Fotemustine IN COMBINATION with BORTEZOMIB and DEXAMETHASONE: Encouraging PRELIMINARY RESULTS FROM A PHASE II STUDY On Relapsed REFRACTORY MYELOMA PATIENTS

Abstract 3037

Fotemustine (Muphoran), a nitrosourea alkylating agent approved for use in the treatment of metastatic melanoma, has proven to be effective as single agent in relapsed/refractory multiple mieloma (MM). We report preliminary data of a phase II single centre study exploring the feasibility and the efficacy of the combination bortezomib (B) + fotemustine (Mu) + dexamethasone (D) (B-MuD) in relapsed/refractory MM patients. This study has been approved by local ethical committee; all patients (pts) signed written informed consent before the enrolment. MM pts relapsed or refractory after at least one therapy were eligible for the study. Pts who received prior bortezomib-containing regimen were included only if not considered bortezomib-refractory. Fotemustine at the escalating doses of 80 and 100 mg/m² i.v. on day 1 was associated to Bortezomib 1,3 mg/m² i.v. on days 1,4,8,11 + Dexamethasone 20 mg orally on days 1–2, 4–5, 8–9, 11–12 of 21-day cycle for a total of 6 cycles. Protocol was amended after the enrolment of the first five pts due to a considerable toxicity. We observed 3 grade 3–4 peripheral neuropathy, 1 grade 3 pneumonia, 4 grade 4 thrombocytopenia and two pts dropped-out (one for grade 3 pneumonia at 2° cycle, and one for grade 4 peripheral neuropathy at 3° cycles). Thus the schedule was modified as following: Fotemustine at escalating doses of 80 and 100 mg/m² i.v. on day 1, Bortezomib 1,3 mg/m² i.v. once weekly on days 1, 8, 15, 22, Dexamethasone 20 mg i.v. on days 1, 8, 15, 22 for six 35-day cycles. An interim analysis of feasibility and efficacy was planned after the inclusion of the first two cohort of 6 pts each, treated with escalating dose of Fotemustine according to the amended schedule. Up to now, 18 pts have been enrolled (5 pts before and 13 after the amendment): M/F 10/8, median age 69 years (44-82), median number of previous therapies 2 (1-5). Previous treatments included autologous transplant in 10 pts (59%), bortezomib in 8 pts (44%), oral melphalan in 7 pts (41%) and thalidomide in 12 (71%). After the inclusion of 12 pts the MTD for Fotemustine was established to be 100 mg/m². No drop-outs were registered after the amendment. Preliminary data on response are available in 10 pts. Nine pts (90%) obtained at least a PR, 8 pts (80%) registered ≥VGPR (CR 10%). At time of this analysis 79 cycles were delivered: 14 before, 65 after the amendment. Eighty-nine AE of any grade were observed, 43 hematological and 46 non-hematological. Thrombocytopenia was the most common AE either before and after the amendment. Need for dose reduction was significantly lower after the amendment. In detail fotemustine was reduced in 14% of cycles before and never after the amendment (p=0.0001), bortezomib dose reduction were performed in 36% of cycles before and 15% after the amendment (p=0.08), dexamethasone dose reduction occurred in 64% of cycles before and 13% after the amendment (p=0.0001). In conclusion, this interim analysis shows that fotemustine in combination with bortezomib and dexamethasone is safe and gives encouraging results in relapsed/refractory myeloma patients with 80% of ≥VGPR. Updated results will be presented at the meeting.