2. OUTLINE
Introduction
PD-L1 DISTRIBUTION
PD-L1 on Tumor Cells
PD-1/PD-L1 Based Cancer Immunotherapy
Silencing & Regulating PD-L1 Expression in Tumor Cells
Application of PD-L1 antibodies in cancer combination
therapy
3. Introduction
• Programmed death-ligand 1 (PD-L1) also known as CD274 or
B7-H1 is encoded by the CD274 gene
• PD-L1 is type 1 transmembrane protein
• ligand for the inhibitory receptor PD-1
• typically expressed on immune cells so they don’t destroy each
other in inflammation
• expression can be detected in other non-immune cells, vascular
endothelium, tumor cells
• suppress the adaptive immune system during pregnancy, tissue
allografts, autoimmune disease and hepatitis.
• blockage of PD-L1 pathway provide a rationale for cancer
immunotherapy.
• Co-stimulate T-cell subsets that produce interleukin-10 (IL10)
6. • PD-L1 expressed in cancers like Urothelial carcinoma
and non-small cell lung cancer.
• The PD-L1 pathway help tumors to attenuate anti-
tumor immunity and escape destruction by the
immune system
• A number of checkpoint blockade inhibitors including
Atezolizumab and Avelumab have been developed
that target the PD1/PDL1 interaction in order to allow
T-cells to recognize tumor cells without being
deactivated by the tumor.
7.
8. • Broad distribution of PD-L1 in different cellular
compartments can lead to deactivate of the CTLs
• mPD-L1 holds the structure integrity and can bind
to its receptor, PD-1, to modulate cancer cell
• The antibody has limited influence on
intracellular cPD-L1 and nPD-L1 which affect the
efficacy of therapy
• PD1/PD-L1 blockade achieved via three methods:
(1) antibody blockade
(2) gene silencing
(3) small-molecule pathway inhibition
9. • Three PD-L1 antibodies are approved by FDA
• Around half of patients with positive PD-L1 expression benefit from the treatment.
• Very interestingly, there was some responses to PD-L1 antibody in the PD-L1 negative, for uncertain
reasons
• The highlight of this treatment is the relative low rate of treatment related adverse events Compared to
conventional therapies such as docetaxel treatment
• the usage of PD-L1 antibodies brings immune-related adverse events (ir-AE) into safety consideration
• Pneumonitis is the most severe ir-AE, with relative lower rates that PD-1 antibodies
• PD-L1 antibodies respond very positively to blood cancers like leukemia and lymphoma
10. Experimental
•KN035
PD-L1 antibody with subcutaneous formulation, its under clinical evaluations in the US, China, and Japan[
•AUNP12
29-mer peptide the first peptic PD-1/PD-L1 inhibitor, evaluated in clinical trial
•CA-170
PD-L1 and VISTA antagonist, as a potent small molecule inhibitor in vitro. currently under phase I clinical trial over
mesothelioma patients.
•BMS-986189
•is a macrocyclic peptide pharmacokinetics, safety and tolerability is currently being studied on healthy subjects
11. • Single interfering RNA “switch off” the protein synthesis
• The intracellular nPD-L1 and cPD-L1, can directly respond to gene silencing, resulting in decreased
levels of mPD-L1
• cancer cells transfected with PD-L1 siRNA are more sensitive to T cell killing anticancer
• the first gene silencing based therapeutics, the liposomal miR-34a mimic, underwent Phase I clinical
trials, then halted
• PD-L1 expression is mainly regulated via MAPK (RAS/RAF/MEK/ERK) and PI3K/Akt pathways
• Chemical inhibitors PD-L1 based treatment Inhibiting these pathways downregulate cellular PD-L1
expression
• signaling pathway inhibition take time to reduce PD-L1 expression, this approach not as sufficient as
antibody at a very early stage, while still sufficient to regulate PD-L1 at the later stage
12. At present, 76% of the active trials are testing combination
regimens of PD-1/PD-L1 mAbs with other cancer therapies
Application of PD-L1 antibodies in cancer combination therapy in 2019.
14. • Wu, Yilun, et al. "PD-L1 distribution and perspective for cancer immunotherapy–blockade,
knockdown, or inhibition." Frontiers in Immunology 10 (2019): 2022.
• Sau, Samaresh, et al. "PDL-1 antibody drug conjugate for selective chemo-guided immune modulation
of cancer." Cancers 11.2 (2019): 232.
• https://www.nature.com/articles/d42473-019-00048-0
• https://www.nature.com/articles/d41573-019-00182-w
Editor's Notes
EXPLAN ABOUT PDL1 ROLE IN CANCER/TUMOR CELLS
cluster of differentiation 274 , B7 homolog 1
got it’s name because it was discovered that other immune cells with this receptor/ligand axis were prevented from destroying each other).
inhibitory checkpoint molecule PD-1 Which through their interaction tumor cells evade the immune system
PDL1 is like and “invisible shield for tumors to hide from immune cells”
1- PDL1, is a ligand that binds with the receptor PD1 which promote immune tolerance
Targeting antibodies as checkpoint blockade inhibitors either for pdl1 or pd1 will inhace immunity activation and tumor clearance
3-Cancer immunotherapy is a specific method to eliminate cancer cells by enhancing or modulating the host immune system.
This how the APC like dendritic cells, macrophages, b cells
PD-L1, as well as PD-L2 on antigen-presenting cells (APCs) can interact with PD-1
on T cells, resulting in down-modulation of T cell immune activity.
During inflammation, interferon gamma will upregulate PDL1 expression
The known PD-L1 formats include
membrane PD-L1 (mPD-L1)
cytoplasm PD-L1 (cPDL1)
nuclear PD-L1 (nPD-L1)
serum PDL1 (sPD-L1)
the structures of these PD-L1 proteins are versatile
some lacking transmembrane motifs
Lack potential of glycosylated modification or dimerization
sPD-L1 source is not clear.
possibilities: (1) the fragment from mPD-L1 cleaved by proteolytic enzymes,
(2) endogenous translated integrity protein or splice variant for secretion
The function of cPD-L1 may be related to the promotion of cancer cell growth.
study in circulating tumor cells (CTCs) has showed that the nPD-L1 expression in patients is also significantly associated with a short survival
Why?
The gene variation among individuals further increases this uncertainty and potential risk of PDL1 antibody-based immunotherapy.
Location of pdl1 have motifs?
need for more sensitive approaches to detecting the protein
gene silencing is superior in fully stopping mPD-L1 production and function
PD-L1 knockdown reversed the resistance to cisplatin, suggesting the role of PD-L1 in overcoming cancer drug resistance
The development of gene silencing drugs has highlighted barriers
such as efficient delivery, off-target effects, potential mutagenesis,
and even some ethical arguments that need to be addressed to increase treatment efficiency
main issue for gene silencing is delivery. They are negatively charged, difficult to be internalized and vulnerable to RNase in the circulation.
Therefore, suitable delivery systems are required for efficient transfection.