The discovery of novel auristatin derived antibody drug conjugates (ADCs) with attenuated bystander activity is an area of intense research. Recently, the drug-linker SGD-9501 emerged as a promising clinical candidate possessing favorable off-target toxicity. To support clinical supply of ADCs based on this drug-linker, we set out to develop a synthesis to enable a first-in-human (FIH) amenable Good Manufacturing Practice (GMP) delivery. This presentation will describe the process development activities that enabled kilogram-scale supply. Highlights of the fragment synthesis include the development and implementation of a crystallization platform, the use of process analytical technology (PAT) to control impurities formed in a direct coupling of N,N-dimethyl-O-unprotected serine, and the discovery of mild and selective deprotection conditions. The late stages of the synthesis will be presented with a focus on how we address certain problems that are unique to large molecules such as gelation risks caused by eutectic effects, and trifluoroacetate ester impurities formed during lyophilization.