On 15 May, Eiger BioPharmaceuticals (Eiger Bio) announced that its Phase II LIBERTY study completed patient enrollment, bringing ubenimex closer to fulfilling an unmet need.

The LIBERTY study is designed as a Phase II, multicenter, randomised, double-blind, placebo controlled study comparing ubenimex with a placebo in pulmonary arterial hypertension (PAH) patients with slight or marked limitations to their physical abilities.

Overall, the objectives of the study are to evaluate the efficacy, safety, and tolerability of ubenimex in PAH patients.

The estimated primary completion date of the study is September 2017.

PAH is a rare, fatal cardiopulmonary disease that is a subset (Group 1) within the WHO’s classification of the different types of pulmonary hypertension (PH).

The disease is characterised by an abnormal rise in the resting mean pulmonary artery pressure (PAP) (>25mmHg compared with normal levels of around 14mmHg), a pulmonary vascular resistance of more than three Wood units, and a pulmonary capillary wedge pressure less than 15mmHg.

The increased PAP is caused by pulmonary arterial obstruction and increased resistance due to endothelial dysfunction and vascular remodelling.  

Since PAH is a progressive disorder, the pulmonary pressure builds up as the patient advances through the later stages of the disease, leading to reduced cardiac output and right heart failure.

PAH is categorised according to its clinical severity into four functional classes (FC), which are based on the classification system used for heart failure by the New York Health Association (NYHA) and modified by the World Health Organization (WHO).

The more limitations PAH has on physical activity, the higher the FC.

NYHA/WHO FC I PAH patients present with PH but without resulting limitation of physical activity. NYHA/WHO FC II PAH patients present with PH resulting in slight limitation of physical activity. NYHA/WHO FC III PAH patients present with PH resulting in marked limitation of physical activity. NYHA/WHO FC IV PAH patients present with PH with inability to carry out any physical activity without symptoms.

The LIBERTY study includes patients classified as NYHA/WHO FC II and III.

The currently marketed drugs that are indicated for PAH address the deficiencies that accompany impaired secretion of vasodilators such as nitric oxide (NO) and prostacyclin (PGI2), or correct the prolonged overexpression of vasoconstrictors such as endothelin.

If approved, ubenimex would be a first-in-class oral small-molecule dual inhibitor of aminopeptidase and leukotriene A4 hydrolase (LTA4H). LTA4H catalyses the formation of proinflammatory mediator, LTB4, an agent that contributes to the development of PAH.

According to GlobalData, since there are currently no anti-inflammatory drugs indicated for PAH, the potential approval of ubenimex would address an unmet need for the PAH patient population and should be able to capture market share with ease.

Historically, Nippon Kayaku’s Bestatin (ubenimex) has been used in Japan for the treatment of acute non-lymphocytic leukemia in adults.

The US Food and Drug Administration (FDA) and the European Medicines Agency (EMA) have granted Orphan Drug status to ubenimex for the treatment of PAH.