Ponder and Srivastava make two basic arguments in defense of the practice: 1- they represent a good therapeutic option for persons living in low and middle-income countries (LMICs) who can't afford standard of care of high-income countries, and 2- we needn't worry about exploitation at all, because such studies might produce medical applications that can be used in LMICs.
Could be. But the latter argument strikes me as logical and doubtful as any generic ethical claim, such as "We needn't worry about safety in gene transfer trials, because gene transfer can be safe." At any rate, look for a full response to their letter in an upcoming issue of Haemophilia. (photo credit: wallyg 2008– Rothko No.25/28).