Development background

Since the discovery that Nitroglycerin and related compounds operate through the release of nitric oxide (NO), considerable resources have been invested in attempts to develop new and better NO donors in the hope that these could be used in life-threatening conditions where there is a large need for effective and safe medicines. 

It has now been more than 30 years since the groundbreaking discoveries of NO were made, but no such drug has yet reached the market. How can it be that Attgeno has succeeded where all the other and major pharmaceutical giants have failed? 

The first phase of the discovery of Supernitro began already in the mid-1980s at a meeting between two brilliant researchers, Professor Salvador Moncada who discovered and in detail mapped the synthesis path of how the human body produces NO, and the now unfortunately deceased Professor Lars E. Gustafsson from Karolinska Institutet. The two geniuses began a research collaboration where Professor Moncada was generous enough to lend a newly constructed machine to measure NO gas in extremely low concentrations. 

When Lars E. Gustafsson investigated the instrument in various ways, he made the groundbreaking discovery that it was possible to measure NO production in the lungs, on-line, by analyzing NO gas in the exhaled air. 

Lars’ discovery not only laid the foundation for a completely new field of research (today over 14,000 published articles worldwide), but he was also wise enough to realize the commercial potential of the discovery. Based on Lars E. Gustafsson’s discovery, exhaled NO was patented and the company Aerocrine founded for further development of the methodology. The technique is currently used for the diagnosis and treatment control of asthma. Aerocrine was sold to Circassia in 2015 for Euro 1.8 billion. 

Despite the success of the discovery of NO in exhaled air and having contributed to improved asthma treatment for millions of patients, Lars was not satisfied. He wanted to be able to use his unique knowledge also to develop new drug treatments for cardiovascular diseases and lung diseases. 

To achieve this, Lars Gustafsson and his disciples, among them Associate Professor Magnus Persson began to develop in vivo models that enabled them to use the technique of exhaled NO to be able to study NO formation from various NO-donating drugs in the cardiovascular system, with high resolution of time. 

These unique research conditions gave the basis for the discovery of a completely new method of creating solutions with NO-donating properties, the method won first prize in Karolinska Institutet’s major Innovation Competition in 2005. Through the method, the researchers who founded Attgeno have been able to screen a large number of NO compounds and find new molecules with unique properties, including Supernitro. Most who have tried to develop new NO donors have done this by traditional drug development, i.e. starting with trials in test tubes or cell cultures to identify new mechanisms of action and design molecules that are tested and taking only the most promising candidates to in vivo tests. 

The problem with NO is that the molecule has an extremely complex and rapid metabolism that is affected by a range of biological conditions such as the presence of blood, partial pressure of various gases, tissue levels of various reactive molecules, etc. The biological half-life of NO in the body’s tissues is usually a single second and in contact with the blood, NO breaks down in fractions of a second. NO-metabolism is so complex that it is almost impossible to draw conclusions from in vitro studies of what will happen in vivo. It was this insight, built on decades of work at the forefront of research on NO that led to Lars E. Gustafsson and his group to go the opposite way, to start screening in vivo and thus enabling the discovery of Supernitro.

Scientific basis for the treatment of Pulmonary Hypertension with NO donors

In all forms of pulmonary hypertension there is some degree of damage or impaired function of the endothelium, a thin cell layer that covers the inside of blood vessels of the lung.The impaired function of the endothelial cells leads to diminished production of NO that is normally produced in these cells and NO is important to relax the smooth muscle in the vessels to keep them dilated (widened). NO works by activating the enzyme guanylate cyclase in the smooth muscle cells in and increases the formation of cyclic guanosine monophosphate (cGMP) that initiate the cascade leading to smooth muscle relaxation and pulmonary vasodilation. Therefore, an optimal treatment should restore the endothelial NO production and the most logical way is that NO should be delivered from the endothelial side of the pulmonary blood vessels. 

The intravenous NO donors available today release NO from the blood into the blood vessels via the endothelium but these NO donors are not selective for the pulmonary circulation and elicits systemic vasodilation (hypotension) as well. Another problem, as previously described, is the tolerance development of these drugs. Furthermore, many of the NO-donors quickly enter the red blood cells where they react with hemoglobin and form methemoglobin that cannot bind and transport oxygen. 

The optional administration route is to let a patient inhale NO (INOmax) and this form of treatment is selective for lung circulation. Unfortunately, many critically ill patients have pathological changes in the airways including inflammation and edema that makes it difficult for the inhaled NO molecules to reach the blood vessels smooth muscles. This diffusion issue is one explanation to why inhaled NO often is ineffective in many conditions with acute pulmonary hypertension. In addition, a lung tissue with inflammation and edema, inhaled NO risks interacting with the increased levels of reactive oxygen species in the airways and form tissue-damaging molecules that promotes inflammation 

Thus, the optimal treatment for Pulmonary hypertension is to give NO intravenously so that all the pulmonary blood vessels can be exposed to NO so that the blood vessels are fully dilated (widened). However, all the NO must be released in the lung so that when the blood reaches the systemic circulation there is no remaining NO that otherwise could lead to a fatal drop in systemic blood pressure. Optimal NO treatment in Pulmonary hypertension should be free of tolerance development or increased formation of methemoglobin. Supernitro is a new organic nitrite, an intravenous NO donor with a potent vasodilator effect in the pulmonary circulation, with no tolerance development or methemoglobin production. 

Supernitro is thought to be used in acute pulmonary hypertension in severely ill patients. Supernitro has been shown effective in several preclinical experimental animal models of Pulmonary Hypertension and with a broad safety profile in the toxicological studies carried out.