio of 1.56 (95% confidence interval [CI]: 1.08-2.26, p = 0.02) for strong PD-L1 positivity, 1.18 (95% CI: 0.96-1.46; p = 0.12) for weak PD-L1 positivity, and 1.23 (95% CI: 1.00-1.51; p = 0.05) for the combined strongly and weakly positive groups compared with PD-L1 negativity. Negative prognostic effect of PD-L1 expression was not statistically significant after adjustment for postoperative chemotherapy or radiotherapy. Similar results were observed for progression-free survival. Among stage I patients, the disease recurrence rate was higher in the PD-L1-positive versus in the PD-L1-negative group (48% versus 27%, p < 0.001), with an adjusted hazard ratio for disease-free survival of 2.01 (95% CI, 1.08-3.73; p = 0.03) for strong PD-L1 positivity and 1.57 (95% CI, 1.17-2.11; p = 0.003) for weak PD-L1 positivity compared with PD-L1 negativity.

CONCLUSIONS

Tumor PD-L1 expression may be associated with poor prognosis in patients with NSCLC, although its significance weakens when postoperative therapy is considered.

Blocking immune checkpoints in prostate, kidney, and urothelial cancer: An overview

Despite a long history of immunotherapeutic approaches to treatment, most genitourinary malignancies are not cured by existing immunotherapy regimens. More recently, cell surface molecules known as immune checkpoints have become the focus of efforts to develop more effective immunotherapies. Interactions between these molecules and their ligands inhibit the proliferation and function of tumor-specific lymphocytes. A monoclonal antibody blocking 1 of these checkpoints was approved for the treatment of metastatic melanoma and is now being tested in other malignancies. The objective responses seen in these early trials of checkpoint blockade are driving renewed enthusiasm for cancer immunotherapy. There are several ongoing and planned trials in genitourinary malignancies of single-agent inhibitors, as well as combinations targeting multiple checkpoints or adding other types of therapies to checkpoint blockade.

Diagnosis of Renal Cell Carcinoma: A Clinician's Perspective

Renal cell carcinoma (RCC) is a heterogeneous disease. A rigorous diagnostic assessment by a pathologist with close communication with the clinician provides more accurate prognostication and informed treatment decisions. In the localized setting, an accurate prognostic assessment directs patients to potential adjuvant clinical trials. For patients with advanced disease, the pathologic assessment may have a direct impact on the systemic therapy algorithm. Additionally, it provides the basis for continuous efforts in biomarker development. In rare histologic subtypes, the interaction between clinicians and pathologists provides an opportunity to offer patients specific clinical trials. Molecular characterization platforms may identify targets for therapeutic intervention.

Radiologic Heterogeneity in Responses to Anti-PD-1/PD-L1 Therapy in Metastatic Renal Cell Carcinoma

Radiologic assessment of tumor response remains a challenge in patients treated with immune checkpoint inhibitors. In metastatic melanoma, for example, a spectrum of imaging patterns in response to immunotherapies have been recognized and associated with clinical benefit. In metastatic renal cell carcinoma (mRCC), less than half of patients treated with immune checkpoint inhibitors achieve objective responses, but some of the responses have been durable. In this series, five different imaging patterns of response and progression are described in mRCC patients treated with anti-PD-1/PD-L1 agents: (i) early and complete response, (ii) pseudoprogression, (iii) disease stability before ultimate response, (iv) mixed response with new lesions, and (v) early progression/primary refractory disease. The implications of the different imaging patterns of patient responses on disease prognosis are discussed and highlight the need for individualized patient assessment when using these novel immune-targeted agents.

The Immune Checkpoint Regulator PD-L1 Is Highly Expressed in Aggressive Primary Prostate Cancer

PURPOSE

Therapies targeting the programmed death 1 (PD-1)/programmed death ligand 1 (PD-L1) pathway promote anti-tumor immunity and have shown promising results in various tumors. Preliminary data further indicate that immunohistochemically detected PD-L1 may be predictive for anti-PD-1 therapy. So far, no data are available on PD-L1 expression in primary prostate cancer.

EXPERIMENTAL DESIGN

Following validation of a monoclonal antibody, immunohistochemical analysis of PD-L1 expression was performed in two independent, well-characterized cohorts of primary prostate cancer patients following radical prostatectomy (RP), and resulting data were correlated to clinicopathological parameters and outcome.

RESULTS

In the training cohort (n= 209), 52.2% of cases expressed moderate to high PD-L1 levels, which positively correlated with proliferation (Ki-67,P< 0.001), Gleason score (P= 0.004), and androgen receptor (AR) expression (P< 0.001). Furthermore, PD-L1 positivity was prognostic for biochemical recurrence [BCR;P= 0.004; HR, 2.37; 95% confidence interval (CI), 1.32-4.25]. In the test cohort (n= 611), moderate to high PD-L1 expression was detected in 61.7% and remained prognostic for BCR in univariate Cox analysis (P= 0.011; HR, 1.49; 95% CI, 1.10-2.02). The correlation of Ki-67 and AR with PD-L1 expression was confirmed in the test cohort (P< 0.001). In multivariate Cox analysis of all patients, PD-L1 was corroborated as independently prognostic for BCR (P= 0.007; HR, 1.46; 95% CI, 1.11-1.92).

CONCLUSIONS

We provide first evidence that expression of the therapy target PD-L1 is not only highly prevalent in primary prostate cancer cells but is also an independent indicator of BCR, suggesting a biologic relevance in primary tumors. Further studies need to ascertain if PD-1/PD-L1-targeted therapy might be a treatment option for hormone-naïve prostate cancers.

Clinical impact of checkpoint inhibitors as novel cancer therapies

Immune responses are tightly regulated via signaling through numerous co-stimulatory and co-inhibitory molecules. Exploitation of these immune checkpoint pathways is one of the mechanisms by which tumors evade and/or escape the immune system. A growing understanding of the biology of immune checkpoints and tumor immunology has led to the development of monoclonal antibodies designed to target co-stimulatory and co-inhibitory molecules in order to re-engage the immune system and restore antitumor immune responses. Anti-cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) antibodies were among the first to be tested in the clinic, and ipilimumab was the first immune checkpoint inhibitor approved for an anticancer indication. Agents targeting the programmed death 1 (PD-1) pathway, either PD-1 or one of its ligands, programmed death ligand 1, are in active clinical development for numerous cancers, including advanced melanoma and lung cancer. Understanding the different mechanisms of action, safety profiles, and response patterns associated with inhibition of the CTLA-4 and PD-1 pathways may improve patient management as these therapies are moved in to the clinical practice setting and may also provide a rationale for combination therapy with different inhibitors. Additional immune checkpoint molecules with therapeutic potential, including lymphocyte activation gene-3 and glucocorticoid-induced tumor necrosis factor receptor-related gene, also have inhibitors in early stages of clinical development. Clinical responses and safety data reported to date on immune checkpoint inhibitors suggest these agents may have the potential to markedly improve outcomes for patients with cancer.

A Phase I/II Trial of BNC105P with Everolimus in Metastatic Renal Cell Carcinoma

PURPOSE

BNC105P inhibits tubulin polymerization, and preclinical studies suggest possible synergy with everolimus. In this phase I/II study, efficacy and safety of the combination were explored in patients with metastatic renal cell carcinoma (mRCC).

EXPERIMENTAL DESIGN

A phase I study in patients with clear cell mRCC and any prior number of therapies was conducted using a classical 3 + 3 design to evaluate standard doses of everolimus with increasing doses of BNC105P. At the recommended phase II dose (RP2D), patients with clear cell mRCC and one to two prior therapies (including ≥ 1 VEGF-TKI) were randomized to BNC105P with everolimus (arm A) or everolimus alone (arm B). The primary endpoint of the study was 6-month progression-free survival (6MPFS). Secondary endpoints included response rate, PFS, overall survival, and exploratory biomarker analyses.

RESULTS

In the phase I study (N = 15), a dose of BNC105P at 16 mg/m(2) with everolimus at 10 mg daily was identified as the RP2D. In the phase II study, 139 patients were randomized, with 69 and 67 evaluable patients in arms A and B, respectively. 6MPFS was similar in the treatment arms (arm A: 33.82% vs. arm B: 30.30%, P = 0.66) and no difference in median PFS was observed (arm A: 4.7 mos vs. arm B: 4.1 mos; P = 0.49). Changes in matrix metalloproteinase-9, stem cell factor, sex hormone-binding globulin, and serum amyloid A protein were associated with clinical outcome with BNC105P.

CONCLUSIONS

Although the primary endpoint was not met in an unselected population, correlative studies suggest several biomarkers that warrant further prospective evaluation.

Antagonists of PD-1 and PD-L1 in Cancer Treatment

The PD-1 pathway, comprising the immune cell co-receptor Programmed Death 1 (PD-1) and its ligands, PD-L1 (B7-H1) and PD-L2 (B7-DC), mediates local immunosuppression in the tumor microenvironment. Drugs designed to block PD-1 or PD-L1 "release the brakes" on anti-tumor immunity and have demonstrated clinical activity in several types of advanced cancers, validating this pathway as a target for cancer therapy. Two such drugs have recently been approved to treat melanoma and lung cancers, and regulatory approvals in first- and second-line settings for additional cancer types are anticipated. The manageable safety profile of PD-1/PD-L1 blocking drugs identifies them as suitable for outpatient administration and the development of combinatorial therapies. Ongoing studies aim to identify biomarkers to guide patient selection, which would further improve the risk:benefit ratio for these drugs.

PD-1/PD-L1 inhibitors

Tumors may adopt normal physiologic checkpoints for immunomodulation leading to an imbalance between tumor growth and host surveillance. Antibodies targeting the PD-1/PD-L1 checkpoint have shown dynamic and durable tumor regressions, suggesting a rebalancing of the host-tumor interaction. Nivolumab and pembrolizumab are the anti-PD-1 antibodies that are currently the furthest in clinical development, and anti-PD-L1 agents under investigation include MPDL3280A, MEDI4736, and BMS-936559. These agents have been used to treat advanced melanoma, non-small cell lung cancer, renal cell carcinoma, bladder cancer and Hodgkin lymphoma, amongst other tumor types. In this article, we review the updated response results for early clinical trials, note recent FDA actions regarding this class of agents, and summarize results across trials looking at PD-L1 status as a predictor of response to anti-PD-1/PD-L1.

Differential Expression of PD-L1 between Primary and Metastatic Sites in Clear-Cell Renal Cell Carcinoma

PD-L1 expression in primary clear-cell renal cell carcinoma (ccRCC) increases the likelihood of response to anti-PD-1 inhibition, but fails to identify all responders. We hypothesized that PD-L1 levels assessed in randomly selected areas of the primary tumors may not accurately reflect expression levels in metastatic lesions, which are the target of systemic therapy. Therefore, we compared PD-L1 expression in a series of primary ccRCC and their metastases. Tissue blocks from 53 primary ccRCCs and 76 corresponding metastases were retrieved. Areas with predominant and highest nuclear grade were selected. Slides were immunostained with a validated anti-PD-L1 antibody (405.9A11). Membranous expression in tumor cells was quantified using H-score. Expression in tumor-infiltrating mononuclear cells (TIMC) was quantified using a combined score. Discordant tumor cell PD-L1 staining between primary tumors and metastases was observed in 11 of 53 cases (20.8%). Overall, tumor cell PD-L1 levels were not different in primary tumors and metastases (P = 0.51). Tumor cell PD-L1 positivity was associated with higher T stage (P = 0.03) and higher Fuhrman nuclear grade (P < 0.01). Within individual lesions, PD-L1 positivity was heterogeneous and almost exclusively detected in high nuclear grade areas (P < 0.001). No difference was found in PD-L1 levels in TIMCs between primary tumors and metastases (P = 0.82). The heterogeneity of PD-L1 expression in ccRCC suggests that its assessment as a predictive biomarker for PD-1 blockade may require analysis of metastatic lesions. Notably, because PD-L1 expression was mostly detected in high nuclear grade areas, to avoid false-negative results, these areas should be specifically selected for assessment.

PD-1 blockade therapy in renal cell carcinoma: current studies and future promises

RCC is considered an immunogenic tumor with a prominent dysfunctional immune cell infiltrate, unable to control tumor growth. Evasion of immune surveillance, a process defined immune-editing, leads to malignant progression. The striking improvement of knowledge in immunology has led to the identification of immune checkpoints (such as CTLA-4 and PD-1), whose blockage enhances the antitumor immunity. The interaction between PD-1, an inducible inhibitory receptor expressed on lymphocytes and DCs, and PD-L1 ligand, expressed by tumor cells, results in a down-regulation of the T-cell response. Therefore, the PD-1/PD-L1 axis inhibition by targeted-antibodies, increasing the T-cell proliferation and cytotoxicity, represents a promising mechanism to stimulate the anti-tumor activity of the immune system, improving the outcomes of cancer patients. Several PD-1 and PD-L1 inhibitors have been evaluated in different tumor types, showing promising results. The interesting correlation between lymphocytes PD-1 expression and RCC advanced stage, grade and prognosis, as well as the selective PD-L1 expression by RCC tumor cells and its potential association with worse clinical outcomes, have led to the development of new anti PD-1/PD-L1 agents, alone or in combination with anti-angiogenic drugs or other immunotherapeutic approaches, for the treatment of RCC. In this review we discuss the role of PD-1/PD-L1 in RCC, focusing on the biological rationale, current clinical studies and promising therapeutic perspectives to target the PD-1 pathway.

In-situ tumor vaccination: Bringing the fight to the tumor

After decades of development in the shadow of traditional cancer treatment, immunotherapy has come into the spotlight. Treatment of metastatic tumors with monoclonal antibodies to T cell checkpoints like programed cell death 1 (PD-1) or its ligand, (PD-L1), have resulted in significant clinical responses across multiple tumor types. However, these therapies fail in the majority of patients with solid tumors, in particular those who lack PD1(+)CD8(+) tumor-infiltrating lymphocytes within their tumors. Intratumoral "in situ vaccination" approaches seek to enhance immunogenicity, generate tumor infiltrating lymophcytes (TIL) and drive a systemic anti-tumor immune response, directed against "unvaccinated," disseminated tumors. Given the emerging picture of intratumoral immunotherapy as safe and capable of delivering systemic efficacy, it is anticipated that these approaches will become integrated into future multi-modality therapy.

Correlation of PD-L1 tumor expression and treatment outcomes in patients with renal cell carcinoma receiving sunitinib or pazopanib: results from COMPARZ, a randomized controlled trial

PURPOSE

The interaction of programmed death-1 ligand (PD-L1) with its receptor (PD-1) on T cells inactivates antitumor immune responses. PD-L1 expression has been associated with poor outcomes in renal cell carcinoma (RCC) but has not been investigated in advanced RCC patients receiving VEGF-targeted therapy.

EXPERIMENTAL DESIGN

Formalin-fixed paraffin-embedded specimens were collected at baseline from patients in the COMPARZ trial. Tumor cell PD-L1 expression by IHC was evaluated using H-score (HS). Dual PD-L1/CD68 staining was used to differentiate PD-L1 tumor expression from tumor-associated macrophages. Intratumor CD8-positive T cells were quantified morphometrically. Associations between biomarkers and survival were investigated using the log-rank test.

RESULTS

HS data were available from 453 of 1,110 patients. Sixty-four percent of patients had negative PD-L1 expression (HS = 0). Patients with HS > 55 (n = 59, 13%) had significantly shorter overall survival (OS) than those with HS ≤ 55 in both pazopanib and sunitinib arms (median 15.1 vs. 35.6 and 15.3 vs. 27.8 months, respectively, P = 0.03). In both arms, median OS was shortest in patients with HS > 55 and intratumor CD8-positive T-cell counts > 300 (9.6 and 11.9 months with pazopanib and sunitinib, respectively). Median OS in patients with HS ≤ 55 and CD8-positive T-cell counts ≤ 300 was 36.8 and 28.0 months with pazopanib and sunitinib, respectively. Progression-free survival results were similar to OS results.

CONCLUSIONS

Increased tumor cell PD-L1, or PD-L1 plus tumor CD8-positive T-cell counts, were associated with shorter survival in patients with metastatic RCC receiving VEGF-targeted agents. These findings may have implications for future design of randomized clinical trials in advanced RCC.

PD-1 blockade in renal cell carcinoma: to equilibrium and beyond

The past several years have witnessed a resurgence of interest in cancer immunotherapy. The development of blocking antibodies against the inhibitory programmed death-1 (PD-1) pathway represents a clinical breakthrough in the treatment of solid tumors such as melanoma, and these agents show great promise in renal cell carcinoma (RCC). The early data have been surprising in that they demonstrate that blockade of a single immune checkpoint can elicit objective responses in patients with RCC, despite the recognized complexity of the immunosuppressive tumor microenvironment. Reinvigorating the patient's own immune cells to reactivate and to target the tumor has the potential advantages of more selective killing and thus decreased toxicity. In addition, checkpoint blockade immunotherapy has the advantage of inducing a memory response that is unattainable with our current cytotoxic and targeted therapies. This Crossroads overview will highlight the emerging investigation of PD-1 blockade in RCC and how this T cell-targeted strategy may thwart the tumor's escape mechanisms and shift the immune system/tumor balance back to a state of equilibrium and even to tumor elimination.

Therapeutic uses of anti-PD-1 and anti-PD-L1 antibodies

Despite extensive investigation over the past three decades, cancer immunotherapy has produced limited success, with few agents achieving approval by the Food and Drug Administration and even the most effective helping only a minority of patients, primarily with melanoma or renal cancer. In recent years, immune checkpoints that maintain physiologic self-tolerance have been implicated in the down-regulation of anti-tumor immunity. Efforts to restore latent anti-tumor immunity have focused on antibody-based interventions targeting CTL antigen 4 (CTLA-4) and programmed cell death protein 1 (PD-1) on T lymphocytes and its principal ligand (PD-L1) on tumor cells. Ipilimumab, an antibody targeting CTLA-4, appears to restore tumor immunity at the priming phase, whereas anti-PD-1/PD-L1 antibodies restore immune function in the tumor microenvironment. Although ipilimumab can produce durable long-term responses in patients with advanced melanoma, it is associated with significant immune-related toxicities. By contrast, antibodies targeting either PD-1 or PD-L1 have produced significant anti-tumor activity with considerably less toxicity. Activity was seen in patients with melanoma and renal cancer, as well as those with non-small-cell lung, bladder and head and neck cancers, tumors not previously felt to be sensitive to immunotherapy. The tolerability of PD-1-pathway blockers and their unique mechanism of action have made them ideal backbones for combination regimen development. Combination approaches involving cytotoxic chemotherapy, anti-angiogenic agents, alternative immune-checkpoint inhibitors, immunostimulatory cytokines and cancer vaccines are currently under clinical investigation. Current efforts focus on registration trials of single agents and combinations in various diseases and disease settings and identifying predictive biomarkers of response.

Cancer immunotherapy highlights from the 2014 ASCO Meeting

The promise of cancer immunotherapy was validated officially in March 2011 when the FDA approved Yervoy (ipilimumab; Bristol-Myers Squibb) for the treatment of unresectable or metastatic melanoma. The approval was based on results of a randomized, double-blind clinical trial establishing that ipilimumab (a humanized anti-CTLA-4 monoclonal antibody) treatment extended the overall survival of patients with advanced melanoma. CTLA-4 is a member of the so-called family of checkpoint regulators, which are expressed on immune cells that activate or inhibit an immune response. An increasing number of immune checkpoint regulators are now being identified and targeted for immunotherapy. At the 2014 meeting of the American Society of Clinical Oncology (ASCO), it was reported that checkpoint blockade as a monotherapy or combination therapy was used successfully to treat advanced melanoma and non-small cell lung cancer. Checkpoint blockade immunotherapy was also used successfully for the treatment of other cancers, most notably genitourinary cancers such as urothelial bladder cancer and metastatic renal cell carcinoma. This report is a compiled summary of cancer immunotherapy highlights presented at the 2014 ASCO meeting by various investigators.