Maintenance Treatment after Autologous Peripheral Blood Stem Cell Transplantation (PBSCT) in Multiple Myeloma (MM) with a Unique Weekly Dose of Pegylated Interpheron alpha2b (Pegintron®): Preliminary Clinical Results in 30 Patients of a Phase II Multicentric Study.

Introduction Intensification therapy in MM with autologous PBSCT is widely indicated for younger patients with favourable results regarding response, OS and PFS. However, there is no clear plateau in the survival curve. To improve these results and to prolong remission duration, various maintenance treatments have been proposed. Interpheron alpha2b s.c, at low dose, steroids on alternate days and most recently, low dose oral thalidomide, have demonstrated improvements in EFS and OS times but these results needs confirmation. Recently a new formulation of interpheron alpha2b (Pegintron®) is available conjugated with polietilenglicol with the advantage of being administered on a unique weekly dose. This new formulation of Interpheron alpha has been tested scarcely in MM. We present the preliminary results of a spanish, phase II, non comparative, multicentric study (PI-MM-01) with Pegintron® (Schering-Plough) as maintenance treatment after autologous PBSCT.

Patients y Methods From May 2003 to March 2007, 30 patients were included in this study, 64% female and 36% male, with a median 56 years, received Pegintron® once a week subcutaneously as maintenance treatment after favourable response post-HDT with autologous PBSCT when the engraftement was stable and complete. The initial dose was 15 mg/week × 2 week and this dose was escalated to 25 mg/week and then 35 mg/week. The final dose was adopted according clinical and hematological tolerance. The maintenance treatment was continued at least 5 years postransplant or until toxicity, relapse or progressión.

Results 30 patients were evaluable for this preliminary analysis. The median time from transplant to IFN treatment was 3.8m. The median dose of Pegintron was 15 mg/week. 9 patients have suspended the treatment (30%). 5 cases (16%) due to progression, 2 (4%) for toxicity and 2(4%) for other reason. The remainder 21 patients (76%) continue the treatment with clinical response, with median duration of 16 months (2–42). At present all patients are alive. Astenia, “pseudo-flu” symptoms and thrombopenia and neutropenia were the most common adverse effects observed, that limited the dose escalation, being 15 mg/week the best tolerated and mos frequent dose (70%). One patient suspended the treatment due to dermatological reaction with pruritus.

Conclusions and Comments Although these results need completion and further analysis, maintenance treatment with a weekly dose of Interpheron-a2b conjugated with Polietilenglicol (Pegintron®) is well tolerated after autologous PBSCT in MM. No major adverse effects were observed and no relevant negative impact was observed on the autologous graft. Pegintron® sc could be an alternative to standard interpheron sc with the main advantage of therapy simplification with only one dose weekly. More experiences and longer follow up are needed to evaluate the role of this strategy in the global treatment of MM and new approaches for maintenance have to be investigated, including association and comparison with steroids or new drugs as thalidomide, bortezomib or lenalidomide.