Background: Immunotherapy has improved outcomes for patients with recurrent or metastatic cervical cancer whose tumors express PD-L1. Pembrolizumab (PEM), a monoclonal antibody that binds to programmed cell death 1 (PD 1) receptor, inhibits interaction with programmed cell death ligand 1 (PD-L1) and programmed cell death ligand 2 (PD-L2). It is approved for the treatment of recurrent or metastatic cervical cancer. Despite promising results, new strategies are being developed to improve immunotherapy responses. This includes DNA-damaging agents that have the potential to enhance the response to immunotherapy by promoting neo-antigen release, increasing tumor mutational burden, and enhancing PD-L1 expression. Poly-ADP-ribose polymerase (PARP) inhibitors, such as olaparib, have shown synergy with immunotherapy in preclinical and early clinical studies. PARP-based therapy is based on the inhibition of single-strand DNA repair, leading to DNA damage and increased tumor mutational burden. As a result, the tumor becomes a more attractive target for immunotherapy. Based on this, we are investigating the interplay between homologous recombination (HR) repair deficiency, another mechanism of DNA repair, and solid tumor response to ICI. Our approach uses an all-inclusive functional immunofluorescence assay of the Fanconi Anemia triple-staining immunofluorescence (FATSI) we developed and can be performed in paraffin-embedded tumors. Methods: This is a phase II open-label single center trial evaluating the role of PEM and olaparib in patients with metastatic cervical cancer who have progressed on first-line standard of care chemotherapy. FATSI will be performed in all patients. We hypothesize that FATSI negative tumors will be associated with improved responses. Other eligibility criteria include measurable disease by imaging, 18 years of age or older, and no previous exposure to ICI or PARP inhibitor. The primary objective is to evaluate the immune-related objective response rate (iORR) achieved in patients with FA Repair Pathway functionally competent and functionally deficient tumors. Secondary objectives include 20-week progression free survival and overall survival. Other exploratory objectives include evaluation of the mutation load and markers of neo-antigenicity, T cell receptor clonotype analyses (before and after treatment), and alterations in HR repair genes. We will utilize a two-stage phase II design to detect an iORR ≥ 20% in the whole population tested vs. the null hypothesis that the true iORR ≤5%, represents a response by chance alone or other infrequent unknown mechanisms. An interim analysis requires at least 2 of the first 20 evaluable patients enrolled have an objective response. If this occurs, we will accrue 28 additional patients to total 48. Enrollment is ongoing and two patients are currently on treatment. Clinical trial information: NCT04483544