INTRODUCTION: To assess time in range (TIR) (70-180 mg/dL) with postprandial glucose (PPG)-focused titration of ultra rapid lispro (URLi; Lyumjev®) in combination with insulin degludec in people with type 1 diabetes (T1D). METHODS: This phase 2, single-group, open-label, exploratory study was conducted in 31 participants with T1D on multiple daily injection therapy. Participants were treated with insulin degludec and Lispro for an 11-day lead-in and then URLi for a 46-day treatment period consisting of 35-day titration and 11-day endpoint maintenance period. Glucose targets for the titration period were PPG < 140 mg/dL or < 20% increase from premeal, fasting glucose 80-110 mg/dL, and overnight excursion ± 30 mg/dL or less. Participants used the InPen™ bolus calculator and Dexcom G6 continuous glucose monitoring (CGM). RESULTS: Primary endpoint mean TIR (70-180 mg/dL) with URLi during the maintenance period was 70.2%. TIR (70-180 mg/dL) and times below/above range were not significantly different with URLi (maintenance) versus lispro (lead-in). HbA1c decreased from 7.1% at screening to 6.8% at endpoint (least squares mean [LSM] change from baseline, - 0.36%; P < 0.001). Fructosamine and 1,5-anhydroglucitol improved (P < 0.001). Mean hourly glucose using CGM was reduced from 8:00 AM to 4:00 PM with URLi. Overall highest PPG excursion across meals was significantly reduced at URLi endpoint compared with lispro lead-in (mean 56.5 vs 72.4 mg/dL; P < 0.001). Insulin-to-carbohydrate ratio (U/X g) was reduced (more insulin given) at breakfast at URLi endpoint vs lead-in (LSM 9.0 vs 9.7 g; P = 0.002) and numerically decreased at other meals. Total daily insulin dose (TDD) was higher at URLi endpoint compared with lispro lead-in (mean 50.2 vs 47.0 U; P = 0.046) with similar prandial/TDD ratio (mean 52.1% vs 51.2%). There were no severe hypoglycemia events during the study. CONCLUSIONS: URLi in a basal-bolus regimen focusing on PPG targets demonstrated improved overall glycemic control and reduced PPG excursions without increased hypoglycemia in participants with T1D. TRIAL REGISTRATION: ClinicalTrial.gov, NCT04585776.