ProKidney Cuts Phase 3 Power Assumption and Cohort Size for Third Time in Three Months
Company Background
ProKidney Corp. is a clinical-stage cell therapy company developing rilparencel, an autologous kidney cell therapy, for patients with Stage 3b/4 chronic kidney disease and type 2 diabetes. Rilparencel carries the FDA's Regenerative Medicine Advanced Therapy designation and is the only cell therapy currently in a Phase 3 study for that indication. The company has no approved products and generates minimal revenue — $226,000 in the first quarter of 2026.
The company's entire near-term value rests on its pivotal Phase 3 PROACT 1 trial (REGEN-006). ProKidney entered 2026 on what appeared to be solid footing: in July 2025, Phase 2 REGEN-007 data showed a statistically significant 4.6 mL/min/1.73m² improvement in eGFR slope in Group 1, well above the FDA-agreed minimum effect size of 1.5 mL/min/1.73m². That same month, a Type B meeting confirmed eGFR slope as the primary surrogate endpoint for accelerated approval. ProKidney had roughly $375 million in market capitalization and $224.9 million in cash as of March 31, 2026.
Since late 2025, however, ProKidney has repeatedly revised the design parameters of PROACT 1 downward. Total planned enrollment was cut from approximately 685 subjects to approximately 470 in February 2026. The size of the accelerated approval efficacy cohort was listed at approximately 360 patients in the March 2026 full-year earnings release and has now been reduced again to approximately 320. The statistical power assumption for the surrogate endpoint analysis has also been revised.
What Was Disclosed
On May 15, 2026, ProKidney filed an 8-K disclosing first-quarter 2026 financial results, an updated investor presentation, and — in a separate Item 8.01 — a one-sentence update to the statistical design of PROACT 1: the powering assumption for the surrogate endpoint (eGFR slope) analysis has been revised to 80%. The filing also quantifies the current power profile: 80% power to detect a 1.5 mL/min/1.73m² effect size (the FDA's agreed minimum threshold) and 90% power to detect a 1.75 mL/min/1.73m² effect. The investor presentation accompanying the filing shows the accelerated approval analysis cohort has been reduced from approximately 360 patients (as stated in the March 18, 2026 full-year earnings release) to approximately 320. The confirmatory composite endpoint analysis target remains at approximately 470 subjects. The BLA submission timeline has also shifted: the March 2026 milestones table listed Q4 2027; the May 2026 investor presentation now states Early 2028.