IONIZABLE LIPID COMPOUND FOR NUCLEIC ACID DELIVERY AND LNP COMPOSITION THEREOF

Abstract

Provided are an ionizable lipid compound of formula I for nucleic acid delivery and an LNP composition thereof, which can efficiency and stably deliver a biologically active substance to a target cell or an organ. The mRNA LNP prepared by using the lipid compound as a cationic lipid has better stability and transfection efficiency, and can cause a higher specific antibody response in an experimental animal body.

##STR00001##

Claims

1-23. (canceled)

24. A lipid compound having a structure of formula I below; ##STR00037## wherein, at least one of L.sub.1 and L.sub.2 is O(C?O)O or NRa, and the other one of L.sub.1 or L.sub.2 is O, O(C?O)O, (C?O) NRa, NRa(C?O), NRa, O(C?O), (C?O)O, C(?O), S(O) x-, SS, C(?O)S, SC(?O), NRaC(?O) NRa, OC(?O) NRa, or NRaC(?O)O; G.sub.1 and G.sub.2 are each independently unsubstituted C.sub.1-C.sub.12 alkylene or C.sub.1-C.sub.12 alkenylene; G.sub.3 is C.sub.1-C.sub.24 alkylene, C.sub.1-C.sub.24 alkenylene, C.sub.3-C.sub.8 cycloalkylene, or C.sub.3-C.sub.8 cycloalkenylene; Ra is H or C.sub.1-C.sub.12 hydrocarbyl; R.sub.1 and R.sub.2 are each independently C.sub.6-C.sub.24 alkyl or C.sub.6-C.sub.24 alkenyl; R.sub.3 is H, OH, OR.sub.4, CN, C(?O) OR.sub.4, OC(?O) R.sub.4, or NR.sub.5C(?O) R.sub.4; R.sub.4 is C.sub.1-C.sub.12 hydrocarbyl; R.sub.5 is H or C.sub.1-C.sub.6 hydrocarbyl; x is 0, 1 or 2.

25. The lipid compound according to claim 24, wherein L.sub.1 and L.sub.2 are each independently selected from O(C?O)O and NH.

26. The lipid compound according to claim 24, wherein L.sub.1 and L.sub.2 are O(C?O)O, or L.sub.1 and L.sub.2 are NH.

27. The lipid compound according to claim 24, having the following structure (IA); ##STR00038## wherein, R.sub.6 is independently H, OH, or C.sub.1-C.sub.24 hydrocarbyl at each occurrence; n is an integer of 1 to 15.

28. The lipid compound according to claim 27, having the following structure (IB); ##STR00039## wherein y and z are each independently an integer of 1 to 12.

29. The lipid compound according to claim 28, wherein n is an integer of 2 to 12; wherein y and z are each independently an integer of 2 to 10.

30. The lipid compound according to claim 24, wherein R.sub.1 and R.sub.2 each independently have the following structure: ##STR00040## wherein, R.sub.7a and R.sub.7b are independently H or C.sub.1-C.sub.12 hydrocarbyl at each occurrence; and a is an integer of 2 to 12; wherein R.sub.7a, R.sub.7b and a are each selected such that R.sub.1 and R.sub.2 each independently comprise 6 to 20 carbon atoms.

31. The lipid compound according to claim 30, wherein R.sub.7a with at least one occurrence is H.

32. The lipid compound according to claim 30, wherein R.sub.7b with at least one occurrence is C.sub.1-C.sub.8 hydrocarbyl.

33. The lipid compound according to claim 30, wherein R.sub.1 or R.sub.2 or both have one of the following structures; ##STR00041##

34. The lipid compound according to claim 24, having the following structure; ##STR00042##

35. A delivery system, wherein the delivery system comprises a bioactive substance and the lipid compound according to claim 24.

36. The delivery system according to claim 35, wherein the bioactive substance is DNA or RNA, and the RNA is selected from an antisense RNA, a saRNA, a mRNA, a lncRNA, a miRNA, a siRNA, a piRNA, a gRNA, and a tsRNA.

37. The delivery system according to claim 35, wherein the delivery system is a mRNA vaccine.

38. The delivery system according to claim 37, wherein the vaccine is a vaccine for preventing cancer, virus infection, bacterial infection, and fungal infection.

39. The delivery system according to claim 38, wherein the virus is selected from; norovirus, Ebola virus, coronavirus, cytomegalovirus, Dengue virus, Zika virus, coxsackievirus, enterovirus, hepatitis virus, herpes simplex virus, human papilloma virus, influenza virus, Marburg virus, measles virus, poliovirus, rabies virus, rotavirus, and measles virus.

40. The delivery system according to claim 39, wherein the virus is SARS-COV-2.

41. A lipid nanoparticle, wherein the lipid nanoparticle comprises a bioactive substance and the lipid compound according to claim 24.

42. The lipid nanoparticle according to claim 41, wherein the lipid nanoparticle further comprises a polyethylene glycol lipid, a steroidal lipid, and a neutral lipid.

43. The lipid nanoparticle according to claim 42, wherein the polyethylene glycol lipid is selected from: 2-[(polyethylene glycol)-2000]N,N-ditetradecylacetamide (ALC-0159), 1,2-dimyristoyl-sn-glyceromethoxypolyethylene glycol (PEG-DMG), 1,2-distearyl-sn-glycero-3-phosphoethanolamine-N-[amino(polyethylene glycol)] (PEG-DSPE), PEG-disterol glycerol (PEG-DSG), PEG-dipalmitoyl, PEG-dioleyl, PEG-distearyl, PEG-diacylglycerol amide (PEG-DAG), PEG-dipalmitoyl phosphatidylethanolamine (PEG-DPPE), and PEG-1,2-dimyristoylacyloxypropyl-3-amine (PEG-c-DMA); and/or, the neutral lipid is selected from: 1,2-distearoyl-sn-glycerol-3-phosphocholine (DSPC), 1,2-dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC), 1,2-dioleoyl-sn-glycerol-3-phosphoethanolamine (DOPE), 1,2-dipalmitoyl-sn-glycerol-3-phosphoethanolamine (DPPE), 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine (DMPE), 2-dioleoyl-sn-glycero-3-phospho-(1-rac-glycerol) (DOPG), oleoyl phosphatidylcholine (POPC), and 1-palmitoyl-2-oleoyl phosphatidylethanolamine (POPE); and/or, the steroid lipid is selected from: avenasterol, ?-sitosterol, brassicasterol, ergocalciferol, campesterol, cholestanol, cholesterol, coprosterol, dehydrocholesterol, desmosterol, dihydroergocalciferol, dihydrocholesterol, dihydroergosterol, campesterol, epicholesterol, ergosterol, fucosterol, hexahydrosterol, hydroxycholesterol, lanosterol, photosterol, fucosterol, sitostanol, sitosterol, stigmastanol, stigmasterol, cholic acid, glycocholic acid, taurocholic acid, deoxycholic acid, and lithocholic acid.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0074] FIG. 1 shows a Zeta potential detection spectrum of sample 1.

[0075] FIG. 2 shows a Zeta potential detection spectrum of sample 2.

[0076] FIG. 3 shows a Zeta potential detection spectrum of sample 3.

[0077] FIG. 4 shows a Zeta potential detection spectrum of sample 4.

[0078] FIG. 5 shows a Zeta potential detection spectrum of sample 5.

[0079] FIG. 6 shows a Zeta potential detection spectrum of sample 6.

[0080] FIG. 7 shows a Zeta potential detection spectrum of sample 7.

[0081] FIG. 8 shows a Zeta potential detection spectrum of sample 8.

[0082] FIG. 9 shows a Zeta potential detection spectrum of sample 9.

[0083] FIG. 10 shows a Zeta potential detection spectrum of sample 10.

[0084] FIG. 11 shows a Zeta potential detection spectrum of sample 11.

[0085] FIG. 12 shows a Zeta potential detection spectrum of sample 12.

[0086] FIG. 13 shows an average particle size detection spectrum of sample 1.

[0087] FIG. 14 shows an average particle size detection spectrum of sample 2.

[0088] FIG. 15 shows an average particle size detection spectrum of sample 3.

[0089] FIG. 16 shows an average particle size detection spectrum of sample 4.

[0090] FIG. 17 shows an average particle size detection spectrum of sample 5.

[0091] FIG. 18 shows an average particle size detection spectrum of sample 6.

[0092] FIG. 19 shows an average particle size detection spectrum of sample 7.

[0093] FIG. 20 shows an average particle size detection spectrum of sample 8.

[0094] FIG. 21 shows an average particle size detection spectrum of sample 9.

[0095] FIG. 22 shows an average particle size detection spectrum of sample 10.

[0096] FIG. 23 shows an average particle size detection spectrum of sample 11.

[0097] FIG. 24 shows an average particle size detection spectrum of sample 12.

[0098] FIG. 25 shows the encapsulation efficiency of LNP-mRNA prepared from different cationic lipids.

[0099] FIG. 26 shows the average particle size of LNP-mRNA prepared from different cationic lipids.

[0100] FIG. 27 shows the PDI of LNP-mRNA prepared from different cationic lipids.

[0101] FIG. 28 shows the in-vitro expression results of LNP-mRNA prepared from different cationic lipids.

[0102] FIG. 29 shows S protein specific antibody titers (LOG values) after 14 days of primary immunization. Data significance is analyzed by multiple comparisons using a graph-based approach.

[0103] FIG. 30 shows S protein specific antibody titers (LOG values) after 14 days of secondary immunization. Data significance is analyzed by multiple comparisons using a graph-based approach.

[0104] FIG. 31 shows the inhibition rates of 4 sets of mixed samples diluted with different multiples detected by an original strain RBD protein after 14 days of secondary immunization. The protein for ELISA assay plate is ACE2-Fc, while the competitive protein is RBD protein of the original strain.

[0105] FIG. 32 shows the inhibition rates of 4 sets of mixed samples diluted with different multiples detected by Beta variant RBD protein after 14 days of secondary immunization. The protein for ELISA assay plate is ACE2-Fc, while the competitive protein is RBD protein of the Beta variant.

[0106] FIG. 33 shows intracellular cytokine staining (ICS) method for detecting specific CD8+ T cell immune response. N is a negative control group. ns means that no significant difference is found after multiple comparison analysis using a basis method, and **** means that p value is less than 0.0001.

[0107] FIG. 34 shows the detection of specific CD4+ T cell immune response using ICS method. N is a negative control group. ns means that no significant difference is found after multiple comparison analysis using a basis method.

DETAILED DESCRIPTION

[0108] Technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the drawings. It is apparent that the described embodiments are only a part of the embodiments of the present invention, but not all of them. Based on the examples of the present invention, all other examples obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

[0109] The term nucleic acid described herein refers to a polymer containing at least two deoxyribonucleotides or ribonucleotides in either single- or double-stranded form and includes DNA, RNA, and hybrids thereof.

[0110] The term lipid described herein refers to a group of organic compounds that include, but are not limited to, esters of fatty acids and are generally characterized by being poorly soluble in water, but soluble in many organic solvents.

[0111] The term cationic lipid described herein refers to a lipid molecule capable of being positively charged.

[0112] The term neutral lipid described herein refers to an uncharged, non-phosphoglyceride lipid molecule.

[0113] The term polyethylene glycol lipid described herein refers to a molecule comprising a lipid portion and a polyethylene glycol portion.

[0114] The term lipid nanoparticle described herein refers to a particle having at least one nanoscale dimension, which comprises at least one lipid.

[0115] The term vaccine described herein refers to a composition suitable for application to an animal (including a human), which induces an immune response after administration with a strength sufficient to help prevent, improve, or cure clinical diseases caused by microbial infections as a minimum.

[0116] The term delivery system described herein refers to a formulation or composition that regulates the spatial, temporal and dose distribution of a biologically active ingredient in an organism.

Example 1: Synthesis of Compound 1

[0117] ##STR00009##

Synthesis of 6-Bromohexyl(2-Hexyldecyl) Carbonate (1a)

[0118] ##STR00010##

[0119] 6-bromohexanol (0.91 g, 5.0 mmol) was dissolved in 30 mL of dichloromethane, 4-dimethylaminopyridine (0.90 g. 7.5 mmol) was added, and 4-nitrophenyl chloroformate (1.20 g. 6.0 mmol) was further added in portions. The resulting mixture was stirred and reacted at room temperature for 3 h, 2-hexyldecanol (1.36 g, 5.6 mmol) was added to the reaction solution, and the mixture was stirred at room temperature overnight. After the reaction was completed as detected by TLC, 20 mL of dichloromethane was added for dilution, and then the reaction solution was washed with 30 mL of saturated brine. The organic phase was dried over anhydrous sodium sulfate, filtered and concentrated, and the residue was separated by column chromatography to give 6-bromohexyl(2-hexyldecyl) carbonate 1a (1.53 g, light yellow oil) in a yield of 68%.

[0120] MS m/z (ESI): 449.3[M+1].

Synthesis of Compound 1

[0121] ##STR00011##

[0122] 6-bromohexyl(2-hexyldecyl) carbonate (1.12 g, 2.5 mmol) was dissolved in tetrahydrofuran, then acetonitrile, 4-amino-1-butanol (89.2 mg, 1.0 mmol), potassium carbonate (550 mg, 4.0 mmol), and potassium iodide (332 mg, 2.0 mmol) were added, and the resulting mixture was stirred at 83? C. for 16-20 h. The reaction solution was cooled to room temperature, and filtered, the filter residue was washed with dichloromethane, and a saturated sodium bicarbonate solution was added to the obtained filtrate, followed by extraction twice with dichloromethane. The organic phases were combined, dried over anhydrous sodium sulfate, filtered and concentrated, and the residue was separated by column chromatography to give product 1 (454 mg, light yellow oil) in a yield of 55%.

[0123] MS m/z (ESI): 826.9 [M+1].

[0124] .sup.1H NMR (300 MHZ, CDCl.sub.3): ? 4.13 (t, 4H, J=6.6 Hz), 4.05 (d, 4H, J=5.7 Hz), 3.56-3.55 (m, 2H), 2.47-2.42 (m, 6H), 1.72-1.67 (m, 10H), 1.53-1.48 (m, 8H), 1.45-1.28 (m, 52H), 0.69 (t, 12H, J=6.2 Hz).

Example 2: Synthesis of Compound 2

[0125] ##STR00012##

Synthesis of 7-bromoheptylheptadecane-9-ylcarbonate (2a)

[0126] ##STR00013##

[0127] 7-bromoheptanol (0.98 g. 5.0 mmol) was dissolved in 30 mL of dichloromethane, 4-dimethylaminopyridine (1.22 g. 10 mmol) was added, and then 4-nitrophenyl chloroformate (1.11 g. 5.5 mmol) was further added in portions. The resulting mixture was stirred and reacted at room temperature for 3 h. 9-hydroxyheptadecanol (1.44 g. 5.6 mmol) was added to the reaction solution, and the mixture was stirred at room temperature overnight. After the reaction was completed as detected by TLC. 20 mL of dichloromethane was added for dilution, and then the reaction solution was washed with 30 mL of saturated brine. The organic phase was dried over anhydrous sodium sulfate, filtered and concentrated, and the residue was separated by column chromatography to give 7-bromoheptylheptadecane-9-ylcarbonate 2a (1.50 g. light yellow oil) in a yield of 65%.

[0128] MS m/z (ESI): 477.3 [M+1].

Synthesis of heptadecan-9-yl(7-((2-hydroxyethyl)amino) heptyl) carbonate (2b)

[0129] ##STR00014##

[0130] 7-bromoheptylheptadecane-9-ylcarbonate (2a) (1.38 g. 3 mmol) was dissolved in 20 mL of ethanol at room temperature, ethanolamine (2.75 g. 45 mmol) was added, and the mixture was heated to 50? C., and stirred for 8 h. After the starting materials were consumed completely as monitored, the reaction solution was cooled to 45? C. ethanol was removed by rotary drying, and the crude product was dissolved in dichloromethane, and washed with saturated brine for three times. The organic phase was dried over anhydrous sodium sulfate, and concentrated to give the product heptadecan-9-yl(7-((2-hydroxyethyl)amino) heptyl) carbonate (2b) (1.35 g, light yellow oil).

[0131] MS m/z (ESI): 458.4 [M+1].

Synthesis of 5-bromopentylundecvl carbonate (2c)

[0132] ##STR00015##

[0133] 5-bromopentanol (0.84 g. 5.0 mmol) was dissolved in 30 mL of dichloromethane, 4-dimethylaminopyridine (1.22 g. 10 mmol) was added, and 4-nitrophenyl chloroformate (1.11 g. 5.5 mmol) was further added in portions. The mixture was stirred and reacted at room temperature for 3 h, undecanol (0.97 g. 5.6 mmol) was added to the reaction solution, and the mixture was stirred at room temperature overnight. After the reaction was completed as detected by TLC, 20 mL of dichloromethane was added for dilution, and then the reaction solution was washed with 30 mL of saturated brine. The organic phase was dried over anhydrous sodium sulfate, filtered and concentrated, and the residue was separated by column chromatography to give 5-bromopentylundecyl carbonate 2c (1.20 g, light yellow oil) in a yield of 66%.

[0134] MS m/z (ESI): 365.2 [M+1].

Synthesis of compound 2

[0135] ##STR00016##

[0136] Heptadecan-9-yl(7-((2-hydroxyethyl)amino) heptyl) carbonate (457 mg, 1.0 mmol) was dissolved in tetrahydrofuran, then acetonitrile, 5-bromopentylundecyl carbonate (437 mg, 1.2 mmol), potassium carbonate (550 mg, 4.0 mmol), and potassium iodide (332 mg, 2.0 mmol) were added, and the resulting mixture was stirred at 83? C. for 16-20 h. The reaction solution was cooled to room temperature, and filtered, the filter residue was washed with dichloromethane, and a saturated sodium bicarbonate solution was added to the obtained filtrate, followed by extraction twice with dichloromethane. The organic phases were combined, dried over anhydrous sodium sulfate, filtered and concentrated, and the residue was separated by column chromatography to give product 2 (440 mg, light yellow oil) in a yield of 57%.

[0137] MS m/z (ESI): 742.8 [M+1].

[0138] .sup.1H NMR (300 MHZ, CDCl.sub.3): ? 4.71-4.68 (m, 1H), 4.15-4.10 (m, 6H), 3.53 (t, 2H, J=5.4 Hz), 2.94 (br, 1H), 2.58 (t, 2H, J=5.4 Hz), 2.45 (t, 4H, J=5.7 Hz), 1.75-1.34 (m, 62H), 0.90 (t, 9H, J=6.3 Hz).

Example 3: Synthesis of Compound 3

[0139] ##STR00017##

Synthesis of 6-bromohexylundecyl carbonate (3a)

[0140] ##STR00018##

[0141] 6-bromohexanol (0.91 g, 5.0 mmol) was dissolved in 30 mL of dichloromethane, 4-dimethylaminopyridine (0.90 g. 7.5 mmol) was added, and 4-nitrophenyl chloroformate (1.20 g, 6.0 mmol) was further added in portions. The mixture was stirred and reacted at room temperature for 3 h, undecanol (0.97 g. 5.6 mmol) was added to the reaction solution, and the mixture was stirred at room temperature overnight. After the reaction was completed as detected by TLC, 20 mL of dichloromethane was added for dilution, and then the reaction solution was washed with 30 mL of saturated brine. The organic phase was dried over anhydrous sodium sulfate, filtered and concentrated, and the residue was separated by column chromatography to give 6-bromohexylundecyl carbonate 3a (1.25 g, light yellow oil) in a yield of 66%.

[0142] MS m/z (ESI): 379.2 [M+1].

Synthesis of compound 3

[0143] ##STR00019##

[0144] 6-bromohexylundecyl carbonate (948 mg. 2.5 mmol) was dissolved in tetrahydrofuran, then acetonitrile, 4-amino-1-butanol (89.2 mg, 1.0 mmol), potassium carbonate (550 mg, 4.0 mmol), and potassium iodide (332 mg, 2.0 mmol) were added, and the resulting mixture was stirred at 83? C. for 16-20 h. The reaction solution was cooled to room temperature, and filtered, the filter residue was washed with dichloromethane, and a saturated sodium bicarbonate solution was added to the obtained filtrate, followed by extraction twice with dichloromethane. The organic phases were combined, dried over anhydrous sodium sulfate, filtered and concentrated, and the residue was separated by column chromatography to give product 3 (412 mg, light yellow oil) in a yield of 60%.

[0145] MS m/z (ESI): 686.8 [M+1].

[0146] .sup.1H NMR (300 MHz, CDCl.sub.3): ? 4.13 (t, 8H, J=6.6 Hz), 3.58 (t, 2H, J=5.7 Hz), 2.52 (t, 6H, J=8.4 Hz), 1.74-1.64 (m, 12H), 1.63-1.53 (m, 5H), 1.52-1.39 (m, 39H), 0.86 (t, 6H, J=6.2 Hz).

Example 4: Synthesis of Compound 4

[0147] ##STR00020##

Synthesis of 6-bromohexylheptadecan-9-ylcarbonate (4a)

[0148] ##STR00021##

[0149] 6-bromohexanol (0.91 g, 5.0 mmol) was dissolved in 30 mL of dichloromethane, 4-dimethylaminopyridine (0.90 g, 7.5 mmol) was added, and 4-nitrophenyl chloroformate (1.20 g, 6.0 mmol) was further added in portions. The mixture was stirred and reacted at room temperature for 3 h, 9-heptadecanol (1.44 g. 5.6 mmol) was added to the reaction solution, and the mixture was stirred at room temperature overnight. After the reaction was completed as detected by TLC, 20 mL of dichloromethane was added for dilution, and then the reaction solution was washed with 30 mL of saturated brine. The organic phase was dried over anhydrous sodium sulfate, filtered and concentrated, and the residue was separated by column chromatography to give 6-bromohexylheptadecan-9-ylcarbonate 4a (1.53 g, light yellow oil) in a yield of 66%.

[0150] MS m/z (ESI): 464.3 [M+1].

Synthesis of compound 4

[0151] ##STR00022##

[0152] 6-bromohexylheptadecan-9-ylcarbonate (1.16 g. 2.5 mmol) was dissolved in tetrahydrofuran, then acetonitrile, 4-amino-1-butanol (89.2 mg, 1.0 mmol), potassium carbonate (550 mg, 4.0 mmol), and potassium iodide (332 mg, 2.0 mmol) were added, and the resulting mixture was stirred at 83? C. for 16-20 h. The reaction solution was cooled to room temperature, and filtered, the filter residue was washed with dichloromethane, and a saturated sodium bicarbonate solution was added to the obtained filtrate, followed by extraction twice with dichloromethane. The organic phases were combined, dried over anhydrous sodium sulfate, filtered and concentrated, and the residue was separated by column chromatography to give product 4 (502 mg, light yellow oil) in a yield of 59%.

[0153] MS m/z (ESI): 855.4 [M+1].

[0154] .sup.1H NMR (300 MHz, CDCl.sub.3): ? 4.71-4.68 (m, 2H), 4.13 (t, 4H, J=6.6 Hz), 3.57 (t, 2H, J=5.4 Hz), 2.49-2.44 (m, 6H), 1.74-1.28 (m, 76H), 0.90 (t, 12H, J=6.3 Hz).

Example 5: Synthesis of Compound 5

[0155] ##STR00023##

[0156] 6-bromohexyl(2-hexyldecyl) carbonate (1.12 g, 2.5 mmol) was dissolved in tetrahydrofuran, then acetonitrile, ethanolamine (61.0 mg, 1.0 mmol), potassium carbonate (550 mg, 4.0 mmol), and potassium iodide (332 mg, 2.0 mmol) were added, and the resulting mixture was stirred at 83? C. for 16-20 h. The reaction solution was cooled to room temperature, and filtered, the filter residue was washed with dichloromethane, and a saturated sodium bicarbonate solution was added to the obtained filtrate, followed by extraction twice with dichloromethane. The organic phases were combined, dried over anhydrous sodium sulfate, filtered and concentrated, and the residue was separated by column chromatography to give product 5 (487 mg, light yellow oil) in a yield of 61%.

[0157] MS m/z (ESI): 798.9 [M+1].

[0158] .sup.1H NMR (300 MHz, CDCl.sub.3): ? 4.14 (t, 4H, J=6.6 Hz), 4.04 (d, 4H, J=5.7 Hz), 3.54 (t, 2H, J=5.4 Hz), 2.58 (t, 2H, J=5.4 Hz), 2.46 (t, 4H, J=7.2 Hz), 1.72-1.65 (m, 6H), 1.49-1.28 (m, 61H), 0.69 (t, 12H, J=6.2 Hz).

Example 6: Synthesis of Compound 6

[0159] ##STR00024##

[0160] 5-bromopentylundecyl carbonate (910 mg. 2.5 mmol) was dissolved in tetrahydrofuran, then acetonitrile, ethanolamine (61.0 mg, 1.0 mmol), potassium carbonate (550 mg, 4.0 mmol), and potassium iodide (332 mg, 2.0 mmol) were added, and the resulting mixture was stirred at 83? C. for 16-20 h. The reaction solution was cooled to room temperature, and filtered, the filter residue was washed with dichloromethane, and a saturated sodium bicarbonate solution was added to the obtained filtrate, followed by extraction twice with dichloromethane. The organic phases were combined, dried over anhydrous sodium sulfate, filtered and concentrated, and the residue was separated by column chromatography to give product 6 (410 mg, light yellow oil) in a yield of 65%.

[0161] MS m/z (ESI): 630.7 [M+1].

[0162] .sup.1H NMR (300 MHZ, CDCl.sub.3): ? 4.10 (t, 8H, J=6.6 Hz), 3.52 (d, 2H, J=5.4 Hz), 2.83 (br, 1H), 2.57 (t, 2H, J=5.4 Hz), 2.45 (t, 4H, J=7.2 Hz), 1.73-1.62 (m, 8H), 1.52-1.39 (m, 40H), 0.69 (t, 6H, J=6.2 Hz).

Example 7: Synthesis of Compound 7

[0163] ##STR00025##

[0164] 6-bromohexyl(2-hexyldecyl) carbonate (1.12 g, 2.5 mmol) was dissolved in tetrahydrofuran, then acetonitrile, 3-methoxypropylamine (89 mg, 1.0 mmol), potassium carbonate (550 mg, 4.0 mmol), and potassium iodide (332 mg. 2.0 mmol) were added, and the resulting mixture was stirred at 83? C. for 16-20 h. The reaction solution was cooled to room temperature, and filtered, the filter residue was washed with dichloromethane, and a saturated sodium bicarbonate solution was added to the obtained filtrate, followed by extraction twice with dichloromethane.

[0165] The organic phases were combined, dried over anhydrous sodium sulfate, filtered and concentrated, and the residue was separated by column chromatography to give product 7 (495 mg, light yellow oil) in a yield of 60%.

[0166] MS m/z (ESI): 826.7 [M+1].

Example 8: Synthesis of Compound 8

[0167] ##STR00026##

[0168] 6-bromohexyl(2-hexyldecyl) carbonate (1.12 g, 2.5 mmol) was dissolved in tetrahydrofuran, then acetonitrile, 3-aminopropiononitrile (70 mg, 1.0 mmol), potassium carbonate (550 mg, 4.0 mmol), and potassium iodide (332 mg, 2.0 mmol) were added, and the resulting mixture was stirred at 83? C. for 16-20 h. The reaction solution was cooled to room temperature, and filtered, the filter residue was washed with dichloromethane, and a saturated sodium bicarbonate solution was added to the obtained filtrate, followed by extraction twice with dichloromethane.

[0169] The organic phases were combined, dried over anhydrous sodium sulfate, filtered and concentrated, and the residue was separated by column chromatography to give product 8 (469 mg, light yellow oil) in a yield of 58%.

[0170] MS m/z (ESI): 807.7 [M+1].

Example 9: Synthesis of Compound 9

[0171] ##STR00027##

[0172] 6-bromohexyl(2-hexyldecyl) carbonate (1.12 g, 2.5 mmol) was dissolved in tetrahydrofuran, then acetonitrile, ethyl 4-aminobutyrate hydrochloride (167 mg, 1.0 mmol), potassium carbonate (550 mg, 4.0 mmol), and potassium iodide (332 mg, 2.0 mmol) were added, and the resulting mixture was stirred at 83? C. for 16-20 h. The reaction solution was cooled to room temperature, and filtered, the filter residue was washed with dichloromethane, and a saturated sodium bicarbonate solution was added to the obtained filtrate, followed by extraction twice with dichloromethane. The organic phases were combined, dried over anhydrous sodium sulfate, filtered and concentrated, and the residue was separated by column chromatography to give product 9 (546 mg, light yellow oil) in a yield of 63%.

[0173] MS m/z (ESI): 868.8 [M+1].

Example 10: Synthesis of Compound 10

[0174] ##STR00028##

[0175] 6-bromohexyl(2-hexyldecyl) carbonate (1.12 g, 2.5 mmol) was dissolved in tetrahydrofuran, then acetonitrile, N-(4-aminobutyl)-acetamide hydrochloride (167 mg, 1.0 mmol), potassium carbonate (550 mg, 4.0 mmol), and potassium iodide (332 mg. 2.0 mmol) were added, and the resulting mixture was stirred at 83? C. for 16-20 h. The reaction solution was cooled to room temperature, and filtered, the filter residue was washed with dichloromethane, and a saturated sodium bicarbonate solution was added to the obtained filtrate, followed by extraction twice with dichloromethane. The organic phases were combined, dried over anhydrous sodium sulfate, filtered and concentrated, and the residue was separated by column chromatography to give product 10 (560 mg, light yellow oil) in a yield of 69%.

[0176] MS m/z (ESI): 867.8 [M+1].

Example 11: Synthesis of Compound 11

[0177] ##STR00029##

Synthesis of 8-bromo-N-(heptadecan-9-yl) octanamide (11a)

[0178] ##STR00030##

[0179] 8-bromooctanoic acid (1.12 g. 5.0 mmol) was dissolved in 50 mL of dichloromethane, 1-ethyl-(3-dimethylaminopropyl) carbonyldiimine hydrochloride (1.05 g. 5.5 mmol) was added in portions at 0? C., and 9-aminoheptadecane (1.28 g. 5.0 mmol) was added dropwise to the reaction solution after stirring for 30 min. After completion of the dropwise addition, the mixture was stirred at room temperature overnight, and after the reaction was completed as detected by TLC, the reaction solution was washed twice with 100 ml of water. The organic phase was dried over anhydrous sodium sulfate, filtered and concentrated to give compound 11a (1.95 g. yellow oil) in a yield of 82%.

[0180] MS m/z (ESI): 461.3 [M+1].

Synthesis of compound 11b

[0181] ##STR00031##

[0182] 8-bromo-N-(heptadecan-9-yl) octanamide (1.15 g. 2.5 mmol) was dissolved in tetrahydrofuran, then acetonitrile, 4-amino-1-butanol (89.2 mg, 1.0 mmol), potassium carbonate (550 mg. 4.0 mmol), and potassium iodide (332 mg. 2.0 mmol) were added, and the resulting mixture was stirred at 83? C. for 16-20 h. The reaction solution was cooled to room temperature, and filtered, the filter residue was washed with dichloromethane, and a saturated sodium bicarbonate solution was added to the obtained filtrate, followed by extraction twice with dichloromethane. The organic phases were combined, dried over anhydrous sodium sulfate, filtered and concentrated, and the residue was separated by column chromatography to give product 11b (534 mg, light yellow oil) in a yield of 63%.

[0183] MS m/z (ESI): 848.8 [M+1].

[0184] .sup.1H NMR (300 MHz, CDCl.sub.3): ? 8.10 (s. 2H), 4.21 (s, 1H), 3.46-3.4 (m, 4H), 3.02 (t, 6H, J=6.2 Hz), 2.14 (t, 4H, J=4.8 Hz), 1.57-1.47 (t, 14H, J=6.3 Hz), 1.36-1.26 (m. 66H), 0.90 (t, 12H, J=6.3 Hz).

Synthesis of compound 11

[0185] ##STR00032##

[0186] Compound 11b (1.70 g. 2 mmol) was added slowly to a solution of lithium aluminium hydride (379 mg, 10 mmol) in anhydrous tetrahydrofuran (10 mL) at 0? C., and the mixture was heated and refluxed for 5 h. After the reaction was completed, the mixture was cooled, and then water was added to the system to make the excess reducing agent be completely decomposed. The mixture was filtered, the filter residue was washed with ethyl acetate, and the obtained filtrate was washed with water, dried over anhydrous sodium sulfate, filtered and concentrated to give compound 11 (1.45 g, yellow oil) in a yield of 90%.

[0187] MS m/z (ESI): 820.8 [M+1].

[0188] .sup.1H NMR (300 MHz, CDCl.sub.3): ? 4.11 (s, 1H), 3.44 (t, 2H, J=4.8 Hz), 3.32 (s, 2H), 3.00 (t, 6H, J=6.3 Hz), 2.52 (t, 4H, J=6.3 Hz), 2.48-2.43 (m, 2H), 1.61-1.56 (m, 2H), 1.36-1.26 (m, 82H), 0.86 (t, 12H, J=4.8 Hz).

Example 12: Preparation of Novel Coronavirus LNP-mRNA

[0189] Novel coronavirus mRNA lipid complexes were prepared using the cationic lipids I-II prepared in Examples 1 and 2 of the present invention and control lipids III-IV, respectively, and the structures of the four cationic lipids are shown in the table below.

TABLE-US-00001 TABLE 1 Cationic lipid structural formula Ca- tion- ic lipid Structural formula I [00033] II [00034] III [00035] IV [00036]

[0190] The preparation process of novel coronavirus lipid nanoparticle mRNA vaccine was as follows: mRNA stock solution was diluted to a concentration of 135 ?g/mL with sodium acetate buffer, and a lipid mixed solution was prepared according to a molar ratio of cationic lipid:DSPC:cholesterol:DMG-PEG 2000 of 49:10:39.5:1.5; after the encapsulation was completed on the nano-drug manufacturing equipment, the solution was ultra-filtered and changed, and the sample was collected. The encapsulation efficiency, average particle size, PDI and Zeta potential were measured by sampling, and the results are shown in the table below and FIGS. 1-24.

TABLE-US-00002 TABLE 2 Detection results of novel coronavirus lipid nanoparticle mRNA vaccine after different cationic lipid encapsulation Average Encapsulation particle Zeta Samples N/P efficiency (%) size (nm) PDI (mV) 1 2 95.4 68.76 0.175 ?3.11 2 96.3 91.43 0.220 ?3.27 3 90.0 90.74 0.114 ?2.37 4 86.1 72.42 0.158 ?1.91 5 4 96.4 89.62 0.105 ?1.77 6 96.7 88.00 0.089 ?1.47 7 90.2 88.95 0.097 ?7.40 8 87.4 83.10 0.064 ?4.63 9 6 98.4 72.24 0.087 ?4.71 10 97.5 79.40 0.095 ?6.15 11 91.4 79.10 0.103 ?3.72 12 90.6 78.48 0.088 ?4.83 Note: samples 1, 5 and 9 used the cationic lipid I, respectively; samples 2, 6 and 10 used the cationic lipid II, respectively; samples 3, 7 and 10 used the cationic lipid III, respectively; samples 4, 8 and 12 used the cationic lipid IV, respectively.

[0191] From the above results, it could be seen that under the same N/P conditions, the encapsulation efficiencies of samples 1, 2, 5, 6, 9 and 10 prepared by using the cationic lipids I and II were higher than those of samples 3, 4, 7, 8, 11 and 12 prepared by using the control cationic lipids III and IV, and thus it could be preliminarily concluded that the cationic lipids I and II had a better encapsulation effect on mRNA antigen.

Example 13: Stability Investigation of LNP-mRNA Prepared From Different Cationic Lipids

[0192] Four LNP-mRNAs of samples 9, 10, 11 and 12 prepared in Example 12 were placed in a constant temperature incubator at 25? C. for 1, 2, 3 and 4 weeks, respectively, to investigate their stability.

[0193] The results are shown in FIGS. 25-27, and it could be seen from the above results that the encapsulation efficiency, the average particle size and the PDI of samples 9 and 10 did not change significantly during the acceleration period, while the encapsulation efficiency of samples 11 and 12 decreased significantly and the average particle size and the PDI increased significantly during the acceleration period, and thus it could be preliminarily concluded that the stability of LNP-mRNAs prepared by the cationic lipids I and II was better than that thereof prepared by the cationic lipids III and IV.

Example 14: In-Vitro Expression Investigation of LNP-mRNAs Prepared from Different Cationic Lipids

[0194] Four LNP-mRNAs of samples 9, 10, 11 and 12 prepared in Example 12 were taken for detecting target gene expression of a test sample by WB method.

[0195] Cell plating: Hep3B cells were prepared, trypsinized, adjusted to a cell density of 6.5?10.sup.5 cell/mL, and seeded onto a 6-well cell culture plate at 1 mL/well, and an EMEM complete medium was supplemented to make up to 3 mL. The cells were cultured overnight in a cell incubator with 5% CO.sub.2 at 37? C.

[0196] Sampling: (1) RNase in the working environment was removed. The EMEM complete medium was replaced with an EMEM serum-free medium (3 mL/well). (2) The test sample was added to a 6-well cell culture plate in an amount of 25 ?L/well (about 2500 ng mRNA), and meanwhile, a negative control (blank control) was set. (3) The cell culture plate was placed in a cell incubator with 5% CO.sub.2 at 37? C. for culturing for 22-26 hours.

[0197] Cell harvesting and lysis: (1) the cells were pipetted to be completely detached from the bottom of the culture plate, the cell suspension was centrifuged at 1000 rpm for 5 minutes, and then the supernatant was discarded. (2) The cell pellet was pipetted using 150 ?L of RIPA lysate and uniformly mixed, and then lysed on ice for 30 minutes, during which vortex oscillation was carried out for 4-6 times. (3) The cells after lysis were centrifuged at 15000? g for 20 min at 4? C., and the supernatant was transferred to a new EP tube and stored in a freezer at ?20? C. for later use. (4) The sample from (3) was taken, the corresponding volume of 6? protein loading buffer was added, and the mixture was uniformly mixed and placed in a boiling water bath or at 100? C. for 5 minutes to be tested.

[0198] Electrophoresis: a sample to be tested and protein Marker were added to a sample cell of the protein electrophoresis gel. At constant pressure, electrophoresis was stopped when a bromophenol blue indicator ran out of the gel.

[0199] Membrane transfer: the protein on the protein electrophoresis gel was transferred to a nitrocellulose membrane.

[0200] Blocking: the nitrocellulose membrane was placed in a blocking solution and blocked overnight at 2-8? C., or on a shaker at room temperature for 1-2 hours.

[0201] Primary antibody incubation: the nitrocellulose membrane was immersed into a certain concentration of novel coronavirus S protein specific antibody, and the mixture was incubated overnight at 2-8? C., or on a shaker at room temperature for 2 hours.

[0202] Membrane washing: the membrane was washed with PBST washing liquid for 3 times, 5 minutes per time.

[0203] Primary antibody incubation: the nitrocellulose membrane was immersed into a certain concentration of horseradish peroxidase-labeled goat anti-rabbit IgG, and the mixture was incubated on a shaker at room temperature for 1 hour.

[0204] Membrane washing: the membrane was washed with PBST washing liquid for 6 times, 5 minutes per time.

[0205] Imaging: a luminescent substrate was added for imaging.

[0206] The detection results are shown in FIG. 28, wherein protein strips could be expressed in vitro in samples 9, 10, 11 and 12, but the protein strips of samples 9 and 10 were darker than those of samples 11 and 12, and thus it could be preliminarily concluded that the in-vitro transfection efficiencies of the cationic lipids I and II were better than those of the cationic lipids III and IV.

Example 15: Mouse Immunization and Detection of LNP-mRNAs Prepared from Different Cationic Lipids

[0207] Female BALB/c mice aged 6-8 weeks were divided into 5 groups with 6 mice per group at random, and immunized by the intramuscular injection of hind leg. Animals in groups 1, 2, 3 and 4 were immunized with samples 9, 10, 11 and 12 (prepared in Example 12), respectively; group 5 served as a negative control group, immunized with physiological saline. Immunization was performed on day 0 and day 14, respectively, with a single immunization dose of 5 ?g mRNA-LNP. Blood was collected on day 14 and day 28 of immunization and serum was isolated; mice were dissected and splenocytes were isolated after blood collection on day 28 of immunization.

[0208] Serum samples on day 14 of immunization were used to detect the specific antibody titer against novel coronavirus S protein by ELISA. The detection results are shown in FIG. 29, where four samples all elicited higher specific antibody responses, and there was no significant difference in antibody response levels between the groups. Serum samples on day 28 of immunization were also used to detect the specific antibody titer against novel coronavirus S protein by ELISA. The detection results are shown in FIG. 30, where four samples all elicited higher specific antibody responses, wherein group 1 (sample 9) elicited the highest antibody response level, with no significant difference from group 2 (sample 10), but significantly higher than that of the positive control samples in groups 3 and 4 (samples 11 and 12).

[0209] After mixing the immune serum samples on day 28 of each group, the neutralizing antibody titer was detected using a competitive ELISA method. The protein for ELISA assay plate was ACE2-Fc, while the competitive proteins were RBD protein of original strain and RBD protein of Beta variant, respectively. As shown in FIG. 31, the neutralizing antibody titers of four groups of mixed samples detected by original strain RBD protein was 2591, 2644, 1707 and 1313, respectively. As shown in FIG. 32, the neutralizing antibody titers of four groups of mixed samples detected by Beta variant RBD protein was 4144, 3542, 3534 and 2567, respectively. The trend of the detection results of the two RBD proteins was consistent, and the trend of the antibody titer detection results was also consistent. It was demonstrated that the formulation comprising the lipid compound of the present invention could elicit a higher antibody response compared to a positive control sample.

[0210] Splenocytes isolated after mouse dissection were stimulated with a full-length overlapping peptide library of S protein, and the ICS method was used to detect antigen specificity and frequency of CD4+ T cells and CD8+ T cells secreting IL-2, IFN?, TNF?, IL-4 and IL-5, respectively. The cellular immune response of specific CD8+ T cells is shown in FIG. 33, and all experimental groups elicited Th1 class biased immune responses, with almost no CD8+ T cells secreting IL-2. IL-4 and IL-5. There was no significant difference in the ratios of IFN? secretion specific CD8+ T cells and TNF? secretion specific CD8+ T cells in mice of each experimental group. The cellular immune response of specific CD4+ T cells is shown in FIG. 34, and all experimental groups elicited Th1 class biased immune responses, with almost no CD4+ T cells secreting IL-4 and IL-5. The ratios of IFN? secretion specific CD8+ T cells. TNF? secretion specific CD8+ T cells and IL-2 secretion specific CD8+ T cells in groups 1-2 (samples 9 and 10) were not significantly different from those in groups 3-4 (samples 11 and 12), respectively, but the mean values were higher. It was demonstrated that the formulation comprising the lipid compound of the present invention did not elicit a specific cellular immune response inferior to the corresponding positive control sample.

[0211] The preferred embodiments of the present invention are described in detail above, which, however, are not intended to limit the present invention. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, all of which will fall within the protection scope of the present invention.

[0212] In addition, it should be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner where the features do not contradict each other. In order to avoid unnecessary repetition, such combinations will not be illustrated separately.