Structural investigation on thiazolo[5,4-d]pyrimidines to obtain dual-acting blockers of CD73 and adenosine A2A receptor as potential antitumor agents

Article abstract of DOI:10.1016/j.bmcl.2020.127067

Adenosine pathway, including its generating enzyme (CD73) and its receptors represents a key target for cancer immunotherapy. Here we aimed to search for novel compounds able to co-target the CD73 and the A_2A adenosine receptor (A_2A

Full text of DOI:10.1016/j.bmcl.2020.127067

Journal Pre-proofs
Structural investigation on thiazolo[5,4-d]pyrimidines to obtain dual-acting
blockers of CD73 and adenosine A2A receptor as potential antitumor agents
Flavia Varano, Daniela Catarzi, Fabrizio Vincenzi, Silvia Pasquini, Julie
Pelletier, Juliana Lopes Rangel Fietto, Nicolly Espindola Gelsleichter, Marine
Sarlandie, Audrey Guilbaud, Jean Sévigny, Katia Varani, Vittoria Colotta
PII:
S0960-894X(20)30145-1
DOI:
Reference:
https://doi.org/10.1016/j.bmcl.2020.127067
BMCL 127067
To appear in:
Bioorganic & Medicinal Chemistry Letters
Received Date:
Revised Date:
Accepted Date:
10 January 2020
24 February 2020
26 February 2020
Please cite this article as: Varano, F., Catarzi, D., Vincenzi, F., Pasquini, S., Pelletier, J., Lopes Rangel Fietto, J.,
Espindola Gelsleichter, N., Sarlandie, M., Guilbaud, A., Sévigny, J., Varani, K., Colotta, V., Structural
investigation on thiazolo[5,4-d]pyrimidines to obtain dual-acting blockers of CD73 and adenosine A2A receptor as
potential antitumor agents, Bioorganic & Medicinal Chemistry Letters (2020), doi: https://doi.org/10.1016/j.bmcl.
2
020.127067
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Structural investigation on thiazolo[5,4-d]pyrimidines to obtain dual-acting blockers of CD73
and adenosine A receptor as potential antitumor agents.
2
A
a,*
a
b
b
c
Flavia Varano , Daniela Catarzi , Fabrizio Vincenzi , Silvia Pasquini , Julie Pelletier , Juliana
Lopes Rangel Fiettoc d e, Nicolly Espindola Gelsleichter , Marine Sarlandie , Audrey Guilbaud
c d
c d
c
d, Jean Sévigny , Katia Varani , Vittoria Colotta
c d
b
a
a
Dipartimento di Neuroscienze, Psicologia, Area del Farmaco e Salute del Bambino, Sezione di
Farmaceutica e Nutraceutica, Università degli Studi di Firenze, via Ugo Schiff, 6, 50019, Sesto
b
Fiorentino, Italy. Dipartimento di Scienze Mediche, Sezione di Farmacologia, Università degli Studi
c
di Ferrara, via Fossato di Mortara 17-19, 44121 Ferrara, Italy. Centre de Recherche du CHU de
Québec–Université Laval, Québec, QC G1V 4G2, Canada. d Département de Microbiologie-
Infectiologie et d'Immunologie, Faculté de Médecine, Université Laval, Québec, QC G1V 0A6,
Canada. e Departamento de Bioquimica e Biologia Molecular, Universidade Federal de Viçosa,
Viçosa, MG, Brazil.
Corresponding author:
*
Tel: +39 055 4573732. Fax: +39 055 4573780. E-mail: flavia.varano@unifi.it.

Abstract.
Adenosine pathway, including its generating enzyme (CD73) and its receptors represents a key target
for cancer immunotherapy. Here we aimed to search for novel compounds able to co-target the CD73
and the A adenosine receptor (A AR) as dual-blockers of adenosine generation and activity. The
2
A
2A
design project was to combine in the same molecule the thiazolo[5,4-d]pyrimidine core, an essential
pharmacophoric feature to block the A2A AR, with a benzenesulfonamide group which is a
characteristic group of CD73 inhibitors. Most of the reported compounds resulted in inverse agonists
of the human (h) A2A AR endowed with high affinity, selectivity and potency. However they were
weak inhibitors of CD73 enzyme. Nevertheless, this study can be considered as a starting point to
develop more active compounds.
KEYWORDS. Thiazolo[5,4-d]pyrimidine, adenosine A receptor inverse agonists, CD73
2
A
inhibitors, cancer immunotherapy, antitumor agents

In recent years cancer immunotherapy has represented a novel, high potential strategy for oncological
treatment. In particular, researchers’ attention was focused on the immune checkpoint targeting
therapy, which aims to interfere with the negative feedback mechanism activated by the tumor on
immune cells, resulting in suppression of the physiological anti-tumor immune response [1]. In
addition to the well known anti-CTLA4 and anti-PD1/PDL1 monoclonal antibodies (mAbs) [2], the
adenosine pathway has recently been proposed as an important target to restore the anti-tumor
immune response [3]. In fact, as a consequence of hypoxia and extracellular stress, in solid tumor
microenvironment (TEM) an accumulation of ATP occurs that is converted into adenosine by the
ectonucleotidases CD39 and CD73 [4]. Adenosine interacts with G-protein-coupled adenosine
receptors (ARs), classified as A , A , A and A based on their affinity for adenosine and on their
1
2A
2B
3
signal transduction pathway [5]. Indeed, physiological concentration of extracellular adenosine (0.3-
000 nM), while it is high enough to activate both A and A2A ARs, is not sufficient for the low
1
1
affinity A and A subtypes. All ARs are primarily coupled to adenylyl cyclase, which is inhibited
2
B
3
(
A and A ) or activated (A and A ), thus reducing or enhancing cAMP levels [6-7]. It is well
1 3 2A 2B
documented that activation of ARs can produce a large variety of effects in different tissues and
organs. In particular, one of the important activities of adenosine is inflammation suppression through
a direct inhibitory effect on diverse immune cells that express the A2A AR [8]. Thus, increased
production of adenosine within the hypoxic microenvironment of inflamed tissue has been shown to
inhibit overactive immunosuppressive cells from attacking healthy tissues. However, in the hypoxic
TME, elevated concentration of adenosine activates A2A AR on immune cells, thus causing
suppression of the antitumor immune response [3-4]. Moreover, the A2A AR is expressed also on
tumor cells and its stimulation induces and increases cell proliferation, survival, chemotaxis and
migration, thus favoring tumor growth [7-8].
In the TME stressed conditions increase of extracellular adenosine concentration is also able to
activate the low affinity A2B AR subtype. Compelling evidence suggests that A2B AR plays an
important role in mediating the pro-tumor effects of adenosine, since its selective blockade can inhibit

tumor growth in some tumor murine models [9-10]. For this reason compounds able to antagonize
the A ARs or both A and A ARs, may be considered as potential therapeutic agents in cancer
2
B
2A
2B
treatment.
CD73 is a glycophosphatidylinositol (GPI)-anchored homodimeric protein that contains two Zn2+
ions as cofactors in its active site, and is classified as a metallophosphatase. The enzyme catalyzes
the dephosphorylation of purine and pyrimidine ribo- and deoxyribonucleoside monophosphates to
the corresponding nucleosides. CD73 has high affinity for adenosine monophosphate (AMP) and
catalyzes its conversion to the bioactive adenosine, thus it is an important regulator of the adenosine
signaling pathway [11-12]. The underlying regulatory role of CD73 renders this enzyme a promising
therapeutic target in many pathological conditions [13]. In particular, inhibition of CD73,
overexpressed in TME and mainly responsible for the high concentration of adenosine, has proved
useful in counteracting adenosine-induced tumor immunosuppression through A2A ARs. Indeed,
inhibition of CD73 by small molecules or antibodies has been shown to reduce tumor growth and
metastasis [14-16].
Taking into account these considerations, it is evident that the adenosine pathway, including its
generating enzymes and its receptors, may represent a key target for cancer therapy, acting in TEM
to restore an efficient anti-tumor immune response.
Thus, the purpose of this study was to develop novel compounds as potential anti-tumor drugs, able
to co-target the CD73 and the A AR to block at the same time adenosine generation and its activity.
2
A
This working plan was also supported by the studies of Young et al. [17] which demonstrated that the
anti-tumor activity, derived from combined inhibition of CD73 and A2A AR signaling, is more
powerful than blockade of each target alone.
Multi-target compounds can be obtained by using different strategies of rational drug design. One of
these is molecular hybridization through which new chemical entities are obtained by combining into
a single molecule two or more pharmacophoric units from different bioactive compounds [18].
Following this design approach, and with the aim to find A AR/CD73 bifunctional blockers, we
2
A

carried out the synthesis of a series of compounds based on two active scaffolds, namely thiazolo[5,4-
d]pyrimidines and benzenesulfonamides (Figure 1).
Figure 1. Design strategy to obtain dual blockers of CD73/hA AR.
2
A
CD73
A2A AR
NH2
N
H NO S
2
2
O
O
N
S
N
Cl
N
O
HN
H
O
B: IC = 1.90 M
A: K = 22 nM
5
0
i
NH2
N
H NO S
2
2
N
N
S
O
linker
1
-9 (see Table 1)
Recently, as a part of our efforts to find novel AR antagonists [19-29], we identified the thiazolo[5,4-
d]pyrimidine as a privileged scaffold to obtain potent and selective hA2A AR antagonists/inverse
agonists (see compound A as an example) [21, 25-26]. On the other hand, benzenesulfonamide
represents a characteristic group of some potent CD73 inhibitors reported in the literature (see
2
+
compound B as an example) [30]. The SO NH moiety seems to interact with a Zn ion present into
2
2
the catalytic site of the enzyme thus reinforcing the inhibitory activity of the compounds. Thus, novel
-amino-2-(2-furanyl)thiazolo[5,4-d]pyrimidine derivatives 1-9 all bearing terminal
7
a
benzensulfonamide group, attached to the 5 position of the bicyclic core through linkers of different
length and flexibility, were synthesized. Moreover, to broaden structure affinity/activity relationship
studies of this new class of dual-acting agents, compounds 10-11 and 12, bearing as terminal group
of the 5-substituent a saccharinyl 10-11 or an ethyl benzoate 12 moiety, were synthesized.

All the newly synthesized thiazolopyrimidines 1-12 were evaluated both for their affinity at hARs
expressed in Chinese Hamster Ovary (CHO) cells, and for their inhibitory activity at human
recombinant CD73 enzyme.
Compounds 1-7, 12 were prepared according to the procedure depicted in Scheme 1, which involves
as starting material the 5-chloro-7-amino 13 previously synthesized by us [21].
NH2
N
N
NH2
N
S
O
N
S
HN
n
N
N
1
2
n=1
n=2
O
N
3
1
R=SO NH
2 2
2 R=COOEt
N
SO NH
2
2
R
H N
2
n
a
a
SO NH2
2
1
1
4 n=1
5 n=2
N
R
HN
1
1
6 R=SO NH2
7 R=COOEt
NH2
N
2
N
S
N
NH2
O
HN
a
N
N
H N
2
S
O
Cl
N
N
N
SO2NH2
N
N
1
3
1
8
4
O
a
SO NH2
2
n
2
SO NH2
N
NH2
N
N
H
H N
2
1
9 n=0
0 n=1
1 n=2
N
S
N
2
2
O
HN
O
5 n=0
6
7
n=1
n=2
N
N
n
H
H NO S
2
2
Scheme 1. Reagents and conditions: (a) n-BuOH, 200 °C MW, 20 min, 23-87% yield.

Displacement of the 5-chlorine atom of 13 by amines 14-21 was obtained by microwave irradiation
of a mixture of derivative 13 and an excess of the proper amine in butanol. While the 4-aminomethyl-
1
1
4 and 4-(2-aminoethyl)-benzensulfonamide 15, and the N -substituted piperazine derivatives 16-17
were commercial (14-15) or prepared according to literature (16-17) [31-32], the others amines 18-
2
1
1 were synthesized as shown in Schemes 2 and 3. Briefly, the 4-(piperazin-1-yl)benzenesulfonamide
6 [31] was reacted with N-(2-bromoethyl)phtalimide 22 to yield the N-(2-ethylsubstituted)-
phtalimide 23 which furnished the corresponding ethyl amine 18 by hydrazinolysis (Scheme 2).
O
Br
N
O
2
2
N
N
SO NH
2 2
O
HN
N
SO NH
2 2
N
a
1
6
23
O
N
N
SO NH
2 2
b
H N
2
18
Scheme 2. Reagents and
conditions: (a) Et N, CH CN, reflux, 12 h, 90% yield; (b)
3 3
NH NH ·H O, MeOH, reflux, 2 h, 80% yield.
2
2
2
Reaction of 4-aminomethylpiperidine 24 and benzaldehyde in absolute ethanol gave the imino
derivative 25 [33] which was then reacted with the proper chloroacetamido derivative 26-28 [34] to
yield the corresponding N-substituted piperidine derivatives 29-31 which were not isolated because
they were unstable (Scheme 3).

NH2
N
N
O
b
a
N
N
H
SO2NH2
N
H
SO NH
H
2
2
N
H
24
25
N
n
Cl
n
O
2
6-28
29-31
n
0
1
2
NH2
2
2
2
6, 29, 19
7, 30, 20
8, 31, 21
b
SO NH
2
2
N
H
N
n
O
1
9-21
Scheme 3. Reagents
and conditions: (a) benzaldheyde, EtOH, reflux, 24 h; (b) i) K CO ,
2 3
CH COCH , rt, 12 h; ii) oxalic acid, CH Cl /H O, 50 °C, 3 h, 55-75% yield.
3
3
2
2
2
Hydrolysis of the protecting imino group of 29-31 was performed in acidic aqueous medium to
furnish the desired 4-aminomethyl-piperidine derivatives 19-21. Scheme 4 reports the synthetic
procedure to prepare the thiazolo[5,4-d]pyrimidine derivatives 8-11 bearing at position 5 of the
bicyclic core a 1-piperidinyl moiety.
H N
2
NH2
N
NH2
NH
N
S
N
S
N
N
24
O
O
Cl
N
N
a
13
32
NH2
R
NH2
N
3
3, 8
4, 9
SO NH
2
2
N
S
N
b
SO NH2
2
3
O
N
O
R
OH
NH
R
8-11
3
3-36
O

O
3
5, 10
6, 11
O
S
N
O
O
3
O
S
N
O
Scheme 4. Reagents and conditions: (a) n-BuOH, 200 °C, MW, 20 min, 85% yield; (b) DMAP,
EDCI, BtOH, DMF, rt, 5 h, 40-90% yield.
Thus, the 5-chloro-7-amino 13 was reacted with the commercial 4-aminomethylpiperidine 24, under
microwave irradiation at 200 °C, to furnish derivative 32. Reaction of the latter with the proper
carboxylic acids 33-36, in the presence of EDCI, DMAP, and hydroxybenzotriazole, yielded the
corresponding amide derivatives 8-11. While the sulfamoylbenzoic acids 33 and 34 were commercial,
the N-(saccharinyl) acids 35 and 36 were synthesized as reported in Scheme 5.
O
S
O
S
O
S
O
O
O
a
b
NH
N
N
Na
n COOH
Cl
COOH
O
n
O
O
37
38
39 n=1
0 n=2
35 n=1
36 n=2
4
Scheme 5. Reagents and conditions: (a) MeONa, MeOH, reflux, 30 min; (b) sealed tube, 110 °C,
h, 30-50% yield.
3
Briefly, commercial saccharin 37, after deprotonation with sodium methoxide, was reacted with the
appropriate chloroacid 39-40 to give the corresponding carboxylic acids 35-36 with high yields.
Derivatives 1-12 were evaluated for their affinity to hA , hA , and hA ARs stably expressed in
1
2A
3
CHO cells by using competition binding assays. Binding experiments at hA and hA ARs were
1
3
performed to establish the A2A selectivity of the tested compounds versus A and A AR subtypes.
1
3

Due to the lack of a suitable radioligand for the A ARs the activity at this receptor subtype was
2
B
determined by measuring the inhibition of NECA-stimulated adenylyl cyclase activity in hA CHO
2
B
cells. Binding and potency data of the newly synthesized compounds 1-12 and of the reference
thiazolo[5,4-d]pyrimidine derivative A, are reported in Table 1.
Several compounds (2-7, 9) display high affinity for the hA subtype (2.02<K < 87 nM), while the
2
A
i
most (compounds 1-12) show a poor affinity for the hA AR (K values > 100 nM), except derivative
1
i
4
which was able to bind this subtype with a K falling in the nanomolar range (K = 84 nM). None of
i i
the reported derivatives binds the hA AR with the exception of 3 which displayed some affinity
3
(
K =582 nM). Finally, the majority of compounds do not interact with the hA AR subtype apart
i
2
B
from four (1-2, 6-7) which displayed high (1 IC =28 nM; 2 IC =34 nM) or good potencies (6
5
0
50
IC =146 nM; 7 IC =156 nM).
5
0
50
Detailed analysis of the binding results revealed that the aminomethyl- and the aminoethyl-
benzenesulfonamide derivatives 1 and 2, which differ only for the length of the chain between the
bicyclic core and the benzenesulfonamide residue, displayed a very different binding behavior. In
fact, the ethylamino derivative 2 shows a hA AR affinity about 50 fold higher than that of its lower
2
A
homologue 1. In contrast, the length of the chain does not influence the potency at the hA2B AR.
Indeed, compounds 1-2 showed IC values falling in the nanomolar range. It is worth noting that the
5
0
aminoethyl-benzensulfonamide derivative 2 while is equiactive to the reference compound A at the
hA AR, it is 5-fold more active at the A subtype. Moreover, it shows hA and hA AR binding
2
B
2A
1
3
affinities falling in the micromolar range, as to be considered a very interesting dual hA /hA AR
2
A
2B
antagonist, highly selective versus the hA and hA AR subtypes (more than 200-fold).
1
3
Table 1. Affinity (K ) and potency (IC ) of the novel thiazolo[5,4-d]pyrimidines on ARs.
i
50
NH2
N
S
N
O
R
N
1
-12; A

a
b
c
d
compd
R
hA AR
hA AR
hA AR
hA AR
3
1
2A
2B
K (nM)
i
K (nM)
i
IC (nM)
K (nM)
i
50
(
I%)
(I%)
N
H
1
2
2
36±18
295±23
28±3
3,458±303
SO NH
2
2
H
N
1
,326±256 5.73±0.48
34±3
1,874±158
SO NH
2
2
3
4
5
>10,000
N
N
SO NH2
2
3
87±32
89±8
86±7
582±49
(
12%)
>10,000
30%)
10,000
N
H
>10,000
(22%)
N
N
SO NH2
2.02±0.18
2
(
SO NH
2
2
N
H
O
>
>10,000
(15%)
N
119±9
57±5
87±7
60±6
N
(28%)
H
O
6
7
>10,000
(27%)
N
H
N
N
6
87±48
146±13
2
SO NH2
H
SO NH2
2
N
H
O
>
10,000
N
603±56
156±15
>10,000
N
(29%)
H
SO NH2
2
8
9
N
N
H
N
>10,000
(12%)
5,703±487
488±42
41±4
(9%)
O
O
H
N
>10,000
>10,000
(31%)
5
68±53
SO NH2
2
(17%)
O
O
1
1
1
0
1
2
S
H
>10,000
5%)
>10,000
(6%)
N
N
N
N
1,671±28
488±39
(
O
O
O
O
S
>10,000
12%)
>10,000
(22%)
H
N
1
,068±28
639±55
N
(
O
O
>10,000
38%)
N
N
COOEt
4
,536±312
279±23
22±3
2,679±221
(
Ae
N
H
45±6
32±2
37±3
3
a
3
b
125
Affinity values obtained from displacement of specific [ H]DPCPX , [ H]ZM241383 or [ I]AB-
d
c
MECA binding to hA ARs, hA ARs or A ARs, respectively (n=3–6). Potency (IC ) in cAMP
1
2A
3
50
assays to hA ARs. Percentage of inhibition (I%) is determined at 10 μM concentration of the
2
B
e
tested compounds. Data are expressed as means ± SEM. Ref. 21.
In derivatives 3 and 4 the benzenesulfonamide group was attached through a piperazine moiety
directly linked to the thiazolopyrimidine system (3) or spaced by an ethylamino chain (4). This
structural difference makes the more flexible and longer derivative 4 about 40 fold more active than
the more rigid and shorter compound 3. Indeed, the aminoethylpiperazin substituted 4 displays the
highest hA AR affinity (K hA =2.02 nM) among the herein reported compounds. Furthermore, it
2
A
i
2A
was more active and selective toward the hA AR with respect to the reference A.
2
A

Compounds 5-7 possess the same 2-(4-(aminomethyl)piperidin-1-yl)acetamide fragment at 5-
position, which is directly linked to the benzenesulfonamide moiety (derivative 5) or through an alkyl
chain of different length (derivatives 6, 7). These compounds show a similar good affinity for the
hA AR indicating that, in this set, moving away the benzenesulfonamide residue from the bicyclic
2
A
core doesn’t seem to influence the binding to this receptor. On the contrary, distancing the
benzenesulfonamide group while decreases the hA AR affinity, increses that for the A subtype.
1
2B
Indeed, also compounds 6 and 7 can be considered dual hA /hA AR antagonists less potent than
2
A
2B
2
.
Derivatives 8 and 9, which exhibit the benzenesulfonamido moiety connected to the bicyclic core by
a N-(piperidin-4ylmethyl)acetamide group, differ only for the position (para or meta) of the
sulfonamide residue. While the para-sulfonamide substituted derivative 8 binds scarcely the hA2A
AR, the corresponding meta-substituted 9 displays a good binding affinity (K = 41 nM).
i
Compounds 10-11, showed a low hA AR binding affinity probably due to an excessive hindrance
2
A
of the appended saccharinyl moiety.
Finally, when the sulfonamide group of derivative 3 was substituted with a carboxyethyl moiety, a
drop of hA AR affinity was obtained. In fact, the carboxyethyl derivative 12 exhibit a 3 fold lower
2
A
affinity than that of the corresponding sulfonamide compound 3.
All the reported compounds 1-12 were assayed against CD73, in order to evaluate their capability to
block also adenosine generation (Table 2). In general, the tested derivatives showed weak inhibitory
activity, whereas compounds 6, 9, and 10 were devoid of effects on CD73 activity.
In vitro activity of some selected compounds (2-4, 12) was also studied, in order to evaluate their
antagonist/inverse agonist profile toward the hA2A AR. In particular, the ability of the tested
compounds to modulate cAMP production was tested. As shown in Table 3, derivatives 2-4 and 12
behaved as inverse agonists being able to inhibit basal cAMP accumulation at nanomolar
concentration.
Table 2. Percent of CD73 activity in the presence of 0.1 mM of compounds 1-12.a

compound
% Activity CD73
85±5 (2)
compound
% Activity CD73
90±20 (2)
97±5 (2)
1
2
3
4
5
6
7
8
84±21 (2)
81±8 (5)
9
100±6 (2)
100±15 (2)
80±5 (2)
89±1.6 (2)
90±4 (2)
10
11
12
100±13 (2)
77±4 (2)
a
Data are expressed as means ± SEM. The number of assay are presented in the parentheses.
Table 3. Potency (IC ) of selected compounds on the reduction of cyclic AMP levels in CHO cells
5
0
expressing hA AR.
2
A
Compounds
Potency (IC nM)
Pharmacological behaviour
Inverse agonist
5
0
2
3
4
5.20±0.46
58±5
Inverse agonist
0.34±0.03
334±28
29±3
Inverse agonist
1
2
Inverse agonist
A a
Ref. 21. Data are expressed as means ± SEM.
In accordance with the binding results, compounds 2 and 4 displayed higher potencies than those of
and 12, and also in this assay compound 4 is the most active showing a potency value in the
subnanomolar range (IC =0.34 nM). Moreover, compounds 2 and 4 resulted inverse agonists more
Inverse agonist
a
3
5
0
potent than the reference compound A.
In conclusion, the reported compounds were hA AR inverse agonists endowed with high affinity,
2
A
selectivity and potency for this receptor subtype. However, they were weak CD73 inhibitors.
Furthermore, compounds with an intriguing dual hA /hA AR inverse agonist/antagonist profile (2,
2
A
2B
6
-7) were identified, compound 2 being also highly selective versus hA and hA AR subtypes. These
1 3
results allow us to use these compounds as lead structure to design more active derivatives

characterized by dual inhibition of the adenosine producing enzyme CD73, and of adenosine
receptors.
Notes
The authors declare no competing financial interest. All authors have given approval to the final
version of the manuscript.
Acknowledgments
V.C. received financial support from the Università degli Studi di Firenze and from Fondazione AIRC
per la Ricerca sul Cancro (AIRC-MFAG project identification number 21753). K.V. received
financial support from the Università degli Studi di Ferrara. J.S. received support from the Natural
Sciences and Engineering Research Council of Canada (NSERC; RGPIN-2016-05867) and was the
recipient of a “Chercheur National” Scholarship from the Fonds de Recherche du Québec – Santé
(FRQS). J.F. received a scholarship from Conselho Nacional de Desenvolvimento Científico e
Tecnológico of Brazil (CNPq).
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Declaration of interests
☒
The authors declare that they have no known competing financial interests or personal relationships
that could have appeared to influence the work reported in this paper.

☐
The authors declare the following financial interests/personal relationships which may be considered as
potential competing interests:
Graphical abstract
Highlights
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The synthesis of novel 7-amino-thiazolo[5,4-d]pyrimidine derivatives is reported
Compounds were tested for their affinity and potency at human adenosine receptors
Compounds were tested for their inhibitory activity at recombinant human CD73