Mifamurtide for Osteosarcoma in the United States: A Single-Center Real-World Experience
- 1Memorial Sloan Kettering Cancer Center
Abstract
PurposeMifamurtide (liposomal muramyl tripeptide phosphatidylethanolamine [L-MTP-PE]) is approved in many countries for osteosarcoma but remains unavailable for routine use in the United States (US). We describe the feasibility and outcomes of patients with osteosarcoma treated with mifamurtide at Memorial Sloan Kettering Cancer Center (MSK) through expanded access (EAP) and compassionate use (SPU) pathways.
MethodsMedical records were retrospectively reviewed for patients with completely resected, high-grade osteosarcoma treated with mifamurtide at MSK from 2016-2026 through EAP or SPU protocols. Mifamurtide 2 mg/m{superscript 2} was administered intravenously twice weekly for 12 weeks, followed by weekly administration for 24 weeks. Outcomes were evaluated by treatment setting and, for upfront therapy, metastatic status and histologic necrosis.
ResultsFifty-seven patients received mifamurtide (median age, 14 years; range, 2-60); 72% had localized and 28% metastatic disease at diagnosis. No serious adverse events were considered possibly or probably related to mifamurtide, and no new grade 3-4 safety signals emerged. Five patients with localized disease and [≥]90% necrosis at resection had no events, with 100% progression-free survival (PFS) and overall survival (OS) at median follow-up of 29 months. Among 22 patients with localized disease and <90% necrosis treated upfront, PFS was 82%, 66%, and 59% at 12, 24, and 48 months, respectively; OS was 95% at 12, 24, and 60 months. Among 8 patients with metastatic disease treated upfront, PFS was 73%, 58%, and 39% at 12, 24, and 36 months, respectively; OS was 100%, 86%, and 86%. Among 22 patients treated after relapse, PFS was 34%, 23%, and 17% at 12, 24, and 36 months, respectively; OS was 91%, 70%, and 35% at 12, 24, and 60 months.
ConclusionsIn this real-world US cohort, mifamurtide was feasible and safe to administer. Despite limitations of the EAP/SPU setting, single-institution administration, and patient heterogeneity, overall survival outcomes were encouraging.
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BibTeX
@misc{slotkin2026mifamurtide,
title = {{Mifamurtide for Osteosarcoma in the United States: A Single-Center Real-World Experience}},
author = {E. K. Slotkin and A. Mauguen and J. Roach and F. S. Dela Cruz and J. L. Glade Bender and M. V. Ortiz and J. Pavisic and O. O. Babatunde and L. B. Banks and P. Chi and S. P. D'Angelo and M. A. Dickson and M. M. Gounder and C. M. Kelly and M. L. Keohan and R. G. Maki and S. Movva and W. D. Tap and L. Berman and K. Diamantis and J. Hennessy and C. Henelley and P. Kelly and T. Sauerhaft and J. Voccola and D. R. Reed and L. H. Wexler and P. A. Meyers},
howpublished = {medRxiv},
year = {2026},
month = oct,
doi = {10.64898/2026.10.04.26364693},
url = {https://www.medrxiv.org/content/10.64898/2026.10.04.26364693v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Mifamurtide for Osteosarcoma in the United States: A Single-Center Real-World Experience
AU - E. K. Slotkin
AU - A. Mauguen
AU - J. Roach
AU - F. S. Dela Cruz
AU - J. L. Glade Bender
AU - M. V. Ortiz
AU - J. Pavisic
AU - O. O. Babatunde
AU - L. B. Banks
AU - P. Chi
AU - S. P. D'Angelo
AU - M. A. Dickson
AU - M. M. Gounder
AU - C. M. Kelly
AU - M. L. Keohan
AU - R. G. Maki
AU - S. Movva
AU - W. D. Tap
AU - L. Berman
AU - K. Diamantis
AU - J. Hennessy
AU - C. Henelley
AU - P. Kelly
AU - T. Sauerhaft
AU - J. Voccola
AU - D. R. Reed
AU - L. H. Wexler
AU - P. A. Meyers
PY - 2026
DA - 2026/10/04
PB - medRxiv
DO - 10.64898/2026.10.04.26364693
UR - https://www.medrxiv.org/content/10.64898/2026.10.04.26364693v1
AB - PurposeMifamurtide (liposomal muramyl tripeptide phosphatidylethanolamine [L-MTP-PE]) is approved in many countries for osteosarcoma but remains unavailable for routine use in the United States (US). We describe the feasibility and outcomes of patients with osteosarcoma treated with mifamurtide at Memorial Sloan Kettering Cancer Center (MSK) through expanded access (EAP) and compassionate use (SPU) pathways. MethodsMedical records were retrospectively reviewed for patients with completely resected, high-grade osteosarcoma treated with mifamurtide at MSK from 2016-2026 through EAP or SPU protocols. Mifamurtide 2 mg/m{superscript 2} was administered intravenously twice weekly for 12 weeks, followed by weekly administration for 24 weeks. Outcomes were evaluated by treatment setting and, for upfront therapy, metastatic status and histologic necrosis. ResultsFifty-seven patients received mifamurtide (median age, 14 years; range, 2-60); 72% had localized and 28% metastatic disease at diagnosis. No serious adverse events were considered possibly or probably related to mifamurtide, and no new grade 3-4 safety signals emerged. Five patients with localized disease and [≥]90% necrosis at resection had no events, with 100% progression-free survival (PFS) and overall survival (OS) at median follow-up of 29 months. Among 22 patients with localized disease and <90% necrosis treated upfront, PFS was 82%, 66%, and 59% at 12, 24, and 48 months, respectively; OS was 95% at 12, 24, and 60 months. Among 8 patients with metastatic disease treated upfront, PFS was 73%, 58%, and 39% at 12, 24, and 36 months, respectively; OS was 100%, 86%, and 86%. Among 22 patients treated after relapse, PFS was 34%, 23%, and 17% at 12, 24, and 36 months, respectively; OS was 91%, 70%, and 35% at 12, 24, and 60 months. ConclusionsIn this real-world US cohort, mifamurtide was feasible and safe to administer. Despite limitations of the EAP/SPU setting, single-institution administration, and patient heterogeneity, overall survival outcomes were encouraging.
ER -