Design, synthesis, in silico studies, and apoptotic antiproliferative activity of novel thiazole-2-acetamide derivatives as tubulin polymerization inhibitors

Abstract

Introduction: Tubulin polymerization inhibitors have emerged as interesting anticancer therapies. We present the design, synthesis, and structural elucidation of novel thiazole-based derivatives to identify novel tubulin inhibitors with potent antiproliferative efficacy and strong inhibition of tubulin polymerization.

Methods: The novel compounds consist of two scaffolds. Scaffold A compounds 10a-e and scaffold B compounds 13a-e. the structures of the newly synthesized compounds 10a-e and 13a-e were validated using ¹H NMR, ¹³C NMR, and elemental analysis.

Results and discussion: The most effective antitubulin derivative was 10a, exhibiting an IC₅₀ value of 2.69 μM. Subsequently, 10o and 13d exhibited IC₅₀ values of 3.62 μM and 3.68 μM, respectively. These compounds exhibited more potency than the reference combretastatin A-4, which displayed an IC₅₀ value of 8.33 μM. These compounds had no cytotoxic effects on normal cells, preserving over 85% cell viability at 50 μM. The antiproliferative experiment demonstrated that compounds 10a, 10o, and 13d displayed significant activity against four cancer cell lines, with average GI₅₀ values of 6, 7, and 8 μM, equivalent to the reference's doxorubicin and sorafenib. Compounds 10a, 10o, and 13d were demonstrated to activate caspases 3, 9, and Bax, while down-regulating the anti-apoptotic protein Bcl2. Molecular docking studies demonstrated superior binding affinities for 10a (-7.3 kcal/mol) at the colchicine binding site of tubulin, forming key hydrophobic and hydrogen bonding interactions that enhance its activity. ADMET analysis confirmed favorable drug-like properties, establishing these compounds as promising candidates for further development as anticancer agents targeting tubulin polymerization.

Keywords: CA-4; antiproliferative; cell viability; colchicine; docking; tubulin.

FIGURE 1

Structures of Dasatinib, thia-netropsin, and Alpelisib.

FIGURE 2

Structures of compound IV and CA-4 (V).

FIGURE 3

Structures of previously reported compound IV and new compounds 10a-o and 13a-e.

SCHEME 1

Synthesis of the chalcone intermediates 5a–e. Reagents and Reaction conditions: (i) SO₂Cl₂, toluene, 0°C, 12 h; (ii) NH₃, CS₂, EtOH, RT, 6 h; (iii) appropriate aromatic aldehyde, 60% NaOH, EtOH, 0°C, 18 h.

SCHEME 2

Synthesis of the key intermediates 9a-c. Reagents and Reaction conditions: (iv) NBS, PTSA. H₂O, acetonitrile, reflux, 10 h; (v) thiourea, Na₂CO₃, EtOH, reflux, 5 h; (vi) Chloroacetyl chloride, DCM, Na₂CO₃, H₂O, 0°C, 12 h.

SCHEME 3

Synthesis of the target compounds 10a-o and 13a-e. Reagents and Reaction conditions: (vi) Chloroacetyl chloride, DCM, Na₂CO₃, H₂O, 0°C, 12 h; (vii) Na₂CO₃, NaI, acetone, RT, 6 h.

FIGURE 4

Superimposition of redocked (brown) and co-crystallized (green) poses of CA-4 in the colchicine binding site (RMSD = 0.4994 Å).

FIGURE 5

(A) 2D interaction diagram and (B) 3D binding mode of CA‐4 within the colchicine binding site.

FIGURE 6

(A) 2D interaction diagram and (B) 3D binding mode of 10a within the colchicine binding site.

FIGURE 7

(A) 2D interaction diagram and (B) 3D binding mode of 13d within the colchicine binding site.

FIGURE 8

Bioavailability radar of 10a as retrieved from SwissADME server.