Design, synthesis and evaluation of 2, 6, 8-substituted Imidazopyridine derivatives as potent PI3Kα inhibitors

Figures & data

Figure 1. Representative structures of reported PI3K inhibitors.

Figure 2. The design of novel Imidazo[1,2-a]pyridine derivatives based on PIK-75.

Scheme 1. Reagents and conditions: (i) substituted benzene-1-sulfonyl chloride, pyridine, room temperature, overnight; (ii) (BPin)₂, PdCl₂(dppf), KOAc, dioxane, 100 °C, 8 h; (iii) NBS, CH₃CN, 0 °C, 4 h; (iv) ethyl bromopyruvate, EtOH, 80 °C, 4 h; (v) NaOH, EtOH, 80 °C, 3 h; (vi) amines, HBTU, Et₃N, DMF, rt, overnight; (vii) aryl boronic acid or 9a-c, Pd(PPh₃)₄, K₂CO₃, 1,4-Dioxane/H₂O, 100 °C, overnight.

Table 1. In vitro enzyme inhibitory activity of target compounds on PI3Kα at 10 μM.

Compd.	R1	-NR2R3	Ar	% Inhibition at 10 μM^a
15	-CH3			31.9 ± 2.9
16	-CH3			38.2 ± 3.6
17	-CH3			14.1 ± 2.7
18	-CH3			47.6 ± 3.9
19	-CH3			58.5 ± 1.6
20	-CH3			30.2 ± 2.1
21	-CH3			39.9 ± 3.0
22	-CH3			33.3 ± 4.2
23	-CH3			43.9 ± 1.8
24	-CH3			29.6 ± 2.1
25	-CH3			44.3 ± 1.5
26	-CH3			57.9 ± 4.6
27	-CH3			60.9 ± 6.0
28	-CH3			66.1 ± 4.4
29	-CH3			30.4 ± 3.1
30	-CH3			9.3 ± 1.7
31	-CH3			28.5 ± 1.6
32	-CH3			50.6 ± 0.9
33	-CH3			44.5 ± 1.2
34	-CH3			49.8 ± 1.6
35	-CH3			98.6 ± 0.4
36	-CH3			85.1 ± 2.2
37	-CH3			67.5 ± 0.3
38	-CH3			81.6 ± 2.8
39	-CH3			70.2 ± 3.6
40	-CH3			90.1 ± 4.0
41	-CH3			75.7 ± 2.9
42	-CH3			69.2 ± 6.4
43	-CH3			62.8 ± 4.6
44	-CH3			53.4 ± 5.1
45	-Cl			59.8 ± 3.5
46	-H			40.2 ± 3.0
PIK-75^b				98.2 ± 1.6

^aData presented is the mean ± SD value of three independent determinations.

^bUsed as positive control.

Figure 3. SAR of compound 35 represented in diagram.

Table 2. Enzymatic and cellular effects of compounds against PI3Kα and five Human Cancer Cells.

Compound	IC50 in μM^a
	PI3Kα	SKOV-3	T47D	NCI-H1975	NCI-H460	MCF-7
35	0.15 ± 0.02	26.6 ± 1.3	7.9 ± 0.8	32.1 ± 2.4	17.7 ± 2.0	9.4 ± 0.6
36	1.12 ± 0.15	35.3 ± 4.2	15.9 ± 1.5	>50	30.2 ± 3.1	8.1 ± 0.8
40	0.50 ± 0.11	25.5 ± 3.9	12.5 ± 1.8	41.4 ± 3.4	21.8 ± 1.9	7.6 ± 0.5
Alpelisib^b	0.0074 ± 0.0021	9.7 ± 0.7	0.46 ± 0.05	2.7 ± 0.2	8.9 ± 0.7	2.2 ± 0.3

^aIC₅₀ values were determined after exposure of cells to derivatives for 72 h, and data are expressed as the mean ± SD of two independent experiments; ^bUsed as a positive control.

Figure 4. Compound 35 induces S cell cycle arrest and apoptosis in T47D cells. Exponentially growing cells were exposed to DMSO or indicated concentration of compound 35 for 24 h in T47D cells.

Table 3. In Vitro ADME properties for compound 35.

Metabolic stability^a
Species		T1/2 (min)		CL int (μL/min/mg)			Remaining (T = 60min)
RLM		31.9		43.4			31.5%
HLM		45.1		30.7			42.7%
Permeability assay^b
Egg-PAMPA		Mean Pe (nm/s)		Incubation Time (h)			Permeability
–		15.4		4			High
CYP450 inhibition^c
isozyme	CYP1A2		CYP2D6		CYP2C9	CYP2C19		CYP3A4
% inhibition	9.8		13.5		30.6	25.9		42.6

^aTestosterone and Diclofenac were used at positive control. ^bThe permeability assay was Performed at 10 μM concentration. High permeability: Pe > 10.0 nm/s. ^cPerformed at 10 μM concentration. α-Naphthoflavone (CYP1A2), Squinidine (CYP2D6), (+)-N-3-benzylnirvanol (CYP2C19), Quinidine (CYP2D6), and ketoconazole (CYP3A4) were used as the positive controls.

Figure 5. (A) Proposed binding mode of compound 35 to PI3Kα (4JPS). Hydrogen bonds are indicated by yellow dashed lines, and hydrophobic interactions are indicated in wheat lines. Images are generated using PyMol. (B) The overlay of compound 35 with PIK-75 in PI3Kα (4JPS). (C) Dynamics of compound 35 bound to FLT3 PI3Kα (4JPS) during 90 ns simulation time.