Leaders in Pharmaceutical Business Intelligence (LPBI) Group

Abstract

Introduction

Cell-mediated (CM) immunotherapies for cancer treatment are designed to activate the body’s adaptive immune responses against a malignant growth.^1,2 Generally, the goal of a CM response is to activate a cytotoxic T-cell response against a tumor to eliminate cancer cells. The principle of these treatments is straightforward, yet current work studying the complexity of the tumor micro-environment^2,3 as well as methods that attempt to directly activate T cells against tumor antigens^4,5,6 demonstrate the difficulty associated generating an immune response against a tumor.

Several CM cancer immunotherapies exist today. Major examples include PD-1 inhibitors, injection of live virus or viral particles into tumors, and adoptive T-cell therapies.^1,6,7,8 However, concerns regarding efficacy, safety, and/or cost have limited the use of many of these treatments. To address these concerns, we sought to develop a novel treatment based on developing a fully synthetic, minimal delivery system that facilitates presentation of human leukocyte antigen (HLA) class I restricted immunogenic peptides specifically on cancer cells without using live virus, viral subunits, or biologically derived material.

Based on these requirements, we developed a liposomal based agent consisting of a neutral, stealth liposome that encapsulates a synthetically manufactured immunogenic HLA class I restricted peptide derived from measles virus.^1,2,9 In addition, the liposome has a targeting peptide on the external surface that both specifically accumulates in cancer cells and facilitates presentation of the immunogenic peptide in HLA class I molecules (Figure 1a). Thus, this treatment is designed to generate a secondary CM immune response specifically against the tumor if the patient was previously vaccinated against or infected with measles.

In this proof-of-concept study, we synthesized a liposome that encapsulates H250,¹ an immunogenic HLA class 1 restricted peptide identified from measles hemagglutinin protein. The liposome is designed to specifically internalize in cancer cells by displaying the recently identified targeting peptide H1299.3 on the exterior surface (Figure 1b).¹⁰ H1299.3 is a 20mer, cancer-specific targeting peptide that was recently identified by our group. The peptide was identified using a novel phage display technique that allows for selection of cancer-specific targeting peptides that preferentially internalize in cancer cells via a defined mechanism of endocytosis. This peptide was dimerized on a lysine core and is fully functional outside the context of the phage particle. The H1299.3 peptide accumulates specifically in a panel of non-small cell lung cancer (NSCLC) cell lines compared to a normal bronchial epithelial cell control cell line via a clathrin-dependent mechanism of endocytosis. In this study, we demonstrate that H1299.3 facilitates functional presentation of an immunogenic antigen in both major histocompatibility complex (MHC) and HLA class I molecules as indicated by CD8⁺-specific interferon (IFN)γ secretion. In addition, H1299.3 facilitated presentation utilizes an autophagy-dependent mechanism. Finally, treatment with H1299.3 targeted liposomes containing H250 substantially reduces the growth rate of subcutaneous LLC1 tumors implanted in vaccinated C57BL/6 mice compared to treatment with vehicle control.

Result summarized:

1. The H1299.3 targeting ligand specifically accumulates in cancer and facilitates HLA class I presentation: H250 is an immunogenic peptide identified from sequencing peptides present in HLA A*0201 molecules following measles infection. identified two donors that were HLA A*02 positive and had previously been vaccinated against measles virus (the human NSCLC cell line, H1993, which we determined to be HLA A*02 positive)
2. identified three different cancer-specific targeting peptides that internalize into H1993 that have been previously published: H1299.2, H2009.1, and H1299.3. Each of these peptides specifically internalize in NSCLC cell lines compared to normal bronchial epithelial cells
3. H1299.3 facilitated HLA class I presentation requires autophagy. H1299.3 peptide colocalizes with Lamp-1 which is a marker of both lysosomes and autolysosomes, therefore it was possible autophagy involved and shown that H1299.3 colocalizes with autophagosomes.  Chlorpromazine, which inhibits clathrin coated mediatated endocytosis, decreased the HLA1 presentation of H250.
4. H1299.3-targeted liposomes encapsulating H250 reduce tumor burden in vivo. Mice were first vaccinated against H250.  The J1299.3 targeted liposome encapsulation H250 reduced tumor growth of LLC1 s.c. xenograpfts  by 50%.

Enhanced presentation of MHC class Ia, Ib and class II-restricted peptides encapsulated in biodegradable nanoparticles: a promising strategy for tumor immunotherapy.

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