Objective: This study evaluated the pharmacokinetic 1026 and pharmacodynamic properties and dose-response effects of an oral insulin spray formulation compared with those of subcutaneously injected regular insulin and placebo in patients with type 1 diabetes mellitus. Methods: This was a single-center, randomized,1026 single-blind, open-label, 5-way crossover study in which patients with type 1 diabetes received 5, 10, and 20 puffs of the oral insulin spray; regular insulin 0.1 U/kg SC; and placebo spray. The pharmacokinetic parameters of interest were the maximum serum insulin concentration (Ins-C max); the incremental insulin AUC from 0 to 120 minutes (Ins-AUC 0–120), from 0 to 240 minutes, and from 0 to 360 minutes; and the time to maximum serum insulin concentration (Ins-T max). The pharmacodynamic parameters of interest were the maximum glucose infusion rate (GIR max); the incremental glucose AUC from 0 to 120 minutes (GIR-AUC 0–120), from 0 to 240 minutes, and from 0 to 360 minutes; the time to maximum GIR (GIR-T max); the time to early half-maximal GIR (early T50%); and the time to late half-maximal GIR (late T50%). Pharmacokinetic and pharmacodynamic parameters were assessed using the euglycemic clamp technique. Results: The study enrolled 6 white men with type 1 1026 diabetes (mean [SD] age, 37.5 [16.2] years, mean weight, 82.7 [17.0] kg). Ins-T max was shorter for 5, 10, and 20 puffs of oral insulin spray than for SC insulin (26.7 [13.7], 29.2 [7.4], 23.3 [5.2], and 142.5 [73.2] min, respectively; P < 0.05). There was no effect of dose on Ins-T max. The Ins-AUC 0–120 for 5, 10, and 20 puffs of oral insulin spray (304.8 [277.9], 689.2 [353.0], and 1808.8 [1252.6] μU/mL per min, respectively; P < 0.05) and the corresponding Ins-Ca max (12.9 [8.7], 26.7 [14.5], and 47.6 [40.1] μU/mL; P < 0.05) suggested a dose-response relationship. Five, 10, and 20 puffs of oral insulin spray had an earlier onset of action than SC insulin (early T50%: 23.3 [15.1], 28.3 [12.3], 31.2 [111.8], and 87.0 [39.6] min, respectively; P < 0.05), an earlier maximal effect (GIR-T max: 40.0 [23.7], 45.8 [22.7], 44.2 [5.8], and 145.0 [43.7] min; P < 0.05), and a shorter duration of action (late T50%: 56.5 [31.0], 70.2 [12.9], 75.5 [6.0], and 290.8 [84.0] min; P < 0.05). Dose-dependent increases in maximal metabolic effect were observed with 5, 10, and 20 puffs: the GIR max was 0.9 (0.5), 2.0 (1.3), and 3.9 (2.5) mg/kg per minute, respectively ( P < 0.05), and the GIR-AUC 0–120 was 39.6 (34.9), 76.8 (67.4), and 189.1 (163.0) mg/kg per minute ( P < 0.05). Conlusions: In this study in patients with type 1 1026 diabetes, oral insulin spray had a faster onset and shorter duration of action than subcutaneously injected regular insulin. A dose-response relationship was noted in the metabolic effect and absorption of oral insulin spray.