Background: The Worldwide Innovative Network (WIN) Consortium has developed the Simplified Interventional Mapping System (SIMS) algorithm in order to predict treatment response by comparing tumor and normal tissue biopsies on both genomic and transcriptomic platforms. SPRING is the first trial to assess a SIMS-based tri-therapy regimen in advanced non-small cell lung cancer (NSCLC). Methods: Patients with advanced NSCLC (no EGFR or ALK alterations; no ROS1 alterations if tested; PD-L1 unrestricted; ≤2 prior therapy lines) were treated with avelumab, axitinib, and palbociclib (3+3 dose escalation design). Tumor and normal endobronchial mucosal biopsies were obtained on all patients for retrospective SIMS algorithm validation. Results: Fifteen patients were treated: 6 at dose level 1 (DL1); 6, dose level 2 (DL2); 3, dose level 3 (DL3). Three dose-limiting toxicities (DLTs) at least possibly drug-related occurred: 1 DLT at DL2 (Grade 3 (G3) infusion reaction); 2 patients with DLTs at DL3 (1 with G3 hand/foot syndrome and G3 fatigue and 1 with G5 respiratory failure). Among 14 evaluable patients, the partial response (PR) rate was 28.6% (4/14 patients including 2/6 patients at DL1; two PRs in patients who failed prior pembrolizumab; two PRs in patients with PD-L1 < 1%). The maximum tolerated dose was avelumab 10 mg/kg IV q2weeks, axitinib 5 mg PO BID continuous, palbociclib 75 mg PO daily on days 8-28 of a 28 day cycle (DL2). DL2 was above the recommended phase II dose (RP2D), since 5/6 patients treated at DL2 required later treatment delays and/or dose reductions, mostly due to neutropenia. To further evaluate DL1, 3 patients were added to this cohort (total of 6). Since no DLTs were seen at DL1, and 5 of 6 patients did not require dose reduction, DL1 (avelumab 10 mg/kg IV q2weeks, axitinib 3 mg PO BID continuous, palbociclib 75 mg PO daily on days 8-28 of a 28 day cycle) is the RP2D. Conclusions: The RP2D was determined to be dose level 1. This triplet showed antitumor activity in patients with NSCLC, including those progressing on prior pembrolizumab. SIMS algorithm correlates of response are being assessed. Clinical trial information: NCT03386929.