Design, synthesis and evaluation of PD-L1 peptide antagonists as new anticancer agents for immunotherapy
Ala Orafaie1, Hamid Sadeghian2, Ahmad Reza Bahrami3
1Department of Biology, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran.
Abstract:
Blocking the interaction of programmed cell death protein 1 (PD-1) and its ligand PD-L1 is known as a promising immunotherapy for treatment of a variety of tumors expressing PD-L1 on their cell surface. In the last decade, several antibodies against the PD-1/PD-L1 interaction have been approved, while there are few reports of small-molecule inhibitors against PD-1/PD-L1 axis. Due to many advantages of cancer treatment with small molecules over antibodies, we developed several peptidic PD-L1 antagonists using computational peptide design methods, and evaluated them both in vitro and in vivo. Importantly, among six peptides with best affinity to PD-L1, four peptides exhibited significant potency to block PD-1/PD-L1 axis at molecular level. Moreover, the PD-L1 expression in nine human colorectal cancer cell lines stimulated with interferon-γ was compared and LoVo cells with the highest expression were selected for further experiments. The peptides could also restore the function of activated Jurkat T cells, which had been suppressed by stimulated LoVo cells. A blockade assay in tumor-bearing mice experiments indicated that peptides HS5 and HS6 consisting of a d-amino acid in their structures, could also effectively reduce tumor growth in vivo, without induction of any observable liver or renal toxicity, tissue damages and loss of body weight. As new designed peptides showed no toxicity against murine colon cancer cells in vitro, the observed anti-tumor results in mice are most probably due to disrupting the PD-1/PD-L1 interaction. Thus, peptides described in this study can be considered as proper low molecular weight candidates for immunotherapy of cancer.
Insights
New small-molecule peptides targeting the programmed cell death protein 1 (PD-1) and PD-L1 interaction show promise for cancer immunotherapy. These novel peptide antagonists effectively reduce tumor growth in vivo with no observed toxicity, offering a potential alternative to antibody therapies.
Area of Science:
- Oncology
- Immunology
- Drug Discovery
Background:
- The programmed cell death protein 1 (PD-1) and its ligand PD-L1 pathway is a critical target for cancer immunotherapy.
- While antibody-based therapies blocking PD-1/PD-L1 are established, small-molecule inhibitors remain less explored.
- Small molecules offer potential advantages over antibodies for cancer treatment.
Purpose of the Study:
- To design and evaluate novel small-molecule peptide antagonists targeting the PD-1/PD-L1 interaction.
- To assess the in vitro and in vivo efficacy and toxicity of these designed peptides.
- To explore a new therapeutic avenue for cancer immunotherapy.
Main Methods:
- Computational peptide design was employed to generate PD-L1 antagonists.
- In vitro assays assessed peptide affinity, blockade potency, and T-cell restoration.
- In vivo studies in tumor-bearing mice evaluated anti-tumor efficacy and toxicity.
Main Results:
- Four out of six designed peptides demonstrated significant potency in blocking the PD-1/PD-L1 axis.
- Peptides HS5 and HS6 effectively reduced tumor growth in vivo without inducing observable toxicity.
- The designed peptides restored the function of suppressed T-cells in vitro.
Conclusions:
- Novel small-molecule peptides effectively inhibit the PD-1/PD-L1 interaction.
- These peptides demonstrate significant anti-tumor activity and a favorable safety profile in preclinical models.
- The designed peptides represent promising candidates for future cancer immunotherapy development.
