Abstract 2562: Efficacy of RG7204 (PLX4032), a selective BRAFV600E inhibitor, in combination with pegylated interferon alpha-2a (Pegasys), paclitaxel, carboplatin, and anti-VEGF MAb B20-4.1 in the LOX-IMVI human melanoma xenograft model

Abstract

Abstract Few drugs are currently approved for the treatment of melanoma, including dacarbazine (chemotherapy) and interferon alpha (immunotherapy). However, only a small fraction of patients with metastatic melanoma respond to dacarbazine and a survival benefit has not been shown with this or any other chemotherapy regimen. Taxanes have demonstrated some activity in melanoma, including modest response rates in combination with carboplatin or bevacizumab. These results contrast with the extraordinary Phase I clinical data reported with the BRAFV600E kinase inhibitor RG7204 (PLX4032), which has demonstrated a remarkable response rate (N Engl J Med 363(9):809-819, 2010). Here we report our preclinical investigation of RG7204 in combination with the biologics interferon alpha-2a (Pegasys) or B20-4.1 (B20) (mouse/ human cross-reactive anti-VEGF MAb), and the chemotherapies paclitaxel and carboplatin in the BRAFV600E mutant LOX-IMVI melanoma model in nude mice.The combination of RG7204 and paclitaxel provided superior survival as compared to either monotherapy. Conversely, the combination of RG7204 plus carboplatin or RG7204 plus B20 did not extend survival as compared to RG7204 monotherapy. When RG7204, paclitaxel, and B20 were given in triplet combination, no improvement in survival was observed over any doublet. Similarly, the triplet combination with RG7204, carboplatin and B20 failed to demonstrate improved survival over any doublets or RG7204 monotherapy. Although complete suppression of tumor growth was readily achieved with either RG7204 or Pegasys monotherapy, the combination provided a remarkable survival benefit with median survival extended by nearly a year as compared to either monotherapy. Taken together, these data support clinical testing of RG7204 with interferon alpha in melanoma patients harboring BRAFV600E mutation in order to extend survival, and may allow for use of lower dose interferon. Clinical investigation of RG7204 and paclitaxel combination may also be warranted. While our data do not support combined therapy with RG7204 plus anti-VEGF therapy, it should be noted that the LOX model was resistant to B20 monotherapy, and therefore these findings might not apply to tumors with intrinsic sensitivity to anti-VEGF therapy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2562. doi:10.1158/1538-7445.AM2011-2562