While reading up about infectious diseases, I came upon the case of the Tuskegee study, which in 1932 was set out to observe a group of people for 6 months and then cure them of the observed ailment syphilis, without informing the observed people that they were looking for that illness - or that it was highly transmissible. But then it was extended and ran on for more than 40 years. During the runtime researchers interfered with anyone who might treat their study group or even try to inform them. In other words, the whole thing became an ethical nightmare. The aftermath in 1974 did result in new guidelines for studies.
The CDC (linked above) does note that the class action lawsuit Pollard v U.S. Public Health Service, was brought in 1972 by Fred Gray, and settled for an amount above 9 million dollars. Which brings us to the question at hand:
What were the allegations of the class, and could the allegations have been brought had the study never been extended?