CLINICAL CANCER RESEARCH | CLINICAL TRIALS: IMMUNOTHERAPY A Frameshift Peptide Neoantigen-Based Vaccine for Mismatch Repair-De ﬁcient Cancers: A Phase I/IIa Clinical Trial Matthias Kloor1,2,3, Miriam Reuschenbach1,2,3, Claudia Pauligk4, Julia Karbach5, Mohammad-Reza Ra ﬁyan5, Salah-Eddin Al-Batran4, Mirjam Tariverdian6, Elke J €ager5, and Magnus von Knebel Doeberitz1,2,3 ABSTRACT ◥ Purpose: DNA mismatch repair (MMR) de ﬁciency is a hallmark of Lynch syndrome, the most common inherited cancer syndrome. MMR-de ﬁcient cancer cells accumulate numerous insertion/deletion mutations at microsatellites. Mutations of coding microsatellites (cMS) lead to the genera- tion of immunogenic frameshift p eptide (FSP) neoantigens. As the evolution of MMR-de ﬁcient cancers is triggered by muta- tions inactivating de ﬁned cMS-containing tumor suppressor genes, distinct FSP neoantigens are shared by most MMR- deﬁcient cancers. To evaluate safety and immunogenicity of an FSP-based vaccine, we performed a clinical phase I/IIa trial (Micoryx). Patients and Methods: The trial comprised three cycles of four subcutaneous vaccinations (FSP neoantigens derived from mutant AIM2, HT001, TAF1B genes) mixed with Montanide ISA-51 VGover 6 months. Inclusion criteria were history of MMR-de ﬁcient colorectal cancer (UICC stage III or IV) and completion of che- motherapy. Phase I evaluated safety and toxicity as primary end- point (six patients), phase IIa addressed cellular and humoral immune responses (16 patients). Results: Vaccine-induced humoral and cellular immune responses were observed in all patients vaccinated per protocol. Three patients developed grade 2 local injection site reactions. No vaccination-induced severe adverse events occurred. One heavily pretreated patient with bulky metastases showed stable disease and stable CEA levels over 7 months. Conclusions: FSP neoantigen vaccination is systemically well tolerated and consistently induces humoral and cellular immune responses, thus representing a promising novel approach for treat- ment and even prevention of MMR-de ﬁcient cancer. Introduction The success of immune therapy in cancer is linked to the presence of appropriate cancer antigens that can be recognized and targeted by the immune system. The number of nonsynonymous mutations deter- mines the load of mutational neoantigens and may represent a valuable biomarker predicting the ef ﬁcacy of immune intervention (1). Micro- satellite-unstable (MSI, in the present article used synonymous with high-level microsatellite-unstable or MSI-H) cancers represent a particularly promising tumor type for immune therapy. They arise as a consequence of DNA mismatch repair (MMR) de ﬁciency (2) andtherefore accumulate more than 10-fold higher numbers of somatic mutations than microsatellite-stable tumors (3, 4). MSI occurs in about 15% of colorectal cancers, about 25% of endometrial cancers, and a variety of other tumors. MSI cancers have a heterogeneous pathogenesis. Notably, tumors developing in the context of the most frequent inherited cancer syndrome, Lynch syndrome, are characterized by MSI (2, 5). Lynch syndrome is caused by monoallelic germline mutations of one of the four DNA MMR genes, MLH1, MSH2 , and, with lower penetrance, MSH6 followed by PMS2 (5). Individuals with Lynch syndrome have a lifetime risk of up to 80% to develop MSI cancer, predominantly in the colorectum and the endometrium (6). Independent from Lynch syndrome, MSI cancers can also develop sporadically, either as a consequence of MLH1 promoter methylation in frame of the CpG island methylator phenotype (CIMP), or of biallelic MMR gene inactivation caused by two somatic mutations (7, 8). Families with clinical evidence for an inherited risk of developing MSI cancer, but no identi ﬁable MMR gene mutations are commonly referred to as “Lynch-like ”(9). In MSI cancers, MMR de ﬁciency leads to the accumulation of a plethora of insertion or deletion mutations at microsatellite sequence stretches, which, if located in gene-encoding regions, cause transla- tional frameshifts and give rise to the generation of frameshift peptide (FSP) antigens (10 –12). Several such MMR de ﬁciency-induced FSP antigens have been characterized in detail (13 –15), and patients with MSI cancer spontaneously develop immune responses towards FSP antigens (12, 16). The evolution of MSI cancers is promoted by mutational inactiva- tion of a limited number of coding microsatellites (cMS)-containing tumor suppressor genes. This concept of recurrent and shared muta- tional events with functional relevance has ﬁrst been described in a1Department of Applied Tumor Biology, Institute of Pathology, University Hospital Heidelberg, Heidelberg, Germany.2Clinical Cooperation Unit Applied Tumor Biology, DKFZ (German Cancer Research Center) Heidelberg, Heidelberg, Germany.3Molecular Medicine Partnership Unit (MMPU), EMBL Heidelberg, Heidelberg, Germany.4Institute of Clinical Cancer Research (IKF), Krankenhaus Nordwest, UCT University Cancer Center, Frankfurt, Germany. 5Clinic for Oncology and Hematology, Krankenhaus Nordwest, Frankfurt, Germany.6Department of Surgery, University Hospital Heidelberg, Heidelberg, Germany. Note: Supplementary data for this article are available at Clinical Cancer Research Online (http://clincancerres.aacrjournals.org/). Clinical Trial registration ID: NCT01461148 (EudraCT No. 2011-000765-12) Corresponding Author: Matthias Kloor, Heidelberg University, Heidelberg 69120, Germany. Phone: 4962-2156-5210; Fax: 4962-2156-5981; E-mail: matthias.kloor@med.uni-heidelberg.de Clin Cancer Res 2020;26:4503 –10 doi: 10.1158/1078-0432.CCR-19-3517 /C2112020 American Association for Cancer Research. AACRJournals.org | 4503Downloaded from http://aacrjournals.org/clincancerres/article-pdf/26/17/4503/2062752/4503.pdf by guest on 29 November 2024 landmark study identifying TGFBR2 as a commonly mutated cMS- containing target gene in MSI cancers (17). Consequently, MSI cancer development is associated with the generation of de ﬁned FSP neoanti- gens that are shared by the majority of MSI cancers, rendering them potentially targetable by an FSP vaccine ( Fig. 1A ). In addition, the fact that MSI cancers occur in the context of Lynch syndrome provides a unique opportunity to evaluate cancer-preventive vaccines in a real- istic scenario, because Lynch syndrome mutation carriers are at very high risk of developing cancer and develop suf ﬁcient numbers of tumors to evaluate the ef ﬁcacy of a preventive vaccine in a short time span. Starting from a bioinformatics-based model (18) our group has deﬁned a set of such shared FSP antigens, which occur particularly frequently as a result of functionally relevant “driver ”mutations and which elicit T-cell responses in patients with MSI cancer ( Fig. 1 ; refs.