The anticancer therapeutic potential of pyrimidine–sulfonamide hybrids

Abstract

Cancer as a devastating malignancy, seriously threatens human life and health, but most chemotherapeutics have long been criticized for unsatisfactory therapeutic efficacy due to drug resistance and severe off-target toxicity. Pyrimidines, including fused pyrimidines, are privileged scaffolds for various biological cancer targets and are the most important class of metalloenzyme carbonic anhydrase inhibitors. Pyrimidine–sulfonamide hybrids can act on different targets in cancer cells simultaneously and possess potent activity against various cancers, revealing that hybridization of pyrimidine with sulfonamide is a promising approach to generate novel effective anticancer candidates. This review aims to summarize the recent progress of pyrimidine–sulfonamide hybrids with anticancer potential, covering papers published from 2020 to present, to facilitate further rational design of more effective candidates.

Graphical abstract

The current review outlines the anti-breast cancer potential along with mechanisms of action and structure–activity relationships of sulfonamide hybrids reported since 2020 to shed light on the development of more effective and multitargeted candidates.

Plain language summary

Executive summary.

• Pyrimidine and sulfonamide derivatives could exert the anticancer activity through different mechanisms.

• Pyrimidine–sulfonamide hybrids demonstrated potent in vitro and/or in vivo anticancer efficacy.

• Rational hybridization of pyrimidine and sulfonamide may provide novel anticancer candidates.

• The enriched SARs facilitate further rational design of more effective candidates.

Cancer, proliferates uncontrollably and infects neighboring tissues, it is one of the most common noncommunicable diseases and usually associated with severe health issues as well as death [1,2]. Nowadays, cancer results in over 18 million new cases and nearly 10.0 million deaths each year [3,4]. Chemotherapy remains a largely opted therapeutic option, but current available chemotherapeutics are still far from meeting the treatment needs of patients since conventional chemotherapeutics are usually associated with many drawbacks, especially multidrug resistance and severe side effects [5–8].

Pyrimidines including fused pyrimidines such as benzo[d]pyrimidines (quinazolines) can exert the anticancer potential through various mechanisms of action, inclusive of inhibition of CDKs, DHFR, EGFR, DNA, TRK, PI3K and thymidylate synthase (TS) [9,10]. Moreover, several pyrimidine-based agents which are exemplified by gefitinib, lapatinib, raltitrexed and idelalisib have already been utilized in clinical anticancer therapy [11,12].

Sulfonamides have the advantages of rapid absorption, excellent in vivo stability, good blood–brain barrier permeability and broad-spectrum biological activities including antibacterial, anti-tubercular, anti-obesity, antiviral, anti-inflammatory, diuretic, hypoglycemic, antithyroid and anticancer activities [13–16]. Sulfonamide moiety presents in many US FDA-approved drugs and therapeutic agents such as sulfamethoxazole, probenecid and sulfadiazine [17,18]. Notably, sulfonamides are the most important class of the metalloenzyme carbonic anhydrase (CA) inhibitors and can inhibit cancer cell proliferation, induce apoptosis, cause cell cycle arrest and retard migration, invasion and metastasis, representing useful scaffolds for the discovery of new anticancer candidates [19,20].

Hybrid molecules, incorporating different molecular entities with distinct modes of action on biological targets into one new molecule, have shown promising results in terms of reducing side effects, minimizing drug–drug interactions, improving pharmacokinetics, enhancing biological activity and overcoming drug resistance [21,22]. Thus, hybridization is an emerging paradigm in the contemporary drug development. Pyrimidine and sulfonamide are two different anticancer pharmacophores with distinct modes of action, so rational hybridization of the two pharmacophores may generate novel candidates for cancer therapy [23,24]. This review aims to shed light on the recent progress of pyrimidine–sulfonamide hybrids (Figure 1) with anticancer potential, covering papers published from 2020 to present, to facilitate further rational design of more effective candidates.

Figure 1.

General chemical structures of pyrimidine–sulfonamide hybrids.

Pyrimidine/pyrimidinone–sulfonamide hybrids

The antiproliferative structure–activity relationships (SARs) of pyrimidine–sulfonamide hybrids 1 (Figure 2; half maximal inhibitory concentration [IC₅₀]: 1.73–6.25 μM, cell counting kit-8/CCK-8 assay) against HCT-116 colon cancer cells elucidated that (1) piperidinyl ring was more favorable than pyrrolidinyl ring at C-2 position of pyrimidine moiety; (2) combination of hydrogen-bond donors (carboxylic acid and hydroximic acid) with sulfonamide fragment enhanced the activity [25]. Hybrids 1a,b (IC₅₀: 1.73 and 3.94 μM) showed the highest activity against HCT-116 cancer cells, and in particular, hybrid 1a (IC₅₀: >50 μM) was non-toxic toward normal LO2 cells and possessed excellent selectivity profile (selectivity index [SI]: IC_{50(normal cells)}/IC_{50(cancer cells)} >28.9). Mechanistically, hybrid 1a could efficiently block the heat shock protein 90 (Hsp90)-cell division cycle 37 (Cdc37) protein–protein interaction (PPI) through a direct binding mode, resulting in a specific down-regulation of kinase clients of Hsp90 and cell cycle arrest in G0-G1 phase. The metabolic stability studies revealed that hybrid 1a possessed good stability both in mouse and human plasma, with half-life (t_1/2) values of 96.3 and 124.5 min, respectively. Moreover, hybrid 1a (80 mg/kg, oral administration) also possessed favorable pharmacokinetic properties with the elimination half-life (t_1/2) values of 1.46 and 4.66 h, the plasma clearance (CL) values of 186.5 and 167.9 ml/h/kg, and the area under the concentration–time curve (AUC_0-∞) values of 533.4 and 132.3 μgoh/ml in plasma and tumor tissue, respectively. In the HCT-116 xenografted mice model, hybrid 1a (80 mg/kg, intragastric administration) suppressed ∼80% tumor growth without loss of body weight and exhibited negligible influence on different organs of mice, representing a potential clinical candidate for colon cancer management.

Figure 2.

Chemical structures of pyrimidine–sulfonamide hybrids 1–12.

DDO-5994 (2, IC₅₀: 6.34 μM, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide [MTT assay]), an analogue of hybrid 1a, also possessed potential antiproliferative activity against HCT-116 colon cancer cells [26]. The mechanistic studies showed that DDO-5994 could disturb Hsp90-Cdc37 PPI, induce kinase degradation, and inhibit cell cycle progression through arresting in G0/G1 phase by down-regulating CDK4/6. In the HCT-116 xenografted mice model, DDO-5994 (tumor growth inhibition/TGI: ∼45% at a dose of 20 mg/kg via oral administration) was slightly more potent than hybrid 1a (TGI: ∼40%) at the same condition, and this hybrid did not influence the body weight of mice. Taken together, DDO-5994 could serve as a promising anti-colon cancer candidate for further preclinical evaluations.

Pyrimidine–sulfonamide hybrids 3a,b (IC₅₀: 5.66 and 9.59 μM, MTT assay) exhibited promising antiproliferative activity against HCT-116 colon cancer cells, and the activity was not inferior to that of doxorubicin (IC₅₀: 3.30 μM) [27]. In addition, hybrids 3a,b (IC₅₀: 57.42 and 37.05 μM) displayed relatively low cytotoxicity toward normal MRC-5 cells, and SI values were 10.1 and 3.8, respectively. Mechanistically, hybrid 3a inhibited the formation of colony as well as cell migration, and induced apoptosis of HCT-116 cancer cells.

Pyrimidine–sulfonamide hybrids 4a,b (IC₅₀: 6.99–9.87 μM, MTT assay) were comparable to sorafenib (IC₅₀: 5.47 and 7.26 μM) and doxorubicin (IC₅₀: 8.07 and 6.75 μM) against HCT-116 colon and MCF-7 breast cancer cell lines, and the antiproliferative SAR revealed that methyl group on the pyrimidine moiety was beneficial for the activity [28]. Additionally, hybrids 4a,b (IC₅₀: 62.12 and 66.67 μM) displayed relatively low cytotoxicity toward normal green monkey kidney cells (VERO), and SI values were in a range of 6.1 to 9.9, demonstrating their good selectivity profiles. Moreover, hybrids 4a,b (IC₅₀: 120 and 100 nM) were also potent inhibitors of VEGFR2, and the inhibitory effects were in the same level with that of sorafenib (IC₅₀: 100 nM).

Pyrimidine–sulfonamide hybrid 5 (IC₅₀: 2.40, 2.50 and 2.40 μM, MTT assay) was comparable to 5-fluorouracil (IC₅₀: 6.70, 2.46 and 3.50 μM) against T-47D, MCF-7, and MDA-MB-231 breast cancer cell lines, and it also showed excellent antiproliferative activity (IC₅₀: 2.50, 4.30 and 4.50 μM) against HCT-116, HT-29 and SW-620 cancer cell lines [29]. The antiproliferative SARs demonstrated that (1) dimethoxyphenyl ring at C-6 position of pyrimidine motif was essential for the high activity [29]; (2) introduction of cyclohexyl group into C-5 and C-6 positions of pyrimidine moiety was permitted as evidenced by that hybrid 6 (IC₅₀: 3.93 μM, MTT assay) showed decent antiproliferative activity against T-47D breast cancer cells [30]. Mechanistically, hybrid 5 could cause MCF-7 and MDA-MB-231 cell cycle arrest in G2/M phase and induce late apoptosis as well as necrotic cell death.

Pyrimidine–sulfonamide hybrid 7 (IC₅₀: 1.3, 1.5 and 1.7 μM, MTT assay) exhibited higher antiproliferative activity than cefitinib (IC₅₀: 4.0, 14.5 and 4.9 μM) and cisplatin (IC₅₀: 18.1, 34.2 and 25.7 μM) against KKU-100, KKU-452 and KKU-M156 cholangiocarcinoma cell lines [31], whereas hybrids 8a,b (IC₅₀: 1.61 and 1.41 μM, MTT assay) were not inferior to doxorubicin (IC₅₀: 1.03 μM) against MDA-MB-231 cancer cells [32]. Mechanistically, hybrid 7 could induce early apoptosis, suppress colony formation and inhibit cholangiocarcinoma cell migration through suppression of epidermal growth factor (EGF)-mediated activation of EGFR phosphorylation.

Pyrimidine–sulfonamide hybrid 9a (IC₅₀: 9.64 μM, MTT assay) showed promising antiproliferative activity against HCT-116 colon cancer cells, whereas hybrid 9b (IC₅₀: 9.95 μM) possessed considerable antiproliferative activity against HT-29 colon cancer cells, and the activity was superior to that of 5-fluorouracil (IC₅₀: 37.22 and 16.07 μM, respectively) [33]. The SAR illustrated that cyclopentyl group at C-4 position of pyrimidine moiety was favorable to the activity, but sulfonamide moiety was not essential for the high activity. Further mechanistic studies indicated that these hybrids could cause cell cycle arrest and induce apoptosis in HCT-116 cells. Hence, hybrids 9a,b could act as lead compounds for the treatment of colon cancers.

Pyrimidine–sulfonamide hybrids 10a–c (IC₅₀: 11–81 nM, MTT assay) and 11a,b (IC₅₀: 12.5–67 nM, MTT assay) exhibited great antiproliferative activity against H2228 and H1975 cancer cell lines [34]. In particular, hybrid 10a (IC₅₀: 1.60 and 3.30 μM) displayed relatively low cytotoxicity toward normal EA.hy926 and HK-2 cells, and SI values were ranging from 19.7 to 300, suggesting its excellent selectivity profile. Moreover, hybrid 10a (IC₅₀: 3.31 and 17.74 nM) was also an excellent dual inhibitor of anaplastic lymphoma kinase (ALK) and EGFR. Mechanistically, hybrid 10a could induce apoptosis, and inhibit invasion as well as migration of H1975 and H2228 cancer cell lines.

PS14 (12; IC₅₀: 12.64–22.20 μM, MTT assay), a pyrimidine–sulfonamide hybrid, showed moderate antiproliferative activity against HeLa, HCT-116, A549 and HepG2 cancer cell lines, and the activity was not inferior to that of 5-fuorouracil (IC₅₀: 13.09–24.78 μM) [35]. In addition, PS14 (IC₅₀: 102.46 μM) displayed low cytotoxicity toward normal LO2 cells, and SI values were in a range of 4.6 to 8.1, revealing its good selectivity. Mechanistically, PS14 caused cell cycle arrest at S phase and induced the apoptosis.

Pyrimidine–sulfonamide hybrid 13 (Figure 3; IC₅₀: 100–760 nM, MTT assay) possessed profound antiproliferative activity against HCT-15, DU-145 and HT-29 cancer cell lines [36]. Mechanistically, hybrid 13 could induce the apoptosis by generation of reactive oxygen species (ROS) and alteration of mitochondrial membrane potential. The SARs demonstrated that (1) methoxy group at C-2 and C-3′ positions of phenyl ring was favorable to the activity [36]; (2) phenyl ring at C-4 and C-6 positions of pyrimidine moiety was critical for the high activity, and replacement by methyl group led to significant loss of activity as evidenced by that hybrid 14 (IC₅₀: 43.00–46.45 μM, MTT assay) only showed moderate antiproliferative activity against Capan-1, DND-41, HL-60 and Z138 cancer cell lines [36–39].

Figure 3.

Chemical structures of pyrimidine–sulfonamide hybrids 13–21.

Aniline tethered pyrimidine–sulfonamide hybrid 15 (IC₅₀: 5.98–10.34 μM, MTT assay) was active against MDA-MB-468, MDA-MB-231 and MCF-7 breast cancer cell lines, and the SAR demonstrated that methoxy group at para-position of phenyl ring was beneficial for the activity [40]. Further studies showed that hybrid 15 (IC₅₀: 6.24 μM) was a potent inhibitor of family with sequence similarity 20, member C (Fam20C) and induced apoptosis via inhibition of the mitochondrial pathway and suppression of cell migration. In the MDA-MB-231 xenografted mice model, hybrid 15 (50 mg/kg, intragastric administration) reduced ∼70% tumor growth without affecting body weight of mice. Therefore, hybrid 15 could serve as a potent anti-breast cancer candidate and deserved further preclinical evaluations.

Further structural modification revealed that replacement of aniline at C-4 position of pyrimidine moiety by cycloalkylamino was permitted, and hybrid 16 (IC₅₀: 420–690 nM, MTT assay) was highly active against MCF-7, SKOV3 and MDA-MB-231 cancer cell lines [41]. In addition, hybrid 16 (IC₅₀: 8.0 nM) was also an excellent aurora kinase inhibitor and possessed acceptable pharmacokinetic properties with lower volume of distribution at stead state (V_dss: 1.93 l/kg), higher bioavailability (73%) along with good exposure (AUC: 1360 ngoh/ml) which correlated well with low clearance (CL: 55.1 ml/min/kg).

Thioether-containing pyrimidine–sulfonamide hybrid 17 (IC₅₀: 2.40–2.50 μM, MTT assay) showed excellent antiproliferative activity against MDA-MB-231, MCF-7 and T-47D breast cancer cell lines, and the activity was not inferior to that of 5-fluorouracil (IC₅₀: 2.46–6.70 μM) [42]. Additionally, hybrid 17 (K_i: 1.72 nM) was more potent than acetazolamide (K_i: 5.70 nM) in terms of inhibition of CA II. Mechanistically, hybrid 17 caused cell cycle arrest in G2/M phase with significant accumulation of cells in the pre-G1 phase and induced late apoptosis as well as necrotic cell death.

Indole-containing pyrimidine–sulfonamide hybrids 18a,b (IC₅₀: 160–250 nM, MTT assay) and 19 (IC₅₀: 170 and 200 nM) were highly potent against BaF3 cell lines with EGFR^{Del19/T790M/C797S} (KC-0116) and EGFR^{L858R/T790M/C797S} (KC-0122) mutations, and the activity was superior to that of brigatinib (IC₅₀: 350 and 450 nM) and osimertinib (IC₅₀: 1.42 and 1.44 μM) [43]. The SARs illustrated that (1) sulfonamide moiety was critical for the high activity, and piperidine fragment was favorable to the activity [43]; (2) movement of sulfonamide fragment from phenyl ring to N-1 position of indole moiety was tolerated, and hybrid 20 (IC₅₀: 1.71 and 26.03 nM, CellTiter-Glo assay assay) was more potent than osimertinib (IC₅₀: 18.21 and 795.2 nM) against H1975 and A431 cancer cell lines [44]; (3) replacement of indole fragment by 7-azaindole couldn't enhance the activity [45]. In particular, hybrid 18a (Os30, IC₅₀: 18 and 113 nM) was an excellent dual inhibitor of EGFR^{Del19/T790M/C797S} tyrosine kinase and EGFR^{L858R/T790M/C797S} tyrosine kinase [43]. Moreover, Os30 could suppress EGFR phosphorylation, cause cell cycle arrest at G1 phase and induce apoptosis [43]. In the KC-0116 xenografted mice model, Os30 (40 mg/kg, oral administration) suppressed 77.6% tumor growth without obvious impact on body weight, and the in vivo efficacy was comparable to that of brigatinib (TGI: 28.4 vs 36.8% at 10 mg/kg through oral administration) at the same condition. Collectively, Os30 was a highly potential candidate of the fourth-generation EGFR tyrosine kinase inhibitor to treat non-small cell lung cancer (NSCLC) with EGFR^C797S mutation.

The antiproliferative SARs of pyrrole-containing pyrimidine–sulfonamide hybrids 21 (IC₅₀: 0.034->10 μM, MTT assay) against H2228, Karpas299 and A549 cancer cell lines illustrated that sulfonamide moiety was critical for the high activity, and replacement by formamide led to loss of activity; amide and carboxylic acid at C-2 position of pyrrole fragment were more favorable than ester [46]; replacement of pyrrole by maleimide was permitted [47]. Among them, hybrids 21a–d (IC₅₀: 34–81 nM) exhibited pronounced antiproliferative activity against H2228 and Karpas299 cancer cell lines, and the activity was comparable to that of ceritinib (IC₅₀: 39 and 41 nM). Particularly, hybrid 21a (IC₅₀: 1.9 and 3.1 nM) was superior to ceritinib (IC₅₀: 2.4 and 7.6 nM) in inhibition of wide-type anaplastic lymphoma kinase (ALK) and ALK^L1196M mutant.

Pyrazole-containing pyrimidine–sulfonamide hybrids 22a,b (Figure 4; GI₅₀: 88–780 and 25–162 nM respectively, Sulforhodamine B/SRB assay) exhibited pronounced antiproliferative activity against MDA-MB-231, U937, MV4-11, H82, H460, HCT-116, U251, HT29, KM12, ES2, COLO205, OVCAR5, OAW28, OV90, COV318 and COV504 cancer cell lines [48], whereas pyrimidine–sulfonamide-3,5-dioxopyrazolidin-4-ylidene hybrid 23 (IC₅₀: 6.43–9.66 μM, MTT assay) was not inferior to doxorubicin (IC₅₀: 7.94 and 8.08 μM) and sorafenib (IC₅₀: 9.18 and 5.47 μM) against HepG2 and HCT-116 cancer cell lines [49]. The mechanistic studies demonstrated that hybrid 22a could reduce the phosphorylation of retinoblastoma at Ser807/811, cause cell cycle arrest at the G2/M phase and induce apoptosis. Moreover, hybrid 23 (IC₅₀: 140 nM) was comparable to sorafenib (IC₅₀: 100 nM) in terms of inhibition of VEGFR-2.

Figure 4.

Chemical structures of pyrimidine/pyrimidinone-sulfonamide hybrids 22–32.

Imidazole-containing pyrimidine–sulfonamide hybrid 24 (growth inhibition rates: 12.76–97.23% at 10 μM, SRB assay) possessed broad-spectrum antiproliferative activity against a panel of 60 cancer cell lines derived from leukemia, lung, colon, CNS, melanoma, ovarian, renal, prostate and breast [50], whereas hybrid 25 (IC₅₀: 900 nM, MTT assay) was superior to staurosporine (IC₅₀: 7.15 μM) against LOX-IMVI melanoma cells [51]. The antiproliferative SARs of benzimidazole-containing pyrimidine–sulfonamide hybrids 26 (IC₅₀: 1.85–20.45 μM, MTT assay) against SK-MEL-5 and A375 cancer cell lines illustrated that fluoro-containing substituent at para-position of phenyl ring as well as three-carbon linker between pyrimidine and sulfonamide moieties were beneficial for the activity [52]. Among them, the representative hybrids 26a,b (IC₅₀: 1.85–3.36 μM) were 2.6–4.5-times more potent than sorafenib (IC₅₀: 9.22 and 5.25 μM) against SK-MEL-5 and A375 cancer cell lines. Moreover, these two hybrids were potent dual inhibitors of BRAF^V600E (IC₅₀: 530 and 490 nM) and rapidly accelerated fibrosarcoma kinase isoform C (CRAF, IC₅₀: 980 and 840 nM), and the inhibitory effects were not inferior to that of sorafenib (IC₅₀: 814 and 910 nM).

Imidazo[2,1-b]thiazole-containing pyrimidine–sulfonamide hybrids 27a,b (mean GI₅₀: 3.07 and 2.72 μM, SRB assay) possessed broad-spectrum antiproliferative activity against a panel of 60 cancer cell lines, and the activity was not inferior to that of lapatinib (mean GI₅₀: 2.90 μM), nilotinib (mean GI₅₀: 2.90 μM), gefitinib (mean GI₅₀: 3.20 μM), erlotinib (mean GI₅₀: 5.50 μM) and imatinib (mean GI₅₀: 15.0 μM) [53]. In addition, these two hybrids (IC₅₀: 80 and 76 μM) displayed low cytotoxicity toward human embryonic pulmonary epithelial cells (L132), and both (IC₅₀: 21 and 35 nM) were comparable to vemurafenib (IC₅₀: 31 nM) in terms of inhibition of v-raf murine sarcoma viral oncogene homolog B1 (BRAF) V600E.

Pyrimidine–sulfonamide–diazepam hybrid 28 (IC₅₀: 6.99–8.98 μM, MTT assay) was comparable to doxorubicin (IC₅₀: 6.75–8.07 μM) and sorafenib (IC₅₀: 5.47–9.18 μM) against HepG2, HCT-116 and MCF-7 cancer cell lines, and the SAR indicated that methyl group on the pyrimidine moiety was beneficial for the activity [54]. Hybrid 28 (IC₅₀: 66.67 μM) displayed low cytotoxicity toward VERO cells, and SI values were 7.4–9.5, revealing its good selectivity profile. Moreover, hybrid 28 (IC₅₀: 100 nM) was equal to sorafenib (IC₅₀: 100 nM) in terms of inhibition of VEGFR-2.

Pyrimidinone–sulfonamide hybrid DG1 (29, IC₅₀: 960 and 710 nM, MTT assay) was 2.1 and 3.0 folds more potent than pemetrexed (IC₅₀: 2.07 and 2.13 μM) against A549 as well as H1975 NSCLC cell lines and displayed low cytotoxicity (IC₅₀: 136.16 and >600 μM) toward normal Beas-2b and HLMVEC cell lines [55]. Mechanistically, DG1 (IC₅₀: 17.21 nM) could bind directly to TS proteins intracellularly, inhibit lung cancer angiogenesis as well as induce apoptosis of A549 and H1975 cells by promoting caspase-3 activation. In the A549 xenografted mouse model, DG1 (80 mg/kg, intraperitoneal injection) reduced 65% tumor growth without loss of body weight, and the in vivo efficacy was superior to that of pemetrexed (TGI: 43%). Collectively, DG1 was a useful candidate for the development of novel anti-NSCLC chemotherapeutics.

Pyrimidinone–sulfonamide hybrid 30a (IC₅₀: 7.56 μM, SRB assay) was comparable to staurosporine (IC₅₀: 4.52 μM) against T-47D breast cancer cells, and hybrid 30b (IC₅₀: 2.45 and 6.86 μM) was not inferior to staurosporine (IC₅₀: 4.52 and 4.25 μM) against T-47D and MDA-MB-231 breast cancer cell lines [56]. The SAR demonstrated that incorporation of 1,2,3-triazole between sulfonamide and pyrimidinone moieties decreased the antiproliferative activity. Mechanistically, hybrids 30a,b could exert the antiproliferative activity through arresting T-47D cells mainly in the G2/M phase and inducing apoptosis.

Hybrids 31 (IC₅₀: 1.62–17.21 μM, MTT assay) showed considerable antiproliferative activity against A2780, HT-29, MCF-7 and HepG2 cancer cell lines, and the representative hybrids 31a–c (IC₅₀: 1.67–2.52 μM, 1.62–7.31 μM and 2.29–5.10 μM, respectively) were more potent than 5-fluorouracil (IC₅₀: 3.92–38.44 μM) against the tested cancer cell lines [57]. In addition, hybrids 31a–c (IC₅₀: 60.21, 70.61 and 71.66 μM, respectively) displayed low cytotoxicity toward normal WI-38 cells, and SI values were ranging from 9.6 to 38.5, suggesting their good selectivity profiles. Mechanistically, hybrid 31a induced cell growth arrest at different phases in different cancer cell lines through enhanced expression of cell cycle inhibitors p21 and p27 as well as stimulated the apoptotic death of all cancer cells.

Pyrimidinone-sulfonamide-1,3,4-oxadiazole hybrid 32 (IC₅₀: 0.78–2.06 μM, MTT assay) was more active than pemetrexed (IC₅₀: 3.29–6.96 μM) against A549, OVCAR-3, SGC7901, MCF-7 and HepG2 cancer cell lines and displayed relatively low cytotoxicity (IC₅₀: 15.42–22.60 μM) toward normal IOSE80, GES-1, MCF-10A and LO2 cell lines [58]. Additionally, hybrid 32 (IC₅₀: 110 nM) was more potent than pemetrexed (IC₅₀: 2.44 μM) in terms of inhibition of TS enzyme, and it induced apoptosis by the mitochondrial pathway. In the A549 xenografted mouse model, hybrid 32 (TGI: 87.36% at a dose of 80 mg/kg via intraperitoneal injection) was superior to that of pemetrexed (TGI: 60.47%) at the same condition and had little influence on body weight of mice. In the Lewis lung cancer (LLC) xenografted mouse model, hybrid 32 (80 mg/kg, intraperitoneal injection) prolonged the survival time of mice from 15.5 days to 45.5 days without significant hepatotoxicity or renal toxicity, while the survival time in pemetrexed treated group was 39.0 days. Taken together, hybrid 32 was a promising candidate for the clinical treatment of NSCLC and merited further preclinical evaluations.

Quinazoline/quinazolinone–sulfonamide hybrids

The antiproliferative SAR of quinazoline-sulfonamide hybrids 33 (Figure 5; IC₅₀: 0.36->50 μM, MTT assay) against MGC-803, HCT-116, PC-3 and MCF-7 cancer cell lines elucidated that sulfonamide and quinazoline moieties were vital for the high activity, and replacement by amide and phenyl ring led to loss of activity [59]. Among them, hybrids 33a,b (IC₅₀: 0.36–1.04 μM and 0.82–1.81 μM, respectively) were more potent than 5-fluorouracil (IC₅₀: 6.82–17.1 μM) against MGC-803, HCT-116, PC-3 and MCF-7 cancer cell lines. In particular, hybrid 33a (IC₅₀: 363–894 nM) was more sensitive to MGC-803, SGC-7901 and HGC-27 gastric cancer cell lines, and the activity was 10.3–18.7-times superior to that of 5-fluorouracil (IC₅₀: 3.88–10.18 μM). Mechanistically, hybrid 33a arrested cell cycle in the G2/M phase, induced intrinsic apoptosis, and inhibited cell colony formation in MGC-803 and SGC-7901 cells via activating the Hippo signaling pathway. In the MGC-803 xenografted mice model, hybrid 33a (TGI: ∼60% at a dose of 15 mg/kg by intraperitoneal injection) possessed higher in vivo efficacy than 5-fluorouracil (TGI: ∼50% at a dose of 15 mg/kg by intraperitoneal injection). Moreover, hybrid 33a didn't cause body weight loss, obvious damage in cell morphology or apparent toxicity to functions of liver or kidney, revealing its excellent safety profiles. Collectively, hybrid 33a was a promising anti-gastric cancer candidate and deserved further preclinical evaluations.

Figure 5.

Chemical structures of quinazoline/quinazolinone–sulfonamide hybrids 33–45.

Quinazoline–sulfonamide–isoxazole hybrid 34 (IC₅₀: 8.62 μM, MTT assay) was more potent than lapatinib (IC₅₀: 11.92 μM) against A549 cancer cells and displayed relatively low cytotoxicity (IC₅₀: 52.6 μM) toward normal WI-38 cells [60]. Moreover, hybrid 34 (IC₅₀: 190 nM) was a potent EGFR inhibitor and could cause cell cycle arrested in the G2/M phase as well as induce apoptosis. Hybrids 35a,b (IC₅₀: 1.94–6.54 μM and 5.67–7.86 μM respectively, MTT assay) and 36 (IC₅₀: 4.16–6.63 μM, MTT assay) exhibited potent antiproliferative activity against A431, A549 and H1975 cancer cell lines, and the activity was superior to that of gefitinib (IC₅₀: 8.37–19.95 μM) and erlotinib (IC₅₀: 11.85–16.43 μM) [61]. In addition, hybrid 35a was a dual EGFR and CAIX inhibitor and could arrest cell cycle in the G2/M phase as well as inhibit migration.

Quinazoline–urea–sulfonamide hybrids 37a,b (IC₅₀: 200 and 300 nM, CellTiterGlo^®3 assay) exhibited profound antiproliferative activity against MCF-7 cancer cells, and the two hybrids (IC₅₀: 3.4 and 18.2 nM against PI3Kα; 95.1 and 42.0 nM against mTOR) were excellent dual PI3Kα and mTOR inhibitors [62]. Hybrid 38 (IC₅₀: 2.54 and 4.14 μM, MTT assay) was comparable to 5-fluorouracil (IC₅₀: 2.46 and 6.70 μM) against MCF-7 and T-47D breast cancer cell lines, and it could arrest the MCF-7 cells at the G2/M phase, potentiate early apoptotic, late apoptotic as well as the necrotic stages [63]. 1,2,4-Triazolo[4,3-c]quinazoline-sulfonamide hybrids 39a,b (IC₅₀: 12.63–25.80 μM, MTT assay) were active against HepG2 and HCT-116 cancer cell lines, but the activity was lower than that of doxorubicin (IC₅₀: 7.94 and 8.07 μM) [64]. However, hybrid 39a exhibited considerable DNA-binding affinities, with an IC₅₀ value of 59.35 μM.

Quinazoline–pyridine–sulfonamide dimer 40 (IC₅₀: 180 and 200 nM, MTT assay) exhibited pronounced antiproliferative activity against HGC-27 and NCI-H1975 cancer cell lines and inhibited all four isoforms of class I PI3Ks with IC₅₀ values of 0.44–22.83 nM [65]. Mechanistically, hybrid 40 significantly blocked the PI3K signal pathway, induced cell cycle arrest in G1 phase, and inhibited colony formation as well as cell migration. In the MGC-803 xenografted mice model, hybrid 40 (40 mg/kg, intraperitoneal injection) showed superior in vivo efficacy with a TGI value as high as 61%, and no significant changes in body weight or severe adverse reactions were observed. Moreover, hybrid 40 (3.0 mg/kg, intravenous injection) displayed a reasonable half-life (t_1/2: 1.17 h) and good blood exposure (AUC_0-t: 4002 ngoh/ml), demonstrating its excellent pharmacokinetic properties.

Quinazolinone–sulfonamide hybrids 41a,b (IC₅₀: 1.34–2.98 and 2.53–4.59 μM respectively, MTT assay) were not inferior to erlotinib (IC₅₀: 2.08–4.27 μM) and doxorubicin (IC₅₀: 5.12–9.78 μM) against HepG2, HCT-116 and MCF-7 cancer cell lines and displayed low cytotoxicity (IC₅₀: 35.17 and 42.31 μM) toward normal MCF-10A cells [66]. Hybrid 42 showed promising antiproliferative activity (IC₅₀: 10.41–14.67 μM, MTT assay) against HepG2, HCT-116 and MCF-7 cancer cell lines and considerable inhibitory activity (IC₅₀: 9.7 μM) against VEGFR-2, and the activity was slightly lower than that of doxorubicin (IC₅₀: 4.17–5.23 μM against cancer cell lines) and sorafenib (IC₅₀: 3.40–5.30 μM against cancer cell lines; 2.4 μM against VEGFR-2) [67], whereas hybrids 43a,b (IC₅₀: 4.12–15.10 μM, MTT assay) were comparable to doxorubicin (IC₅₀: 8.90 and 9.34 μM) and erlotinib (IC₅₀: 10.17 and 12.40 μM) against HepG2 and MCF-7 cancer cell lines [68]. Thus, these hybrids could serve as lead compounds for further investigations.

Further structural modifications revealed that introduction of methoxy group into C-8 position of quinazolinone was tolerated, and hybrids 44a,b (IC₅₀: 4.2–6.5 μM, MTT assay) were not inferior to doxorubicin (IC₅₀: 1.3 and 1.1 μM) against Jurkat and THP-1 leukemia cells [69], whereas hybrid 44b (IC₅₀: 2.5–9.0 μM, MTT assay) was also comparable to doxorubicin (IC₅₀: 1.1–2.8 μM) against A549, HepG2, LoVo and MCF-7 cancer cell lines [70]. Mechanistically, hybrids 44a,b halted cell progression at the G2/M phase and induced apoptosis. In zebrafish embryos, hybrids 44a,b didn't show any toxicity even at the concentration of 50 μM, revealing their good safety profiles. Moreover, hybrids 44a,b perturbed the hematopoiesis process in developing zebrafish embryos. Overall, hybrids 44a,b could be used to explore novel antileukemic candidates.

Quinazolinone–sulfonamide–thiourea hybrids 45a,b (IC₅₀: 4.33 and 4.91 μM, MTT assay) were not inferior to doxorubicin (IC₅₀: 4.50 μM) and sorafenib (IC₅₀: 3.40 μM) against HepG2 cancer cells and exhibited potent inhibitory activities (IC₅₀: 3.1 and 3.4 μM) toward VEGFR-2 [71]. Mechanistically, hybrid 45a induced apoptosis and arrested the cell cycle growth at G2/M phase. In the diethylnitrosamine (DEN)-induced hepatocellular carcinoma (HCC) model, hybrid 45a (10 mg/kg, intraperitoneal injection) showed apoptotic changes in some hepatocytes, increased Kupffer cells, and the hepatic sinusoids were dilated in some areas, demonstrating its significant in vivo tumor growth inhibition.

Other fused pyrimidine–sulfonamide hybrids

Pyrazolo[1,5-a]pyrimidine–sulfonamide hybrid 46 (Figure 6; IC₅₀: 0.96 and 1.07 μM, MTT assay) exhibited excellent antiproliferative activity against MCF-7 and MDA-MB-468 breast cancer cell lines, and the activity was 9.5 and 6.0-times higher than that of staurosporine (IC₅₀: 9.20 and 6.46 μM) [72]. The SAR indicated that introduction of substituent into the phenyl ring at C-5 position of pyrazolo[1,5-a]pyrimidine moiety was detrimental to the activity. Mechanistically, hybrid 46 could disrupt the MCF-7 cell cycle through alteration of the sub-G1 phase, arrest of G2-M stage and induction of apoptosis. Pyrazolo[3,4-d]pyrimidine–sulfonamide hybrid 47 (IC₅₀: 1.58–5.58 μM, MTT assay) was more potent than centrinone (IC₅₀: 2.88–13.01 μM) against MCF-7, BT474 and MDA-MB-231 breast cancer cell lines and showed pronounced inhibitory effect (IC₅₀: 85 nM) against polo-likekinase 4 (PLK4) [73]. Moreover, hybrid 47 (IC₅₀: 30.21 μM) also displayed low cytotoxicity toward HUVECs. Pyridine-containing pyrazolo[3,4-d]pyrimidine–sulfonamide hybrid 48 (IC₅₀: 3.9 nM, MTT assay) was highly potent against TMD8 cancer cells, and it showed great inhibitory effect toward Bruton's tyrosine kinase (BTK, IC₅₀: 4.9 nM) [74].

Figure 6.

Chemical structures of fused pyrimidine–sulfonamide hybrids 46–60.

Pyrrolo[2,3d]pyrimidine–sulfonamide-pyrimidine hybrid 49 (IC₅₀: 8.25 μM, MTT assay) was more active than ribociclib (IC₅₀: 15.65 μM) against MIA PaCa-2 pancreatic cancer cells, and it was a potent inhibitor (IC₅₀: 150 nM) of cyclin dependent kinase 4 (CDK4) [75]. The SAR demonstrated that pyrimidine moiety at the terminal side was not essential for the activity, and hybrids 50a,b (IC₅₀: 450 and 940 nM, MTT assay) were 36.7- and 17.5-times superior to ribociclib (IC₅₀: 16.53 μM) against MIA PaCa-2 pancreatic cancer cells [76], whereas pyrrolo[2,3d]pyrimidine–sulfonamide hybrids 51a,b (IC₅₀: 3.17 and 2.71 μM, MTT assay) showed higher antiproliferative activity than acetazolamide (IC₅₀: 2.83 μM) against HeLa cervical cancer cells [77]. Mechanistically, hybrid 50a caused cell cycle arrest at G1 phase, blocked Rb phosphorylation and induced apoptosis via downregulation of CDK9 down-stream proteins Mcl-1 and c-Myc in MIA PaCa-2 cells, whereas hybrid 50a exerted antiproliferative activity via inhibition of transmembrane CAs. The pharmacokinetic studies demonstrated that hybrid 50a was absorbed into the circulation more rapidly (peak time/t_max: 0.5 h) and reached a slightly higher maximum plasma drug concentration (C_max: 1161 ng/mloh) than that of 50b (t_max: 1.17 h, C_max: 1080 ng/mloh) after oral dosing to rats, and elimination half-life (t_1/2) as well as mean retention time (MRT) of hybrid 50a were calculated as 7.54 and 7.72 h, respectively. In the MIA PaCa-2 xenografted mice model, hybrid 50a (60 mg/kg, oral administration) reduced 46% tumor growth, and no obvious pathological change was observed in main organs of mice.

Pyrrolo[2,3d]pyrimidine–sulfonamide-pyrimidine hybrid 52 (IC₅₀: 550 and 880 nM, MTT assay) was more active than TAE-226 (IC₅₀: 1.60 and 4.84 μM) against A549 and MDA-MB-231 cancer cell lines [78], and the SAR illustrated that movement of sulfonamide fragment from phenyl ring at C-2 position of pyrrolo[2,3d]pyrimidine moiety to phenyl ring at C-4 position was permitted as evidenced by that hybrids 53 (IC₅₀: 10.1–667.1 nM, CellTiterGlo^®3 assay) and 54a,b (IC₅₀: 11.4–370.4 nM and 15.5–713.3 nM) were highly potent against Ba/F3 (wide-type EGFR), A431, HCC827 (EGFR^Del19 single mutation), H1975 (EGFR^L858R/T790M double mutation), PC9 (EGFR^{Del19/T790M/C797S} triple mutation), H1975 (EGFR^{L858R/T790M/C797S} triple mutation) and Ba/F3 (EGFR^{Del19/T790M/C797S} triple mutation) cancer cell lines [79]. In addition, hybrids 53 and 54a,b demonstrated great inhibitory effects against EGFR^{L858R/T790M/C797S} (IC₅₀: 12.7, 4.9 and 4.7 nM) and EGFR^{Del19/T790M/C797S} (IC₅₀: 9.2, 4.0 and 4.2 nM) mutants. Moreover, hybrids 53 (75 mg/kg, oral administration) and 54b (75 mg/kg, oral administration) also possessed promising pharmacokinetic properties with t_max of 0.5 and 2.0 h, t_1/2 of 2.3 and 3.5 h, C_max of 6025.7 and 5480.5 ng/ml, AUC_0-24h of 34023.7 and 35816.0 ngoh/ml, and bioavailability of >100%. In the PC9 (Del19/T790M/C797S) xenografted mouse model, hydrochloride salts of hybrids 53 (TGI: ∼70% at a dose of 50 mg/kg via oral administration) and 54b (TGI: ∼60% at a dose of 50 mg/kg via oral administration) significantly inhibited the tumor growth without any body weight loss or other clinical signs. Therefore, hydrochloride salts of hybrids 53 and 54b were worthy of further preclinical evaluations.

Pteridin-7(8H)-one-sulfonamide hybrid 55 (IC₅₀: 0.39–2.53 μM, MTT assay) exhibited excellent antiproliferative activity against HCT-116, HeLa, MDA-MB-231, and HT-29 cancer cell lines, and the activity was superior to that of palbociclib (IC₅₀: 2.69–13.30 μM) [80]. In addition, hybrid 55 (IC₅₀: 34.0 and 65.1 nM) also possessed potent inhibitory activity against CDK4/cyclin D3 as well as CDK6/cyclin D3 and could cause cell cycle arrest at G2/M phase and induce apoptosis. Purine–sulfonamide hybrid 56 (IC₅₀: 11.2 μM, MTT assay) was more potent than R-roscovitine (IC₅₀: 24.1 μM) against MDA-MB-231 breast cancer cells and was non-toxic (IC₅₀: >100 μM) toward normal 293T cells [81]. Moreover, hybrid 56 (IC₅₀: 19 nM) was also a promising CDK2 inhibitor, and the inhibitory activity was superior to that of R-roscovitine (IC₅₀: 73 nM).

Furo[2,3d]pyrimidin-4(3H)-one-sulfonamide hybrids 57a,b (IC₅₀: 0.3–2.1 and 0.5–4.6 μM respectively, MTT assay) were comparable to SGI-1027 (IC₅₀: 0.6–8.9 μM) against THP-1, HCT-116, U937, K562, A549, DU145 cancer cell lines [82]. In addition, hybrids 57a,b (IC₅₀: 91.0 and 130.8 μM) displayed low cytotoxicity toward peripheral blood mononuclear cells, and SI values were 43.3–303.3 and 28.4–261.6 respectively, revealing their excellent selectivity profiles. Moreover, hybrids 57a,b (IC₅₀: 0.39 and 0.75 nM) showed profound inhibitory activity against DNA methyltransferase 3A (DNMT3A) and were worthy of further investigations.

Thieno[2,3d]pyrimidine–sulfonamide hybrid 58 (IC₅₀: 6.17 and 8.68 μM, MTT assay) possessed potent antiproliferative activity against MCF-7 and MDA-MB-231 breast cancer cell lines, and the activity was not inferior to that of doxorubicin (IC₅₀: 1.6 and 2.2 μM) [83]. In addition, hybrid 58 (IC₅₀: 277.05 μM) displayed low cytotoxicity toward normal MCF-10A breast cells, and SI values were 173.1 and 125.9, revealing its good selectivity profiles. Moreover, hybrid 58 significantly increased the population of late apoptotic cells as well as necrotic cells and merited further evaluations.

Thieno[2,3d]pyrimidine–sulfonamide hybrids 59 (IC₅₀: 0.28–2.3 μM, MTT assay) and thiazolo[5,4-d]pyrimidine–sulfonamide hybrids 60 (IC₅₀: 0.040–1.2 μM, MTT assay) exhibited decent antiproliferative activity against HGC-27 cancer cells, and the SAR indicated that six-membered cycloalkylamino group on the pyrimidine moiety was beneficial for the activity [84]. Among them, hybrids 59a,b (IC₅₀: 390 and 280 nM) and 60a–c (IC₅₀: 40, 47 and 74 nM) not only demonstrated pronounced antiproliferative activity against HGC-27 cancer cells, but also possessed great inhibitory effects against PI3Kα with IC₅₀ values ranging from 1.7 to 7.2 nM. Mechanistically, hybrids 59a and 60a strongly suppressed phosphorylation of the PI3K downstream effectors and arrested cell cycle at the G0/G1 phase. After oral dose of 40 mg/kg, both hybrids 59a and 60a showed promising pharmacokinetic properties with t_1/2 of 13.7 and 6.3 h, C_max of 22.5 and 9.61 μg/ml, AUC_0-∞ of 187 and 142 h·μg/ml, and oral bioavailability of 99.5 and 54.5%, respectively. In the HGC-27 xenografted mice model, hybrids 59a (40 mg/kg, oral administration) and 60a (40 mg/kg, oral administration) also proved potent in vivo efficacy with TGI values of 58.2 and 88.7%, respectively. Collectively, hybrids 59a and 60a could serve as promising candidates for gastric cancer therapy.

Conclusion

Great achievements have been made in cancer therapy in recent decades, but cancer still represents as one of the most common and life-threatening diseases. Chemotherapeutics usually suffer from severe toxicity and drug resistance, resulting in a grave need to develop novel anticancer agents. Pyrimidine and sulfonamide derivatives exhibited promising in vitro and in vivo potential against various cancers via different modes of mechanism, revealing that pyrimidine and sulfonamide are useful anticancer pharmacophores. Accordingly, rational hybridization of pyrimidine with sulfonamide may provide promising hybrids for clinical deployment in the control and eradication of cancers.

Recently, a variety of pyrimidine–sulfonamide hybrids have been designed, synthesized and evaluated for their in vitro antiproliferative and/or in vivo anticancer efficacies. Among them, hybrids 10a–c, 11a,b, 13, 16, 18a,b, 19, 20, 21a–d, 22a,b, 25, 29, 37a,b, 40, 48, 50a,b, 52, 53, 54, 59a,b and 60a–c with IC₅₀ or GI₅₀ values in nanomolar levels were highly potent against the tested cancer cell lines, whereas hybrids 1a, 2, 15, 18a, 29, 32, 33a, 40, 45a, 50a, 53, 54b, 59a and 60a possessed excellent in vivo anticancer efficacy, demonstrating that their potential in the treatment of cancers. From the above results, it can be concluded that rational hybridization of pyrimidine with sulfonamide is a promising strategy to provide novel anticancer candidates; incorporation of sulfonamide moiety into C-2 position of pyrimidine skeleton without linker is tolerated; introduction of the linker between pyrimidine and sulfonamide moieties is permitted, and the nature of the linker influenced the activity remarkably: alkyl, alkylamino, urea, pyridine and indole can be used as linkers, and aniline is the most favorable linker.

Future perspective

The future work can focus on the following issues: rational design of the linker between pyrimidine and sulfonamide moieties; introduction of the third anticancer pharmacophore if necessary; further preclinical evaluations of the current available pyrimidine–sulfonamide hybrids with profound in vitro antiproliferative activity and/or promising in vivo anticancer efficiency to provide more promising candidates for clinical applications.

Financial disclosure

The authors have no financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Competing interests disclosure

The authors have no competing interests or relevant affiliations with any organization or entity with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

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