As Alpern discusses, the targets are typically treatments for relatively uncommon infectious diseases, such as tropical diseases and opportunistic infections. This is because the market for the drug is small enough that it isn't likely to attract competitive manufacturers. These are people who cannot afford high out of pocket costs and may be uninsured or underinsured. As Alpern et al explain:
It seems that a new business model has emerged: companies are acquiring drugs in niche markets where there are few or no therapeutic alternatives in order to maximize their profits. Unlike new brand-name drugs, the patents of the drugs being targeted by this model expired years ago. These companies seem to have no interest in adding value to the health care system by developing new drugs. . . .This is a problem only in the United States. In Europe, drug prices are regulated. The reason they aren't regulated here is because the obscenely wealthy psychopaths who have bought the U.S. political system -- including politicians, the corporate media, and economics departments -- have brainwashed us all into thinking that letting rich bastards screw us is the definition of "liberty." So that's what congress does.
What makes this business model particularly disturbing is that vulnerable patients — such as immigrants, refugees, and people of low socioeconomic status — are often disproportionately affected, since many of the medications are for tropical or opportunistic infections. These patients often have limited or no access to insurance, or have access only through public programs, so already stark health disparities are compounded.