Novel therapeutics for fatty acid oxidation disorders

Paschalis-Thomas Doulias Ph.D.*, Margarita Tenopoulou Ph.D., Gabriella Zura B.Sc., Harry Ischiropoulos Ph.D

The Children’s Hospital of Philadelphia, Philadelphia, PA, USA

*email: doulias@email.chop.edu, tel: +1 267-426-6944

Herein, we are presenting evidence for the therapeutic efficacy of a hybrid molecule named 2-mononitrate-1,3-diheptanoin (MNDH). We reasoned that MNDH will retain the anaplerotic function of triheptanoin (TH) while it furnishes bioactive nitric oxide (NO) equivalents inside the mitochondria to augment enzymatic and transporter activities via selective S-nitrosylation. The scientific premise for this novel molecule is based on our previous observations that NO through selective S-nitrosylation of cysteine residues in enzymes and transporters participating in long- chain fatty acid oxidation confer an increase in function. The coordinated gain-of-function is manifested by an augmented flux for palmitate oxidation and a restoration of a normal acylcarnitine profile.

To begin testing MNDH we exposed non-disease fibroblasts to MNDH and showed a time and concertation dependent increase in the levels of protein S-nitrosocysteine indicating that metabolism of MNDH generates NO equivalents. A dose dependent increase of FAO flux was also documented. For one of the enzymes, VLCAD we also demonstrated selective S-nitrosylation that corresponded with an increase in enzymatic activity.

The efficacy of MNDH was tested in fibroblasts harboring VLCAD mutations G185S/G294E and P91Q/G193R. Treatment with MNDH but not TH restored the VLCAD specific activity and FAO flux concomitant with the S-nitrosylation of VLCAD.

These data provide the first evidence for the efficacy of delivering bioactive NO to prevent biochemical abnormalities caused by VLCAD deficiency. Current studies are investigating the efficacy of MNDH to restore metabolic and phenotypic deficiencies in the setting of VLCAD, carnitine palmitoyltransferase 2, CPT2 and mitochondrial trifunctional protein deficiency. Toxicological, PK/PD studies for MNDH are also in process. Preliminarily, MNDH does not have systemic vasodilator effects and is primarily metabolized within mitochondria to deliver bioactive NO making it a potential candidate for therapeutic development.