Effect of the MDM2 antagonist RG7112 on the P53 pathway in patients with MDM2-amplified, well-differentiated or dedifferentiated liposarcoma: an exploratory proof-of-mechanism study.

[dedifferentiated liposarcoma]

We report a proof-of-mechanism study of RG 7112 , a small -molecule MDM 2 antagonist , in patients with chemotherapy-naive primary or relapsed well-differentiated or dedifferentiated MDM 2 -amplified liposarcoma who were eligible for resection .Patients with well-differentiated or dedifferentiated liposarcoma were enrolled at four centres in France . Patients received up to three 28 -day neoadjuvant treatment cycles of RG 7112 1440 mg /m (2 ) per day for 10 days . If a patient progressed at any point after the first cycle , the lesion was resected or , if unresectable , an end-of-study biopsy was done . The primary endpoint was to assess markers of RG 7112 -dependent MDM 2 inhibition and P 53 pathway activation (P 53 , P 21 , MDM 2 , Ki-67 , macrophage inhibitory cytokine-1 [MIC-1 ], and apoptosis ). All analyses were per protocol . This trial is registered with EudraCT , number 2009 -015522 -10 .Between June 3 , and Dec 14 , 2010 , 20 patients were enrolled and completed pretreatment and day 8 biopsies . 18 of 20 patients had TP 53 wild-type tumours and two carried missense TP 53 mutations . 14 of 17 assessed patients had MDM 2 gene amplification . Compared with baseline , P 53 and P 21 concentrations , assessed by immunohistochemistry , had increased by a median of 4 Â·86 times (IQR 4 Â·38 -7 Â·97 ; p =0 Â·0001 ) and 3 Â·48 times (2 Â·05 -4 Â·09 ; p =0 Â·0001 ), respectively , at day 8 (give or take 2 days ). At the same timepoint , relative MDM 2 mRNA expression had increased by a median of 3 Â·03 times (1 Â·23 -4 Â·93 ; p =0 Â·003 ) that at baseline . The median change from baseline for Ki-67 -positive tumour cells was -5 Â·05 % (IQR -12 Â·55 to 0 Â·05 ; p =0 Â·01 ). Drug exposure correlated with blood concentrations of MIC-1 (p <0 Â·0001 ) and haematological toxicity . One patient had a confirmed partial response and 14 had stable disease . All patients experienced at least one adverse event , mostly nausea (14 patients ), vomiting (11 patients ), asthenia (nine patients ), diarrhoea (nine patients ), and thrombocytopenia (eight patients ). There were 12 serious adverse events in eight patients , the most common of which were neutropenia (six patients ) and thrombocytopenia (three patients ).MDM 2 inhibition activates the P 53 pathway and decreases cell proliferation in MDM 2 -amplified liposarcoma . This study suggests that it is feasible to undertake neoadjuvant biopsy-driven biomarker studies in liposarcoma .F Hoffmann-La Roche .

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