NAMPTinhibitor-linker 2, a drug-linker conjugate for antibody-drug conjugates (ADCs), comprises an NAMPTinhibitor payload and a linker. When combined with an anti-c-Kit monoclonal antibody to form ADC-4, it demonstrates potent efficacy against c-Kit expressing cell lines, including GIST-T1 and NCI-H526, with IC50 values of <7 pM and 40 pM, respectively.