PCI Biotech Holding ASA announced that the company has concluded on the interactions with regulatory authorities in the US (US Food and Drug Administration, FDA) and Europe (European Medicines Agency, EMA) held during 2H 2021. The interactions with the FDA and EMA were initiated to explore the opportunity for a modified study design to address the retention risk in the control arm of the RELEASE study. PCI Biotech argued that enrichment of the control arm of RELEASE with external control data, using existing patient-level data from past clinical trials and real-world data from a patient registry for patients with extra-hepatic cholangiocarcinoma receiving gemcitabine-cisplatin, could address the potential retention issue and that this approach may also benefit recruitment. The company has previously reported that initial responses from the authorities suggested significant challenges for using external control data in a pivotal trial of a first line treatment. The authorities have now reiterated their position and given more granularity on their concerns. Both regulatory authorities recognised the retention and recruitment challenges for RELEASE in bile duct cancer, a rare disease with high unmet medical need. The authorities’ main concern is that the proposed modification would introduce a risk for uncontrolled bias. The feedback suggests that the validity of external control data for inferential statistical tests is not yet sufficiently corroborated for the settings of a global pivotal trial with registration intent.