OncoBayes has developed OB001 — the first orally bioavailable formulation of elacridar, a dual P-gp/BCRP inhibitor. We believe it can reinvigorate multiple GSK assets, open entirely new indications, and generate billions in combination sales that no other partner can unlock.
Our Platform
OB001 simultaneously inhibits both P-glycoprotein (ABCB1) and Breast Cancer Resistance Protein (ABCG2) — the two major efflux transporters limiting oral bioavailability and CNS penetration of most small-molecule oncology and antiviral drugs.
Elacridar's clinical potential has been known for 30 years but was blocked by its own poor oral bioavailability (<5% in standard formulation). Our patented ASD formulation achieves 100% bioavailability with consistent plasma exposure.
By blocking P-gp and BCRP at the BBB, OB001 increases CNS drug concentration of co-administered substrate drugs by 12-fold — making previously ineffective CNS treatment strategies clinically viable.
The original form of Elacridar has extensive phase I data. OncoBayes has built on this and is now poised to enter the clinic.
Portfolio Analysis
We have systematically screened the GSK marketed portfolio and late-stage pipeline against confirmed P-gp and BCRP substrate profiles. Below is our ranked assessment of every combination opportunity.
Niraparib is the single most compelling combination partner in the GSK portfolio. It is a validated P-gp substrate with the best baseline BBB penetration of any approved PARP inhibitor (Kp,brain ≈0.3 vs. olaparib's 0.03). Published data show elacridar co-administration increases niraparib brain concentration 12-fold in wild-type mice — from sub-therapeutic to therapeutically relevant levels. This unlocks brain metastases from ovarian, endometrial and fallopian tube cancers as a wholly new indication with no approved standard of care, plus glioblastoma combination potential. Critically, Zejula's base ovarian cancer indication is declining due to FDA label restrictions — GSK has strong internal motivation to find a lifecycle management solution. OB001 provides it.
Target: Brain mets (OC/EC/FTPC) · GBM · Leptomeningeal diseaseBlenrep's relaunch was nearly killed by dose-dependent corneal keratopathy. The cytotoxic payload MMAF is a P-gp substrate in haematopoietic cells. If OB001 enhances intracellular MMAF accumulation in myeloma cells, a dose reduction strategy becomes viable while maintaining cytotoxic efficacy — directly addressing the toxicity that previously led to market withdrawal. A dose-optimised Blenrep + OB001 combination could be the formulation that finally makes this asset commercially viable at scale. Requires preclinical validation in MM cell lines, but the commercial logic is compelling given Blenrep's history and GSK's significant investment.
Target: Relapsed/refractory multiple myeloma · Dose-reduction lifecycleBuilding on the lead programme, niraparib activates STING/interferon signalling and drives CD8+ T-cell tumour infiltration, creating a mechanistic rationale to combine with anti-PD-1 therapy. A triple combination of niraparib + dostarlimab + OB001 could deliver enhanced tumour cell kill (via PARP inhibition with elacridar improving intracellular accumulation), immune priming (via STING activation), and immune checkpoint release (via dostarlimab) — a highly differentiated regimen for endometrial, ovarian, and cervical cancers. GSK already holds both assets and is exploring PARP + checkpoint combinations. OB001 is the missing third leg.
Target: Endometrial cancer · Ovarian cancer · MSI-H solid tumoursMomelotinib and the broader JAK inhibitor class frequently interact with ABC transporters. OB001 co-administration may allow dose reduction while maintaining JAK inhibition efficacy, reducing haematological toxicities that limit dose escalation in myelofibrosis. There is also an AML-adjacency angle: as myelofibrosis progresses to AML, P-gp overexpression in blast populations can limit momelotinib intracellular concentrations. Elacridar may partially reverse this. Currently a speculative hypothesis requiring preclinical validation, but the commercial trajectory of Ojjaara (£554m, +60% YoY) makes even a modest lifecycle extension commercially significant.
Target: Myelofibrosis dose optimisation · AML transformation settingMonoclonal antibodies (Nucala/mepolizumab, Benlysta/belimumab, Jemperli/dostarlimab standalone) are large-MW biologics not subject to P-gp or BCRP-mediated efflux — mechanism does not apply. Cabenuva is a long-acting injectable bypassing intestinal transporter interactions. Trelegy and other inhaled agents act topically in the lung — systemic transporter modulation is not relevant. These assets are excluded from the OB001 partnership scope.
mAb / Injectable / Inhaled routes — mechanism not applicableLead Programme Deep Dive
Zejula's sales are declining. FDA label restrictions have compressed the addressable ovarian cancer maintenance market. GSK needs a new indication to reinvigorate the asset before the competitive window closes.
The CNS metastasis opportunity is real, urgent, and pharmacologically validated. Brain metastases from gynaecological cancers affect ~20,000–30,000 patients per year in the US and EU. Median survival without treatment is under 3 months. There is no approved targeted therapy. Oncologists are desperate for options.
Niraparib is the only PARP inhibitor with any meaningful baseline BBB penetration (Kp,brain ≈0.3). Data show that elacridar co-dosing increases niraparib brain concentration to levels exceeding the pharmacodynamic threshold for PARP inhibition in CNS tumour tissue. Specifically, elacridar increased niraparib brain-to-plasma ratio at 4 hours by ~12-fold, with no significant increase in plasma AUC0–4h, illustrating selective CNS exposure enhancement through ABCB1/ABCG2 inhibition. A clinical trial (NCT04992013) is already evaluating niraparib in CNS metastases — GSK's own investigators are validating the hypothesis. OB001 provides the PK amplifier that makes it work.
Orphan Drug Designation eligibility extends market exclusivity by 7 years. Breakthrough Therapy Designation would accelerate the path to approval. The OB001 patent extends to 2046 — providing a combination exclusivity horizon well beyond niraparib's base LOE and any ODD extension.
The combination qualifies for multiple regulatory incentives that extend the commercial horizon well beyond the base niraparib LOE and provide significant development cost recovery.
At $180,000 per patient-year pricing (consistent with current PARP inhibitor pricing in refractory settings) and 25% market penetration across 30,000 addressable CNS metastasis patients, peak combination sales exceed £1.5bn. With glioblastoma and leptomeningeal disease expansion, the ceiling is £2.5bn+. This is transformational for a declining asset.
NCT04992013 (Massachusetts General Hospital) is an active Phase II study evaluating niraparib monotherapy in CNS metastases. This validates the clinical hypothesis and provides a clear precedent for regulatory discussion. OB001 enters as the enabling co-formulation — not a new drug, but the PK solution that makes the monotherapy data translatable to a reliable treatment effect.
OncoBayes holds patents on the bioavailable elacridar formulation . This is independent of and complementary to GSK's niraparib patents. The OB001 patent extends to 2046, creating a joint defensible position that materially outlasts niraparib's own exclusivity and any competitor formulation efforts.
Partnership Structure
We are proposing a phased co-development and commercialisation partnership, structured to minimise GSK's upfront commitment while aligning long-term incentives. OncoBayes brings the platform, IP, and Phase I-ready package. GSK brings the partner asset, development infrastructure, and global commercial reach.
Development Roadmap
Partnership Signed
Term sheet executed. Joint steering committee established. IP licences and co-development agreement signed. Orphan Drug Designation filing submitted. IND enabling package transferred to GSK.
Phase I Initiation
Phase I PK/safety study opens. 40-patient dose escalation to determine optimal elacridar exposure for ≥80% P-gp/BCRP inhibition. Adaptive design allows seamless expansion into Phase II CNS metastases cohort.
Phase II Efficacy
Pivotal Phase II opens in BRCA-mutant / HRD+ ovarian and endometrial cancer patients with brain metastases. Primary endpoint: intracranial objective response rate. BTD application submitted on Phase I PK data.
NDA Filing & Approval
Phase II data package supports NDA/MAA filing. Priority Review designation targets 6-month FDA review. Approval anticipated Q4 2031 / Q1 2032. OB001 patent protection to 2046 provides ~15 years of post-approval exclusivity — exceptional commercial runway for the combination franchise.
Next Steps
OncoBayes is proposing a meeting to continue existing discussions and discuss next steps.