Long-term outcomes of innovator versus generic melphalan formulation in autologous hematopoietic cell transplantation for multiple myeloma

Background:
Most data on autologous hematopoietic cell transplantation (auto-HCT) in myeloma are based on the use of innovator formulation of melphalan. Comparative bioequivalence and efficacy studies of generic melphalan are lacking.


Methods:
In this retrospective study, we report long-term outcomes of auto-HCT in myeloma using innovator (Alkeran, Aspen Pharma; n = 41) and generic melphalan (Alkacel, Celon Labs, India; n = 55) formulations. All consecutive patients at a single center from the period 2011–2018 were included.


Results:
The median follow-up in the innovator and generic groups was 61.7 and 32.5 months, respectively. Both groups were matched for age, sex, stage, and myeloma response. There were significantly more patients in the innovator melphalan group who were administered mel- phalan at a reduced dose at physician discretion (26.8% vs. 3.6%, p = .001). There were significantly more patients with grade 3 or higher mucositis (68.3% vs. 38.1%, p < .0001) and grade 3 or higher diarrhea (85.4% vs. 50.1%, p < .0001) in the innovator group. The median duration of hospital stay was significantly longer in the innovator group (19 days vs. 15.5 days, p < .0001). There were significantly more patients in the generic group who received standard maintenance (94.5% vs. 34.1%, p < .0001). Despite the differences in the melphalan dose and post-transplant strategies, the 4-year progression-free survival and overall survival were not significantly different in the two groups (58% vs. 63%, p = .7, 71% vs. 72%, p = .4, respectively).


Conclusion:
Long-term efficacy comparison is helpful in the absence of postmarketing bioequivalence studies of generic melphalan.