Conflict of interest: C.J. Mullin is a consultant for Merck & Co., Rahway, NJ, USA and Regeneron Pharmaceuticals, Inc., Tarrytown, NY, USA; his institution receives clinical trial support from Pulmovant, Inc., Gossamer Bio, Pfizer and Tenax Therapeutics, as well as Merck & Co. for studies related to sotatercept. C.E. Ventetuolo has received consulting fees from Merck & Co. and Regeneron Pharmaceuticals, Inc., and served on advisory boards for Janssen Pharmaceuticals and Merck & Co.; her institution receives clinical trial support from Pulmovant, Inc., Gossamer Bio, Pfizer and Tenax Therapeutics, as well as Merck & Co. for studies related to sotatercept.