A Phase 1 Trial of Lenalidomide (REVLIMID^®) with Bortezomib (VELCADE^®) in Relapsed and Refractory Multiple Myeloma.

Introduction: Bortezomib and lenalidomide are active agents in multiple myeloma (MM), and preclinical data showing additive activity in MM in vitro suggest that enhanced clinical benefit may be derived from combining the two drugs. Bortezomib is approved in MM patients (pts) who have received at least one prior therapy in both the US and EU. Lenalidomide has produced durable responses in the relapsed and refractory MM setting, including in those who received prior bortezomib. Toxicities of bortezomib and lenalidomide do not overlap unfavorably. These observations suggest that this regimen, compared with either agent alone, may provide better clinical anti-MM activity. In phase 1 trials, the maximum tolerated doses (MTD) of single-agent bortezomib and lenalidomide were 1.3 mg/m² (IV bolus twice weekly) and 25 mg/d (PO days 1–21 of a 28–day cycle), respectively. The objective of this phase 1 dose-escalation trial was to determine the MTD and activity of this combination in pts with relapsed and/or refractory MM.

Methods: Eight 3-pt cohorts were planned with bortezomib 1.0 or 1.3 mg/m² and lenalidomide 5, 10, 15, or 20 mg/day. Pts received bortezomib on days 1, 4, 8, and 11 and lenalidomide on days 1–14 of a 21-day cycle. Dexamethasone 20 mg orally could be added on days 1, 2, 4, 5, 8, 9 and 11, 12 in the event of PD. Toxicity was assessed using NCI-CTC, version 3.0. Dose-limiting toxicity (DLT) was defined as grade ≥ 3 nonhematologic toxicity, grade 4 neutropenia lasting ≥ 5 days and/or neutropenic fever, or a platelet count ≤ 10,000 on > 1 occasion despite transfusion. Modified EBMT criteria were used to assess response.

Results: Nineteen pts with MM have been enrolled to date to cohorts 1–5, including 8 with relapsed and 11 with relapsed and refractory disease. Median number of prior therapies was 4 (range, 1–9). Twelve pts had prior SCT; 17 had received thalidomide, 9 bortezomib, 2 lenalidomide. With a median of 7 cycles completed (range, 2–16), pts have received bortezomib 1.0–1.3 mg/m² and lenalidomide 5–15 mg/d. Two pts with rapid disease progression were not evaluable and were removed from study within the first cycle. One DLT was observed (cohort 4, grade 3 hyponatremia). To date, doses of study drugs were reduced in 6 pts beyond cycle 3. Bortezomib was reduced for thrombocytopenia [n = 3] and hypotension [n = 1] and lenalidomide was reduced for neutropenia [n = 1] and fatigue [n = 1]. No significant treatment-emergent PN has been seen. Responses by cohort are shown in the table, and of 17 evaluable pts, 10 (59%) achieved CR + PR.

Conclusions: In heavily treated pts with relapsed and/or refractory MM, the combination of bortezomib and lenalidomide has been well tolerated and has demonstrated very promising activity, even in pts who had previously received either agent alone. Dose escalation is continuing until MTD is reached. Phase II evaluation of this regimen is planned both in relapsed and/or refractory and in newly diagnosed MM.