New Therapies and Clinical Trials

URPP Fellow: Anna Rita Luizzi

1. CTLA-4 checkpoint inhibition plus local IL-12 delivery for glioblastoma; PD-L1 checkpoint inhibition for mesothelioma and non-small cell lung cancer

Patients with glioblastoma, the most common malignant primary brain tumor, experience a median survival in the range of 12 months despite multimodal therapy including surgery, radiotherapy and alkylating agent chemotherapy (Weller et al., 2014). This tumor has become a paradigmatic tumor for cancer-associated immunosuppression for decades. The first pivotal observations were the decrease in immune reactivity of peripheral blood cells harvested from glioblastoma patients. This prompted the search for soluble factors produced by glioblastoma cells that were supposed to be strong enough to confer systemic immunosuppression. Among these, transforming growth factor (TGF)-β assumed a central role in the concept of immunosuppression in this disease (Frei et al., 2015), but other factors like interleukin 10 or prostaglandin E2 received attention, too. Later on it became apparent that there are also cell surface expressed molecules, which may inhibit immune cell responsiveness, such as CD95 ligand, regeneration and tolerance factor (RTF) or, more recently, programmed death ligands (PD). Finally, in recent years it has been increasingly recognized that glioblastoma cells are capable of reshaping the phenotype of tumor-infiltrating host cells which compose a significant proportion of cells within the microenvironment of glioblastoma to support their growth and maintain an immunosuppressive milieu. Accordingly, and because of disappointing results with traditional cancer therapy in this disease, various approaches of immunotherapy have recently gained a lot of interest, and various phase II and phase III clinical trials of immunotherapy are on the way or have already been completed. The most advanced program, vaccination targeting the epidermal growth factor receptor vIII variant, has resulted in the completion of a phase III registration trial with results awaited in late 2015, led by the Brain Tumor Center in Zurich. Furthermore, there is now great interest in integrating antibodies controlling the immune checkpoint receptors CTLA-4 or PD-1 into the treatment of glioblastoma, and again Zurich is participating in clinical trials exploring the use of anti-PD-1 antibodies nivolumab or pembrolizumab in patients with recurrent or newly diagnosed glioblastoma.

In that regard, we have developed a novel approach to immunotherapy for glioblastoma (Vom Berg et al., 2013) that combines peripheral CTLA-4 immune checkpoint inhibition using ipilimumab with the intratumoral delivery of IL-12, a potent immune stimulatory cytokine that, however, was not tolerated by human cancer patients upon systemic delivery. Local delivery of toxic payloads including immunotoxins or antisense oligonucleotides has been explored in various clinical trials for glioblastoma, but investigators have so far failed to establish this approach in the clinic. Reasons for failure include mainly insufficient delivery, i.e., coverage of the target region, as well as the choice of inefficient or poorly tolerated therapeutic agents. Yet, the technical equipment to perform controlled, convection-enhanced local delivery of therapeutic molecules to brain tumor patients has been developed, is currently being explored in various clinical trials, and would thus be available in principle.

Thus, in the second funding period of the URPP, we plan to move this combined immunotherapy approach into the clinic. Meanwhile, ongoing research will seek to better understand the mode of action and possible strategies of augmenting the efficacy of this approach in relevant murine glioblastoma models.

The phase I clinical trial shall determine the feasibility of combining systemic ipilimumab and local interleukin-12-FC in patients with glioblastoma at first relapse, specifically the maximum tolerated dose (MTD) of IL-12-FC when added to a fixed systemically administered dose of ipilimumab. Secondary objectives include tolerability, safety, radiologic response rate, biomarkers, immunological response (FACS, cytokines, T cell reactivity), progression-free survival (PFS) at 6 months and overall survival (OS) at 12 months. The clinical protocol will be developed in cooperation with the Clinical Trial Center in Zurich and the project benefit from the funding provided by the Highly Specialized Medicine II Program 2015-2018 by the Canton of Zurich which has selected a project for funding entitled Innovative immunologische Therapieverfahren in der Neuro-Onkologie (Coordination: M. Weller).

The full clinical trial protocol shall be developed by a clinical fellow, e.g., as part of an MD/PhD thesis, where the clinical fellow would also have the opportunity to recruit and follow up patients within the clinical trial. Moreover, notably in the first two years, the fellow would participate in laboratory research aimed at elucidating the mode of action of the novel treatment approach as outlined above. As a backup to GMP produced IL-12-Fc protein, am mRNA coding for IL-12-Fc and formulated in liposomes will be evaluated.

2. Phase I/II clinical trial using IL-2 complexes in patients with metastatic melanoma

Rationale: Within D2 (project 1) we generated anti-human IL-2 mAbs suitable for clinical development. These anti-human IL-2 mAbs are able, when combined with recombinant human IL-2, to form human IL-2 complexes that show the same features as murine IL-2 complexes in mice, to exert potent anti-tumor immune responses, while toxic adverse effects are minimal in comparison to standard IL-2 immunotherapy (Rosalia et al. 2014). We are currently developing these anti-human IL-2 mAbs in collaboration with a Swiss industrial partner in order to obtain fully humanized, good manufacturing procedure (GMP)-conform, quality checked material for fully human IL-2 complexes. Moreover, we are currently generating a single-molecule version of these fully human IL-2 complexes by engineering a single-chain molecule made of recombinant human IL-2 and the fully humanized anti-human IL-2 mAb interposed by a short flexible linker, as previously established (Rosalia et al. 2014). Notably, we and others have previously shown using recombinant murine IL-2 plus S4B6 anti-IL-2 mAb that a single-molecule version of murine IL-2 complexes shows the same in vivo properties as murine IL-2 complexes. The advantage of a single-molecule version of IL-2 complexes over standard IL-2 complexes is that IL-2 cannot fully dissociate from the anti-IL-2 mAb although the receptor binding sites of IL-2 remain unmodified, which addresses certain concerns of pharmaceutical companies.

Experimental strategy: Firstly, we will aim for the production of clinical-grade, fully humanized IL-2 complexes and a single-molecule version thereof and test these in mouse melanoma models to confirm their efficacy and safety as previously reported for their murine analogs. Then, we will investigate these complexes in purified human lymphocyte subsets to confirm their selectivity for anti-tumor effector T cells. Subsequently, we will plan and conduct a phase I/II clinical trial. This will encompass enrollment of suitable patients with metastatic melanoma, followed by IL-2 complex immunotherapy and measurement of primary endpoints, including tolerability and safety, as well as assessment of secondary endpoints following IL-2 complex immunotherapy in these patients, such as immune response and efficacy. As alternative to GMP produced single chain proteins, the systemic injection of liposome-formulated GMP mRNA coding for the desired protein will be evaluated.

Expected output: This first-in-human trial of IL-2 complexes in patients with metastatic melanoma will constitute a crucial step in the decision making of whether and how to further develop IL-2 complexes for cancer immunotherapy.