Sirolimus plus nintedanib treats vascular pathology in HHT mouse models

Abstract

Hereditary hemorrhagic telangiectasia (HHT), a genetic bleeding disorder leading to systemic arteriovenous malformations (AVMs), is caused by loss-of-function mutations in the ALK1-ENG-Smad1/5/8 pathway. Evidence suggests that HHT pathogenesis strongly relies on overactivated PI3K-Akt-mTOR and VEGFR2 pathways in endothelial cells (ECs). In the BMP9/10immunoblocked (BMP9/10ib) neonatal mouse model of HHT, we report here that the mTOR inhibitor, sirolimus, and the receptor tyrosine-kinase inhibitor, nintedanib, could synergistically fully block, but also reversed, retinal AVMs to avert retinal bleeding and anemia. Sirolimus plus nintedanib prevented vascular pathology in the oral mucosa, lungs, and liver of the BMP9/10ib mice, as well as significantly reduced gastrointestinal bleeding and anemia in inducible ALK1deficient adult mice. Mechanistically, in vivo in BMP9/10ib mouse ECs, sirolimus and nintedanib blocked the overactivation of mTOR and VEGFR2, respectively. Furthermore, we found that sirolimus activated ALK2-mediated Smad1/5/8 signaling in primary ECs-including in HHT patient blood outgrowth ECs-and partially rescued Smad1/5/8 activity in vivo in BMP9/10ib mouse ECs. These data demonstrate that the combined correction of endothelial Smad1/5/8, mTOR, and VEGFR2 pathways opposes HHT pathogenesis. Repurposing of sirolimus plus nintedanib might provide therapeutic benefit in HHT patients. This study was supported by NIH/NHLBI grants R01HL139778 (to PM) and R01HL128525 (to SPO), DOD/CDMRP grant PR161205 (to SPO and PM), a Feinstein Institutes for Medical Research fund (to PM), Leducq foundation (ATTRACT, to SPO), and Barrow Neurological Foundation (to SPO). Conflict of interest:The Feinstein Institutes for Medical Research has filled a U.S. provisional patent application (#62/736,564) entitled "Combined sirolimus and nintedanib therapy for vascular lesions and hereditary hemorrhagic telangiectasia".

Defective flow-migration coupling causes arteriovenous malformations in hereditary hemorrhagic telangiectasia

“…We and others have previously reported that BMP9/10-Alk1 signaling mechanistically links flow sensing and VEGFR2-PI3K/AKT pathway activation 12-15, 17, 20, 50 . Alk1 signaling counteracted both flow and growth factor-induced AKT activation, and the absence of Alk1 overactivated PI3K/AKT signaling in AVMs [51][52][53] . We extend these findings here by demonstrating that ALK1 is required for flow-induced PI3K-AKT polarization against the direction of blood flow.…”

"Recent Advances in Hereditary Hemorrhagic Telangiectasia Pathogenesis and Therapies"

“…Various therapeutic approaches targeting Alk1 are under investigation, including monoclonal antibodies, small molecule inhibitors, and gene therapy to modulate Alk1 expression and signaling [69,119]. Ruiz et al found that Sirolimus and nintedanib in combination prevented vascular pathology in the oral mucosa, lungs and liver of the BMP9/BMP10immunoblocked mice [120]. Sirolimus binds FKBP12 and inhibits mTOR downstream of PI3K and AKT.…”

“…Ruiz et al found that Sirolimus and nintedanib in combination prevented vascular pathology in the oral mucosa, lungs and liver of the BMP9/BMP10-immunoblocked mice [120]. Tacrolimus is a strong activator of the BMP9/ALK1/Smad signaling cascade and it has been used for treatment of animal HHT and decreased the development of retinal AVMs [71].…”