An extended understanding of the molecular characteristics of cancer has led to a revolution within the field of precision medicine. This thesis explores the utilization of two targets for precision medicine, namely, CD44v6 and murine double-minute 2 and X (MDM2/X).

A novel mini-antibody construct targeting CD44v6 (AbD19384), was assessed for possible use in radiodiagnostics, while a recombinant full-length anti-CD44v6 antibody based on the same construct, AbN44v6, was evaluated for radio-immunotherapy (RIT) following labeling with ¹⁷⁷Lu and ¹³¹I. Additionally, normal tissue biodistribution and dosimetry was assessed for radiolabeled AbN44v6. The efficacy and mechanisms behind the observed effects of PM2 therapy, a novel stapled peptide that inhibits MDM2/X, were assessed in vitro and in vivo both as monotherapy and in combination with external beam radiotherapy (EBRT). Lastly, combination therapy using RIT (¹⁷⁷Lu-AbN44v6) and PM2 was evaluated in an in vitro 3D tumor spheroid model.

AbD19384 successfully visualized CD44v6-positive xenografts. Similarly, radiolabeled AbN44v6 bound specifically to CD44v6, and RIT resulted in antigen-dependent, activity-dependent growth inhibition of in vitro 3D tumor spheroids. Biodistribution and dosimetry revealed low-level accumulation in normal tissues and low total effective doses of 0.1 mSv/MBq of injected radioconjugate. PM2-based therapy increased pro-apoptotic protein levels and caused growth inhibition of wt p53 cancer cell lines, which was amplified in combination with radiotherapy. In vivo studies of wt p53 and p53-knockout xenografts demonstrated the specificity of PM2 towards wt p53 cancers and established the potency of combining PM2-based therapy with EBRT.

The work presented in this thesis exemplifies the potency of combination treatments based on a precise understanding of the targeted cancer. Utilizing not one but several of the molecular characteristics of a specific cancer will help turn the tables on cancer and improve patient outcomes in the future.