Differences in Tumor Microenvironment Dictate T Helper Lineage Polarization and Response to Immune Checkpoint Therapy

Immune checkpoint therapy (ICT) shows encouraging results in a subset of patients with metastatic castration-resistant prostate cancer (mCRPC) but still elicits a sub-optimal response among those with bone metastases. Analysis of patients' bone marrow samples revealed increased T_h17 instead of T_h1 subsets after ICT. To further evaluate the different tumor microenvironments, we injected mice with prostate tumor cells either subcutaneously or intraosseously. ICT in the subcutaneous CRPC model significantly increases intra-tumoral T_h1 subsets and improves survival. However, ICT fails to elicit an anti-tumor response in the bone CRPC model despite an increase in the intra-tumoral CD4 T cells, which are polarized to T_h17 rather than T_h1 lineage. Mechanistically, tumors in the bone promote osteoclast-mediated bone resorption that releases TGF-β, which restrains T_h1 lineage development. Blocking TGF-β along with ICT increases T_h1 subsets and promotes clonal expansion of CD8 T cells and subsequent regression of bone CRPC and improves survival.

Neoantigen responses, immune correlates, and favorable outcomes after ipilimumab treatment of patients with prostate cancer

Tumors with high mutational burden (TMB) tend to be responsive to immune checkpoint blockade (ICB) because there are neoantigens available for targeting by reinvigorated T cells, whereas those with low TMB demonstrate limited clinical responses. To determine whether antigen-specific T cell responses can be elicited after treatment with ICB in cancers that have a low TMB, we conducted a clinical trial with ipilimumab in 30 patients with metastatic castration-resistant prostate cancer. We identified two distinct cohorts by survival and progression times: "favorable" (n = 9) and "unfavorable" (n = 10). Patients in the favorable cohort had high intratumoral CD8 T cell density and IFN-γ response gene signature and/or antigen-specific T cell responses. Two patients with a relatively low TMB had T cell responses against unique neoantigens. Moreover, six of nine patients in the favorable group are still alive at the time of analysis, with survival ranging from 33 to 54 months after treatment. All 10 patients in the unfavorable cohort have succumbed to their disease and had survival ranging from 0.6 to 10.3 months. Collectively, our data indicate that immunological correlates associated with effector T cell responses are observed in patients with metastatic prostate cancer who benefit from ICB.

A Phase II Study of Cabozantinib and Androgen Ablation in Patients with Hormone-Naïve Metastatic Prostate Cancer

PURPOSE

Cabozantinib, an oral inhibitor of c-MET/VEGFR2 signaling, improved progression-free survival (mPFS) but not overall survival (OS) in metastatic castrate-resistant prostate cancer. We evaluated cabozantinib plus androgen deprivation therapy (ADT) in hormone-naïve metastatic prostate cancer (HNMPCa).

PATIENTS AND METHODS

Patients received ADT plus cabozantinib starting at 60 mg daily. The primary endpoint was castrate-resistant PFS by radiographic criteria, clinical progression, or receipt of additional therapy. Secondary endpoints included OS, safety, radiographic responses, and biomarker modulation.

RESULTS

Sixty-two patients received treatment. With a median follow-up of 31.2 months, the mPFS was 16.1 months (95% CI, 14.6-22.7 months), and mOS was not reached. Reductions in PSA ≥ 90%, bone-specific alkaline phosphatase ≥ 50%, and urine N-telopeptides ≥ 50% occurred in 83%, 87%, and 86% of evaluable patients, respectively. Responses in bone scan and measurable disease were observed in 81% of and 90% of evaluable patients, respectively. Most common grade 3 adverse events were hypertension (19%), diarrhea (6%), and thromboembolic events (6%), and dose reductions occurred in 85% of patients. Analysis of baseline cytokine and angiogenic factors (CAFs) revealed that higher plasma concentrations of Lumican, CXCL5, CD25, and CD30 were associated with shorter PFS as was high tumor expression of pFGFR1.

CONCLUSIONS

Cabozantinib plus ADT has promising clinical activity in HNMPCa. CAF profiles and tissue markers suggest candidate prognostic and predictive markers of cabozantinib benefit and provide insights for rational therapy combinations.

A candidate androgen signalling signature predictive of response to abiraterone acetate in men with metastatic castration-resistant prostate cancer

BACKGROUND

The unmet need for predictive biomarkers emerged from the unpredictable pattern of response to androgen signalling inhibition in metastatic castration-resistant prostate cancer (mCRPC). Here, we report on the testing of a previously identified candidate androgen signalling signature associated with response to androgen signalling inhibition.

PATIENTS AND METHODS

We report on the outcome of the first module of a phase II trial on abiraterone acetate (AA) followed by combination with dasatinib or sunitinib. Bone marrow biopsies (BMBs) with matched bone marrow aspirate and blood samples were collected at baseline and upon progression. End-points included assessment of a prespecified molecular signature consisting of nuclear androgen receptor (AR) overexpression, cytochrome P450, family 17, subfamily A, polypeptide 1 (CYP17) expression, and AR-C-/N terminal expression ratio of ≥0.8 by immunohistochemistry (IHC) in patients with benefit versus primary resistance to AA (i.e. progression within 4 months). Tumour markers also included v-ets avian erythroblastosis virus E26 oncogene homologue (ERG), androgen receptor splice variant (ARV7) by IHC and steroids by liquid chromatography-tandem mass spectrometry.

RESULTS

Of 170 patients accrued from 03/2011 to 02/2015, 44 (26%) were primary resistant to AA. Forty-eight patients had tumour infiltrated BMB at baseline. Pretreatment androgen signalling signature was linked to benefit from AA (p < 0.001). Presence of ERG was associated with benefit (p = 0.05), whereas nuclear ARV7 presence and 20 or more bone lesions at baseline with primary resistance (p = 0.04 and p = 0.0006, respectively).

CONCLUSION

Testing of a prespecified androgen signalling signature was highly supportive of its predictive value in maximal androgen deprivation strategies in mCRPC. Further validation is under way.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01254864.

Cabazitaxel plus carboplatin for the treatment of men with metastatic castration-resistant prostate cancers: a randomised, open-label, phase 1-2 trial

BACKGROUND

Taxane-platinum combinations have shown promising activity in metastatic castration-resistant prostate cancers in single-group clinical studies but not in randomised trials. Distinct biological subsets of the disease might derive the greatest benefit from the addition of platinum. We aimed to determine whether adding carboplatin to cabazitaxel would improve the outcomes of men with metastatic castration-resistant prostate cancer.

METHODS

We did a phase 1-2, open label, randomised study at two centres in men with progressive metastatic castration-resistant prostate cancer. In phase 1, patients received intravenous cabazitaxel 20-25 mg/m² and intravenous carboplatin area under the curve (AUC) 3-4 mg/mL per min every 21 days. The maximum tolerated dose was defined as the highest dose cohort studied in which one of six or fewer patients experienced a dose-limiting toxicity. In phase 2, patients were randomly assigned (1:1) centrally by a computerised algorithm to intravenous cabazitaxel 25 mg/m² with or without intravenous carboplatin AUC 4 mg/mL per min. All patients received growth factor support and oral prednisone 10 mg daily. The primary endpoints were the maximum tolerated dose of the combination in phase 1 and investigator-assessed progression-free survival in phase 2. This trial is registered at ClinicalTrials.gov, number NCT01505868.

FINDINGS

Between Aug 17, 2012, and May 11, 2015, nine patients completed phase 1 as planned, and 160 were randomly assigned to cabazitaxel (n=79) or cabazitaxel plus carboplatin (n=81) in phase 2. During phase I, grade 3 adverse events were anaemia (n=2), fatigue (n=1), thrombocytopenia (n=1), hypomagnesaemia (n=1), diarrhoea (n=1), hypokalaemia (n=1), anorexia (n=1), and dehydration (n=1), and no grade 4 adverse events occurred. No dose-limiting toxicities were observed, therefore, a maximum tolerated dose of cabazitaxel of 25 mg/m² and carboplatin of AUC 4 mg/mL per min was selected for phase 2. At a median follow-up of 31·0 months (IQR 20·5-37·1), the combination improved the median progression-free survival from 4·5 months (95% CI 3·5-5·7) to 7·3 months (95% CI 5·5-8·2; hazard ratio 0·69, 95% CI 0·50-0·95, p=0·018). In the phase 2 study, the most common grade 3-5 adverse events were fatigue (7 [9%] of 79 in the cabazitaxel group vs 16 [20%] of 81 in the combination group), anaemia (3 [4%] vs 19 [23%]), neutropenia (3 [4%] vs 13 [16%]), and thrombocytopenia (1 [1%] vs 11 [14%]). There were no treatment-related deaths.

INTERPRETATION

Carboplatin added to cabazitaxel showed improved clinical efficacy compared with cabazitaxel alone for men with metastatic castration-resistant prostate cancer. Although adverse events were more common with the combination, the treatment was safe and generally well tolerated. Our data suggest that taxane-platinum combinations have a clinically beneficial role in advanced prostate cancer and a randomised phase 3 study is planned.

FUNDING

Sanofi Genzyme, University of Texas MD Anderson Cancer Center Prostate Cancer Moon Shot Program, and Solon Scott III Prostate Cancer Research Fund.

Characterization and Comparison of GITR Expression in Solid Tumors

PURPOSE

Determine the differential effect of a FcγR-binding, mIgG2a anti-GITR antibody in mouse tumor models, and characterize the tumor microenvironment for the frequency of GITR expression in T-cell subsets from seven different human solid tumors.Experimental Design: For mouse experiments, wild-type C57BL/6 mice were subcutaneously injected with MC38 cells or B16 cells, and BALB/c mice were injected with CT26 cells. Mice were treated with the anti-mouse GITR agonist antibody 21B6, and tumor burden and survival were monitored. GITR expression was evaluated at the single-cell level using flow cytometry (FC). A total of 213 samples were evaluated for GITR expression by IHC, 63 by FC, and 170 by both in seven human solid tumors: advanced hepatocellular carcinoma, non-small cell lung cancer (NSCLC), renal cell carcinoma, pancreatic carcinoma, head and neck carcinoma, melanoma, and ovarian carcinoma.

RESULTS

The therapeutic benefit of 21B6 was greatest in CT26 followed by MC38, and was least in the B16 tumor model. The frequency of CD8 T cells and effector CD4 T cells within the immune infiltrate correlated with response to treatment with GITR antibody. Analysis of clinical tumor samples showed that NSCLC, renal cell carcinoma, and melanoma had the highest proportions of GITR-expressing cells and highest per-cell density of GITR expression on CD4⁺ Foxp3⁺ T regulatory cells. IHC and FC data showed similar trends with a good correlation between both techniques.

CONCLUSIONS

Human tumor data suggest that NSCLC, renal cell carcinoma, and melanoma should be the tumor subtypes prioritized for anti-GITR therapy development.

Resumption of Immune Checkpoint Inhibitor Therapy After Immune-Mediated Colitis

PURPOSE

Immune checkpoint inhibitor (ICI) therapy often is suspended because of immune-mediated diarrhea and colitis (IMDC). We examined the rate of and risk factors for IMDC recurrence after ICI resumption.

METHODS

This retrospective multicenter study examined patients who resumed ICI therapy after improvement of IMDC between January 2010 and November 2018. Univariable and multivariable logistic regression analyses assessed the association of clinical covariates and IMDC recurrence.

RESULTS

Of the 167 patients in our analysis, 32 resumed an anti–cytotoxic T-cell lymphocyte-4 (CTLA-4) agent, and 135 an anti–programmed cell death 1 or ligand 1 (PD-1/L1) agent. The median age was 60 years (interquartile range [IQR], 50-69 years). The median duration from IMDC to restart of ICI treatment was 49 days (IQR, 23-136 days). IMDC recurred in 57 patients (34%) overall (44% of those receiving an anti–CTLA-4 and 32% of those receiving an anti–PD-1/L1); 47 of these patients (82%) required immunosuppressive therapy for recurrent IMDC, and all required permanent discontinuation of ICI therapy. The median duration from ICI resumption to IMDC recurrence was 53 days (IQR, 22-138 days). On multivariable logistic regression, patients who received anti–PD-1/L1 therapy at initial IMDC had a higher risk of IMDC recurrence (odds ratio [OR], 3.45; 95% CI, 1.59 to 7.69; P = .002). Risk of IMDC recurrence was higher for patients who required immunosuppression for initial IMDC (OR, 3.22; 95% CI, 1.08 to 9.62; P = .019) or had a longer duration of IMDC symptoms in the initial episode (OR, 1.01; 95% CI, 1.00 to 1.03; P = .031). Risk of IMDC recurrence was lower after resumption of anti–PD-1/L1 therapy than after resumption of anti–CTLA-4 therapy (OR, 0.30; 95% CI, 0.11 to 0.81; P = .019).

CONCLUSION

One third of patients who resumed ICI treatment after IMDC experienced recurrent IMDC. Recurrence of IMDC was less frequent after resumption of anti–PD-1/L1 than after resumption of anti–CTLA-4.

Immune-Related Thyroiditis with Immune Checkpoint Inhibitors

BACKGROUND

Although immune-related thyroiditis (irT) with immune checkpoint inhibitors (ICI) is a common consequence, its natural course and management recommendations are not well characterized in existing guidelines. This study sought to investigate the evolution of irT and describe its course and sequelae.

METHODS

This was a retrospective study of cancer patients treated with ICI between November 2014 and July 2016 at MD Anderson Cancer Center and referred for endocrinology evaluation for suspected irT. Patients included had normal baseline thyroid function tests prior to starting ICI and developed thyrotoxicosis due to irT.

RESULTS

Of 657 patients treated with ICI during the study period, 43(6.5%) met the inclusion criteria. ICI included: ipilimumab + nivolumab (40%), nivolumab (33%), pembrolizumab (21%), and other (7%). Cancer diagnoses observed were melanoma (23%), renal-cell carcinoma (21%), lung cancer (19%), bladder cancer (12%), colon cancer (9%), and other cancers (15%). Median time from ICI start to thyrotoxicosis was 5.3 weeks (range 0.6-19.6 weeks). Clinically, patients presented with painless thyroiditis, and 67% were asymptomatic during the thyrotoxicosis phase. Thyrotoxicosis lasted a median of six weeks (range 2.6-39.7 weeks). Hypothyroidism developed in 37 (84%) patients at a median of 10.4 weeks (range 3.4-48.7 weeks) after starting ICI. These patients remained on levothyroxine and ICI at a median follow-up of 57.4 weeks (range 1-156.7 weeks) from hypothyroidism onset. Four patients recovered without initiating levothyroxine and remained euthyroid at a median follow-up of 11.35 months (range 4.43-14.43 months). Subgroup analysis of ipilimumab + nivolumab versus nivolumab alone showed a median time to thyrotoxicosis of two weeks [confidence interval (CI) 3.5-8.4] versus six weeks ([CI 1.2-2.8]; p = 0.26) and time to hypothyroidism of 10 weeks [CI 8.1-11.9] versus 17 weeks ([CI 8.8-25.2]; p = 0.029) after starting ICI. Thyroid peroxidase and thyroglobulin antibodies were present in 45% and 33% at the time of irT diagnosis.

CONCLUSIONS

IrT manifests as an early onset of thyrotoxicosis, which is largely asymptomatic, followed by rapid transition to hypothyroidism requiring long-term levothyroxine substitution. The evolution of irT is more rapid with combination ICI. Frequent monitoring of thyroid function tests during ICI is warranted. Future guidelines need to recognize this entity and incorporate their management.

Modulation of EZH2 expression in T cells improves efficacy of anti-CTLA-4 therapy

Enhancer of zeste homolog 2-mediated (EZH2-mediated) epigenetic regulation of T cell differentiation and Treg function has been described previously; however, the role of EZH2 in T cell-mediated antitumor immunity, especially in the context of immune checkpoint therapy, is not understood. Here, we showed that genetic depletion of EZH2 in Tregs (FoxP3creEZH2fl/fl mice) leads to robust antitumor immunity. In addition, pharmacological inhibition of EZH2 in human T cells using CPI-1205 elicited phenotypic and functional alterations of the Tregs and enhanced cytotoxic activity of Teffs. We observed that ipilimumab (anti-CTLA-4) increased EZH2 expression in peripheral T cells from treated patients. We hypothesized that inhibition of EZH2 expression in T cells would increase the effectiveness of anti-CTLA-4 therapy, which we tested in murine models. Collectively, our data demonstrated that modulating EZH2 expression in T cells can improve antitumor responses elicited by anti-CTLA-4 therapy, which provides a strong rationale for a combination trial of CPI-1205 plus ipilimumab.

Anti-CTLA-4 Immunotherapy Does Not Deplete FOXP3+ Regulatory T Cells (Tregs) in Human Cancers

PURPOSE

CTLA-4 was the first inhibitory immune checkpoint to be identified. Two mAbs, ipilimumab (IgG1) and tremelimumab (IgG2), which block the function of CTLA-4, have demonstrated durable clinical activity in a subset of patients with advanced solid malignancies by augmenting effector T-cell-mediated immune responses. Studies in mice suggest that anti-CTLA-4 mAbs may also selectively deplete intratumoral FOXP3⁺ regulatory T cells via an Fc-dependent mechanism. However, it is unclear whether the depletion of FOXP3⁺ cells occurs in patients with cancer treated with anti-CTLA-4 therapies.

EXPERIMENTAL DESIGN

Quantitative IHC was used to evaluate the densities of intratumoral CD4⁺, CD8⁺, and FOXP3⁺ cells in stage-matched melanoma (n = 19), prostate cancer (n = 17), and bladder cancer (n = 9) samples treated with ipilimumab and in paired melanoma tumors (n = 18) treated with tremelimumab. These findings were corroborated with multiparametric mass cytometry analysis of tumor-infiltrating cells from paired fresh melanoma tumors (n = 5) treated with ipilimumab.

RESULTS

Both ipilimumab and tremelimumab increase infiltration of intratumoral CD4⁺ and CD8⁺ cells without significantly changing or depleting FOXP3⁺ cells within the tumor microenvironment.

CONCLUSIONS

Anti-CTLA-4 immunotherapy does not deplete FOXP3⁺ cells in human tumors, which suggests that their efficacy could be enhanced by modifying the Fc portions of the mAbs to enhance Fc-mediated depletion of intratumoral regulatory T cells.See related commentary by Quezada and Peggs, p. 1130.

Current and Future Applications of Novel Immunotherapies in Urological Oncology: A Critical Review of the Literature

CONTEXT

Immunotherapies promote anticancer responses with varying levels of success based on the tumor type.

OBJECTIVE

In this narrative review article, we searched the literature regarding immunotherapies in genitourinary malignancies to define the state of the field, explore future applications of immune checkpoint inhibitors, cytokines, vaccines, and cellular therapies in urological oncology and evaluate possible strategies to improve the selection of patients who might benefit from such approaches.

EVIDENCE ACQUISITION

We reviewed related literature, with a focus on recent studies about immunotherapies, predictors of response, and ongoing clinical trials.

EVIDENCE SYNTHESIS

Immunotherapies based on immune checkpoint blockade are approved as first- and second-line therapies for urothelial carcinoma (UC) and second-line therapies for renal cell carcinoma with limited success in prostate cancer. Programmed death-ligand 1 is the most commonly used predictive biomarker outside of UC; however, a substantial proportion of patients with tumors negative for programmed death-ligand 1 expression benefit from checkpoint inhibition, limiting its sensitivity. A high mutational load and molecular subtypes of UC are emerging as additional potential predictors. Genomic sequencing and gene expression analysis associate alterations of genes implicated in DNA repair pathways, such as BRCA1 and BRCA2, with immune checkpoint therapies. In prostate cancer, the vaccine, sipuleucel-T, is the only Food and Drug Administration-approved immunotherapy.

CONCLUSIONS

Immunotherapies are emerging as exciting new treatment options with a tolerable toxicity profile in urological cancers. Checkpoint inhibitors are effective only in a subset of patients, demanding personalized approaches that consider various clinical and molecular parameters to predict patient response. Clinical trials investigating the optimal timing, sequence, and combination of immunotherapies with standard of care and novel agents will guide therapy choices and improve patient outcome.

PATIENT SUMMARY

Clinical data supports the safety and efficacy of immune checkpoint inhibitors alone or in combination with other therapies in urological cancers.

VISTA is an inhibitory immune checkpoint that is increased after ipilimumab therapy in patients with prostate cancer

To date, anti-CTLA-4 (ipilimumab) or anti-PD-1 (nivolumab) monotherapy has not been demonstrated to be of substantial clinical benefit in patients with prostate cancer. To identify additional immune-inhibitory pathways in the prostate-tumor microenvironment, we evaluated untreated and ipilimumab-treated tumors from patients in a presurgical clinical trial. Levels of the PD-L1 and VISTA inhibitory molecules increased on independent subsets of macrophages in treated tumors. Our data suggest that VISTA represents another compensatory inhibitory pathway in prostate tumors after ipilimumab therapy.

Beyond Seed and Soil: Understanding and Targeting Metastatic Prostate Cancer; Report From the 2016 Coffey-Holden Prostate Cancer Academy Meeting

INTRODUCTION

The 2016 Coffey-Holden Prostate Cancer Academy (CHPCA) Meeting, "Beyond Seed and Soil: Understanding and Targeting Metastatic Prostate Cancer," was held from June 23 to June 26, 2016, in Coronado, California.

METHODS

For the 4th year in a row, the Prostate Cancer Foundation (PCF) hosted the CHPCA Meeting, a think tank-structured scientific conference, which focuses on a specific topic of critical unmet need on the biology and treatment of advanced prostate cancer. The 2016 CHPCA Meeting was attended by 71 investigators from prostate cancer and other fields, who discussed the biology, study methodologies, treatment strategies, and critical unmet needs concerning metastatic prostate cancer, with the ultimate goal of advancing strategies to treat and eliminate this disease.

RESULTS

The major topics of discussion included: the molecular landscape and molecular heterogeneity of metastatic prostate cancer, the role of the metastatic microenvironment, optimizing immunotherapy in metastatic prostate cancer, learning from exceptional responders and non-responders, targeting DNA repair deficiency in advanced prostate cancer, developing and applying novel biomarkers and imaging techniques, and potential roles for the microbiome in prostate cancer.

DISCUSSION

This article reviews the topics presented and discussions held at the CHPCA Meeting, with a focus on the unknowns and next steps needed to advance our understanding of the biology and most effective treatment strategies for metastatic prostate cancer. Prostate 77:123-144, 2017. © 2016 Wiley Periodicals, Inc.

Interdependent IL-7 and IFN-γ signalling in T-cell controls tumour eradication by combined α-CTLA-4+α-PD-1 therapy

Combination therapy with α-CTLA-4 and α-PD-1 has shown significant clinical responses in different types of cancer. However, the underlying mechanisms remain elusive. Here, combining detailed analysis of human tumour samples with preclinical tumour models, we report that concomitant blockade of CTLA-4 and PD-1 improves anti-tumour immune responses and synergistically eradicates tumour. Mechanistically, combination therapy relies on the interdependence between IL-7 and IFN-γ signalling in T cells, as lack of either pathway abrogates the immune-boosting and therapeutic effects of combination therapy. Combination treatment increases IL-7Rα expression on tumour-infiltrating T cells in an IFN-γ/IFN-γR signalling-dependent manner, which may serve as a potential biomarker for clinical trials with immune checkpoint blockade. Our data suggest that combining immune checkpoint blockade with IL-7 signalling could be an effective modality to improve immunotherapeutic efficacy. Taken together, we conclude that combination therapy potently reverses immunosuppression and eradicates tumours via an intricate interplay between IFN-γ/IFN-γR and IL-7/IL-7R pathways.

Abstract 1402: Exploratory biomarkers that predict for clinical outcomes in a Phase II trial with ipilimumab plus finite androgen deprivation therapy for metastatic non-castrate prostate cancer

Background: Androgen deprivation therapy (ADT) is a standard treatment that, although not curative, often induces dramatic responses in patients with advanced prostate cancer by inducing tumor cell death, which may provoke antigen release to initiate T cell responses. Ipilimumab blocks the inhibitory immune checkpoint, CTLA-4, which enhances T cell responses and induces both clinical benefit and unique toxicities in a subset of patients with advanced cancer. We designed a clinical study combining ipilimumab with finite ADT in men with metastatic prostate cancer to estimate therapeutic efficacy, determine safety, and identify predictive biomarkers for clinical outcomes.

Methods: We screened 30 patients and enrolled 27 patients between July, 2011 and June, 2013 for an open-labelled, single-center, Phase II study of ipilimumab plus finite ADT as first-line therapy for metastatic non-castrate prostate cancer. Eligible patients had histological confirmation of prostate carcinoma and radiographic documentation of metastatic disease. ADT was given for a finite duration of eight months with concurrent ipilimumab (10 mg/kg) for up to four doses, each given four-weeks apart. The primary endpoint was the proportion of patients with undetectable PSA (≤0.2 ng/mL) at seven months post-treatment initiation with ADT. In addition, we performed comprehensive immune monitoring of the peripheral blood using multi-parametric flow cytometry and next-generation sequencing of T cell receptors.

Findings: All 27 of the enrolled patients were evaluable for safety and toxicity, and 24 of these patients were evaluable for therapeutic effectiveness. Ten of the 24 (42%) patients achieved the primary endpoint of undetectable PSA levels at seven months post-treatment initiation. The median time to PSA progression was 10.0 (IQR 5.9-13.3) months from treatment initiation, and one (4%) of the 24 patients continues to have a PSA response that is ongoing for 40.7 months. The trial was closed as prespecified due to grade 3 toxicities that occurred in 12 (44%) of 27 patients. The most common grade 3 adverse events were transaminitis, colitis/diarrhea, and hypophysitis. Immunological biomarkers were identified that potentially predict for clinical benefit and grade 3 toxicities in this small study. No grade 4 or 5 toxicities were observed.

Interpretation: Although the combination of 10 mg/kg ipilimumab plus finite ADT led to toxicities that met a prespecified endpoint for closure of the trial, our current knowledge and experience about combination therapies and dose of ipilimumab leads us to postulate that additional clinical trials evaluating ipilimumab at 3 mg/kg plus ADT is warranted. In addition, we identified candidate immunological biomarkers that need to be further tested as predictive markers of clinical benefit and grade 3 toxicities.

Citation Format: Sumit K. Subudhi, Ana Aparicio, Jianjun Gao, Amado Zurita-Saavedra, John C. Araujo, Christopher J. Logothetis, Korivi R. Brinda, Jim P. Allison, Luis Vence, Ryan O. Emerson, Erik Yusko, Marissa Vignali, Harlan S. Robins, Jingjing Sun, Padmanee Sharma. Exploratory biomarkers that predict for clinical outcomes in a Phase II trial with ipilimumab plus finite androgen deprivation therapy for metastatic non-castrate prostate cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1402.

Acute rhabdomyolysis with severe polymyositis following ipilimumab-nivolumab treatment in a cancer patient with elevated anti-striated muscle antibody

Background

Immune checkpoint inhibitors have revolutionized cancer therapy since these drugs target inhibitory pathways on T cells, which result in durable anti-tumor immune responses and significant overall survival for a subset of cancer patients. These drugs can also lead to toxicities, which require additional research to identify mechanisms of toxicities and biomarkers that can help to identify patients who will develop immune-related adverse events.

Case presentation

We describe the first case, to our knowledge, of a patient with metastatic urothelial carcinoma who developed acute rhabdomyolysis with severe polymyositis after treatment with combination immunotherapy consisting of ipilimumab plus nivolumab (Trial registration: NCT01928394. Registered: 8/21/2013). We found that this patient had an elevated pre-existing anti-striated muscle antibody titer, which was likely exacerbated with the immunotherapy treatment thereby resulting in the presentation of acute rhabdomyolysis and severe polymyositis.

Conclusions

This case suggests that immune-related adverse events may be linked to subclinical autoimmune conditions which highlights the need for additional studies to identify patients who are at risk for toxicities.

Localized oncolytic virotherapy overcomes systemic tumor resistance to immune checkpoint blockade immunotherapy

Preexisting lymphocytic infiltration of tumors is associated with superior prognostic outcomes in a variety of cancers. Recent studies also suggest that lymphocytic responses may identify patients more likely to benefit from therapies targeting immune checkpoints, suggesting that therapeutic efficacy of immune checkpoint blockade can be enhanced through strategies that induce tumor inflammation. To achieve this effect, we explored the immunotherapeutic potential of oncolytic Newcastle disease virus (NDV). We find that localized intratumoral therapy of B16 melanoma with NDV induces inflammatory responses, leading to lymphocytic infiltrates and antitumor effect in distant (nonvirally injected) tumors without distant virus spread. The inflammatory effect coincided with distant tumor infiltration with tumor-specific CD4(+) and CD8(+) T cells, which was dependent on the identity of the virus-injected tumor. Combination therapy with localized NDV and systemic CTLA-4 blockade led to rejection of preestablished distant tumors and protection from tumor rechallenge in poorly immunogenic tumor models, irrespective of tumor cell line sensitivity to NDV-mediated lysis. Therapeutic effect was associated with marked distant tumor infiltration with activated CD8(+) and CD4(+) effector but not regulatory T cells, and was dependent on CD8(+) cells, natural killer cells, and type I interferon. Our findings demonstrate that localized therapy with oncolytic NDV induces inflammatory immune infiltrates in distant tumors, making them susceptible to systemic therapy with immunomodulatory antibodies, which provides a strong rationale for investigation of such combination therapies in the clinic.

Glucocorticoid receptor confers resistance to antiandrogens by bypassing androgen receptor blockade

The treatment of advanced prostate cancer has been transformed by novel antiandrogen therapies such as enzalutamide. Here, we identify induction of glucocorticoid receptor (GR) expression as a common feature of drug-resistant tumors in a credentialed preclinical model, a finding also confirmed in patient samples. GR substituted for the androgen receptor (AR) to activate a similar but distinguishable set of target genes and was necessary for maintenance of the resistant phenotype. The GR agonist dexamethasone was sufficient to confer enzalutamide resistance, whereas a GR antagonist restored sensitivity. Acute AR inhibition resulted in GR upregulation in a subset of prostate cancer cells due to relief of AR-mediated feedback repression of GR expression. These findings establish a mechanism of escape from AR blockade through expansion of cells primed to drive AR target genes via an alternative nuclear receptor upon drug exposure.

Prostate cancer progression correlates with increased humoral immune response to a human endogenous retrovirus GAG protein

PURPOSE

Human endogenous retroviruses (HERV) encode 8% of the human genome. While HERVs may play a role in autoimmune and neoplastic disease, no mechanistic association has yet been established. We studied the expression and immunogenicity of a HERV-K GAG protein encoded on chromosome 22q11.23 in relation to the clinical course of prostate cancer.

EXPERIMENTAL DESIGN

In vitro expression of GAG-HERV-K was analyzed in panels of normal and malignant tissues, microarrays, and cell lines, and effects of demethylation and androgen stimulation were evaluated. Patient sera were analyzed for seroreactivity to GAG-HERV-K and other self-antigens by ELISA and seromics (protein array profiling).

RESULTS

GAG-HERV-K expression was most frequent in prostate tissues and regulated both by demethylation of the promoter region and by androgen stimulation. Serum screening revealed that antibodies to GAG-HERV-K are found in a subset of patients with prostate cancer (33 of 483, 6.8%) but rarely in male healthy donors (1 of 55, 1.8%). Autoantibodies to GAG-HERV-K occurred more frequently in patients with advanced prostate cancer (29 of 191 in stage III-IV, 21.0%) than in early prostate cancer (4 of 292 in stages I-II, 1.4%). Presence of GAG-HERV-K serum antibody was correlated with worse survival of patients with prostate cancer, with a trend for faster biochemical recurrence in patients with antibodies to GAG-HERV-K.

CONCLUSIONS

Preferential expression of GAG-HERV-K ch22q11.23 in prostate cancer tissue and increased frequency of autoantibodies observed in patients with advanced prostate cancer make this protein one of the first bona fide retroviral cancer antigens in humans, with potential as a biomarker for progression and biochemical recurrence rate of prostate cancer. Clin Cancer Res; 19(22); 6112-25. ©2013 AACR.

A whole-blood RNA transcript-based prognostic model in men with castration-resistant prostate cancer: a prospective study

BACKGROUND

Survival for patients with castration-resistant prostate cancer is highly variable. We assessed the effectiveness of a whole-blood RNA transcript-based model as a prognostic biomarker in castration-resistant prostate cancer.

METHODS

Peripheral blood was prospectively collected from 62 men with castration-resistant prostate cancer on various treatment regimens who were enrolled in a training set at the Dana-Farber Cancer Institute (Boston, MA, USA) from August, 2006, to June, 2008, and from 140 patients with castration-resistant prostate cancer in a validation set from Memorial Sloan-Kettering Cancer Center (New York, NY, USA) from August, 2006, to February, 2009. A panel of 168 inflammation-related and prostate cancer-related genes was assessed with optimised quantitative PCR to assess biomarkers predictive of survival.

FINDINGS

A six-gene model (consisting of ABL2, SEMA4D, ITGAL, and C1QA, TIMP1, CDKN1A) separated patients with castration-resistant prostate cancer into two risk groups: a low-risk group with a median survival of more than 34·9 months (median survival was not reached) and a high-risk group with a median survival of 7·8 months (95% CI 1·8-13·9; p<0·0001). The prognostic utility of the six-gene model was validated in an independent cohort. This model was associated with a significantly higher area under the curve compared with a clinicopathological model (0·90 [95% CI 0·78-0·96] vs 0·65 [0·52-0·78]; p=0·0067).

INTERPRETATION

Transcriptional profiling of whole blood yields crucial prognostic information about men with castration-resistant prostate cancer. The six-gene model suggests possible dysregulation of the immune system, a finding that warrants further study.

FUNDING

Source MDX.