Givosiran as subcutaneous injection is in clinical development for the treatment of acute hepatic porphyria (AHP). AHP is a rare genetic condition in which patients lack certain enzymes needed to produce haem, a component of the blood pigment haemoglobin. As a result, substances for making haem accumulate in the body (particularly in the liver) and become toxic, causing attacks of severe abdominal pain, vomiting and nervous system disorders, such as seizures (fits), depression and anxiety. Some patients may also experience skin problems, with skin becoming oversensitive to light. AHP is life-threatening due to the possibility of paralysis and respiratory arrest during attacks and debilitating in the long term because of symptoms such as pain, nausea, seizures and skin blistering.
Givosiran is made of a short, synthetic strand of genetic material called ‘small interfering RNA’ (siRNA) that has been designed to interfere with the production of an enzyme involved in an early step in making haem. By blocking this early step of haem production in patients with AHP, givosiran is expected to prevent the next steps which produce substances that accumulate in the body and cause the symptoms of the disease.
Avatrombopag is given as an oral tablet and works by mimicking the action of a hormone called thrombopoietin (TPO) which is responsible for causing pre-curser cells to mature into platelets. Avatrombopag binds to TPO receptors resulting in increased platelet production and increased platelet count. Results from clinical studies have demonstrated that avatrombopag is safe and efficacious. If licensed, avatrombopag could offer an additional treatment option for patients with chronic ITP who have had limited response to previous therapy.