ACTIVIN RECEPTOR TYPE IIB VARIANTS AND USES THEREOF
There are provided polypeptides that include an Activin receptor type IIB (ActRIIB) ectodomain (ECD) variant. In some embodiments, a polypeptide of the disclosure includes an ActRIIB-ECD variant fused to an Fc domain moiety. The disclosure also provides pharmaceutical compositions and methods of using the polypeptides to treat diseases and conditions associated with TGFβ superfamily ligand signaling, such as metabolic disorders, diabetes, obesity, cardiometabolic disease, pulmonary hypertension, fibrosis, muscle weakness and atrophy, bone damage, and/or low red blood cell levels (such as anemia).
1 . A method of improving body composition in a subject comprising administering a TGFβ superfamily ligand binding agent comprising a first and a second polypeptide, wherein each of the first and second polypeptides comprise:
(a) an Activin receptor type JIB (ActRIIB) ectodomain (ECD) variant comprising an amino acid substitution at the position corresponding to position 33 of SEQ ID NO: 2;
(b) a peptide linker; and
(c) an Fc domain monomer.
2 . The method of claim 1 , wherein an improvement in body composition comprises an increase in lean muscle mass and/or decrease in fat mass.
3 . A method of improving exercise tolerance in a subject comprising administering a TGFβ superfamily ligand binding agent comprising a first and a second polypeptide, wherein each of the first and second polypeptides comprise:
(a) an Activin receptor type JIB (ActRIIB) ectodomain (ECD) variant comprising an amino acid substitution at the position corresponding to position 33 of SEQ ID NO: 2;
(b) a peptide linker; and
(c) an Fc domain monomer
4 . The method of claim 3 , wherein an improvement in exercise tolerance comprises reduced Left ventricular end-diastolic pressure (LVEDP) and/or an increased 6-minute walk distance.
5 . The method of claim 1 , wherein the subject suffers from a metabolic disorder.
6 . The method of claim 5 , wherein the metabolic disorder is obesity.
7 . The method of claim 1 , wherein the subject does not suffer from a cardiometabolic disorder.
8 . The method of claim 1 , wherein the ActRIIB ECD variant comprises the amino acid substitution L33W.
9 . The method of claim 8 , wherein the ActRIIB ECD variant
(a) comprises an amino acid sequence that is at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to SEQ ID NO: 16; or
(b) comprises or consists of the amino acid sequence of SEQ ID NO: 4-613.
10 . The method of claim 1 , wherein the first and second polypeptides comprise the following structure, from N- to C-terminus: ActRIIB-ECD-peptide linker-Fc domain monomer.
11 . The method of claim 1 , wherein the Fc domain monomer is an IgG1 isotype
12 . The method of claim 11 , wherein the Fc domain monomer comprises or consists of the amino acid sequence set forth in SEQ ID NO: 253, SEQ ID NO: 255, or SEQ ID NO: 256.
13 . The method of claim 1 , wherein the Fc domain monomer forms a dimer.
14 . The method of claim 1 , wherein the peptide linker is Glycine-rich.
15 . The method of claim 1 , wherein the peptide linker is between 10 and 40 amino acids long.
16 . The method of claim 15 , wherein the peptide linker is 14 amino acids long, 19 amino acids long, or 39 amino acids long.
17 . The method of claim 1 , wherein the first and second polypeptides comprise or consist of the amino acid sequence selected from SEQ ID NOs: 211 and 230-234, or an amino acid sequence that is at least 95%, 96%, 97%, 98%, or 99% identical thereto.