Phase 1 Clinical Trial of the Novel Structure Proteasome Inhibitor NPI-0052 in Patients with Relapsed and Relapsed/Refractory Multiple Myeloma (MM).

NPI-0052 has a novel, non-peptide based, bicyclic structure resulting in a unique proteasome inhibition and safety profile. In contrast to other proteasome inhibitors, NPI-0052 produces rapid, broad and prolonged inhibition of all 3 catalytic activities. Preclinical data subsequently suggested improvements in toxicology and efficacy, including activity MM resistant to bortezomib (BZ) and other agents (Chauhan et al, Cancer Cell 2005), thus this Phase 1 dose escalation trial in patients (pts) with relapsed/refractory MM was initiated.

Patients (pts) were treated with NPI-0052 IV weekly for 3 weeks in 4-week cycles. Measurable disease by EBMT criteria was not required. The dose of NPI-0052 was escalated using a combination of accelerated titration and 3+3 design. PK and proteasome inhibition (blood and PBMCs) were assayed after the first and third doses.

27 pts have been treated at doses ranging from 0.025 to 0.7 mg/m²; median age is 62; 18 males/9 females; IgG/IgA/light chain/non-secretory 14/4/2/6; median of 4 prior regimens and 27% refractory to prior bortezomib. Reversible DLT was observed in two out of eight patients treated at 0.7 mg/m² (Grade 3 fatigue; Grade 3 mental status changes and loss of balance), with 2 additional pts undergoing dose reductions in Cycle 1 (nausea and vomiting; vertigo and confusion/word-finding difficulties). Prophylactic anti-emetics have been instituted with a decrease in infusion-related nausea; similarly, pts with dizziness/vertigo have been administered meclizine with symptomatic improvement. Other drug-related adverse events have consisted principally of mild-to-moderate fatigue, nausea, vomiting, dizziness, headache and diarrhea; interestingly, myelosuppression, neuropathy and thrombosis do not appear to be elicited by NPI-0052. PK assessment demonstrates a rapid elimination half-life (<20 minutes) and relatively large Vz. NPI-0052 produces dose dependent proteasome inhibitions. At 0.7 mg/m², Day 1/Day 15 inhibition of chymotrypsin-like activity in whole blood is 73% and 99%, respectively (the value for bortezomib at 1.3 mg/m2 is 65%). One patient with IgA MM (4 prior regimens plus ASCT; relapsed after prior BZ, not refractory) had a 71% decrease in M-protein (unconfirmed PR; off study after 3 cycles). A second pt with non-secretory disease (4 prior regimens;relapsed after prior BZ, not refractory) had a nearly 50% reduction in involved light chain; this pt remains active on study at 5+ months. In addition, 8 pts with relapsed/refractory MM remained on study for between 6-15 months (3 pts were on-study for over one year) with stable disease and no significant toxicity; 2 of these pts were BZ-refractory.

Tolerability of 0.7 mg/m² continues to be investigated in pts with MM, with prophylactic antiemetics and meclizine to reduce common drug-related toxicities of nausea and dizziness. The safety profile of NPI-0052 is importantly different from bortezomib in spite of higher and more durable proteasome inhibition; peripheral neuropathy and thrombocytopenia were not seen. Accrual continues to expand upon these results and assess the new lyophile formulation of NPI-0052.

Richardson:Millennium: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Celgene: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Keryx: Membership on an entity's Board of Directors or advisory committees; Gentium: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; Merck: Membership on an entity's Board of Directors or advisory committees. Off Label Use: Vorinostat is a histone deacetylase (HDAC) inhibitor that was approved in the FDA in October 2006 for the treatment of cutaneous manifestations in patients with cutaneous T-cell lymphoma (CTCL) who have progressive, persistent, or recurrent disease on or following two systemic therapies. Jakubowiak:Celgene: Consultancy, Honoraria; Millennium: Consultancy, Honoraria; Centocor Ortho Biotech: Consultancy, Honoraria; Exelixis: Consultancy, Honoraria; Bristol-Myers-Squibb: Consultancy, Honoraria. Spear:Nereus Pharmaceuticals: Employment, Equity Ownership. Palladino:Nereus Pharmaceuticals: Employment, Equity Ownership. Longenecker:Nereus Pharmaceuticals: Employment, Equity Ownership. Neuteboom:Nereus Pharmaceuticals: Employment, Equity Ownership. Cropp:Nereus Pharmaceuticals: Consultancy. Lloyd:Nereus Pharmaceuticals: Employment, Equity Ownership. Hannah:Nereus Pharmaceuticals: Consultancy. Anderson:Nereus Pharmaceuticals: Consultancy, Research Funding.