The development of telangiectasia in four patients in this study (three with a primary diagnosis of HCC) suggests vascular targeting and in vivo inhibition of the ALK‐1 pathway by PF‐03446962, consistent with the genetically determined loss of ALK‐1 functions reported in patients with type 2 HHT 7, 8, 9. The gene discussed is ACVRL1; the disease is hepatocellular carcinoma.