Which undergraduate major leads to a research career in development of new medical drugs? Let's say someone wants to study biochemistry and his main goal is to do research in drug design  (development of new drugs). So, his main interests concerns with Pharmacology, right?

However, there are few undergraduate programs available in Pharmacology (there are some in England and other European countries) because most of Pharmacology programs are graduate programs.

So, the question is, what should this person do? 


Go directly to a undergraduate pharmacology program.
Take another undergraduate program. In this case, what would that be? Chemistry? Medicine? Biochemistry?
There isn't a single "correct" undergraduate major for people interested in research careers in this field. Any of biology, biochemistry, biomedical science, chemistry, pharmacology, and several others would be fine.

Much more important than finding an undergraduate degree with the right "name" would be finding a program where students have the opportunity to carry out undergraduate research with faculty doing the kind of research you want to do. 

For example, the profile of the Einstein 2016 incoming PhD class in biomedical science includes the following range of undergraduate majors:


  Undergraduate majors: Biology, Biochemistry, Biological Sciences, Microbiology, Biochemistry and Molecular Biophysics, Molecular Biology, Biotechnology, Chemistry, Genetics, and Learning Sciences


But all had a lot of prior research experience:


  100% have had a sustained research experience in a scientific laboratory
  
  57% have published a scientific paper in a peer reviewed journal
  
  65% have presented their work at a scientific meeting
  
  31% have also spent a summer in a research program
  
  Mean Months of Prior, Full‐Time Research Experience: 32