Immunological alterations, therapies with immune check-point inhibitors and beyond in patients with metastatic melanoma

Abstract

In the last decade the treatment of metastatic melanoma (MM) has been revolutionized and changed the life of many patients, offering prolonged survival and improved symptom control. These treatment strategies have also changed the way we treat malignancies in general and the treatment of melanoma has been the role model for new treatment strategies. Even though there has been a revolution that we have been part of, this revolution comes with responsibilities as many patients do not benefit from the new treatments and many patients experience toxicity. One key responsibility is to broaden our knowledge about tumor immunology and immunotherapy and to identify predictive biomarkers that allow for preselection of patients in order to identify patients who benefit from specific therapies and spare other patients from treatments, with side effects, that they will not benefit from. In addition, we have a societal and an ethical responsibility, as the treatments are costly and some of the side effects result in prolonged hospitalizations and lowered quality of life for the patients affected. We also have a responsibility not to be totally blinded by the success of the newly approved therapies, but to be open-minded and keep other well documented therapies in mind when recommending treatment strategies. As many new treatments target the immune system, the chance to identify predictive biomarkers most likely lies within studies of the immune system before, during and after treatment, to see if changes in different immune cell compartments can be related to response and toxicity.

The overall aim of this thesis is to find biomarkers that correlate with response and toxicity to therapy with immune check-point inhibitors (ICI) and to study mechanisms in the immune system, in addition to those related to T-cells, during treatment with anti-CTLA 4 and anti-PD1 antibodies. In addition, we conducted a phase I trial with adoptive T cell therapy (ACT) with or without dendritic cell (DC) vaccination, with the intention to explore an additional safe and effective treatment strategy to patients progressing on or not responding to immune checkpoint inhibitors (ICI). In paper I and II we performed comprehensive immune monitoring of patients treated with ICI; in paper I with anti-CTLA-4 antibodies and in paper II with anti-PD-1 antibodies. In paper I we observed that patients benefitting from treatment with anti-CTLA-4, and experiencing prolonged overall survival, had decreasing monocytic myeloid-derived suppressor cells (MDSCs) during treatment. It was also observed that CD8+ effector memory T cell frequencies at the end of treatment were higher in patients with clinical benefit and correlated with longer survival. In addition to this, it was observed that in patients experiencing toxicity from treatment there was a correlation between the amount of eosinophil granulocytes and the onset of toxicity. In paper II it was observed that two distinct cell types could be correlated with overall survival, neutrophil granulocytes and MDSCs. In addition, it was observed that patients experiencing long progression free survival (PFS) had low frequency of CD69+ natural killer (NK) cells and low frequency of monocytic MDSCs at baseline. In paper III we could state that it was feasible and safe, with limited toxicity, to conduct a clinical trial with ACT with or without DC vaccination. In addition, we observed that four out of five patients treated with ACT and DC vaccination responded to the treatment.

It is of great importance to find predictive biomarkers that could offer pre-selection of patients and the data shown in paper I-II suggest that some of the explored markers could be implemented in a clinical setting, but need to be further validated in prospective clinical studies. In paper III it was shown that ACT with DC vaccination, as a novel treatment is safe, brings benefit to patients and could be offered to a limited number of appropriately selected patients.