Background: Tyrosine kinase inhibitors (TKI) and Nivolumab (NIVO) are standard treatment options for mRCC. We tested whether TKI followed by early switch to NIVO improved outcome in mRCC patients (pts). Methods: Main inclusion criteria: measurable advanced or metastatic clear cell RCC, ECOG PS 0-2, adequate organ function, PR or SD to induction therapy with sunitinib (50 mg, 4-2 regime) or pazopanib (800 mg OD). 1:1 randomization at 12 wks.: TKI continuation vs. switch to NIVO (240 or 480 mg IV q2-4wks). Strata were MSKCC risk, TKI used and response to TKI. Imaging was performed q12w. 49 of 244 planned pts were randomized between Dec 2016 and Aug 2018, which led to premature closure of the trial. We report the second interim analysis with data base lock on 31.07.19. ORR was assessed according to RECIST 1.1. Efficacy and safety analyses were performed in ITT and safety population, respectively. Log-Rank analyses were used for survival analyses. Results: 25 and 24 pts received NIVO or TKI, respectively. Median age was 65 y (range: 35-79), 82% were male and 4% had ECOG PS 2. Metastases occurred predominantly in lung (47%), lymph nodes (27%) and liver (24%). MSKCC risks were: favorable (31%), intermediate (65%), and poor (4%), which were balanced between arms. 55% received sunitinib. ORR for NIVO vs. TKI differed when assessed from start of induction therapy (64 vs. 70%, P=0.76) or from time of randomization (16 vs. 48%; P=0.032). Accordingly, PFS from randomization was 3.0 vs. 11.9 mo. (HR = 1.72 [95% CI: 1.19 – 2.48]; P=0.0026) in favor of TKI continuation. At a median follow-up of 12.9 mo. median OS was not reached, but HR = 1.86 (95% CI: 0.85 – 4.07) P=0.10 showed a trend for TKI continuation. All grades AE for NIVO vs. TKI occurred in 96% vs. 100%, grade 3-5 48% vs. 71% and serious AE 40% vs. 46%. Conclusions: In TKI-sensitive pts, continuation of TKI is more efficacious than early switch to NIVO. The major limitation of our trial is the premature closure and its limited sample size. Clinical trial information: NCT02959554