Study of BO-112 With Pembrolizumab for Colorectal or Gastric/GEJ Cancer With Liver Metastasis

The purpose of this Phase II study is to evaluate the safety, tolerability, antitumoural activity and systemic exposure of repeated IT administrations of BO-112 percutaneously injected into a hepatic metastatic lesion in combination with pembrolizumab administered intravenously. This is an open-label, non-comparative, 2-cohort study with a Simon's 2-stage design which will include up to 69 evaluable adult subjects with un resectable liver metastasis suitable for IT injection from CRC or GC/GEJ who are naive to anti-PD1/PDL1 therapy. Cohort A will consist of up to 26 subjects with metastatic CRC who have received at least 2 prior standard of care systemic anticancer therapies for advanced/metastatic disease. Bevacizumab may have been previously administrated. Prior Anti-EGFR drugs are mandatory if applicable depending on the RAS status. Cohort B will consist of up to 43 subjects with gastric or GC/GEJ who have received at least 1 prior standard of care systemic anticancer therapy for advanced/metastatic disease. Prior Her2 blockade will be mandatory in those patients with Her2 positive tumors. The aim of this study is to reverse the primary resistance that the subgroup of patients from these 2 cohorts who present microsatellite stability (MSS), in which data from previous clinical trials have demonstrate that the inhibition of PD-1 has no proven efficacy. For that purpose, the MSI status will be determined in the pre-treatment biopsy, done on C1D1, before the first BO-112 administration. Those patients with a MSI status will continue under study treatment but will be replaced and will not be considered for the efficacy assessment, only for the safety assessment. Those patients having a MSS status will be considered bot both assessments. The recommended dose for further clinical development of BO-112 is 1 mg administered in 1.7 mL volume, based on the data from the 112/2016-IT study, the fist-in-human trial with BO-112. The planned dose of pembrolizumab for this study is 200 mg. Study treatment will consist of BO-112 IT injections in combination with IV pembrolizumab infusions and will be administered in 3-week cycles. For each cycle, BO-112 IT injections will be administered after the pembrolizumab infusion, either the same day or within a period of up to 36 hours after the pembrolizumab infusion (for organisational feasibility at the site). On the first cycle, BO-112 will be administered on D1 and D8. The BO-112 IT injections will be administered by an interventional radiologist under ultrasound guidance, or occasional CT scan guidance, at the discretion of the interventional radiologist. Study treatment should continue as long as there is clinical benefit and it is tolerated, up to a maximum of approx. 2 years (corresponding to 35 treatment cycles).