This is a phase I patient-individualized multi-peptide vaccination study in combination with the novel TLR1/2 ligand XS15 in CLL patients under ibrutinib treatment and based on the following rationale:~With the development and clinical success of targeted therapies, the treatment landscape for CLL, which is the most common leukemia in adults, has faced profound changes in the recent years. The disease control achieved by ibrutinib, an inhibitor of the Brutons tyrosine kinase (BTK), has led to its approval as first line therapy. However, in most cases only partial remissions are achieved, and so far perpetual ibrutinib treatment bearing the risk of side effects and development of drug resistance is required. Therefore, current efforts are focusing on the further reduction/elimination of residual CLL cells to allow for reduced treatment time as well as the achievement of long-lasting remissions. A rational and promising approach to achieve this goal is peptide-based immunotherapy, which represents a low side-effect treatment relying on specific immune recognition of tumor-associated HLA presented peptides. Several peptide vaccination studies have reported promising result in terms of in vivo immunogenicity, but so far lacked broad clinical responses. This likely is due to several so far unmet prerequisites for clinical effective peptide vaccination, including the selection of antigens, adjuvants, combinatorial drugs and vaccination time points.~The investigators here adresse these issues as follows:~The reportedly distorted relationship of gene expression and HLA-restricted presentation of the corresponding gene product requires direct methods for peptide target identification for vaccination approaches. This is realized by mass spectrometry-based analysis of the entirety of naturally presented HLA ligands, termed the HLA ligandome of cancer cells. In the recent years, the investigators worked intensively on the characterization of such TAA in HM based on the direct isolation of naturally presented HLA class I and II ligands from leukemia cells and the subsequent identification by mass spectrometry. To allow for the timely and cost-effective production of personalized vaccine cocktail for patients in clinical studies based on HLA ligandome analyses, the investigators have established a so called warehouse concept providing premanufactured highly frequent TAA for the formulation of personalized vaccine cocktails. The feasibility of such a warehouse concept, which is utilized in the iVAC-XS15-CLL01 study, was already proven by the investigator's first clinical peptide vaccination study (iVAC-CLL01, NCT02802943). The warehouse has been built based on comprehensive HLA ligandome analysis of CLL cells and composites of a modified cocktail used for the iVAC-CLL01 study as described above. On basis of the individual HLA allotype and a HLA ligandome analysis of CLL cells of the respective patient, 10 tumor-associated peptides are selected from the peptide warehouse. The so-called CLL peptide cocktails (drug substance) are designed to trigger the cellular part of the patients' immune system by activation of CLL-specific T cells. Once activated, these cells can destroy malignant cells presenting the respective antigens. Applying several CLL-associated antigens simultaneously increases the likelihood that a multi-clonal, broad and at the same time highly specific T-cell response is mounted, therebypreventing potential tumor escape mechanisms.~Besides the selection of optimal antigen targets, a further important prerequisite is the use of suitable adjuvant drugs capable to induce potent and long-lasting immune responses. The investigators will use the novel TLR1/2 ligand (XS15, developed in Tübingen) that (i) is water-soluble and (ii) GMP-amenable, (iii) non-toxic and (iv) effective in inducing T cells specific for peptides in vivo.~Another important factor for the clinical effectiveness of peptide-based immunotherapy is the rational combination with standard therapies. In this iVAC-XS15-CLL01 trial, peptide vaccination will be applied in CLL patients under ibrutinib treatment which have achieved at least a partial remission. The remission stage or, even better, the stage of MRD ensures an optimal effector to target cell ratio for peptide-based immunotherapy, as most of the tumor cells are eliminated and the T-cell compartment is recovered. Notably, several studies have proven that ibrutinib does not impair and even can show positive effects on T-cell response.
The aim of this study is to evaluate the efficiency along with safety and toxicity of a personalizied multi-peptide vaccine in combination with the TLR1/2 ligand XS15 in CLL patients undergoing ibrutinib-based regimes.