- The Food and Drug Administration told Merck KGaA not to give an experimental drug for multiple sclerosis to new patients and to pause treatment for study participants who have been on it for less than 70 days amid concerns about possible liver damage.
- Regulators acted after laboratory tests suggested the livers of two patients might have been adversely affected by the drug, known as evobrutinib. However, neither patient exhibited symptoms and their liver enzyme levels returned to normal after they stopped taking the medicine, Merck KGaA said Wednesday.
- The German drugmaker had already fully enrolled a Phase 3 study known as Evolution, and that program will continue as planned because all the patients have already had received the medication for at least 70 days. Results are still expected in the fourth quarter.
Evobrutinib is part of a class of drugs known as BTK inhibitors, which target a protein called Bruton’s tyrosine kinase known to play a role in helping certain cancer cells proliferate. The FDA has approved four BTK inhibitors to treat blood cancers, with Lilly’s Jaypirca joining the mix in January. AbbVie and Johnson & Johnson’s Imbruvica is the market leader, pulling in net revenue of $4.6 billion last year.
In recent years, the class of drugs has drawn interest from scientists who believe that blocking BTK may also help treat so-called autoimmune conditions, in which a person’s immune system malfunctions and starts attacking healthy cells. In MS, the area under attack is the protective covering for nerves in the brain and spinal cord.
To treat MS, researchers are focusing on a subset of BTK inhibitors designed to penetrate the blood-brain barrier. Drugmakers are hopeful the medicines can delay MS symptoms while also helping preserve essential immune system cells.
The potential for new uses for BTK inhibitors prompted Sanofi to buy Principia Biopharma for $3.7 billion three years ago. A year later, Biogen acquired rights to a BTK inhibitor from China’s Innocare. Novartis and Roche are also testing drugs in the class for MS.
But safety issues have cropped up. In 2022, the FDA told Sanofi to stop treating some patients in studies in MS and the autoimmune disorder myasthenia gravis after seeing signs of liver damage. The French drugmaker later paused all of its trials and eventually decided to give up on the myasthenia gravis indication. Biogen, meanwhile, exited development of the Innocare drug in February.
Merck KGaA emphasized that an independent committee has been carefully monitoring trials of its medicine. The company said it’s “working closely with the FDA to establish the path forward” for evobrutinib in current and future trials.