ASMS 2024 -- According to Verified Market Research, at-home microsampling blood collection market size was valued at USD 8.9 billion in 2021 and is projected to reach USD 13.2 billion by 2027, growing at a CAGR of 5.1% from 2022 to 2030 (Jersey City, NJ, Aug. 17, 2022). Along with at-home sample collection, over the last three decades, monoclonal antibodies (mAbs, a class of large protein therapeutics) have been gaining popularity as an immunotherapy approach to treat some diseases. Quantitative analysis of large protein therapeutics for bioanalytical studies raises several key challenges when compared to small drug molecules. This includes developing assays that are both sensitive and specific enough for modern analytical validation requirements. This work builds on previous studies within our lab demonstrating the feasibility of working with this technology for small molecule therapeutics. Pembrolizumab, a humanized monoclonal IgG4 antibody directed against PD-1 (commonly prescribed for the treatment of various cancer types), was selected to assess the practicality of protein analysis via LC-MS/MS analysis coupled with VAMS technology. Due to previous experience with pembrolizumab analysis via LC-MS, we utilized whole protein digestion without any immunoaffinity enrichment or SPE cleanup.