Phase I first-in-human study of the polo-like kinase-1 selective inhibitor, GSK461364, in patients with advanced solid tumors.
Olmos D., Allred A., Sharma R., Brunetto A., Smith D., Murray S., Barker D., Taegtmeyer A., de Bono J., Blagden S.
3536 Background: Polo-like kinase-1 (Plk1), part of a family of highly conserved serine-threonine kinases, has multiple roles in mitotic progression, is over-expressed and also associated with poor prognosis in some tumor types. GSK461364 is a potent and selective ATP-competitive inhibitor of Plk1 (Ki 2.2nM) with demonstrated antiproliferative activity in vitro and in vivo. METHODS: Adult patients (pts) with relapsed/refractory advanced solid tumors with performance status of 0-2 and adequate organ function were eligible. Sequential cohorts of 2-6 patients each received escalating doses of GSK461364 administered as a 4h intravenous infusion (Schedule [Sch] 1: D1,8,15 q28 or Sch 2: D1,2,8,9,15,16 q28). Primary objectives were to determine the maximum tolerated dose (MTD) and pharmacokinetics (PK) of GSK461364. Secondary objectives included preliminary evaluation of anti-tumor activity. RESULTS: 27 pts (20 male, 7 female) were evaluated. Four dose levels, 50mg (n = 2), 100 mg (n = 3), 150 mg (n = 3) and 225 mg (n = 8) were evaluated in Sch 1. Three dose levels, 25 mg (n = 2), 50 mg (n = 2) and 100 mg (n = 7) were evaluated in Sch 2. Dose-limiting toxicities (DLTs) observed were Gr 4 sepsis, in Sch 1 at 225 mg dose, Gr 4 pulmonary embolism (PE) and Gr 4 neutropenia >7d in Sch 2, both at 100 mg dose. Other Sch 1 adverse events (AEs) with a maximum grade ≥3 were fatigue and anemia (both, n = 2), pleuritic pain, pelvic pain, abdominal discomfort, constipation, vomiting, neutropenia, and deep vein thrombosis (all, n = 1). Other Sch 2 AEs with a maximum grade ≥3 were PE, renal failure, thrombocytopenia, and catheter-related infection (all n = 1). The most common adverse events (AEs) regardless of attribution, Sch and dose level were phlebitis (n = 9), fatigue (n = 9), nausea (n = 7), anemia (n = 6), anorexia (n = 6), diarrhea (n = 6), and infusion site reaction (n = 5). Preliminary PK data indicate that AUC and Cmax were proportional across doses; mean values were CLs ∼72-85L/hr, Vss ∼550-1200L and t1/2 ∼11.5hr. Phospho-histone H3, a marker of mitotic arrest, was detected, in circulating tumor cells, 24 hrs after first dose. Stable disease >5m has been observed in 2 esophageal cancer pts. CONCLUSIONS: Dose escalation continues in Sch1, Sch2 has been expanded at 75mg. An MTD has not yet been defined. [Table: see text].