Clinical trials with the mTOR inhibitor everolimus alone and in combination with chemotherapy or with molecularly targeted therapies, including EGFR and MEK inhibitors have mostly shown increased toxicity and limited activity.37-40PI3K inhibitors were similarly ineffective.41,42 There is currently little clinical trial-level biomarker data to determine if there are specific PDA subsets that benefit from PI3K pathway inhibition. The gene discussed is PIK3CA; the disease is Patent ductus arteriosus.