Ipilimumab in the treatment of prostate cancer

Combination immunotherapy induces distinct T-cell repertoire responses when administered to patients with different malignancies

Background

CTLA-4 blockade with ipilimumab is Food and Drug Administration-approved for melanoma as a monotherapy and has been shown to modulate the circulating T-cell repertoire. We have previously reported clinical trials combining CTLA-4 blockade with granulocyte-macrophage colony-stimulating factor (GM-CSF) in metastatic melanoma patients and in metastatic castration resistant prostate cancer (mCRPC) patients. Here, we investigate the effect that cancer type has on circulating T cells in metastatic melanoma and mCRPC patients, treated with ipilimumab and GM-CSF.

Methods

We used next-generation sequencing of T-cell receptors (TCR) to compare the circulating T cells of melanoma and mCRPC patients receiving the same treatment with ipilimumab and GM-CSF by Wilcoxon rank sum test. Flow cytometry was utilized to investigate specific T-cell populations. TCR sequencing results were correlated with each T-cell subpopulation by Spearman’s rank correlation coefficient. Of note, 14 metastatic melanoma patients had samples available for TCR sequencing and 21 had samples available for flow cytometry analysis; 37 mCRPC patients had samples available for sequencing of whom 22 have TCR data available at both timepoints; 20 of these patients had samples available for flow cytometry analysis and 16 had data available at both timepoints.

Results

While melanoma and mCRPC patients had similar pretreatment circulating T-cell counts, treatment induces greater expansion of circulating T cells in melanoma patients. Metastatic melanoma patients have a higher proportion of clones that increased more than fourfold after the treatment compared with mCRPC patients (18.9% vs 11.0%, p=0.017). Additionally, melanoma patients compared with mCRPC patients had a higher ratio of convergent frequency (1.22 vs 0.60, p=0.012). Decreases in clonality induced by treatment are associated with baseline CD8+ T-cell counts in both patient groups, but are more pronounced in the melanoma patients (r=−0.81, p<0.001 vs r=−0.59, p=0.02).

Trial registration numbers

NCT00064129; NCT01363206.

Emerging dynamics pathways of response and resistance to PD-1 and CTLA-4 blockade: tackling uncertainty by confronting complexity

Immune checkpoint inhibitors provide considerable therapeutic benefit in a range of solid cancers as well as in a subgroup of hematological malignancies. Response rates are however suboptimal, and despite considerable efforts, predicting response to immune checkpoint inhibitors ahead of their administration in a given patient remains elusive. The study of the dynamics of the immune system and of the tumor under immune checkpoint blockade brought insight into the mechanisms of action of these therapeutic agents. Equally relevant are the mechanisms of adaptive resistance to immune checkpoint inhibitors that have been uncovered through this approach. In this review, we discuss the dynamics of the immune system and of the tumor under immune checkpoint blockade emanating from recent studies on animal models and humans. We will focus on mechanisms of action and of resistance conveying information predictive of therapeutic response.

Modeling the effect of immunotherapies on human castration-resistant prostate cancer

In this paper we analyze the potential effect of immunotherapies on castration-resistant form of human Prostate Cancer (PCa). In particular, we examine the potential effect of the dendritic vaccine sipuleucel-T, the only currently available immunotherapy option for advanced PCa, and of ipilimumab, a drug targeting the Cytotoxic T-Lymphocyte Antigen 4 (CTLA4), exposed on the CTLs membrane, currently under Phase II clinical trial. The model, building on the one by Rutter and Kuang, includes different types of immune cells and interactions and is parameterized on available data. Our results show that the vaccine has only a very limited effect on PCa, while repeated treatments with ipilimumab appear potentially capable of controlling and even eradicating an androgen-independent prostate cancer. From a mathematical analysis of a simplified model, it seems likely that, under continuous administration of ipilimumab, the system lies in a bistable situation where both the no-tumor equilibrium and the high-tumor equilibrium are attractive. The schedule of periodic treatments could then determine the outcome, and mathematical models could help determine an optimal schedule.

CAR-T cell therapy: a potential new strategy against prostate cancer

Prostate cancer (PCa) is one of the main causes of cancer-related death in men. In the present immunotherapy era, several immunotherapeutic agents have been evaluated in PCa with poor results, possibly due to its low mutational burden. The recent development of chimeric antigen receptor (CAR)-T cell therapy redirected against cancer-specific antigens would seem to provide the means for bypassing immune tolerance mechanisms. CAR-T cell therapy has proven effective in eradicating hematologic malignancies and the challenge now is to obtain the same degree of in solid tumors, including PCa. In this study we review the principles that have guided the engineering of CAR-T cells and the specific prostatic antigens identified as possible targets for immunological and non-immunological therapies. We also provide a state-of-the-art overview of CAR-T cell therapy in PCa, defining the key obstacles to its development and underlining the mechanisms used to overcome these barriers. At present, although there are still many unanswered questions regarding CAR-T cell therapy, there is no doubt that it has the potential to become an important treatment option for urological malignancies.

Acute liver injury in the context of immune checkpoint inhibitor-related colitis treated with infliximab

Background

Immune checkpoint inhibitors (ICPIs), used to treat different advanced malignancies, are associated with a wide range of immune-related adverse reactions (irAEs) that deserve close monitoring of patients. Gastrointestinal reactions and hepatotoxicity may occur, which warrant careful evaluation to confirm the etiology and attribution to ICPIs as these events could affect future management.

Case presentation

We describe a case of a patient with prostate adenocarcinoma, treated with dual ICPIs comprised of ipilimumab and nivolumab, who developed elevated liver enzymes in the context of infliximab therapy prescribed to treat gastrointestinal irAE from his ICPIs. The patient’s grade 3 colitis became steroid-refractory, requiring a one-time infusion of infliximab, a biologic agent used commonly in inflammatory bowel disease, as a rescue therapy, to which he responded. The patient subsequently developed liver injury. This presented a diagnostic dilemma involving differential diagnoses of hepatotoxicity due to ICPI or infliximab exposure. A careful review of the clinical history, evaluation of the chronology of events, and exclusion of other causes of acute hepatitis were employed to make the final diagnosis of this event as infliximab-associated hepatotoxicity.

Conclusion

ICPIs such as CTLA-4 and PD-1 inhibitors have the potential to cause both gastrointestinal reactions and hepatotoxicity. An additional confounding factor in our patient’s case was the exposure to infliximab used to manage an established irAE that developed after the last exposure to ICPIs. The clinical history and data supported infliximab-associated hepatotoxicity, rather than an irAE. With the increasing application of ICPIs for different cancers, in conjunction with potential risks for irAE, the liver profile should be closely monitored during treatment with ICPI as well as with anti-TNF-α agents in this patient population.

Highlights on immune checkpoint inhibitors in non-small cell lung cancer

The treatment of advanced or refractory non-small cell lung cancer has been historically difficult owing to the lack of studies on effective systemic cure. The progress in lung cancer treatment has plateaued, necessitating new options for additional benefits. Immune checkpoint proteins are co-inhibitory factors that can diminish the antigen-specific immune responses by attenuating the regulatory role of cytotoxic T-lymphocyte-associated protein 4, programmed cell death-1, lymphocyte-activation gene 3, and T-cell immunoglobulin mucin-3. The therapeutic strategies targeting immune checkpoints mainly focus on the monoclonal antibody of these regulatory factors, which may facilitate clinical decision making. An enhanced understanding of the drug-resistance mechanisms and the therapeutic efficacy regulation will provide opportunities to improve the clinical outcomes of non-small cell lung cancer patients. Preclinical and clinical trials on these key immune-regulatory agents, which has heralded a new era in immuno-oncology in non-small cell lung cancer treatment, are currently in development.

Development of PROSTVAC immunotherapy in prostate cancer

PROSTVAC immunotherapy is a heterologous prime-boost regimen of two different recombinant pox-virus vectors; vaccinia as the primary immunotherapy, followed by boosters employing fowlpox, to provoke immune responses against prostate-specific antigen. Both vectors contain transgenes for prostate-specific antigen and a triad of T-cell costimulatory molecules (TRICOM). In a placebo-controlled Phase II trial of men with minimally symptomatic, chemotherapy-naive metastatic castration-resistant prostate cancer, PROSTVAC was well tolerated and associated with a 44% reduction in death. With a novel mechanism of action, and excellent tolerability, PROSTVAC has the potential to dramatically alter the treatment landscape of prostate cancer, not only as a monotherapy, but also in combination with other novel agents, such as immune check point inhibitors and novel androgen receptor blockers. A Phase III trial recently completed accrual.

Anti-PD-1/PD-L1 therapy of human cancer: past, present, and future

Major progress has been made toward our understanding of the programmed death-1/programmed death ligand-1 (PD-1/PD-L1) pathway (referred to as the PD pathway). mAbs are already being used to block the PD pathway to treat human cancers (anti-PD therapy), especially advanced solid tumors. This therapy is based on principles that were discovered through basic research more than a decade ago, but the great potential of this pathway to treat a broad spectrum of advanced human cancers is just now becoming apparent. In this Review, we will briefly review the history and development of anti-PD therapy, from the original benchwork to the most up-to-date clinical results. We will then focus the discussion on three basic principles that define this unique therapeutic approach and highlight how anti-PD therapy is distinct from other immunotherapeutic approaches, namely tumor site immune modulation, targeting tumor-induced immune defects, and repairing ongoing (rather than generating de novo) tumor immunity. We believe that these fundamental principles set the standard for future immunotherapies and will guide our efforts to develop more efficacious and less toxic immune therapeutics to treat human cancers.

Prostate Cancer Immunotherapy: Exploiting the HLA Class II Pathway in Vaccine Design

Prostate cancer is the second most diagnosed cancer in men and current treatment of advanced prostate cancer is ineffective. Immunotherapy has emerged as a promising treatment option for metastatic prostate cancer but its clinical application is still in the early stages of development. In order to treat metastatic prostate tumors, new directions must be taken to improve current immunotherapeutic strategies. These include the identification of effective tumor antigens (Ags), the induction of the HLA class II pathway for Ag processing and CD4⁺ T cell activation, and the ability of tumor cells to act like Ag presenting cells. In this review, we suggest a model for tumor Ag selection, epitope modification and self-processing for presentation by class II proteins as a means of restoring immune activation and tumor clearance. We also outline the importance of a Gamma-IFN-inducible Lysosomal Thiol reductase (GILT) in Ag and modified peptide processing by tumor cells, generation of functional epitopes for T cell recognition, and inclusion of immune checkpoint blockers in cancer immunotherapy. Taken together, this review provides a framework for the future development of novel cancer vaccines and the improvement of existing immunotherapeutics in prostate cancer.