Abstract 12164: Inhibition of NOTCH3 Cleavage Effectively Reverses Pulmonary Hypertension in Rat and Mouse Models of Disease

Background: NOTCH3 signaling is required for the proliferation of vascular smooth muscle cells. NOTCH3 signaling has been implicated in the development of pulmonary arterial hypertension (PAH) as reflected by increased levels of cleaved NOTCH3 and its downstream effector, HES-5 in small pulmonary artery smooth muscle cells (PASMCS) of PAH patients. Gamma-secretase inhibitor drugs that block NOTCH cleavage are effective in treating pulmonary hypertension (PH) in rodents, but they are associated with toxic side effects. Hypothesis: We hypothesize that a monoclonal antibody that specifically blocks NOTCH3 cleavage will effectively reverse PH in rodent models of disease, with an acceptable safety profile. Methods/Results: A monoclonal antibody specific to rodent and human NOTCH3 (Anti-NOTCH3 Ab) was made and shown to block Jagged-1/Delta-like 4-mediated NOTCH3 cleavage in PASMCs in vitro . We tested Anti-NOTCH3 Ab for its ability to reverse PH in mouse hypoxia and rat Sugen models. After 4 weeks of hypoxia, mice treated with Anti-NOTCH3 Ab for 6 weeks demonstrated normalization of right ventricular systolic pressure (mean 17 mmHg), compared to RVSP in control mice (mean 35mmHg). Treated mice demonstrated reversal of small vessel remodeling and had angiograms consistent with normal vasculature. In the Sugen model, rats treated with Anti-NOTCH3 Ab for 10 weeks showed reversal of established disease. This included normalization of RVSPs (mean 18 mmHg - treated group vs. 70 mmHg - control group), normalization of TAPSE values (mean 3.7 mm - treated group vs. 2.4 mm - control group) and normalization of PAAT values (mean 42 msec - treated group vs. 17 msec - control group). The lungs of Anti-NOTCH3 Ab-treated rats had reversal of small vessel remodeling with loss of medial hypertrophy. Western blot analysis showed significantly decreased cleavage of NOTCH3 in the treated group vs. control group. Anti-NOTCH3 Ab-treated rodents did not manifest clinical side effects and had normal organ histology of brain, liver, kidney, intestine, skin, ovary, and heart. Conclusion: Inhibition of cleavage of NOTCH3 by a monoclonal Anti-NOTCH3 Ab effectively treats PH in mouse hypoxia and rat Sugen models. Anti-NOTCH3 Ab treatment was associated with an acceptable safety profile.