Vaccination of MSI-H colorectal cancer patients with frameshift peptide antigens – a phase I/IIa clinical trial Matthias Kloor1), Miriam Reuschenbach1), Julia Karbach2), Reza Rafiyan2), Salah-Eddin Al Batran3), Claudia Pauligk3), Elke Jäger2), Magnus von Knebel Doeberitz1)

1 Department of Applied Tumour Biology, Institute of Pathology, University of Heidelberg, Heidelberg, Germany and Collaboration Unit Applied Tumor Biology, German Cancer Research Center (DKFZ), Heidelberg, Germany, 2 Oncology and Hematology, Krankenhaus Nordwest, Frankfurt, Germany, 3 Institute for Clinical Research, Krankenhaus Nordwest, Frankfurt, Germany

Background

Colorectal cancer is a heterogeneous tumor type. Whereas the majority of colorectal cancers show

chromosomal instability, a subset of about 15% of colorectal cancers (CRC) have a deficient DNA

mismatch repair (MMR) system and accumulate small mutations at repetitive DNA sequences, a

phenotype termed high level microsatellite instability (MSI-H). MSI-H cancers are particularly

characteristic for individuals with the inherited HNPCC (hereditary non-polyposis colorectal cancer) or

Lynch syndrome, which is caused by germline mutations of the MMR genes. Mutation carriers have a

high lifetime risk for the development of MSI-H cancers. Dense infiltration with lymphocytes is

commonly observed in MSI-H CRC lesions. These pronounced immune responses may be explained

by the generation of defined MMR deficiency-induced antigens (frameshift peptides, FSP).

We here report the results of a phase I/IIa peptide vaccination trial (Micoryx, NCT01461148) that

evaluates FSP vaccination in patients with MSI-H colorectal cancer

FSP antigens can be recognized by the immune system as foreign. MSI-H cancer

cells produce FSP antigens as the result of insertion/deletion mutations at cMS

sequences (arrows). Mutant genes, which are translated, can give rise to non-

functional proteins. These proteins encompass an N-terminal wild type amino acid

sequence (gray) and a C-terminal neopeptide or frameshift peptide sequence (red,

blue). Through processing via the HLA class I and HLA class II antigen processing and

presentation machinery, epitopes derived from FSP antigens can be presented on the

surface of MSI-H cancer cells. Antigens presented by HLA class I antigens can be

targets of CD8-positive T cell attack, whereas antigens presented by HLA class II

antigens can be recognized by CD4-positive T cells.

Methods

The Vaccine We developed a vaccine (Micoryx) to strengthen these immune responses and to potentially treat or prevent the formation of MSI-H CRC. For the Micoryx FSP vaccine, three coding microsatellite instability-derived FSP antigens were selected (AIM2(-1), HT001(-1), TAF1B(-1)). These antigens are highly promising targets, because

1.  They are shared among the majority of MSI-H CRC and other MSI-H cancers, so that a combination vaccine of these three FSPs covers about 98.5% of MSI-H CRCs,

2.  they encompass long immunogenic neo-antigen peptide stretches, which allow induction of immune responses against multiple epitopes, independent from the patients‘ HLA type,

3.  the FSPs are directly derived from functionally relevant driver mutations, so immune escape by loss of the antigens is unlikely.

Study Design Phase I/IIa study of immunization with frameshift peptides administered with Montanide® ISA-51 VG in patients with advanced MSI-H colorectal cancer (MICORYX)

EudraCT No.: 2011-000765-12 Sponsor: Oryx GmbH & Co. KG

clinicaltrials.gov/show/NCT01461148

Study size: 22 patients

Inclusion criteria: History of MSI-H colorectal cancer, UICC

stage III or IV, after completion of standard chemotherapy

Study end points: Safety, immunological efficacy, clinical

response

Vaccination scheme:

Peptide ELISA IFN-gamma ELISpot

Results

•  The Micoryx vaccine strongly induced T cell (mainly CD4-positive) and humoral immune

responses in all patients vaccinated per protocol

•  No FSP antigen-associated severe adverse events have been observed.

•  The majority of patients included were tumor-free and had history of MSI-H CRC (UICC stage

III).

Conclusions M S I - H C R C a r e h i g h l y immunogenic tumors that occur sporadically (15% of CRC) or in the context of Lynch syndrome.

Preliminary evaluation of Micoryx demonstrates that vaccination with FSPs is safe and induces strong humora l and ce l lu la r immune responses in vaccinated patients

FSP vaccination holds high potential as a novel adjuvant treatment option in MSI-H colorectal cancer patients, and for cancer prevention in Lynch syndrome mutation carriers

The immunogenicity of MSI-H CRCs is associated with the generation of mismatch repair deficiency-induced neopeptides (FSPs).

References •  Kloor M, Michel S, Buckowitz B, et al. Beta2-microglobulin mutations in microsatellite unstable colorectal tumors. Int J Cancer. 2007 Jul 15;121(2):454-8. •  Schwitalle Y, Kloor M, Eiermann S, et al. Immune response against frameshift-induced neopeptides in HNPCC patients and healthy HNPCC mutation carriers. Gastroenterology. 2008 Apr;134(4):988-97. •  Surmann EM, Voigt AY, Michel S, et al. Association of high CD4-positive T cell infiltration with mutations in HLA class II-regulatory genes in microsatellite-unstable colorectal cancer. Cancer Immunol Immunother. 2015 Mar;64(3):357-66. •  Reuschenbach M, Dörre J, Waterboer T, et al. A multiplex method for the detection of serum antibodies against in silico-predicted tumor antigens. Cancer Immunol Immunother. 2014 Dec;63(12):1251-9.

Abstract #3020 miriam.reuschenbach@med.uni-heidelberg.de matthias.kloor@med.uni-heidelberg.de