MST-188 (purified poloxamer 188)
MST-188 is a purified form of a nonionic, triblock copolymer (poloxamer 188). It is an investigational agent that binds to hydrophobic surfaces on damaged cells and improves membrane hydration and lowers adhesion and viscosity, particularly under low shear conditions. MST-188 has the potential to reduce ischemic tissue injury and end-organ damage by restoring microvascular function, which is compromised in a wide range of serious and life-threatening diseases and conditions. We initially are developing MST-188 as a treatment for complications arising from sickle cell disease.
How MST-188 Works…
Non-purified forms of poloxamer 188 (P188) have been used in foods, drugs and cosmetics since the 1950s. In the 1980s, extensive research on the mechanisms and potential clinical applications of P188 was conducted. Research has demonstrated that P188 binds to hydrophobic surfaces that develop when cells are damaged and restores normal hydrated surfaces, while having little or no activity in normal, healthy tissues. Research also has demonstrated that P188 prevents adhesion and aggregation of soluble fibrin and formed elements in the blood and maintains the deformability of red blood cells, the non-adhesiveness of unactivated platelets and granulocytes and the normal viscosity of blood. In addition, it is believed that P188 is not metabolized, but is excreted unchanged in the urine with a half-life of approximately four to six hours.
Formulations of P188 (non-purified and purified) have been studied in clinical trials involving nearly 4,000 individuals. It has been evaluated in the clinic to treat acute myocardial infarction, sickle cell disease and malaria, including a 2,950-patient, randomized, controlled study of P188 (non-purified) in acute myocardial infarction. The effectiveness of P188 also has been investigated in nonclinical studies of stroke, hemorrhagic shock, bypass surgery, adult respiratory distress syndrome, neurologic protection in deep hypothermic circulatory arrest, vasospasm, spinal cord injury, angioplasty, frostbite, amniotic fluid embolism, acute ischemic bowel disease and burns.
Our purified form of P188, or purified P188, which is the active ingredient in MST-188, was designed to eliminate certain low molecular weight substances present in P188 (non-purified), which we believe were primarily responsible for the moderate to moderately severe elevations in serum creatinine levels (acute renal dysfunction) observed in prior clinical studies of P188 (non-purified). Purified P188 has been evaluated in multiple clinical studies by a prior sponsor, including a 255-patient, phase 3 study. In that study, purified P188 was generally well tolerated and there were no clinically significant elevations in serum creatinine among subjects who received purified P188 compared to placebo.
We believe that, as a rheologic, antithrombotic and cytoprotective agent, MST-188 has potential application in treating a wide range of diseases and conditions resulting from microvascular-flow abnormalities.
Sickle Cell Disease Market & Opportunity
More than $1.0 billion is spent annually in the U.S. to treat patients with sickle cell disease. Sickle cell disease is a genetic disorder characterized by the “sickling” of red blood cells, which normally are disc-shaped, deformable and move easily through the microvasculature carrying oxygen from the lungs to the rest of the body. Sickled, or crescent-shaped, red blood cells, on the other hand, are rigid and sticky and tend to adhere to each other and the vascular endothelium. Patients with sickle cell disease are known to experience severely painful episodes associated with the obstruction of small blood vessels by sickle-shaped red blood cells. These painful episodes are commonly known as acute crisis or vaso-occlusive crisis. Reduced blood flow to organs and bone marrow during vaso-occlusive crisis not only causes intense pain, but can result in tissue death, or necrosis. The frequency, severity and duration of these acute crises can vary considerably.
We estimate that, in the U.S., sickle cell disease results in over 95,000 hospitalizations and, in addition, approximately 69,000 emergency department treat-and-release encounters each year. When a patient with sickle cell disease makes an institutional visit, vaso-occlusive crisis is the primary diagnosis in approximately 77% of hospital admissions and 64% of emergency room treat-and-release encounters. In addition, although the number is difficult to measure, we estimate that the number of untreated sickle cell crisis events is substantial and in the hundreds of thousands in the U.S. each year. We believe that, if MST-188 is approved, as people with sickle cell disease are made aware of the new therapy, more people who suffer from acute crisis will seek treatment.
We have initiated a Phase 3 clinical study of MST-188 for the treatment of sickle cell disease. The primary objective will be to demonstrate that MST-188 reduces the duration of vaso-occlusive crisis in patients with sickle cell disease. Please see our Clinical Trials page for more information regarding our phase 3 study of MST-188. In addition to the phase 3 study, we plan to conduct a number of smaller-scale clinical studies to further assess the efficacy, safety and tolerability of MST-188, and expect these studies to overlap with the phase 3 study.