Background: In cancers, the majority of tumor suppressor proteins (TSP) are transported out of the nucleus exclusively by Exportin 1 (XPO1/CRM1), rendering these TSPs non-functional. KPT-330 is a potent inhibitor of XPO1, and forces the nuclear retention and activation of > 10 TSPs resulting in tumor cell death in vitro, in murine preclinical models and in dogs with spontaneous lymphomas. Methods: KPT-330 was administered orally for 10 doses in a 28-day cycle. Detailed pharmacokinetic (PK) and pharmacodynamic (PDn) analyses and serial tumor biopsies were performed. Response evaluation was done every 2 cycles (RECIST 1.1). All pts entering the study had documented progressive disease. Results: 23 pts (10 males; median age 62 yrs; ECOG PS 0/1: 5/18) received KPT-330 across 6 dose levels (3 to 30 mg/m²). There has been no dose limiting toxicity. Nine drug related grade 3/4 adverse events (AEs) post cycle 1 were reported in 6 pts (neutropenia, thrombocytopenia, hyponatremia, increased ALT, fatigue, vomiting [n=2], nausea [n=2]). The most common grade 1/2 AEs were nausea (78%), fatigue (74%) and anorexia (74%). PK analysis demonstrated a fairly proportional increase in C_max and AUC with increasing dose, with no accumulation and without affecting half-life or clearance of KPT-330. At 30 mg/m², AUC_0-last. (4375 ng*h/mL) was comparable to the anti tumor exposure observed in mice and dogs. T_max (~3 hrs) and T_1/2 (6-7 hrs) were consistent across doses. Significant increase (2-20x) in XPO1 mRNA levels (PDn marker) in circulating leukocytes was observed at all doses, with higher doses demonstrating higher levels of XPO1 mRNA induction. Analysis of tumor biopsies confirmed nuclear localization of TSPs (e.g. p53, FOXO3A, IκB) and apoptosis of cancer cells following KPT-330 administration. RECIST response was evaluable in 13 pts. Stable disease (SD) was noted in 9 pts, with 3 (colon, endocervical & endometrial stromal tumors) remaining with SD at 6+ months (dose levels 3 & 6 mg/m²), as well as one minor response (colon). Conclusions: KPT-330 treatment is generally well tolerated, with favorable PK and PDn properties. Preliminary signals of clinical antitumor activity were observed. Clinical trial information: NCT01607905.