ITPP

Myo-inositol trispyrophosphate (ITPP) is a synthetic pyrophosphate derivative of phytic acid that functions as a membrane-permeant allosteric effector of hemoglobin, reducing the affinity of hemoglobin for oxygen and shifting the oxyhemoglobin dissociation curve to the right, thereby enhancing the release of molecular oxygen from erythrocytes into tissues under conditions of low partial pressure of oxygen. The compound was conceived in the laboratory of Jean-Marie Lehn (Nobel Laureate in Chemistry, 1987) and Claude Nicolau in the early 2000s as a rationally designed analog of the endogenous erythrocyte effector 2,3-diphosphoglycerate (2,3-DPG), engineered to bear three cyclic pyrophosphate rings on the myo-inositol scaffold that confer net negative charge sufficient to bind the positively charged central cavity of deoxyhemoglobin while maintaining membrane permeability across the erythrocyte plasma membrane via the band 3 anion transport complex. Unlike 2,3-DPG and the structurally related phytic acid (inositol hexakisphosphate), which cannot traverse the red blood cell membrane, ITPP enters the erythrocyte intact and engages the allosteric T-state binding site of hemoglobin in situ, producing a dose-dependent rightward shift of the P50 (the partial pressure of oxygen at which hemoglobin is 50 percent saturated) without altering cooperativity or total oxygen-carrying capacity.

The preclinical pharmacology of ITPP spans three principal therapeutic domains. In oncology, ITPP-mediated tumor reoxygenation produces downregulation of hypoxia-inducible factor 1-alpha (HIF-1alpha) and vascular endothelial growth factor (VEGF), normalization of tumor vasculature through activation of the endothelial PTEN/AKT signaling axis, and potentiation of subsequent chemotherapy and radiation therapy in rodent models of pancreatic, hepatocellular, colorectal, melanoma, glioblastoma, and rhabdomyosarcoma tumors. In cardiovascular medicine, ITPP treatment in rodent models of myocardial infarction and monocrotaline-induced pulmonary hypertension has produced improved myocardial oxygenation, attenuation of adverse left and right ventricular remodeling, reduction of pulmonary hypertension-related mortality, and dose-dependent increases in maximal exercise capacity of up to 57 percent in normal mice and 63 percent in transgenic mice with severe heart failure. In metabolism, ITPP has demonstrated reduction of adipose tissue accumulation in high-fat-diet rodent models through reversal of adipose tissue hypoxia.

The compound entered clinical development under the designation OXY111A through Normoxys, Inc. A Phase Ib dose-escalation study (NCT02528526) conducted at University Hospital Zurich enrolled 28 patients with advanced hepatopancreatobiliary malignancies and colorectal cancer liver metastases across eight dose levels (1,866 to 14,500 mg/m2 per dose), administered as nine 8-hour intravenous infusions over three weeks. The maximum tolerated dose was established at 12,390 mg/m2. The compound was well tolerated, with the principal treatment-related adverse event being asymptomatic hypercalcemia attributable to calcium chloride in the formulation rather than to the compound itself. Pharmacokinetic analysis demonstrated dose-proportional exposure with a terminal half-life of 1.3 to 3.3 hours, no systemic accumulation, and plasma clearance of 3.1 to 4.8 L/h. Morphological disease stabilization was observed in 52 percent of patients under ITPP monotherapy, and subsequent chemotherapy produced stable disease in 60 percent and partial response in 10 percent. Decreases in circulating angiogenic markers (VEGFA, angiopoietin-1, angiopoietin-2, EGF, PECAM1) were observed in a majority of patients and correlated with improved survival following chemotherapy. ITPP is prohibited in competitive sport by the World Anti-Doping Agency as a substance with potential to enhance oxygen transfer, and analytical methods for its detection in human urine and equine plasma have been developed for anti-doping enforcement.