What is the mechanism of action of voclosporin compared to cyclosporine?

Both voclosporin and cyclosporine are calcineurin inhibitors (CNIs) that suppress the immune system by inhibiting calcineurin, a calcium-sensitive phosphatase. This prevents dephosphorylation of the Nuclear Factor of Activated T-cells (NFAT), blocking its nuclear translocation and subsequent transcription of pro-inflammatory cytokines such as IL-2, thereby suppressing T-lymphocyte activation. Voclosporin is an analogue of cyclosporine designed to achieve a more consistent pharmacokinetic profile and a more favorable therapeutic index, though both share the same fundamental immunosuppressive mechanism.

How does sparsentan differ mechanistically from traditional immunosuppression?

Sparsentan is a non-immunosuppressive dual endothelin angiotensin receptor antagonist (DEARA) that simultaneously blocks the Endothelin A receptor (ETAR) and the Angiotensin II subtype 1 receptor (AT1R). Unlike cyclosporine or voclosporin, it does not target the immune system at all. Instead, it addresses hemodynamic and fibrotic drivers of kidney injury — vasoconstriction, podocyte damage, inflammation, and fibrosis — leading to reduced proteinuria and nephroprotection without compromising immune function.

Why does cyclosporine cause nephrotoxicity, and how do newer agents address this?

Cyclosporine's nephrotoxic effects are partly caused by its upregulation of TGF-β, a profibrotic cytokine. Patented strategies to reduce this toxicity include co-administration of TGF-β antagonists (MCW Research Foundation patent) and cyclosporine formulations combined with omega-3 fatty acids such as eicosapentaenoic acid (Brigham and Women's Hospital patent). Voclosporin aims to reduce nephrotoxicity through improved pharmacokinetics and pharmacodynamic dosing protocols. Sparsentan avoids nephrotoxicity entirely by using a non-immunosuppressive mechanism.

What clinical evidence supports sparsentan's efficacy in IgAN and FSGS?

Sparsentan demonstrated superior efficacy in reducing proteinuria compared to irbesartan (an angiotensin receptor blocker) in patients with IgAN and FSGS. In FSGS trials, achieving partial remission — defined as a urinary protein-creatinine ratio (UPCR) ≤1.5 g/g and >40% reduction from baseline — within 9 months was associated with a significantly slower long-term eGFR decline (-2.70 vs -6.56 mL/min/1.73 m²). Sparsentan was administered at doses of 200, 400, and 800 mg/d in clinical trials.

Which companies hold the key patents for voclosporin and sparsentan?

Aurinia Pharmaceuticals Inc. holds patents for voclosporin use and dosing protocols. Travere Therapeutics, Inc. holds patents for sparsentan use in IgA-mediated diseases. Enanta Pharmaceuticals, Inc. owns a patent for cyclosporin analogues (US20100209390A1). The MCW Research Foundation, Inc. holds a patent for using TGF-β antagonists to limit CNI nephrotoxicity, and Brigham and Women's Hospital holds a patent for low-nephrotoxicity cyclosporine compositions.

What are the main side effects of sparsentan compared to cyclosporine?

Sparsentan is associated with higher rates of hypotension and peripheral edema compared to irbesartan, although these events tend to decrease after the first year of treatment. It does not carry the immunosuppression-related risks of cyclosporine, such as nephrotoxicity, gastrointestinal effects, hematological side effects, or metabolic complications like diabetes. Cyclosporine's significant nephrotoxicity and broad adverse-event profile limit its widespread and long-term use.