Treatment of pulmonary arterial hypertension

1 . A method for treating or preventing pulmonary endothelial cell (PEC) dysfunction, the method comprising administering a therapeutically effective amount of a translocator protein (TSPO) modulator.

2 . The method of claim 1 , wherein the TSPO modulator inhibits pro-inflammatory activation of pulmonary endothelial cells.

3 . The method of claim 2 , wherein inhibition of pro-inflammatory activation of pulmonary endothelial cells comprises:

(a) reducing or attenuating an increase in expression of E-selectin, ICAM1 and/or VCAM1; and/or

(b) reducing the level of one or more pro-inflammatory mediator, wherein optionally said one or more pro-inflammatory mediator is selected from IFN-gamma; IL1, 2, 6, 8, 10,17, 18, 21; IP10; I-TAC; G-CSF; MCP-1; PAI1, TNF-alpha, RANTES and/or SDF-1.

4 . The method of claim 1 , wherein the TSPO modulator:

(a) reduces or attenuates an increase in pulmonary endothelial cell apoptosis;

(b) reduces or attenuates an increase in reactive oxygen species (ROS) production;

(c) reduces or attenuates an increase in vascular tone;

(d) reverses the active metabolic changes seen in pulmonary endothelial cell dysfunction;

(e) increases or attenuates a decrease in anticoagulant properties;

(f) increases or attenuates a decrease in vascular tubule formation;

(g) increases or attenuates a decrease in vascular repair;

(h) reduces or attenuates an increase in disordered pulmonary endothelial cell proliferation and associated neoangiogenesis;

(i) increases or attenuates a decrease in mitochondrial membrane potential; and/or

(j) reduces or attenuates an increase in expression of markers of endothelial to mesenchymal transition.

5 . The method of claim 4 , wherein the TSPO modulator reduces hypoxia-induced pulmonary endothelial cell proliferation by at least 30%, preferably at least 40%.

6 . The method of claim 1 , wherein the TSPO modulator:

(a) reduces or attenuates an increase in pulmonary arterial pressure;

(b) reduces or attenuates an increase in pulmonary vascular remodelling;

(c) reduces or attenuates an increase in infiltration of inflammatory cells, particularly CD68+ cells, into the lungs; and/or

(d) reduces or attenuates an increase in glucose uptake in the lung.

7 . The method of claim 6 , wherein the TSPO modulator reduces pulmonary arterial pressure by at least 30%.

8 . The method of claim 6 , wherein pulmonary vascular remodelling corresponds with the percentage of smooth muscle cells within the pulmonary vasculature, and wherein optionally the TSPO modulator reduces the percentage of smooth muscle cells within the pulmonary vasculature by at least 30%.

9 . The method of claim 6 , wherein the TSPO modulator reduces the infiltration of inflammatory cells, particularly CD68+ cells by at least 30%.

10 . The method of claim 6 , wherein the TSPO modulator reduces glucose uptake by the pulmonary endothelial cells by at least 40%.

11 . The method of claim 1 , wherein the dysfunction of the pulmonary endothelial cells is associated with:

(a) pulmonary hypertension; and/or

(b) heart failure.

12 . The method of claim 11 , wherein the pulmonary hypertension is pulmonary arterial hypertension (PAH), optionally idiopathic pulmonary arterial hypertension (IPAH).

13 . The method of claim 12 , wherein the heart failure is heart failure with preserved ejection fraction and associated pulmonary hypertension (PH-HFpEF).

14 . The method of claim 11 , wherein the TSPO modulator:

(a) reduces or attenuates an increase in right ventricular systolic pressure;

(b) reduces or attenuates an increase in right ventricular hypertrophy, particularly cardiomyocyte hypertrophy in the right ventricle;

(c) reduces or attenuates an increase in glucose uptake in the right ventricle;

(d) reduces or attenuates an increase in remodelling of the right ventricle;

(e) increases capillary density within the cardiac tissue; and/or

(f) improves cardiac performance.

15 . The method of claim 1 , wherein the TSPO modulator has no effect on systemic blood pressure.

16 . The method of claim 1 , wherein the TSPO modulator is a TSPO binding member.

17 . The method of claim 16 , wherein the TSPO binding member is selected from a small molecule, an antibody or antigen-binding fragment thereof, a peptide, a peptidomimetic, a nucleic acid or an aptamer.

18 . The method of claim 1 , wherein the TSPO modulator is a TSPO binding member is selected from XBD-173, ONO-2952, PK11195, PBR28, DPA713, DPA714, Ro 5-4864, FGIN-1-27, diazepam, lorazepam, midazolam, etifoxine, or a derivative or analogue thereof, optionally in the form of a pharmaceutically acceptable salt.

19 . The method of claim 1 , wherein the TSPO modulator is comprised within a pharmaceutical composition.

20 . The method of claim 1 , wherein the TSPO modulator is administered by oral administration, intravenous or intra-arterial administration or by inhalation.

21 . The method of claim 1 , wherein the TSPO modulator is the TSPO binding member XBD-173 and the pulmonary endothelial cell dysfunction is associated with pulmonary arterial hypertension, particularly idiopathic pulmonary arterial hypertension.

22 . The method of claim 6 , wherein the TSPO modulator reduces pulmonary arterial pressure by at least 40%.

23 . The method of claim 6 , wherein pulmonary vascular remodelling corresponds with the percentage of smooth muscle cells within the pulmonary vasculature by at least 40%.

24 . The method of claim 6 , wherein the TSPO modulator reduces the infiltration of inflammatory cells, particularly CD68+ cells by at least 40%.

25 . The method of claim 6 , wherein the TSPO modulator reduces glucose uptake by the pulmonary endothelial cells by at least 50%.

26 . The method of claim 16 , wherein the TSPO binding member is a small molecule.