Novel 2-(5-Aryl-4,5-Dihydropyrazol-1-yl)thiazol-4-One as EGFR Inhibitors: Synthesis, Biological Assessment and Molecular Docking Insights

Abstract

Introduction: Epidermal growth factor receptor (EGFR) regulates several cell functions which include cell growth, survival, multiplication, differentiation, and apoptosis. Currently, EGFR kinase inhibitors are of increasing interest as promising targeted antitumor therapeutic agents.

Methods: Different thiazolyl-pyrazoline derivatives (7a-o) were synthesized and were first tested for anti-proliferative effect towards the A549 lung cancer cell line and the T-47D breast cancer cell line in MTT assay. Thereafter, thiazolyl-pyrazolines (7b, 7g, 7l, and 7m) were subsequently evaluated for their PK inhibition for EGFR. Moreover, representative promising derivatives (7g and 7m) in cytotoxic and PK inhibition assays were tested to investigate their impact on the apoptosis and cell cycle phases in T-47D cells in order to explore more insights into the antitumor actions of the target thiazolyl-pyrazolines. Furthermore, docking studies were accomplished to evaluate the patterns of binding of thiazolyl-pyrazolines 7b, 7g, 7l, and 7m in the EGFR active pocket (PDB ID: 1M17).

Results: Testing the thiazolyl pyrazoline compounds 7a-o on A549 and T-47D cell lines showed IC₅₀ arrays between 3.92 and 89.03 µM, and between 0.75 and 77.10 µM, respectively. Also, the tested thiazolyl-pyrazolines (7b, 7g, 7l, and 7m) demonstrated significant sub-micromolar EGFR inhibitory actions with IC₅₀ values 83, 262, 171 and 305 nM, respectively, in comparison to erlotinib (IC₅₀ =57 nM).

Discussion: Generally, it was observed that the tested thiazolyl pyrazolines showed more potent antiproliferative activity toward breast cancer cells T-47D than toward lung cancer cell lines A549. In particular, thiazolyl pyrazolines 7g and 7m showed the best activity against A549 cells (IC₅₀ = 3.92 and 6.53 µM) and T-47D cells (IC₅₀ = 0.88 and 0.75 µM). Compounds 7g and 7m provoked a sub-G1 phase arrest and cell apoptosis which are in agreement with the expected outcome of EGFR inhibition. Finally, the molecular docking of 7g and 7m in the active site of EGFR revealed a common binding pattern similar to that of erlotinib which involves the accommodation of the 1,3 thiazol-4-one ring and pyrazoline ring of target compounds in the binding region of erlotinib's quinazoline ring and anilino moiety.

Keywords: EGFR inhibitors; antitumor; breast cancer; lung cancer; molecular docking; pyrazolo.

Figure 1

Structures of certain pyrazoline- and/or thiazole-bearing small molecules (I–X) endowed with anticancer and kinases inhibitory activities.

Figure 2

Design of the target thiazolyl pyrazolines 7a-o, based on the structure of compounds IV, V, VII and X.

Figure 3

Pro-apoptotic effect of thiazolyl pyrazolines 7g and 7m toward breast cancer cells T-47D.

Scheme 1

Preparation of key thiazolyl-pyrazolines 7a-o products; Reagents and conditions: (i) 40% NaOH, 95% ethanol, stirring R.T. 8 hr; (ii) NaOH, ethanol, reflux 2 hr; (iii) Ethyl bromoacetate, absolute ethyl alcohol, reflux 4 hr; (iv) Glacial acetic acid, sodium acetate, reflux 5 hr.

Figure 4

2D diagram of thiazolyl pyrazoline 7b in the binding site of EGFR.

Figure 5

2D diagram for thiazolyl pyrazoline 7g in the binding site of EGFR.

Figure 6

2D diagram of thiazolyl pyrazoline 7l in the binding site of EGFR.

Figure 7

2D diagram of thiazolyl pyrazoline 7m in the EGFR binding site.