A group of researchers led by Dr. Peter H. Mundel at Massachusetts General Hospital has recently identified the first targeted therapy for a specific type of kidney disease, focal segmental glomerulosclerosis, or FSGS.

Using a drug that has already been approved for rheumatoid arthritis–abatacept, also known as Orencia–Mundel’s group reported success in treating FSGS in five patients. Their work was published online on Nov. 8 in the New England Journal of Medicine.

“Similar to what is now being seen with cancer where researchers are looking for personalized treatments based on genetics, we found a specific biomarker, B7-1, which has been attributed to a subset of FSGS,” said Mundel, who is also an associate professor of medicine at Harvard Medical School.

Mundel’s group first identified the relationship between B7-1 and FSGS in 2004. Although previously believed to be a biomarker that was exclusive to immune cells, Mundel’s group demonstrated that B7-1 was also expressed by podocytes, kidney cells that play a major role in blood filtration.

Further work showed that the presence of B7-1 in podocytes was associated with a deterioration of the kidney’s normal filtration system. Mundel said one of the problems that occurs as a result is proteinuria, or the loss of protein in the urine,

“In addition to the immediate and obvious effects of protein loss on the body, proteinuria is also significant because it is a prognostic indicator of progressive kidney disease and potentially cardiovascular disease,” Mundel said.

After uncovering the role of the biomarker B7-1 in proteinuria, Mundel’s team discovered that suppressing the B7-1 biomarker could potentially remedy the FSGS disease. Abatacept, a drug that was previously approved for rheumatoid arthritis, is coincidentally a B7-1 inhibitor and the group decided to test the drug on five patients with FSGS who expressed B7-1.

Follow-up testing showed that all five patients saw improvements in proteinuria.

“Orencia [abatacept] is now in use in 50,000 to 100,000 patients for rheumatoid arthritis, and we can repurpose the drug for kidney disease,” Mundel said. “We also know that it is relatively safe to use the drug, based on this arthritis experience.”

A large-scale clinical trial to confirm the findings and test the efficacy of abatacept is currently in the works. In addition, Mundel said he also hopes to tackle the bigger challenge of understanding why only a subset of patients with FSGS have the particular B7-1 biomarker and how to treat those individuals as well.