Dogs with naturally occurring cancers can serve as a better model system for evaluating novel cancer immuno-therapeutics than the traditional mouse model systems, and also provide a target patient group. However, use of canine cancer patients is currently limited by the availability of suitable reagents to monitor canine immune responses. The majority of commercially-available reagents for canine biomarkers are rabbit polyclonal reagents, which are not renewable and suffer from lot-lo-lot variability. Following their success in Phase I, here the company proposes to use their novel yeast rabbit antibody display platform to discover high affinity, highly specific rabbit monoclonal antibodies against an expanded panel of 26 canine biomarkers. In parallel, AvantGen plans to optimize the caninized anti-canine-PD-1 antibody isolated in Phase I as a canine immunotherapeutic, then perform a pilot study in pet dogs with lymphoma to assess its safety and efficacy as concurrent therapy with standard of care chemotherapy using the biomarker reagents generated during this project to assess in vivo immune responses to treatment. A successful outcome will result in a panel of high quality, well characterized, renewable reagents for canine biomarkers that will facilitate future development of immunotherapeutics plus provide a novel treatment for canine lymphoma.