Phase I-II Trial of Oral Cyclophosphamide, Prednisone and Lenalidomide (Revlimid®) (CPR) for the Treatment of Patients with Relapsed and Refractory Multiple Myeloma.
Authors: Reece Donna E. , Masih-Khan Esther , Khan Arooj , Anglin Peter , Chen Christine , Kukreti Vishal , Mikhael Joseph R. , Trudel Suzanne 
Published: April 2020

Oral cyclophosphamide and prednisone is a convenient regimen in relapsed and refractory multiple myeloma (MM), with a partial response (PR) rate of 40% and median progression-free survival of 19 months in our retrospective analysis of patients in first or second relapse after autologous stem cell transplantation (ASCT) (Trieu Y, et al, Mayo Clin Proc2005; 80: 1582). We sought to enhance the efficacy of this regimen by adding oral lenalidomide (Revlimid®), a potent anti-myeloma agent, in a phase I-II trial. The CPR regimen consisted of cyclophosphamide on days 1, 8 and 15, lenalidomide on days 1–21, and prednisone 100 mg every other day in a 28-day cycle. ASA 81 mg/day was given to all patients (pts) as prophylaxis for DVT. Three dose levels were evaluated using a 3 by 3 dose escalation design. Between 11/2007–07/2008, 15 pts with relapsed/refractory MM were entered onto study. Median age was 60 (45–78) years and 60% were male. Immunoglobulin subtype was IgGκ:λ in 10:1; IgA κ:λ in 2:1 and κ light chain in 1. Median number of prior regimens was 2 (1–3) and 14 had undergone previous ASCT, including double transplants in 2 pts. Prior therapy also included thalidomide in 3 (20%) and bortezomib in 6 (40%). FISH cytogenetics were available in 9, but none had 13q deletion, t(4;14) or p53 deletion. At the time of protocol entry, median β2-microglobulin level was 222 (92–325) nm/L, albumin 38 (35–46) g/L, creatinine 78 (50–100) μmol/L, platelet count 230 (93–318) x 109/L and ANC 2.5 (1.9–9.0) x 109/L. Protocol treatment is summarized in Table 1.

Dose level N Cyclophosphamide dose (mg/m2) Lenalidomide dose (mg) Prednisone dose (mg) Median # cycles given 1 3 150 15 100 9 2 3 150 25 100 6 3 6 300 25 100 4 3 (expanded) 3 300 25 100 1

Dose limiting toxicity was not observed during cycle 1 at any of the dose levels and the maximum tolerated dose of this regimen has not yet been reached at the highest dose level planned; all pts remain on active therapy. Grade 3/4 thrombocytopenia was seen in 1 pt (cohort 2) and neutropenia in 4 pts (1 in cohort 1, 1 in cohort 2 and 2 in cohort 3) and were managed with dose reduction and/or growth factor support. No episodes of febrile neutropenia occurred in any pt. Only 1 pt experienced varicella zoster; routine antiviral prophylaxis was not used. Other grade 3/4 non-hematologic toxicities were uncommon and included abdominal pain/bacteremia in 1 pt in cohort 1, hypokalemia in 1 pt in cohort 2, and DVT in 1 pt in cohort 3. Mild grade 1/2 constipation (47%), muscle cramps (33%) and fatigue (33%) were also noted. To date, best response includes the following: dose level 1 (1 near complete remission [nCR], 2 PR); dose level 2 (3 PR); dose level 3 (4 PR, 2 minimal response [MR]); expanded cohort 3 (1 MR, 2 too early). We conclude: 1) the combination of full doses of the agents in CPR can be given in a 28-day cycle with minimal toxicity; 2) the overall response rate (nCR + PR + MR) in 13 evaluable pts to date is 87%; 3) no pts have progressed in this preliminary analysis; 4) longer follow-up is required to assess the long-term efficacy of this regimen.