Evaluation of Circulating Kidney Injury Marker-1 (KIM-1) As a Prognostic and Predictive Biomarker in Advanced Renal Cell Carcinoma (arcc): Post-hoc Analysis of CheckMate 214.

437 Background: CheckMate 214 established nivolumab and ipilimumab (NIVO+IPI) as a first line standard of care regimen with superior survival and durable response versus sunitinib (SUN) in advanced RCC. Previous studies have shown that high levels of circulating KIM-1 are associated with worse prognosis and reduction in KIM-1 levels is associated with benefit from adjuvant immunotherapy. In this post-hoc analysis we evaluated whether KIM-1 levels at baseline and after 1 cycle of NIVO+IPI or SUN are associated with treatment outcomes in CheckMate 214. Methods: Patients with advanced RCC were randomized to NIVO+IPI or SUN as previously described. Serum KIM-1 was measured at baseline and 3 wks after first treatment dose using an enzyme based electrochemiluminescence assay. The association between KIM-1 levels and clinical outcomes was evaluated using Kaplan-Meier and Cox proportional hazards analyses. Results: We analyzed serum from 821 patients (75% of the CM 214 ITT population). Median KIM-1 at baseline was 660.4 pg/mL. Across both arms, higher KIM-1 levels were associated with shorter overall survival (OS) independent of IMDC risk group, nephrectomy status, and tumor burden. Benefit for NIVO+IPI versus SUN was seen across KIM-1 tertiles. Decrease in KIM-1 from baseline to C2D1 was strongly associated with progression free survival (PFS) and OS among patients treated with NIVO+IPI (Median PFS 70.8 months vs 4.2 months for patients with >30% decrease vs >30% increase in KIM-1, with median OS 85.4 vs 26.6 months, overall response rate (ORR) 69.3 % vs 13.9%), but not in patients treated with SUN. Conclusions: In CheckMate 214, increased levels of baseline circulating KIM-1 were associated with worse clinical outcomes both in NIVO+IPI and SUN arms. The extent of reduction in serum KIM-1 just 3 wks after single cycle of NIVO+IPI was associated with long term efficacy of this IO doublet. Circulating KIM-1 may be a useful minimally invasive biomarker for monitoring patients on RCC immunotherapy. KIM-1 change at 3 weeks (prior to second dose of NIVO+IPI) and association with outcomes (NIVO+IPI arm). 3 week KIM-1 change N (%) ORR, % (95% CI) mPFS, months (95% CI) mOS, months (95% CI) >30% Decrease 140 (31.7) 69.29 (60.94-76.80) 70.80 (17.84- NA) 85.36 (63.08- NA) >10-30% Decrease 87 (19.7) 36.78 (26.69-47.80) 11.43 (6.28-18.20) 66.14 (40.44-80.10) <10% Change 86 (19.5) 30.23 (20.79-41.08) 15.41 (10.32-20.73) 52.70 (30.26-70.67) >10-30% Increase 56 (12.7) 23.21 (12.98-36.42) 7.13 (4.17-16.79) 40.34 (23.82-58.41) >30% Increase 72 (16.3) 13.89 (6.87-24.06) 4.17 (3.02-8.08) 26.61 (18.79-38.44)