The term "researcher" may be what you want (from Oxford Dictionaries):
A person who carries out academic or scientific research:
"a medical researcher who pioneered the development of antibiotics"
This would be appropriate for listing the people conducting the study if those people are doing work that requires some knowledge of pharmacology or work that was central to the study. If your list included people doing other tasks which didn't require pharmacological knowledge, you could refer to one of those people as an:
A person who ranks below a senior person:
"the managing director and his assistant"
[AS MODIFIER]: "an assistant manager"
[WITH ADJECTIVE OR NOUN MODIFIER] A person who helps in particular work:
"a care assistant"
In this case specifically, you might call them a lab assistant.
Again, depending on their role, you may also call them a:
A person employed to look after technical equipment or do practical work in a laboratory:
"a laboratory technician"
If you had a mixture of these roles, I think the option which would best convey that they were responsible for the carrying out of the study would be personnel. You wouldn't need to prepend "study" because it would be obvious from context that these were the personnel who conducted the study.
However, I don't have experience writing academic papers. There may be an established convention or terminology that someone with experience can suggest.