The development of high-throughput screening technologies and cell culture methods has made it feasible to perform large-scale in vitro drug screens also using patient derived primary tumor cell cultures [
1‐
3]. These techniques are collectively called as ex vivo drug screening methods. The utility of ex vivo drug screening has emerged as a novel approach to complement pathological cancer diagnostic procedures to track patient specific drug sensitivity to hundreds of cancer therapeutics in a single experiment [
3]. The results can be used to confirm drug sensitivity patterns predicted from molecular genetics [
2] or to inform treatment decision and personalized care of individual cancer patients when standard treatment options have been exhausted [
3]. In context of rare cancers, the low number of patients limits the clinical evaluation and validation of novel treatment strategies using conventional trial mechanisms. Thus, demonstration of the efficacy of novel therapeutics in rare cancer types through empirical evidence from ex vivo tests or similar alternative models may be the only option to motivate clinical development of these treatments [
3‐
5]. One such rare cancer, for which ex vivo evidence could be used as motivation for development of novel treatment strategies, is urachal cancer, an aggressive non-urothelial bladder malignancy accounting for less than 1% of all bladder cancers [
6]. Urachal adenocarcinoma (UrAC) arises in adults from the vestigial musculofibrous remnant band that connects the allantois and the bladder during embryonic development. A large proportion of patients with UrAC initially present with an advanced disease [
7] and patients with metastatic urachal cancer have a poor prognosis [
8‐
11]. Given the rarity of urachal cancers, prospective trials to guide the treatment of patients with advanced disease are lacking, there are no standard chemotherapeutic regimens, and surgery remains the mainstay of therapy shown to improve the overall survival outcome of UrAC [
12]. To date, no randomized trials of urachal carcinomas have been reported and the most comprehensive reviews to date have concluded 420 [
10] and 456 [
11] patients reported regionally and 1010 patients reported globally [
13]. As a result, limited information exists regarding the effective management of these cancers beyond the use of chemotherapy including 5-fluorouracil based, 5-fluorouracil and cisplatin [
14‐
17] or hyperthermic intraperitoneal chemotherapy [
18‐
20]. Especially, knowledge concerning the efficacy of new genome aberration targeted chemotherapeutic agents is limited to a handful of case reports from individual institutions [
14,
21‐
25]. Moreover, comprehensive tumor genomic profiling of UrAC samples has not been described and the only common genetic features described in the limited number of reported cases have included aberration of APC, BRAF, EGFR, KRAS, PIK3CA, TP53 and microsatellite instability [
21‐
26]. To improve our understanding of the disease pathogenesis and therapy sensitivity of UrAC, we performed a large-scale ex vivo drug screening of 1160 drugs with vital tumor cells derived from a patient with a metastatic urachal adenocarcinoma. In this study, we also compared the reproducibility of results derived with three different high-throughput drug screening approaches to assess assay dependency of the ex vivo measured dose responses of the patient derived tumor cell cultures. Last we describe establishment of a new human urachal adenocarcinoma cell line (MISB18) which is the first described UrAC cell line with a known genetic background.