The initial treatment success surrounding the efficacy of abatacept, an inhibitor of B7-1 co-stimulatory molecule in achieving clinical remission in 5 patients with FSGS (4 patients with rituximab-resistant recurrent FSGS post-kidney transplant and 1 patient with steroid-resistant primary FSGS; all with positive B7-1 immunostaining of podocytes) has not been corroborated in other cohorts (100). This evidence concerns the gene CD80 and focal segmental glomerulosclerosis.