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Improved antitumor activity of immunotherapy combined with BRAF and MEK inhibitors in BRAFV600E mutant melanoma

ABSTRACT: The first clinical trial testing the combination of targeted therapy with a BRAF inhibitor vemurafenib and immunotherapy with a CTLA-4 antibody ipilimumab was terminated early due to significant liver toxicities, possibly due to paradoxical activation of the MAPK pathway by BRAF inhibitors in tumors with wild type BRAF. MEK inhibitors can potentiate the MAPK inhibition in tumor, while potentially alleviating the unwanted paradoxical MAPK activation. With a mouse model of syngeneic BRAFV600E driven melanoma (SM1), we tested whether the addition of the MEK inhibitor trametinib would enhance the immunosensitization effects of the BRAF inhibitor dabrafenib. Combination of dabrafenib and trametinib with pmel-1 adoptive cell transfer (ACT) showed complete tumor regression. Bioluminescent imaging and tumor infiltrating lymphocyte (TIL) phenotyping showed increased effector infiltration to tumors with dabrafenib, trametinib or dabrafenib plus trametinib with pmel-1 ACT combination. Intracellular IFN gamma staining of the TILs and in vivo cytotoxicity studies showed trametinib was not detrimental to the effector functions in vivo. Dabrafenib increased tumor associated macrophages and T regulatory cells (Tregs) in the tumors, which can be overcome by addition of trametinib. Microarray analysis revealed increased melanoma antigen, MHC expression, and global immune-related gene upregulation with the triple combination therapy. Given the up-regulation of PD-L1 seen with dabrafenib and/or trametinib combined with antigen specific ACT, we tested the triple combination of dabrafenib, trametinib with anti-PD1 therapy, and observed superior anti-tumor effect to SM1 tumors. Our findings support the testing of these combinations in patients with BRAFV600E mutant metastatic melanoma.

ORGANISM(S): Mus musculus

PROVIDER: GSE64102 | GEO | 2014/12/12

SECONDARY ACCESSION(S): PRJNA270119

REPOSITORIES: GEO

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Project description:The first clinical trial testing the combination of targeted therapy with a BRAF inhibitor vemurafenib and immunotherapy with a CTLA-4 antibody ipilimumab was terminated early due to significant liver toxicities, possibly due to paradoxical activation of the MAPK pathway by BRAF inhibitors in tumors with wild type BRAF. MEK inhibitors can potentiate the MAPK inhibition in tumor, while potentially alleviating the unwanted paradoxical MAPK activation. With a mouse model of syngeneic BRAFV600E driven melanoma (SM1), we tested whether the addition of the MEK inhibitor trametinib would enhance the immunosensitization effects of the BRAF inhibitor dabrafenib. Combination of dabrafenib and trametinib with pmel-1 adoptive cell transfer (ACT) showed complete tumor regression. Bioluminescent imaging and tumor infiltrating lymphocyte (TIL) phenotyping showed increased effector infiltration to tumors with dabrafenib, trametinib or dabrafenib plus trametinib with pmel-1 ACT combination. Intracellular IFN gamma staining of the TILs and in vivo cytotoxicity studies showed trametinib was not detrimental to the effector functions in vivo. Dabrafenib increased tumor associated macrophages and T regulatory cells (Tregs) in the tumors, which can be overcome by addition of trametinib. Microarray analysis revealed increased melanoma antigen, MHC expression, and global immune-related gene upregulation with the triple combination therapy. Given the up-regulation of PD-L1 seen with dabrafenib and/or trametinib combined with antigen specific ACT, we tested the triple combination of dabrafenib, trametinib with anti-PD1 therapy, and observed superior anti-tumor effect to SM1 tumors. Our findings support the testing of these combinations in patients with BRAFV600E mutant metastatic melanoma. SM1 tumors were implanted into C57BL/6 mice. Mice were treated by ACT of pmel-1 splenocytes or C57BL/6 splenocytes as control. Pmel-1 treated mice were additionally treated with either vehicle, dabrafenib, trametinib, or combination of both drugs and control mice were treated with vehicle or combination of both drugs.

Project description:Importance: Autophagy has been identified as a resistance mechanism to BRAF and MEK inhibition in BRAF mutant melanoma. In the BAMM trial, hydroxychloroquine (HCQ) was used to inhibit autophagy in combination with dabrafenib and trametenib in BRAF mutant melanoma patients. Objective: To a) determine safety and maximal tolerated dose (MTD) of hydroxychloroquine when combined with dabrafenib and trametinib and b) determine antitumor activity of the combination. Design: Open label non-randomized phase I/II clinical trial Setting: Prospective therapeutic clinical trial conducted in 4 centers Participants: Unresectable Stage III or Stage IV BRAF mutant melanoma patients Intrevention: HCQ twice daily, dabrafenib 150 mg twice daily and trametinib 2 mg daily (D+T) Main Outcome: Primary outcomes were safety and 1-year progression-free survival (PFS) rate Results: Between December 2014 and January 2020, 50 patients were screened, 38 patients were enrolled and evaluable for toxicity and 34 patients were evaluable for 1-year PFS rate. Patient demographics were: 29% were ECOG PS 1, 47% had elevated LDH, 52% were Stage IV M1c or M1d and 53% had previously received therapy for advanced melanoma. In the phase I trial there was no dose limiting toxicity of HCQ at either 400 (n=3) or 600 (MTD) mg po bid combined with D+T. For the entire study population, the 1-year PFS rate was 41% (95% CI = ), median PFS was 11.9 months (95% CI = ), overall response rate (ORR) was 85% (95% exact CI=64-95%)and complete response rate of 41% (95% exact CI=25-59%). In a prespecificed subgroup analysis in 18 patients with elevated LDH, the ORR was 88% and median PFS was 8 months Conlusion and Relevance: The combination of HCQ, dabrafenib and trametinib was well tolerated and produced a high response rate but did not meet the prespecified criteria for success with respect to the 1-year PFS rate. In patients with elevated LDH , the response rate and PFS were encouraging. A randomized placebo controlled trial of dabrafenib and trametinib with/without HCQ in advanced BRAF mutant melanoma patients with elevated LDH and previously treated with immunotherapy is being conducted through the National Clinical Trial Network.

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Improved antitumor activity of immunotherapy combined with BRAF and MEK inhibitors in BRAFV600E mutant melanoma

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