Defibrotide (DF) showed antithrombotic properties and remarkable activity in Multiple Myeloma (MM), without significant anticoagulant effects and bleeding risk. DF may abrogate tumor cells interaction with marrow stromal cells and enhance sensitivity to chemotherapy, thus improving activities of Melphalan, Prednisone and Thalidomide, while protecting against thrombotic state. We designed a multicenter phase I/II trial to define efficacy and safety of Melphalan, Prednisone, Thalidomide and DF (MPTD) in relapsed/refractory MM. The MPTD treatment consisted of 6 35-days cycles of oral melphalan (0.25 mg/Kg day 1–4), prednisone (1.5 mg/kg day 1–4), thalidomide (50–100 mg/day continuously), DF at 3 dose levels (17 mg/Kg iv or 2.4 g po D 1–4, 1.6 g po D 5–35; 34 mg/Kg iv or 4.8 g po D 1–4, 3.2 g po D 5–35; 51 mg/Kg iv or 7.2 g po D 1–4, 4.8 g po D 5–35), every 35 days, without deep vein thrombosis (DVT) prophylaxis. Safety was assessed by defining dose-limiting toxicity (DLT) and maximum tolerated dose (MTD). DLT was defined as the occurrence of febrile neutropenia, G4 neutropenia >1 week, any other G4 hematologic toxicity, or any >G3 non-hematologic toxicity. MTD was the dose level prior to that resulting in DLT. Efficacy was evaluated according to EBMT/IBMTR criteria. Twenty-four patients were enrolled between March and November 2006 and 19 patients completed at least 1 MPTD (median age 69, excluding primary refractory and/or patients receiving anticoagulation) and were evaluated for toxicity and response. Fourty-two percent of patients achieved at least partial response (PR) after a median of 3 cycles (including 16% very good PR), without significant differences among DF dose. The MTD was not reached. DLTs observed were not considered related to DF and included: G3 ileus (1st dose level) and acute myocardial infarction (AMI) in the 2nd. Toxicities ≥G3 consisted of neutropenia 47%, thrombocytopenia 10%, anemia 21%, whereas <5% of patients experienced non-hematological toxicities ≥G3. No DVTs or significant bleeding were detected. Treatment discontinuation occurred in 3 patients for adverse events: AMI (additional anticoagulation required), ileus (because of the diagnosis of amyloidosis AL and disease progression), and persistent G4 neutropenia (heavily pre-treated patients). In this phase I/II study we confirm the efficacy and feasibility of MPTD in the setting of advanced myeloma patients, interestingly a protective role of DF against thrombosis is also suggested. Pharmacokinetic studies and analysis of surrogates are ongoing. Updated data will be presented at the meeting.

Author notes

Disclosure:Employment: Dr. Anderson and Dr. Iacobelli are employed by Gentium. Research Funding: The study was partially supported by Gentium. Membership Information: Dr. Richardson is a membership of Gentium. Dr. Anderson is a membership on Board of Directors of Gentium.