Immunohistochemical analyses and transcriptomic profiling

Tumour samples will be assessed by a pathologist who is blinded to the treatment applied to the specimens. Immunostaining using antibodies against phosphorylated forms of the mitogen-activated protein (MAP) kinase pathway and BCL2 (an antiapoptotic protein) will be assessed to determine if TRK inhibition is leading to anticipated cell death via suppression of the expected downstream targets of TRK. Tissue concentrations of pegcantratinib will also be assessed in a representative portion of samples.

Gene expression profiling of tumour samples to compare 12 placebo- and 12 pegcantratinib-treated samples will be performed as indicated above.