Medicinal Chemistry Research
immune response, and thereby facilitate the survival of
tumor cells [7, 8]. Therefore, the ICIs have become one of
the most promising agents in cancer therapy.
Here, we have conducted several biological evaluations
and performed modeling methods to estimate the inhibitory
effects of distinct molecules that target the PD-1/PD-L1
pathway. The monomer 001 (Incyte-001) and dimer com-
pounds 011 (Incyte-011) from Incyte, reported for great
activity in the patents, were selected as representative for
which no other exact experimental data is available. For the
same reason, BMS-1001 was selected from many patents by
BMS in this research (Scheme 1). Their abilities to block the
binding of PD-1/PD-L1 were verified by using the ELISA
assay. And the cytotoxicity profiles were detected in A549
cells. Meanwhile, we also evaluated their abilities to pene-
trate the blood-brain barrier (BBB) and distribution in the
brain. Finally, using computer-aided drug design (CADD),
we analyzed the related amino acid residues that interact
with compounds.
Notably, the monoclonal antibodies (mAbs) of PD-1/PD-
L1 inhibitors have shown significant clinical effectiveness in
various tumors including melanoma, lung cancer, Hodgkin
lymphoma, urothelial carcinoma, bladder cancer, colorectal
cancer, renal cell carcinoma, and glioblastoma [9–12]. And
these monoclonal antibodies showing their advantages, also
have several disadvantages such as lack of oral bioavail-
ability, prolonged half-life, poor permeability, immune-related
adverse effects (irAEs), and relatively lower clinical response
in brain tumors [13–15]. However, these shortcomings can be
overcome by developing small molecular inhibitors.
Recently, a series of small molecular inhibitors,
including macrocyclic peptides, peptide mimetics, and
non-peptide small molecular inhibitors, have been dis-
covered for improvement of treatment [16–19]. Among
them, small molecules discovered by Bristol-Myers
Squibb (BMS) exhibit activity in the nanomolar range.
Their skeletons have a biphenyl group connected to a
substituted aromatic ring by a benzyl ether bond. Shortly,
other companies including Incyte, Gilead, and etc., also
disclosed similar compounds, including a series of
C2 symmetrical skeleton compounds. Interestingly,
through the HTRF (Homogeneous Time-Resolved Fluor-
escence) assay and cell-based co-culture PD-L1 signaling
assay, C2 symmetrical skeleton compounds with dimer-
structure are revealed to be more effective than the
monomers [20]. However, the reason remains unknown.
And their toxicity and druggability still need to be eval-
uated. Furthermore, unlike monoclonal antibodies, these
small molecular inhibitors may have the potent for
crossing the blood-brain barrier (BBB) and for the treat-
ment of central neural system (CNS) tumors. Therefore, it
is vital to evaluate their blood-brain barrier (BBB)
penetrability and distribution in the brain.
Results and discussion
Chemistry
The synthesis of Incyte-001 is shown in Scheme 2 [21].
Starting with commercially available 2-amino-6-
bromobenzonitrile 1, Suzuki coupling reaction with
phenyl-boronic acid produced biphenylnitrile product 2.
The resulting compound was treated with O-(7-Aza-
benzotriazol-1-yl)-N,N,N’,N’-tetramethyluronium hexa-
fluorophosphate (HATU) and coupled with 5-
bromopicolinic acid 3 to provide bromopicolinamide
intermediate 4. Then, this was reacted with pinacol vinyl
boronate in the presence of palladium catalyst to obtain
vinylpicolinamide compound 5. Next, using K OsO /
2
4
NaIO , classical oxidative cleavage of double bond in the
4
compound 5 resulted in formylpicolinamide 6. Lastly,
reductive amination with ethanolamine produced the final
product Incyte-001.
Scheme 1 Structures of Incyte-
0
01, Incyte-011 and BMS-1001