Early Promise Seen With Nilotinib/Trametinib in BRAF/NRAS Wild-Type Melanoma

Marco Ranzani, PhD

Marco Ranzani, PhD

The combination of nilotinib (Tasigna) and trametinib (Mekinist) proved to be synergistic inBRAF/NRASwild-type melanoma, according to a recent study presented at the 2016 Society for Melanoma Research Congress.

The combination offers a potential new therapeutic option in a subtype where few targeted therapies are available.

In the study—which was presented by Marco Ranzani, PhD, postdoctoral fellow in experimental genetics, Sanger Institute—investigators screened 180 combinations of clinically relevant drugs for sensitivity in a collection of 20BRAF/NRASwild-type melanoma cell lines. Few were determined to be synergistic, said Ranzani.

“Synergy is pretty rare,” he said. “It only occurred in about 1% of all our results.”

However, nilotinib plus 3 different MEK inhibitors did prove to be synergistic. The combination was evaluated using 2 independent experimental approaches. Overall, 24% (n = 5) of cell lines displayed synergy for nilotinib plus MEK inhibitors (delta AUC>0.1 for both MEK inhibitors).

The combination of nilotinib and the MEK inhibitor trametinib was then investigated.

The synergy of the two drugs was first confirmed using an independent collection ofBRAF/NRASwild-type melanoma cell lines (n = 7), then a collection ofBRAF/NRASwild-type patient derived xenotransplant cultures (n = 3), and finally a collection ofBRAF V600E melanoma cell lines (n = 9)

“In all the collections that we analyzed, about one-fourth of all the cells lines that we tested are synergistic for this drug combination,” said Ranzani.

Investigators then generated a gene expression signature of synergistic cell lines for the nilotinib/trametinib combination, and used it to classify human melanomas from 2 cohorts. In the first, which looked at 171 tumors samples, nearly 28% of tumors were classified as synergistic. In the second, which looked at 470 tumor samples, nearly 37% of tumors were classified as synergistic. The combination was also associated with a decreased overall and recurrence free survival (P<.05), suggesting that it may be effective in a relevant fraction of aggressive tumors, according to study investigators.

Researchers also attempted to identify biomarkers that would predict synergy of the combination, but nothing was deemed to be statically significant, said Ranzani.

A further evaluation of potential mechanisms of resistance to the combination of nilotinib/trametinib was then investigated.

&ldquo;In order to try and get inside the mechanism of the synergy, we performed a genetic screening to try and identify mechanisms of resistance to the combination,&rdquo; said Ranzani.

Using CRISPR/Cas9 screening, investigator&rsquo;s identifiedTSC2,TSC1,CDKN18as genes that may cause resistance. All 3 genes are part of the tuberous sclerosis complex, suggesting that a loss of tuberous sclerosis complex, which is present in about 10% of melanomas, can confer resistance to nilotinib/trametinib.

Investigators then looked at 6 representative synergistic cell lines and 3 representative non-synergistic cells lines treated with the single-agent trametinib or the combination, to further understand the mechanism of synergy.

They found that trametinib reduced P-ERK antibody in most of the cell lines. This was expected, said Ranzani. What was less expected was that nilotinib induced P-ERK, regardless of synergy in some of the cells lines,

&ldquo;It likely induces RAF paradoxical activation by being a suboptimal BRAF/CRAF inhibitor,&rdquo; said Ranzani.

The combination was the most effective, further inhibiting P-ERK compared with single-agent cell lines and non-synergistic cell lines.

The model showed that the combination is well tolerated and significantly more effective than the 2 drugs alone (P<.01). These data suggest a strong clinical translation potential for the combination, according to study investigators.

&ldquo;The results were pretty clear,&rdquo; said Ranzani. &ldquo;The tumors which were untreated grew pretty fast. The one treated with nilotinib displayed a minor reduction of the cell growth, the one treated with trametinib displayed a significant reduction of the cell growth but still it grew, but the combination induced partial shrinkage of the tumor, up to 6 weeks after treatment.&rdquo;

The key takeaway from the study, which will be published at a later date, was that nilotinib/trametinib has significant potential inBRAF/NRASwild-type melanoma, said Ranzani.

&ldquo;The combination of nilotinib/trametinib is synergistic in a fraction of melanoma models in vitro and in vivo,&rdquo; he said. &ldquo;We are further studying the mechanism of this synergy.&rdquo;

Reference:

Ranzani M, Kemper K , Michaut M. New therapies for the treatment of BRAF/NRAS wild type melanoma. Presented at: Society for Melanoma Research Annual Meeting; Boston, Massachusetts; November 6-9, 2016.

As a final assessment of synergy, the combination of nilotinib/trametinib was tested in a patient derived xenotransplant mouse model using 5 mice and 10 tumors per each of the 4 experimental groups.