Phase I Study of NK012, a Novel SN-38-incorporating Micellar Nanoparticle, in Adult Patients with Solid Tumors

Purpose: We conducted a first-in-human phase I study to determine the dose-limiting toxicity (DLT), evaluate the pharmacokinetic profile, and document any antitumor activity of NK012, a novel SN-38-incorporating micellar nanoparticle.

Experimental Design: Patients with solid tumors refractory to standard therapy, or for which no standard therapy is available, were enrolled. NK012 was administered as a 30-minute infusion every 3 weeks. The starting dose was 2 mg/m(2) as SN-38 equivalent, and an accelerated titration schedule was used. Pharmacokinetic analysis was conducted in cycles 1 and 2.

Results: Twenty-four patients were enrolled in the study. No UGT1A1*28 homozygous patients were enrolled. Predominant toxicity was neutropenia. Nonhematologic toxicity, especially diarrhea, was mostly grade 1 or 2 during study treatments. Two of nine patients had DLT during cycle 1 at the 28 mg/m(2) dose level. DLTs were mostly neutropenia or a related event. Polymer-bound SN-38 (NK012) and SN-38 released from NK012 were slowly eliminated from the plasma, with a terminal-phase half-life of approximately 140 and 210 hours, respectively. Systemic exposure to both polymer-bound SN-38 and SN-38 increased in proportion to the dose. A refractory esophageal cancer patient and a lung carcinoid tumor patient had an objective response and continued the study treatment for 5 and 12 months, respectively.

Conclusions: NK012 was well tolerated and showed antitumor activity including partial responses and several occurrences of prolonged stable disease across a variety of advanced refractory cancers. Phase II studies are ongoing.