A lipid nanoparticle (LNP) composition comprising: an mRNA encoding a Cas nuclease; a guide RNA nucleic acid; and a plurality of component lipids comprising: a helper lipid, wherein the helper lipid is selected from a steroid, a sterol, and an alkyl resorcinol; a neutral lipid, wherein the neutral lipid is a neutral, uncharged, or zwitterionic lipid; a stealth lipid, wherein the stealth lipid has a hydrophilic head group linked to a lipid moiety; and an ionizable lipid selected from: Lipid A: -3-((4,4-bis(octyloxy)butanoyl)oxy)-2-((((3-(diethylamino)propoxy)carbonyl)oxy)methyl)propyl-octadeca-9, 12-dienoate Lipid B: ((5-((dimethylamino)methyl)-1,3-phenylene)bis(oxy))bis(octane-8,1-diyl)bis(decanoate), Lipid C: 2-((4-(((3-(dimethylamino)propoxy)carbonyl)oxy)hexadecanoyl)oxy)pro pane-1,3-diyl (9Z,9'Z,12Z,12'Z)-bis(octadeca-9,12-dienoate), and Lipid D: 3-(((3-(dimethylamino)propoxy)carbonyl)oxy)-13-(octanoyloxy)tridecyl-3-octylundecanoate; wherein the component lipids comprise from 30 mol-% to 60 mol-% of the ionizable lipid, from 30 mol-% to 60 mol-% of the helper lipid, from 1 mol-% to 20 mol-% of the neutral lipid, and from 1 mol-% to 10 mol-% of the stealth lipid. an mRNA encoding a Cas nuclease; a guide RNA nucleic acid; and a plurality of component lipids comprising: a helper lipid, wherein the helper lipid is selected from a steroid, a sterol, and an alkyl resorcinol; a neutral lipid, wherein the neutral lipid is a neutral, uncharged, or zwitterionic lipid; a stealth lipid, wherein the stealth lipid has a hydrophilic head group linked to a lipid moiety; and an ionizable lipid selected from: Lipid A: -3-((4,4-bis(octyloxy)butanoyl)oxy)-2-((((3-(diethylamino)propoxy)carbonyl)oxy)methyl)propyl-octadeca-9, 12-dienoate Lipid B: ((5-((dimethylamino)methyl)-1,3-phenylene)bis(oxy))bis(octane-8,1-diyl)bis(decanoate), Lipid C: 2-((4-(((3-(dimethylamino)propoxy)carbonyl)oxy)hexadecanoyl)oxy)pro pane-1,3-diyl (9Z,9'Z,12Z,12'Z)-bis(octadeca-9,12-dienoate), and Lipid D: 3-(((3-(dimethylamino)propoxy)carbonyl)oxy)-13-(octanoyloxy)tridecyl-3-octylundecanoate; a helper lipid, wherein the helper lipid is selected from a steroid, a sterol, and an alkyl resorcinol; a neutral lipid, wherein the neutral lipid is a neutral, uncharged, or zwitterionic lipid; a stealth lipid, wherein the stealth lipid has a hydrophilic head group linked to a lipid moiety; and an ionizable lipid selected from: Lipid A: -3-((4,4-bis(octyloxy)butanoyl)oxy)-2-((((3-(diethylamino)propoxy)carbonyl)oxy)methyl)propyl-octadeca-9, 12-dienoate Lipid B: ((5-((dimethylamino)methyl)-1,3-phenylene)bis(oxy))bis(octane-8,1-diyl)bis(decanoate), Lipid C: 2-((4-(((3-(dimethylamino)propoxy)carbonyl)oxy)hexadecanoyl)oxy)pro pane-1,3-diyl (9Z,9'Z,12Z,12'Z)-bis(octadeca-9,12-dienoate), and Lipid D: 3-(((3-(dimethylamino)propoxy)carbonyl)oxy)-13-(octanoyloxy)tridecyl-3-octylundecanoate; Lipid A: -3-((4,4-bis(octyloxy)butanoyl)oxy)-2-((((3-(diethylamino)propoxy)carbonyl)oxy)methyl)propyl-octadeca-9, 12-dienoate Lipid B: ((5-((dimethylamino)methyl)-1,3-phenylene)bis(oxy))bis(octane-8,1-diyl)bis(decanoate), Lipid C: 2-((4-(((3-(dimethylamino)propoxy)carbonyl)oxy)hexadecanoyl)oxy)pro pane-1,3-diyl (9Z,9'Z,12Z,12'Z)-bis(octadeca-9,12-dienoate), and Lipid D: 3-(((3-(dimethylamino)propoxy)carbonyl)oxy)-13-(octanoyloxy)tridecyl-3-octylundecanoate; wherein the component lipids comprise from 30 mol-% to 60 mol-% of the ionizable lipid, from 30 mol-% to 60 mol-% of the helper lipid, from 1 mol-% to 20 mol-% of the neutral lipid, and from 1 mol-% to 10 mol-% of the stealth lipid. <EOS>