Sorafenib and everolimus for patients with unresectable high-grade osteosarcoma progressing after standard treatment: a non-randomised phase 2 clinical trial.

BACKGROUND: Results of previous study showed promising but short-lived activity of sorafenib in the treatment of patients with unresectable advanced and metastatic osteosarcoma. This treatment failure has been attributed to the mTOR pathway and might therefore be overcome with the addition of mTOR inhibitors. We aimed to investigate the activity of sorafenib in combination with everolimus in patients with inoperable high-grade osteosarcoma progressing after standard treatment. METHODS: We did this non-randomised phase 2 trial in three Italian Sarcoma Group centres. We enrolled adults (≥18 years) with relapsed or unresectable osteosarcoma progressing after standard treatment (methotrexate, cisplatin, and doxorubicin, with or without ifosfamide). Patients received 800 mg sorafenib plus 5 mg everolimus once a day until disease progression or unacceptable toxic effects. The primary endpoint was 6 month progression-free survival (PFS). All analyses were intention-to-treat. This trial is registered with ClinicalTrials.gov, number NCT01804374. FINDINGS: We enrolled 38 patients between June 16, 2011, and June 4, 2013. 17 (45%; 95% CI 28-61) of 38 patients were progression free at 6 months. Toxic effects led to dose reductions, or short interruptions, or both in 25 (66%) of 38 patients and permanent discontinuation for two (5%) patients. The most common grade 3-4 adverse events were lymphopenia and hypophosphataemia each in six (16%) patients, hand and foot syndrome in five (13%), thrombocytopenia in four (11%), and fatigue, oral mucositis, diarrhoea, and anaemia each in two (5%). One patient (3%) had a grade 3 pneumothorax that required trans-thoracic drainage, and that recurred at the time of disease progression. This was reported as a serious adverse event related to the study drugs in both instances. No other serious adverse events were reported during the trial. There were no treatment-related deaths. INTERPRETATION: Although the combination of sorafenib and everolimus showed activity as a further-line treatment for patients with advanced or unresectable osteosarcoma, it did not attain the prespecified target of 6 month PFS of 50% or greater. FUNDING: Italian Sarcoma Group.

The Combination of Sorafenib and Everolimus Abrogates mTORC1 and mTORC2 upregulation in osteosarcoma preclinical models.

PURPOSE: The multikinase inhibitor sorafenib displays antitumor activity in preclinical models of osteosarcoma. However, in sorafenib-treated patients with metastatic-relapsed osteosarcoma, disease stabilization and tumor shrinkage were short-lived and drug resistance occurred. We explored the sorafenib treatment escape mechanisms to overcome their drawbacks. EXPERIMENTAL DESIGN: Immunoprecipitation, Western blotting, and immunohistochemistry were used to analyze the mTOR pathway [mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2)]. Cell viability, colony growth, and cell migration were evaluated in different osteosarcoma cell lines (MNNG-HOS, HOS, KHOS/NP, MG63, U-2OS, SJSA-1, and SAOS-2) after scalar dose treatment with sorafenib (10-0.625 µmol/L), rapamycin-analog everolimus (100-6.25 nmol/L), and combinations of the two. Cell cycle, reactive oxygen species (ROS) production, and apoptosis were assessed by flow cytometry. Nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice injected with MNNG-HOS cells were used to determine antitumor and antimetastatic effects. Angiogenesis and vascularization were evaluated in vitro by exploiting endothelial branching morphogenesis assays and in vivo in xenografted mice and chorioallantoic membranes. RESULTS: After sorafenib treatment, mTORC1 signaling was reduced (downstream target P-S6), whereas mTORC2 was increased (phospho-mTOR Ser2481) in MNNG-HOS xenografts compared with vehicle-treated mice. Combining sorafenib with everolimus resulted in complete abrogation of both mTORC1 [through ROS-mediated AMP-activated kinase (AMPK) activation] and mTORC2 (through complex disassembly). The sorafenib/everolimus combination yielded: (i) enhanced antiproliferative and proapoptotic effects, (ii) impaired tumor growth, (iii) potentiated antiangiogenesis, and (iv) reduced migratory and metastatic potential. CONCLUSION: mTORC2 activation is an escape mechanism from sorafenib treatment. When sorafenib is combined with everolimus, its antitumor activity is increased by complete inhibition of the mTOR pathway in the preclinical setting.