A Phase I–II Trial of Bortezomib (Velcade) (Vc) and Oral Cyclophosphamide (CY) Plus Prednisone (P) for Relapsed/Refractory Multiple Myeloma (MM).

We have previously reported that a simple, well-tolerated regimen of weekly oral CY (500mg) and alternate day prednisone (50–100mg) produced partial responses (PR) in 40% of 56 patients (pts) in relapse after ASCT; median progression-free survival was 18.6 months (

Patients characteristics: Median age was 59 (48–74) years; 9 were male. The Ig subtypes were: IgG kappa:lambda = 9:2, IgA kappa:lambda = 1:2; kappa light chain = 2. All had received VAD, i.v. CY (2.5 g/m²) + G-CSF mobilization followed by ASCT and 2 had undergone a second ASCT; other prior regimens included melphalan and prednisone in 5 pts, thalidomide in 10, lenalidomide in 1, α-interferon in 3, vaccine therapy in 1 and oral CY + P in 8. The median pretreament ß2-microglobulin level was 279 (147 – 875) nm/L, albumin 39 (30–42) g/L and creatinine 91 (60–112) umol/L. The dose escalation schedule to date is as follows:

Three further dose escalations to a maximum Vc dose of 1.5 mg/m² days 1,8, and 15 are allowed if dose limiting toxicity does not occur.

Toxicities during cycle 1: All pts have completed cycle 1. Three episodes of grade (gr) 3 sinopulmonary infection occurred during a community outbreak at dose level 1; levofloxacin prophylaxis during the first cycle was added and no further infections during the initial cycle were observed. One pt at dose level 3 experienced transient gr 4 hypophosphatemia which reversed without therapy. At dose level 4, cycle 1 was interrupted in one pt due to gr 4 leukopenia (gr 3 neutropenia and thrombocytopenia) related to disease, while a second pt developed grade 4 elevation in transaminases which recovered quickly when Vc was held on d 8. Pt accrual continues.

Toxicities of subsequent cycles: To date, 47 additional cycles have been given. SAE’s consisted of pneumonia during cycle 2 in the same 3 patients with infection during cycle 1 and one of these with progressive disease had another bout during cycle 3. Gr 3 toxicities included anemia in 2 cycles, leucopenia in 2, neutropenia in 4, hypophosphatemia in 1 and hyperglycemia in 2; reversible gr 4 hypophosphatemia recurred in the pt mentioned above in 1 other cycle. No liver or other organ toxicity was observed. Maximum gr of peripheral neuropathy was 1.

Responses: Responses were assessed after cycles 2, 4, 6 and 8. Best response included near CR (1), PR (4), MR (4), stable disease (5), progression (1) and too early (1). Two pts have completed all 8 cycles, while 4 have progressed; 10 remain on study. Preliminary Conclusions: 1) Vc can be added to a continuous program of oral CY + P with acceptable hematologic toxicity; 2) no neurotoxicity > gr 1 has been observed; 3) the maximum tolerated dose (MTD) of this combination regimen has not yet been defined; 4) future plans include a randomized National Cancer Institute of Canada trial comparing the the MTD of this combination to Vc in relpased MM pts.