Trevagrumab and Garetosmabneed need to produced in custom, genetically engineered hamster cells, which could be done in China, but whether the cost and complexity is worth it for the grey market is another story. I suspect one of the reasons monoclonal antibodies are much more popular than peptides in research these days is how easy peptides are to make.
The ACE-031 trials did not go very well, it was tested in humans, but was stopped due to safety concerns, As far as I know it has been abandoned as a drug development target since. It had significant off target effects. Unlike a lot of the popular peptides that have never been tested in humans, this one has and was found to be unsafe. Quoting from my writeup of it which I would have copied from somewhere.
"Non–muscle-related adverse events contributed to the decision to discontinue the study The study was stopped after the second dosing regimen due to potential safety concerns of epistaxis and telangiectasias
ACE-031, a soluble ACVR2B receptor designed by Acceleron Pharma for the treatment of DMD, was prematurely terminated due to severe adverse effects including nosebleed, gum bleeding, telangiectasia, and erythema attributed to cross-inhibition of BMP9 and BMP10, ligands involved in endothelial cell function [50]. In addition, a 43% decrease in serum follicle stimulating hormone (FSH), whose synthesis is stimulated by activins, was observed in healthy, postmenopausal women who received a single dose (3 mg/kg) of ACE-031, which caused a near-maximal suppression of activin signaling"
