OncoBayes, a privately held clinical-stage pharmaceutical company, announced the successful completion of preclinical work with OB-001, demonstrating the product's potential to tackle two major unmet needs in oncology: ADC resistance and the brain penetration of tyrosine kinase inhibitors (TKIs).

OB-001 is a highly selective and effective inhibitor of two key efflux pumps (P-gp and BCRP), which are present both on the blood-brain barrier and on tumour cells. The product is being developed as a once-daily oral tablet, which will be used in combination with a number of gold standard oncology treatments in order to optimise their efficacy.

In perfused-brain mouse studies, OB-001 pretreatment significantly raised brain exposure of four gold standard kinase inhibitors – whilst systemic (plasma) exposure remained broadly unchanged. Data presented at AACR 2026 demonstrated that OB-001 could increase the brain exposure of osimertinib by almost 400% with minimal systemic changes^[1],[2]. Based on a translational PK-PD-TGI model for osimertinib, this increase is projected to deliver a step-change in CNS progression-free survival for EGFRm NSCLC patients. The improved control of brain metastases is still a major area of unmet need in NSCLC and breast cancer.

The same efflux pumps have also been identified as a key resistance mechanism impacting ADCs – with the over-expression of these pumps leading to reduced payload concentrations in the tumour. Preclinical work using a bidirectional transporter assay demonstrated that OB-001 reduces efflux for several leading payloads, including SN-38 (e.g. sacituzumab govitecan, Trodelvy®), DM4 (e.g. mirvetuximab soravtansine, Elahere®) and DXd (e.g. trastuzumab deruxtecan, Enhertu®).

Plans are currently underway to move into a parallel clinical trial programme to generate POC data in combination with osimertinib, and also evaluate T-DXd re-sensitisation.

"This is a critical milestone for our team, and we are now well positioned to initiate our clinical plans with OB-001" said Jim Millen, Chief Executive Officer for OncoBayes. "OB-001 is on track to become a first-in-class drug with broad potential as a simple, oral adjunct to a range of blockbuster oncology therapies. This is truly a pipeline in a product opportunity."