Association between ex vivo pharmacotyping of patient-derived tumor organoids and personalized therapeutic options for patients with biliary tract cancer.

618 Background: Biliary tract cancers (BTC), including cholangiocarcinomas and gallbladder adenocarcinomas, present significant therapeutic challenges due to limited treatment options and poor prognoses. We report findings from the CLIA-certified PARIS assay, evaluating drug sensitivities of patient-derived tumor organoids (PDTOs) to a panel of oncology drugs. Methods: PDTOs were successfully cultured from 27 out of 46 live tumor samples obtained from 43 BTC patients. The majority of patients presented with advanced metastatic disease (60% stage IV, 13% stage III, 10% stage II, 4.4% stage I, 10% unknown) and had exhausted standard therapeutic options. Each PDTO culture underwent testing against an average of 50 drugs, encompassing chemotherapeutic agents and targeted therapies. Results: Comparative analysis of PDTO drug sensitivities with patients' prior treatment histories revealed non-responsiveness to >80% of drugs associated with clinical progression, including gemcitabine, cisplatin, and targeted therapies for FGFR translocations. In contrast, 100% (26/26) of the samples demonstrated significant sensitivity to one or more targeted agents, particularly inhibitors of EGFR, MEK, ERK, mTOR, PI3K, MDM2, BCL2, and BET families. Despite these shared sensitivities, each individual PDTO culture exhibited unique responses to targeted therapies, highlighting the genetic and phenotypic diversity between BTC patients. Comparison of ex vivo drug sensitivities with tumor genomic profiles validated oncogenic drivers such as HER2 amplification, KRAS and PIK3CA pathogenic mutations, correlating with sensitivities to EGFR/HER2 inhibitors, MEK inhibitors, and PI3K inhibitors, respectively. While mutations in KRAS , BRAF , BRCA1 , BRCA2 , ERBB2 , ERBB3 , or MET are present in less than 8% of cases, their role as biomarkers in BTCs requires further validation. PDTOs offer a promising tool to expedite this validation process. The PARIS assay results guided treatment decisions for five patients with metastatic disease, two of whom maintained treatment for over 4 weeks. Notably, two patients showed clinical benefit with everolimus (5 weeks) and dasatinib (11 weeks), experiencing symptom relief and reduced ascites. Intriguingly, 5 out of 7 PDTOs with FGFR alterations exhibited exceptional PARIS test responses to dasatinib, suggesting potential efficacy linked to FGFR activation. Conclusions: In conclusion, our study demonstrates that ex vivo drug testing of PDTO cultures can inform treatment selection and potentially accelerate drug approvals for BTC, leveraging therapies approved for other cancers. Early integration of such assays in patient management, possibly at diagnosis, holds promise for improving outcomes in this challenging disease.