Renalys Pharma’s Filspari Shows Strong Phase III Results, Set for Japanese NDA

Renalys Pharma’s in-licensed IgA nephropathy drug, Filspari (sparsentan), demonstrated significant efficacy in a Japanese Phase III bridging trial (jRCT2051240070), reducing 24-hour urine protein-to-creatinine ratios (UPCR) by 58.5% over 36 weeks. The therapy was also safe and well-tolerated, consistent with prior global studies. Following these results, Renalys will submit a new drug application (NDA) to Japan’s PMDA in 2026.

The drug’s approval would expand treatment options in Japan, where patients primarily rely on renin-angiotensin system blockers and corticosteroids. Chugai Pharmaceuticals, which acquired Renalys for up to $202m, will hold exclusive rights to develop and market Filspari in Japan, South Korea, and Taiwan. Filspari is already approved in the US (FDA, 2024) and EU (EMA, 2025) and endorsed by the UK NHS (NICE, 2025). Analysts predict Filspari could generate $1.44bn in 2031, amid a growing global chronic kidney disease market projected at $13.5bn by 2033.

02-12-2025