Clinical Trial of NPI-0052 (2nd generation proteasome inhibitor) in Patients Having Advanced Malignancies with Expanded RP2D Cohorts in Lymphoma and CLL

Background: NPI-0052 is a novel proteasome inhibitor that produces prolonged inhibition of the 20S proteasome. NPI-0052 has a novel structure leading to a unique proteasome inhibition, toxicology and effect profile. Preclinical research suggests an improved therapeutic ratio and activity in hematologic and solid tumor malignancy models. Secondary to these findings, clinical trials are being conducted in patients with myeloma, lymphomas, leukemias and solid tumors.

Materials and Methods: In this study patients with solid tumor, lymphoma or leukemia diagnoses were treated with NPI-0052 administered weekly, for 3 weeks in 4-week cycles in a 3+3 design dose escalation. The dose of NPI-0052 was escalated in 50–100% increments dependent on observed adverse events (AE). In addition to regular safety monitoring, proteasome inhibition (PI) (baseline, D1 & D15) and pharmacokinetics PK (D1 & D15) were assayed in blood. Once a Recommended Phase 2 Dose (RP2D) is identified, RP2D cohorts of 10 patients in each lymphoma and CLL are enrolled.

Results: 25 patients have been treated at doses ranging from 0.1 mg/m² to 0.7 mg/m². The AE profile has been very tolerable with fatigue, transient peri-infusion site discomfort and lymphopenia being commonly ascribed to NPI-0052. Whole blood pharmacokinetics were calculated for all patients on study. At the highest dose assessed PK parameters were (mean ± SD) AUCtot =215±129 ng/mL*min; Cmax =22.8 ±14 ng/mL; t1/2 =13.5 ± 9.2 mins; clearance= 7.8 ± 8.2 L/min and Vss = 132 ± 192 L. AUC and Cmax increased linearly with dose and the kinetics are apparently not dose dependant. PI has been assayed in blood, indicating a dose:response relationship with inhibition of chymotrypsin-like activity up to 100% observed and mean Day 1 inhibition of 78%. This level of proteasome inhibition is higher than that reported with standard doses of bortezomib, yet the profile of adverse drug reactions associated with bortezomib has not been observed. A total of 7 patients (33%) have had stable disease for at least 2 cycles (8 weeks; 2months), including one each with mantle cell lymphoma (4 cycles), Hodgkin’s lymphoma (4 cycles), follicular lymphoma (4 cycles) and sarcoma (5 cycles) and prostate adenocarcinoma, and two with melanoma (4 cycles).

Conclusions: NPI-0052 produces dose-dependent pharmacologic effects through the predicted efficacious range while producing a toxicity profile that is tolerable and dissimilar to that of the standard of care proteasome inhibitor bortezomib. These data have supported additional studies being initiated in hematologic malignancies and solid tumors.