A new drug is poised to enter the PAH market and offers great promise for patients. This new drug works in a completely different way from all the currently approved medications. Sotatercept is an injection (shot) that is given subcutaneously (under the skin) every 3 weeks. The medication acts by blocking activin. In PAH there are good signals and bad signals within the blood vessels of the lungs. BMPR2 is a good signal. Activin is a molecule that works against BMPR2. When BMPR2 is activated, it leads to healthy pulmonary artery development. If there is not enough BMPR2 this leads to an excess of activin signaling, which in turn leads to the development of pulmonary arterial hypertension. Sotatercept binds activin and effectively lowers the level of signaling down the pathway. As a result of this “rebalancing”, the signals received by the pulmonary arteries are more normal and the vessels of the lungs become less stiff and the pressure in the pulmonary artery decreases.
Two studies have now been completed that showed how effective Sotatercept is at lowering pulmonary artery pressure and pulmonary vascular resistance (a measure of how difficult it is for blood to flow through the pulmonary arteries). The medication is well tolerated well. In the phase 2 study the two most important side effects were an increase in the number of red cells (hemoglobin) and a reduction in the number of platelets. These side effects were mild to moderate most of the time. Howevere, as a result of these findings, we expect the FDA to require regular blood tests to monitor blood counts. There were rare reports of tiny new blood vessels on the skin called telangiectasias in a few patients.
What’s next? The phase 3 study has been completed and the top line results reported. They showed similar findings to the phase 2 study. Over the next six months we expect to see a full report of the phase 3 study and the data will be submitted to the FDA for review. I am very optimistic the drug will be approved.
Who will be a candidate for Sotatercept? I expect the drug to be used widely in PAH. The study included patients on background therapy with other PAH medications and had to have at least a moderately elevated pulmonary vascular resistance. Based on the types of patients included in the study, I anticipate using the medication in patients who are on two or three other PAH medications and still have not normalized or nearly normalized their pulmonary artery pressures and pulmonary vascular resistance. Additionally, I anticipate using Sotatercept to help PAH patients who are on pump-based therapies perhaps transition to a non-pump-based regimen (switching from subcutaneous Treprostinil or intravenous Treprostinil/Epoprostenol to an inhaled medication and adding Sotatercept).