Case Report: Combined Liver-Kidney Transplantation to Correct a Mutation in Complement Factor B in an Atypical Hemolytic Uremic Syndrome Patient

Inhibiting the alternative pathway of complement by reducing systemic complement factor B: Randomized, double-blind, placebo-controlled phase 1 studies with Sefaxersen

An over-active alternative complement pathway has been implicated in the pathophysiology of multiple diseases, including IgA nephropathy and geographic atrophy secondary to age related macular degeneration. In first-in-human double-blind, placebo-controlled phase 1 studies, the safety and pharmacodynamic effects of sefaxersen (RO7434656), a GalNAc-conjugated 2'-MOE antisense oligonucleotide targeting the complement factor B mRNA, was investigated. Healthy volunteers received either single or repeated (for 6 weeks) subcutaneous administrations of investigational drug or placebo. Safety and plasma complement protein levels were assessed throughout the studies and during 90-day follow-up periods. All subjects (54) completed the studies and no safety signals or clinically meaningful changes in blood chemistry, urinalysis, hematology, ECG, vital signs or ocular endpoints were observed. Mean levels of systemic complement factor B (FB) were reduced up to 38 % after single administration and 69 % after repeated administration. Lowering of FB protein was paralleled by similar reductions of plasma Bb levels. There was a strong correlation between reduction of plasma levels of FB and alternative complement pathway activity (AH50), but no meaningful changes in classical complement pathway activity (CH50). The long duration of lowering of FB levels following the last dose supports monthly dosing in future clinical trials. These clinical results support the ongoing Phase 2 development for geographic atrophy secondary to age-related macular degeneration and Ph 2/3 development for IgA nephropathy.

Thrombotic microangiopathy after kidney transplantation: Expanding etiologic and pathogenetic spectra

Thrombotic microangiopathy (TMA) is an uncommon but serious complication that not only affects native kidneys but also transplanted kidneys. This review is specifically focused on post-transplant TMA (PT-TMA) involving kidney transplant recipients. Its reported prevalence in the latter population varies from 0.8% to 14% with adverse impacts on both graft and patient survival. It has many causes and associations, and the list of etiologic agents and associations is growing constantly. The pathogenesis is equally varied and a variety of patho genetic pathways lead to the development of microvascular injury as the final common pathway. PT-TMA is categorized in many ways in order to facilitate its management. Ironically, more than one causes are contributory in PT-TMA and it is often difficult to pinpoint one particular cause in an individual case. Pathologically, the hallmark lesions are endothelial cell injury and intravascular thrombi affecting the microvasculature. Early diagnosis and classification of PT-TMA are imperative for optimal outcomes but are challenging for both clinicians and pathologists. The Banff classification has addressed this issue and has developed minimum diagnostic criteria for pathologic diagnosis of PT-TMA in the first phase. Management of the condition is also challenging and still largely empirical. It varies from simple maneuvers, such as plasmapheresis, drug withdrawal or modification, or dose reduction, to lifelong complement blockade, which is very expensive. A thorough understanding of the condition is imperative for an early diagnosis and quick treatment when the treatment is potentially effective. This review aims to increase the awareness of relevant stakeholders regarding this important, potentially treatable but under-recognized cause of kidney allograft dysfunction.

TMA in Kidney Transplantation

Thrombotic microangiopathy (TMA) is a rare and devastating complication of kidney transplantation, which often leads to graft failure. Posttransplant TMA (PT-TMA) may occur either de novo or as a recurrence of the disease. De novo TMA can be triggered by immunosuppressant drugs, antibody-mediated rejection, viral infections, and ischemia/reperfusion injury in patients with no evidence of the disease before transplantation. Recurrent TMA may occur in the kidney grafts of patients with a history of atypical hemolytic uremic syndrome (aHUS) in the native kidneys. Studies have shown that some patients with aHUS carry genetic abnormalities that affect genes that code for complement regulators (CFH, MCP, CFI) and components (C3 and CFB), whereas in 10% of patients (mostly children), anti-FH autoantibodies have been reported. The incidence of aHUS recurrence is determined by the underlying genetic or acquired complement abnormality. Although treatment of the causative agents is usually the first line of treatment for de novo PT-TMA, this approach might be insufficient. Plasma exchange typically resolves hematologic abnormalities but does not improve kidney function. Targeted complement inhibition is an effective treatment for recurrent TMA and may be effective in de novo PT-TMA as well, but it is necessary to establish which patients can benefit from different therapeutic options and when and how these can be applied.