pembrolizumab + rucaparib

The combination of pembrolizumab and rucaparib is being investigated as a maintenance therapy for various cancers, particularly non-squamous non-small cell lung cancer (NSCLC) and ovarian cancer. ## Drug Information Pembrolizumab + rucaparib is a combination therapy consisting of two distinct drugs: 1. **Pembrolizumab**: An immune checkpoint inhibitor that targets PD-1 (programmed cell death protein 1) 2. **Rucaparib**: A PARP (poly ADP-ribose polymerase) inhibitor This combination is being studied for its potential synergistic effects in treating cancer. PARP inhibitors like rucaparib have been shown to upregulate PD-L1 expression, which may enhance the response to pembrolizumab in NSCLC[6]. The combination aims to leverage both DNA damage repair inhibition and immune checkpoint blockade mechanisms to improve treatment outcomes. ## Clinical Development The combination is currently being investigated in a multi-center, Phase I/II, single-arm trial (NCT03559049) to assess its safety and efficacy as maintenance therapy in patients with stage IV non-squamous NSCLC without progressive disease after induction therapy with carboplatin/pemetrexed/pembrolizumab triplet therapy[4][6]. In this trial: - Pembrolizumab is administered at 200mg IV on day 1 of every 21-day cycle - Rucaparib is given at 600mg PO BID (twice daily) on days 1-21 of each 21-day cycle[4] The phase I cohort, consisting of 6 patients treated with the approved full doses of rucaparib and pembrolizumab, was completed without dose-limiting toxicity[6]. The study is designed to enroll 55 patients in total if predefined progression-free survival parameters are met[6]. ## Mechanism of Action The combination leverages two distinct mechanisms: 1. **Rucaparib**: Inhibits PARP enzymes, preventing repair of single-strand DNA breaks, which is particularly effective in tumors with deficiencies in homologous recombination repair (HRR) pathways, such as those with BRCA mutations or other factors affecting DNA damage response[5][8]. 2. **Pembrolizumab**: Blocks the interaction between PD-1 and its ligands, enhancing T-cell responses and anti-tumor immunity[2][8]. The synergistic effect between PARP inhibitors and immune checkpoint inhibitors has been observed in clinical settings, potentially due to PARP inhibitors increasing tumor immunogenicity and upregulating PD-L1 expression[8]. ## Potential Applications While the current focus is on NSCLC, similar combinations of PARP inhibitors with immune checkpoint inhibitors have shown promise in other cancers: - The TOPACIO trial investigated niraparib (another PARP inhibitor) with pembrolizumab in platinum-resistant ovarian cancers and metastatic triple-negative breast cancers[8] - The MEDIOLA trial explored olaparib with durvalumab in various cancers including BRCA-mutated ovarian and breast cancers[8] These studies suggest that the combination approach may be effective across multiple cancer types, particularly those with deficiencies in DNA repair pathways.