Kim is of Korean descent. Kim grew up in Ridgewood, New Jersey the son of a single mother, and his first job was in 1974 at a Roy Rogers restaurant, where he earned money to pay for college. Kim earned his A.B. in chemistry at Cornell University in 1979 and trained as a Ph.D. in Biochemistry at Stanford University under the guidance of Robert Baldwin. While at Stanford, he was also a Medical Scientist Training Program Fellow.
During his tenure, Merck gained approval of more than 20 new medicines and vaccines. These include Januvia (the first DPP-4 inhibitor for type 2 diabetes), Gardasil (the first vaccine for prevention of cervical cancer), Isentress (the first HIV integrase inhibitor), Zostavax (the first vaccine for the prevention of shingles in adults), Rotateq (an oral vaccine for the prevention of rotavirus infection in infants), and Victrelis (the first hepatitis C protease inhibitor). In 2013, he retired from Merck and was succeeded by Roger Perlmutter
