Bioavailable Elacridar × GSK Portfolio

Dolutegravir is a known P-gp/BCRP substrate. HIV CNS reservoir is a major unresolved clinical problem — viral persistence in macrophages and microglia despite undetectable plasma viral load drives HAND (HIV-Associated Neurocognitive Disorders). Elacridar enhanced brain penetration of amprenavir (an HIV protease inhibitor) in preclinical models; the same mechanism applies to dolutegravir. Enhanced CNS exposure could suppress or eradicate the CNS reservoir.

Dolutegravir is the leading HIV drug globally. The CNS HIV reservoir is a documented, high-priority unmet need with no current regimen adequately addressing it. A CNS-penetrant enhanced dolutegravir regimen via bioavailable elacridar would be scientifically and commercially landmark — 50m+ PLHIV globally with validated willingness to pay for superior viral suppression. Must be developed fast given the 2028 LOE.

The MMAF payload of belantamab mafodotin is a P-gp substrate. In myeloma cells with MDR phenotype, P-gp efflux reduces intracellular MMAF concentrations — a recognised resistance mechanism. Elacridar could sensitise resistant MM cells to Blenrep by blocking payload efflux, potentially allowing dose reduction and reducing the hallmark keratopathy that led to original withdrawal.

Highly novel — elacridar as a sensitiser to reduce ADC payload efflux and enable dose reduction is unexplored clinically. Directly addresses Blenrep's Achilles heel. If lower doses maintain efficacy, the eye toxicity driving mandatory ophthalmic monitoring would be reduced, unlocking a far broader patient population. Genuine lifecycle extension and market re-expansion play.

As a monoclonal antibody, Jemperli itself is not a P-gp/BCRP substrate. However, elacridar could be used in the RUBY Part 2 regimen (dostarlimab + niraparib maintenance) to specifically enhance niraparib's CNS exposure. The triple combination — dostarlimab/niraparib/elacridar — addresses the subset of patients with brain metastatic disease, a major unmet need in MMRp/MSS endometrial cancer.

Indirect benefit via niraparib enhancement — Jemperli itself is not a P-gp substrate. Most compelling use is in the triple maintenance regimen context for brain-met patients. Jemperli's strong trajectory (£861m, +89%) means it doesn't need elacridar as a standalone combination, but the triple regimen represents a differentiated premium product in a subset of hard-to-treat patients.

Momelotinib is a known P-gp substrate. Gut P-gp limits oral bioavailability — elacridar could enhance systemic momelotinib exposure, allowing dose reduction while maintaining JAK inhibition and potentially reducing on-target haematological toxicities. CNS benefit exists for the rare blast-phase patients with CNS infiltration.

Momelotinib has strong commercial momentum but already has reasonable oral bioavailability. Elacridar enhancement would be incremental rather than transformational. Early EU LOE (2028) limits the lifecycle extension window considerably. Better opportunities exist elsewhere in the portfolio.

Gepotidacin is predicted to be a P-gp substrate based on its physicochemical properties. For complicated UTI or upper urinary tract infections, higher systemic and renal tissue exposure is needed. Elacridar could boost gepotidacin oral bioavailability and renal tissue concentration for complicated/recurrent UTI.

Interesting long-runway opportunity but the UTI market is largely commoditised with limited willingness to pay for premium formulations. Complicated UTI is a niche subset. Worth monitoring but not a priority programme — gepotidacin P-gp substrate status requires formal laboratory confirmation before committing resources.