Although TUXEDO-3 is, to our knowledge, the first trial investigating HER3-DXd in patients with LMD, data in this disease setting are available for another ADC, as the activity of the related ADC T-DXd targeting HER2 in patients with LMD was investigated in a few small studies, and results corroborate evidence of T-DXd activity in LMD. The gene discussed is ERBB2; the disease is Langer mesomelic dysplasia.