Background: TP-3654 is an oral, second generation, potent PIM-1 kinase inhibitor with activity against PIM 2, 3 and favorable selectivity against other kinases. These cytoplasmic serine/threonine kinases are highly expressed in many cancers and their oncogenic potential has been largely attributed to supressing apoptosis downstream of stimuli including inflammatory cytokines and other immune effectors. TP-3654 has efficacy in various hematologic and solid tumor models inducing stromal Pim-1 also has been shown to mediate various aspects of the tumor microenvironment. Thus, Pim kinases are attractive targets for the treatment of many human malignanices. Methods: A first in human, multicenter, phase 1, dose escalation study using a standard 3+3 design with a modified Fibonacci scheme to examine the safety and clinical activity of TP-3654 in patients with advanced solid tumors. Results: Ten patients were enrolled between 30Apr and 31Dec2019 receiving 480, 720, and 1080 mg respectively. Grade 3 AEs were scrotum wound infection, altered mental status, anemia, fall, and lower extremity edema, none were related to study drug and all were manageable with supportive care. There were no Grade 4 or 5 AEs and no DLTs. Median duration of SD was 5.5 months (6/10) and with prolonged SD > 16wks (4/10). One CRC patient with 4 lines of prior therapy had a 22% reduction in tumor volume (SD > 5+ mos). TP-3654 plasma PK values (C_max, AUC) continuously increased through all 3 cohorts. Average C_max (ng/mL) and AUC_0-24 (ng*hours/mL) were 195, 1965 (480mg); 357, 3310 (720mg); 735, 6922 (1080mg), respectively. PK values increased linearly with higher doses without reaching saturation. Peripheral Blood Mononuclear Cells were isolated from subjects prior and up to 24hours after treatment. Western Blot from protein lysates revealed a decrease in phosphorylation of BAD and p70s6K proteins, both regulated by PIM-1 kinase. Conclusions: These findings suggest that TP-3654 is tolerated as a monotherapy in patients with heavily pretreated, relapsed, and resistant solid tumors warranting further clinical development in selected indications.